منهج الرابع العلمي 2024 PDF

 Ecology Introduction No microorganism, plant or animal species including man is an isolated organism living in a void. Each of them is surrounded by a host of physical conditions that can be measured in terms of chemical composition, texture, pressure, temperature, and humidity, as well as being...

 Ecology Introduction No microorganism, plant or animal species including man is an isolated organism living in a void. Each of them is surrounded by a host of physical conditions that can be measured in terms of chemical composition, texture, pressure, temperature, and humidity, as well as being surrounded by a host of other living organisms which can be described in such terms as microorganism, plants, animals, food, parasites, and enemies. Studies of the interrelationships of organisms with their physical and biotic environments are termed environmental biology or ecology. It is important for everyone to know and appreciate the principles of this aspect of biology so that one can form an intelligent opinion regarding topics such as insecticides, detergents, mercury pollution, sewage disposal, power dams, urbanization and their effects on mankind, on human civilization, and on the world we live in. The term ecology (oekologie) is derived from two Greek words–oikos=means ‘house’ or ‘place to live’ and–logos means ‘a discussion or study’. Definition of ecology According to Charles H. Southwick (1976). ‘ecology is the scientific study of the relationships of living organisms with each other and with their environments’. Thus, it is the science of biological interactions among individuals, populations, and communities. Ecology is also the science of ecosystems–the interrelations of biotic components with their non-living environments. Branches Of Ecology The science of ecology is often divided into autecology and synecology. Autecology deals with the study of the individual organism or an individual species. In this, life histories and behaviour as a means of adaptation to the environment are usually emphasized. Synecology deals with the study of groups of organisms which are associated together as a unit (i.e., community).. Early ecologists have recognized two major subdivisions of ecology in relation to plants and animals—plant ecology and animal ecology. But when it was found that in the ecosystems plants and animals are very closely associated and interrelated, then, both of these major subdivisions of ecology into plant ecology and animal ecology became vague. Besides these major subdivisions the ecology has been classified in the following branches according to the level of organization, kind of environments or habitats and taxonomic position : 1. Habitat ecology. It deals with the study of different habitats of the biosphere. According to the kind of habitat, ecology is subdivided into marine ecology, freshwater ecology, and terrestrial ecology. The terrestrial ecology too is further subdivided into forest ecology, cropland ecology, grassland ecology, etc., according to the kind of study of its different biomes. 2. Ecosystem ecology. It deals with the analysis of ecosystem from structural and functional point of view including the interrelationship of physical (abiotic) and biological (biotic) components of environment. 3. Conservation ecology. It deals with methods of proper management of natural resources such as land, water, forests, sea, mines, etc., for the benefit of human beings. 4. Production ecology. It is the modern subdivision of ecology which deals with the gross and net production of different ecosystems such as freshwater, sea water, cropfields, orchards, etc., and tries to do proper management of these ecosystems so that maximum yield can be obtained from them. 5. Radiation ecology. It deals with the study of gross effects of radiations and radioactive substances over the environment and living organisms. 6. Taxonomic ecology. It is concerned with the ecology of different taxonomic groups and eventually includes following subdivisions of ecology–plant ecology, insect ecology, invertebrate ecology, vertebrate ecology, microbial ecology and so on. 7. Human ecology. It deals with the study of relationship of man with his environment. 8. Space ecology. It is a modern subdivision of ecology which remains concerned with the development of partially or completely regenerating ecosystems for supporting life of man during long space flights or during extended exploration of extra-terrestrial environments. 9. Systems ecology. The systems ecology is the most modern branch of ecology which is concerned with the analysis and understanding of the function and structure of ecosystem by the use of applied mathematics such as advanced statistical techniques, mathematical models and computer science. Significance Of Ecology For Man Man is himself an organism within an environment. Like other animals man is influenced by the physical features of his environment, he is absolutely dependent upon other species for his food, clothing, medicine, and other similar aspects and he has to adjust to other individuals of his own species. Therefore, the basic laws of ecology apply well to him and its fundamental knowledge is must for man for his own existence on this planet (Earth). Man almost always has a modifying influence, and without proper regulation he often has a destructive effect. For instance, by applying certain ecological principles to such fields as agriculture, biological surveys, game management, pest control, forestry, horticulture, and fishery biology, he has received tremendous economic gains. Its knowledge is found critically important for intelligent conservation whether in relation to soil, forest, wildlife, water supply or fishery resources. Further, though man has been known to control his environment successfully to meet his needs, but indiscriminate control of different pathogens or pests such as bacteria, fungi, weeds, insects, rodents, etc., through use of different chemical-poisons or pesticides (bacteriocides, fungicides, insecticides, etc.), the release of massive quantities of radioactive debris, xenobiotics (i.e., chemical compounds synthesized by humans which are not naturally found in living organisms and cannot normally be metabolized (broken down) by them; see Green et al., 1990), discarded chemicals and industrial wastes into rivers result in atmospheric and aquatic pollution, which may have short and long term ecological effects. Further, rapid growth of urbanization and fast rate of multiplication of human population have resulted in fatal threat of scarcity of wild life, food, open space, and of survival. Q 1 / Define the term ecology , xenobiotics Q2/ classify ecology according to the level of organization, kind of environments or habitats and taxonomic position Q3 / different between auecology and synecology Abiotic Environmental Factors Environment of an organism has two components abiotic and biotic. The first includes the atmosphere (air), hydrosphere (water) and lithosphere (land including soil). The abiotic components are characterized by physical and chemical factors such as light, temperature, rainfall, pressure, pH, the content of oxygen and other gases, and so on. These factors exhibit diurnal, nocturnal, seasonal, and annual changes. The biotic components include all living organisms which interact with each other and with the abiotic components. Earth’s living organisms interacting with their physical or abiotic environment (including air, land and water) form a giant and vast ecosystem, called ecosphere or biosphere which is largest and most nearly self-sufficient biological system. Types of abiotic environmental factors The distribution, abundance, growth and reproduction of the organisms comprising the individual members of populations are controlled by certain environmental or ecological factors. An environmental factor is any external force, substance or condition which surrounds and affects the life of an organism in any way. Abiotic environmental factors are customarily classified as follows : 1. Climatic factors (i) Light ; (ii) Temperature ; (iii) Water (including atmospheric water, rainfall or precipitation, soil moisture, etc.) ; (iv) Atmosphere (gases and wind) ; (v) Fire. 2. Topographic or physiographic factors (i) Altitude ; (ii) Direction of mountain chains and valleys ; (iii) Steepness and exposure of slopes. 3. Edaphic factors (soil formation, physical and chemical properties of soil, nutrients). Essential elements and limiting factors The individual organisms of species population, in order to grow and multiply, must be supplied with certain essential materials. Of the hundred four (i.e., 104) naturally occurring chemical elements on the earth, all living organisms are believed to utilize only 16 different chemical elements for their survival. These are called essential elements. Several other elements are needed in small quantities by some species. They are summarized below. Essential elements Macronutrients : Elements Micronutrients : Micronutrients : used in relatively large Elements generally Elements needed by quantities needed in relatively certain species in small quantities relatively small quantities Carbon Iron Sodium Hydrogen Manganese Vanadium Oxygen Boron Cobalt Nitrogen Molybdenum Iodine Phosphorus Copper Selenium Calcium Zinc Silicon Magnesium Chlorine Fluorine Sulphur Barium Some of these tabulated elements are used in relatively large quantities as the fundamental building blocks of organic tissues and are called macronutrients. Others, the micronutrients, are used in much smaller quantities. The micronutrients are also known as trace elements. For instance, a crop such as corn will remove over 45 kg. of nitrogen per acre from the soil but only 10–15 g. of boron. In addition to the nutrients required by all species, some organisms have special nutrient requirements.  1- Light and radiations The radiant energy from the sun is the basic requirement for the existence of life on the earth. This source of energy is of fundamental importance to the photosynthetic production of food by plants and as mentioned previously, the heat budget of the world is dependent on solar radiation. Although we generally, think only in terms of visible light, the sun emits other radiations of different wavelengths— cosmic rays, gamma rays, X- rays, ultraviolet rays, infra-red rays, heat waves, spark discharges, radar waves, radio waves, slow electro-magnetic waves. Biologists have been primarily interested in only three regions near the centre of the electromagnetic spectrum (1) the infra-red, (2) the visible light (3) ultraviolet regions.  The infrared wavelengths, which are the longest of these three, not visible to the human eye and they contribute to the warmth of the earth at the high altitudes in the terrestrial atmosphere.  Visible light - is only a small fraction of the radiation spectrum -contains the frequency of wavelengths ranges from 390 to 700 millimicrons (mµ).  The wavelength of ultraviolet light from the sun is - shorter than that of visible light, - it produces the upper levels of the earth known as the ionosphere. Light Variations in Different Environments Light energy varies with different media. The transparency of air and water is important in regulating the amount and quantity of light that may be available in particular habitats. For example The intensity of light reaching the earth’s surface varies with the angle of incidence, degree of latitude and altitude, season, time of day, amount absorbed and dispersed by atmosphere and a number of climatic and topographical factors such as fog, clouds, suspended water drops, dust particles, etc., About 10% of the sunlight which falls over the water surface, is reflected back and rest 90% of that pass downward in the water and is modified in respect to intensity, spectral composition, angular distribution (refraction) and time distribution. The phytoplankton, zooplankton, suspended organic and inorganic particles either reflect or absorb the light rays. Further, in water there is a selective absorption of light at various depths. Depending upon the penetration of light, oceans are divided into euphotic zone (up to 50 metres depth), disphotic zone (up to 80 to 200 meters depth) and aphotic zone (below 200 meters of depth). In the ocean, algae are distributed according to length of light rays that their colours are best suited to absorb and to utilize. Photosynthesis in deeper waters occurs with blue and green rays, which are absorbed by the brown and red pigments of red algae (Phyllophora). The red and blue-green algae use pigments of photocyanin and photoerythrin for photosynthesis. Effect of Light on the Plants Light energy influences almost all the aspects of plant life directly or indirectly. Thus, it controls plant’s structure, form, shape, physiology, growth, reproduction, development, local distribution, etc. A. Direct effects of light on plants. Light affects directly the following physiological processes of the plants 1. It is an essential factor in the formation of chlorophyll pigment in chlorophyllous plants. 2. It has a very strong influence on the number and position of chloroplasts. The upper part of the leaf which receives full sunshine has larger number of chloroplast which are arranged in line with the direction of light. In leaves of plants which grow under shade, chloroplasts are very few in number and are arranged at right angle to the light rays, thus, increasing the surface of light absorption. 3. Light has its most significant role in photosynthesis. During photosynthesis, the green plants which are the “primary producers” of an ecosystem, synthesize their carbohydrate food from water and CO2 in the presence of sunlight. Thus, during photosynthesis, the solar radiant energy is transformed into the chemical or molecular energy which remains stored in chemical bonds of carbohydrates and this chemical energy is utilized by other chlorophyllous and non-chlorophyllous parts of plants, all animals, bacteria and viruses in their different life activities. 4. Light inhibits the production of auxins or growth hormones as a result of which it influences the shape and sizes of plants. Plants grown in insufficient light or in the total darkness, produce maximum amount of growth hormones, as a result of which they are elongated with weak pale yellow stems with very few branches. 5. Light also influences certain chemical compounds of plants which affect the differentiation of specialized tissues and organs. 6. Leaf structure too is influenced by the intensity of light. 7. The development of flowers, fruits and seeds is greatly affected by light intensity. Diffused light or reduced light promotes the development of vegetative structures and causes delicacy. For example, vegetative crops such as turnips, carrots, potato and beets give highest yield in regions with high percentage of cloudy days. Intense light favours the development of flowers, fruits and seeds. 8. Duration of light is also very important. Actual duration or length of the day (photoperiod) is a significant factor in the growth and flowering of a wide variety of plants. The controlling effect of photoperiod is called photoperiodicity. According to the response to length of photoperiods, the plants have been classified into following three groups : (i) Short day plants. Which bloom when the light duration is less than 12 hours per day e.g., Nicotiana tabacum (tobacco), Dahlia variabilis, Chrysanthemum indicum, Cosmos bipinnatus, Cannabis sativa (hemp), etc. (ii) Long day plants. Which bloom when the light duration is more than 12 hours per day, e.g., Allium cepa (onion), Beta vulgaris (beet root), Daucus carota (carrot), Papaver somniferum (opium poppy), Vicia faba (broad bean), Brassica rapa (turnip), Avena sativa (oat), Secale cereale (rye), Sorghum vulgare (sorghum), etc. (iii) Day neutral plants. Which show little response to length of day light, e.g., Cucumis sativus (cucumber), Gossypium hirsutum (cotton), Solanum tuberosum (potato), etc. 9. Light also affects the movement in some plants. The effect of sunlight on the plant movement is called heliotropism or phototropism. The stems elongate towards light (positive phototropism) and the roots are negatively phototropic. The leaves grow transversely to the path of light. 10. The seeds when moist are very sensitive to light. In some cases the germination of seeds is delayed in light. 11. Light is an important factor in the distribution of plants. Some plants grow in full sunlight, while others prefer to grow in the shades. B. Indirect effects of light on plants. Light affects opening and closing of stomata, influences the permeability of plasma membrane and has heating effect. All these in turn affect transpiration which in turn affects absorption of water. Light affects respiration of plants indirectly, as in the presence of light the respiratory substrates are synthesized. Effects of Light on Animals Light affects divergent aspects of animal’s life. It influences cellular metabolism, growth, pigmentation, locomotion, reproduction, ontogenetic development, and also controls the periodicity and biological clocks of animals. Some of its significant effects can be discussed as follows : 1. Effect of light on protoplasm. Though the bodies of most animals remain protected by some sort of body covering which save animal tissues from the lethal effects of solar radiations. But, sometimes sun rays penetrate such covers and cause excitation, activation, ionization and heating of protoplasm of different body cells. Ultraviolet rays are known to cause mutational changes in the DNA of various organisms. 2. Effect of light on metabolism. The metabolic rate of different animals is greatly influenced by light. The increased intensity of light results in an increase in enzyme activity, general metabolic rate and solubility of salts and minerals in the protoplasm. Solubility of gases, however, decreases at high light intensity. Cave dwelling animals are found to be sluggish in their habits and to contain slow rate of metabolism. 3. Effect of light on pigmentation. Light influences pigmentation in animals. Cave animals lack skin pigments. If they are kept out of darkness for a long time, they regain skin pigmentation. The darkly pigmented skin of human inhabitants of the tropics also indicate the effect of sunlight on skin pigmentation. The skin pigment’s synthesis is dependent on the sunlight. Light also determines the characteristic patterns of pigments of different animals which serve the animals in sexual dimorphism and protective colouration. Animals that dwell in the depths of the ocean where the environment is monotonous, though pigmented do not show patterns in their colouration. 4. Effect of light on animal movements. The influence of light on the movement of animals is evident in lower animals. Oriented locomotory movements towards and away from a source of light is called phototaxis. Positively phototactic animals such as Euglena, Ranatra, etc., move towards the source of light, while, negatively phototactic animals such as planarians, earthworms, slugs, copepodes, siphonophores, etc., move away from the source of light. The light directed growth mechanisms are called phototropisms which occur in sessile animals. Phototropisms also include responsive movement of some body part of some active animals to the light stimulus, such as the movement of flagellum of Euglena towards light and movements of polyps of many coelenterates. The velocity or speed of the movement of certain animals is also regulated by light. It has been observed that animals when responding to light reduce their velocity of movement and these movements which are non-directional are called photokinesis. Photokinesis may be a change in linear velocity (rheokinesis) or in the direction of turning (klinokinesis). During photokinesis when only a part of the body of an animal deviates away from the source of light, the reaction is termed photoklinokinesis. Larvae of Musca domestica show such movements. When animals are confronted with two lights of equal brightness they move towards or away to a position that is distanced between the two lights. This is termed phototropotaxis. Attraction of males towards the flash of the female is called telotaxis. Movement of animals at a constant angle towards the source of light is called light compass reaction or celestial orientation. 5. Photoperiodism and biological clocks (Biorhythms). During evolution, organisms have acquired a variety of endogenous rhythms, their periods are matched with the rhythmic events in the environment. A rhythm is a recurring process which is wave like in character, because maximum and minimum states appear at identical intervals of time. The time taken between two maxima (peaks) or two minima (troughs) is called a period or cycle and consists of two phases, a rise and fall in the biological process. The amplitude is the range of fluctuations from an average value. The response of different organisms to environmental rhythms of light and darkness is termed photoperiodism. Each daily cycle inclusive of a period of illumination followed by a period of darkness is called the photoperiod. The term photophase and scatophase are sometimes used to denote the period of light and the period of darkness respectively. Biological clocks Are internal mechanisms in organisms used to control the periodicity of varies functions or activities for example releasing hormones ( melatonine and serotonin ) that play a role in the sleep cycle , metabolic rate , body temperature and etc ‫توضيح بسيط للطالب ماذا نقصد بالساعه البايلوجيه‬ Recent findings suggest that in invertebrates both neural and neuroendocrine products (hormones) are responsible for biological rhythms. In higher vertebrates, the central regulation of rhythms is largely performed by the hypothalamus-pituitary complex which is genetically controlled and influenced by environmental factors such as photoperiod. For example, in birds and mammals, the pineal gland receives light stimuli and entrains to show biological rhythms. In amphibians, reptiles and birds the pineal gland is located under the skull but in some terrestrial forms of vertebrates, it is placed over the brain in the form of the third eye. The information of photoperiod is received first by the eye and then via neural pathways reaches the pineal body which secretes hormones such as melatonin which has antigonadotropic effects in various organisms such as rats, mice and many other mammals. Melatonin is believed to pass to the anterior pituitary gland and decrease secretion of gonadotropic hormones Pineal body partly controls circannual rhythms of reproduction. In case of turtles, serotonin is synthesized during the day whereas melatonin during the night but this mechanism is completely lost during hibernation period. 6. Effect of light on reproduction. In many animals (e.g., birds) light is necessary for the activation of gonads and in initiating annual breeding activities. The gonads of birds are found to become active with increased illumination during summer and to regress during shorter periods of illumination in winter. 7. Effect of light on development. Light in some cases (e.g., Salmon larvae) accelerates development, whereas, in other (e.g, Mytilus larvae) it retards it. Q / Enumerate only effects of light on animals Q / Define Biological clocks 2- Temperature Effect of Temperature on Plants and Animals Temperature has been found to affect the living organisms in various ways. Some of well-studied effects of temperature on living organisms are the following : 1- Temperature and cell. The minimum and maximum temperatures have lethal effects on the cells and their components. If too cold, cell proteins may be destroyed as ice forms, or as water is lost and electrolytes become concentrated in the cells; heat coagulates proteins 2. Temperature and metabolism. Most of metabolic activities of microbes, plants and animals are regulated by varied kinds of enzymes and enzymes in turn are influenced by temperature, consequently increase in temperature, up to a certain limit, brings about increased enzymatic activity, resulting in an increased rate of metabolism. In plants, the absorption rate is retarded at low temperature. Photosynthesis operates over a wide range of temperature. Most algae require lower temperature range for photosynthesis than the higher plants. The rate of respiration in plants, however, increases with the rise of temperature, but beyond the optimum limit high temperature decreases the respiration rate. 3. Temperature and reproduction. The maturation of gonads, gametogenesis and liberation of gametes takes place at a specific temperature which varies from species to species. For example,  Some species breed uniformly throughout the year,  Some only in summer or in winter,  While some species have two breeding periods, one in spring and other in fall. Temperature also affects fecundity of animals. Fecundity of an animal is defined as its reproductive capacity, i.e., the total number of young ones given birth during the life time of the animal. For example, females of the insect, became sexually mature at 30°C and 35°C than at 25°C, and the highest number of eggs per female was laid at temperature of 30°C. 4. Temperature and sex ratio. In certain animals the environmental temperature determines the sex ratio of the species. For example, the sex ratio of the copepod Macrocyclops albidu is found to be temperature dependent. As the temperature rises there is a significant increase in number of males. Similarly in plague flea, Xenopsylla cheopis, males outnumbered females on rats, on days when the mean temperature remains in between 21–25°C. But the position becomes reverse on more cooler days. 5. Temperature and ontogenetic development. Temperature influences the speed and success of development of poikilothermic animals. In general, complete development of eggs and larvae is more rapid in warm temperatures. Trout eggs, for example, develop four times faster at 15°C than at 5°C.. 6. Temperature and growth. The growth rate of different animals and plants is also influenced by temperature. For example,  the adult trouts do not feed much and do not grow until the water is warmer than 10°C.  Sea urchin Echinus esculentus shows maximum size in warmer waters. 7. Temperature and colouration. The size and colouration of animals are subject to influence by temperature. In warm humid climates many animals such as insects, birds and mammals bear darker pigmentation than the races of some species found in cool and dry climates. This phenomenon is known as Gloger rule. 8. Temperature and morphology. Temperature also affects the absolute size of an animal and the relative properties of various body parts (Bergman’s Rule). Birds and mammals, for example attain a greater body size when they are in cold regions than in warm regions, and colder regions harbour larger species. But poikilotherms tend to be smaller in colder regions. Body size has played a significant role in adaptation to low temperature because it has influenced the rate of heat loss. Further, the extremities of organism such as tail, ears and legs of mammals often appear to be shorter in colder climate (Allen’s Rule). Mice reared at 31° to 33.5°C have longer tails than those of the same strain reared at 15.5° to 20°C. Moreover, the races of birds with relatively narrow and more acuminate (i.e., tapered to a slender point) wings tend to occur in colder regions, while those in warmer climates tend to be broader (Rensch’s Rule). Temperature also influences the morphology of certain fishes and is found to have some relation with the number of vertebrae (Jordon’s Rule).. Q // what do you mean by the ecogeographic rules above ? 9. Temperature and cyclomorphosis. The relation between seasonal changes of temperature and body form is manifested in a remarkable phenomenon termed cyclomorphosis exhibited by certain cladocerans such as Daphnia during the warm months of summer. These crustaceans show a striking variation in the size of their helmet or head projection between the winter and summer month. The helmet develops on the Daphnia head in spring, it attains its maximum size in summer and disappears altogether in winter to provide usual round shape to the head. Such a kind of cyclomorphosis in the terms of size of the helmet is clearly showing a correlation to the degree of warmth of different seasons. 10. Temperature and animal behaviour. Temperature generally influences the behavioural pattern of animals. In temperate waters the influence of temperature on the behaviour of wood borers is profound. For example,  in the winter months in general, both Martesia and Teredo occur in smaller numbers in comparison with Bankia campanulata whose intensity of attack is maximum during the winter months.  Ticks locate their warm blooded hosts by a turning reaction to the heat of their bodies.  Certain snakes such as rattle snake, copper heads, pit vipers are able to detect mammals and birds by their body heat which remains slightly warmer than the surroundings. Even in the dark these snakes strike on their prey with an unnerving accuracy, due to heat radiation coming from the prey. The arrival of cold weather in temperate zones causes the snakes to coil up and huddle together. 11. Temperature and animal distribution. Because the optimum temperature for the completion of the several stages of the life cycle of many organisms varies, temperature imposes a restriction on the distribution of species. Generally the range of many species is limited by the lowest critical temperature in the most vulnerable stage of its life cycle, usually, the reproductive stage. Not only temperature affects on breeding in the geographical distribution but also temperature affects on survivality (i.e., lethal effect of temperature), feeding, and other biological activities which are responsible in geographic distribution of animals. As noted earlier in this chapter, the animals from colder geographic regions are generally less heat tolerant and more cold tolerant than those animals from warmer regions ; for example, members of Aurelia, a jelly fish from Nova Scotia die at a water temperature of 29°–30°C, while Aurelia from Florida can tolerate temperatures up to 38.5°C. Terrestrial invertebrates, particularly arthropods generally are distributed in all thermal environments where life is found. Many arthropods that have invaded the colder areas have one stage in their life cycle which is very resistant to cold, enabling them to over-winter until warmer weather returns. Birds and mammals are also adapted to live in nearly all thermal environments. The distribution of amphibians and reptiles, however, is limited to the relatively warmer thermal climates. has listed three factors that limit the invasion of reptiles into cold environments 12. Temperature and moisture. The differential heating of the atmosphere resulting from temperature variation over the earth’s surface produces a number of ecological effects, including local and trade winds and hurricanes and other storms, but more importantly it determines the distribution of precipitation Thermal Adaptations of Plants and Animals Most animals and plants of different ecological habitats have developed various sorts of thermal adaptations during the course of evolution to overcome the harmful effects of extremes of temperature. Some of the significant thermal adaptations of plants and animals are the following : 1. Formation of heat resistant spores, cysts, seeds, etc. Some of the animals and plants produce heat resistant cysts, eggs, pupae, spores and seeds which can tolerate extremes of temperatures.  Amoeba in encysted conditions, can tolerate temperature below 0°C.  Similarly, rye seeds remain active even at 0°C and can germinate at that temperature. As an adaptation against frost the starch of plants changes to fats or oils in the autumn. The fatty oils diminish the freezing points and, thus, increase the power of resistance in plants against frost.  Many leaves, that grow in the coldest lands, store fats.  Pentosans mucilage and pectic substances which have high moisture retaining power are abundant in many plants. They decrease the danger of  plants from desiccation during extremes of heat and save them from death. 2. Removal of water from tissue. Dried seeds, spores and cysts avoid because there remains no liquid in them that can freeze. Due to removal of water from seeds, the cold resistance of seeds of certain plants increases up to the extent that freezing their exposure for 3 weeks to 190°C, does not diminish their germinating capacity. 2. Dormancy. Dormancy includes two already discussed phenomena namely hibernation and aestivation. During both kinds of dormancies metabolic rate becomes reduced, body temperature becomes low and heart beat rate is also reduced. 3. Thermal migration. Thermal migrations occur only in animals. The journeys taken by animals that enable them to escape from extremely hot or cold situations are referred to as thermal migrations. For example, desert animals move to shaded places to avoid burning heat of noon and some animals such as desert reptiles and snakes become nocturnal to avoid heat of the day. The frogs, toads, other amphibians, turtles, etc., make short trips into or out of water (or moist places) and this provides desired cooling and warming to the animal. Q define Hibernation , aestivation , thermal migration , cyclomorphosis Daphnia Teredo worm  3- Precipitation (rain fall) The moisture falling on an area in liquid, vapours or frozen form is termed as precipitation. Thus, precipitation includes all moisture that comes to earth in the form of rain, snow, hail and dew. Precipitation is the chief source of soil water. The water available to plants and animals from soil comes as a result of rainfall. Due to water cycle or hydrological cycle, there occurs an interchange of water between the earth’s surface and the atmosphere. In this cycle following, two important events are involved :precipitation and evapotranspiration. The ecofactor of precipitation depends upon season, wind, air pressure and temperature. Precipitation occurs as a result of the cooling and condensation of water vapour at high altitudes. The low temperature at high altitudes cools the air, which gets saturated and loses its water-holding capacity. As the temperature starts falling, the water vapour condenses and falls as rain due to gravity. Depending on the environmental conditions, precipitation falls as hail, snow or rain. In winter the ground temperature falls and as a result, atmospheric vapour gets condensed as dew or frost on the surfaces of objects, plants, animals, soils, etc. Dew becomes an important source of moisture to plants in the winter season. Drizzle involves minute drops appearing as to float in air. Rain is the drops of liquid water, which are larger than drizzle and also heavier. Snow is the moisture as solid state. Sleet is the form of small grains or pellets of ice, hail consists of balls or lumps of ice Light drizzle is of little importance as very little moisture penetrates the soil because much of it evaporates rapidly. Snow is injurious to plants, breaking tender branches, flowers and fruits. Hail and sleet also cause similar damage. Some sedges grow in snow patches. Of all the above forms of precipitation, the rain is most important. It is the source of soil water and also affects humidity of atmosphere. The areas with heavy rainfall during summer and low during winter are characterized by the presence of grasslands. 4- Humidity of air Atmospheric moisture in the form of invisible vapour is known as humidity. The humidity of air is expressed in terms of values of relative humidity which is the amount of moisture in air as percentage of the amount which the air can hold at saturation at the existing temperature. Relative humidity is measured by the instrument called psychrometer or by paper strip hygrometer or a thermo-hydrograph. Humidity is greatly affected by intensity of solar radiation, temperature, altitude, wind exposure, cover and water status of soil. High temperature increases the capacity of the air to retain moisture and results in lower relative humidity. Low temperatures result in higher relative humidity by decreasing the capacity of air for moisture and reaches 100% or saturation point. Further cooling results in condensation of vapour into water and this temperature/moisture point is called the dew point. Humidity plays an important role in the life of plants and animals. It affects the life processes such as transpiration, absorption of water, etc. Parasitic fungi becomes abundant in moist weather and reduces primary production. Some plants such as orchids, lichens, mosses, etc., make direct use of atmospheric moisture. In fungi, and other microbes, humidity plays an important role in germination of spores and subsequent stages in life cycle.  Fire Fire is an interesting ecofactor. Fire is of a common occurrence in natural vegetation all over the world; it is more common in drier habitats than the wet. Cause of fire: Natural : (1) Lightening is the commonest natural cause of fire initiation. Our earth’s surface is hit by lightening every second in one or another part of the globe and many of these are of great magnitude. (2) abrassive effects of falling rocks or of dried plant material such as bamboos, (3) spontaneous combination of very dry and hot material (4) volcanic activities. man-made: i.e., by incendiarists (such as poachers), debris burners, smokers, campers, short-circuiting of high-tension electric lines, and nearby railway lines.. Types of Fire Fires are generally classified as: (i) Ground fires which develop in such conditions where organic matter (litter) accumulates richly as heaps and they catch fire which generally smoulder for longer periods. Thus, in dry litter, fire is rapid and extinguishes quickly, while in somewhat moist litter, the fire is slow and with its heat the inner parts of litter r heap also get dried and fire continues for a longer period. (ii) Surface fires which sweep over the ground surface rapidly and their flames consume the litter, living herbaceous vegetation and shrubs and also scorching the tree bases if comes in contact. (iii) Crown fires which are most destructive, burning the forest canopy and are common in dense woody vegetations. They spread in the top layers from the canopy of one tree to the canopy of another and so on. Canopy fires produce a temperature up to 704.5°C, killing the trees, shrubs and herbs. Effects of Fire Fire has direct (e.g., lethal) as well as indirect effects on plants and wild-life. Some well confirmed indirect effects of fire on plants are as follows : 1. Fire causes injury to some plants, resulting large scars on their stems. Such scars may serve as suitable avenues of entry of parasitic fungi and insects. 2. Fire arrests the course of succession and modify the edaphic environment very much. 3. Fire brings about distinct changes of such ecofactors as light, rainfall, nutrient cycles, fertility of soil, litter and humus contents of soil, pH, water holding capacity and soil fauna (earthworms, nematodes, arthropods, etc.) Soil fungi are reduced while bacteria increase due to post-fire changes in the soil. The microclimate too is greatly changed due to addition of ash, loss of shade, loss of raindrop interception, accelerated erosion, etc. 4. Fire plays an important role in the removal of competition for surviving species. Fire tolerant plant species generally increase in abundance at the expense of those killed by fire (fire-sensitive plants) due to considerable reduction in competition and possibly due to alteration in other conditions. 5. Some plants are stimulated to growth by fires. A number of such grasses are stimulated by fire to produce large quantities of seeds. In some grasses and legumes, the seeds would germinate only after these get fire treatment 6. Some fungi, mainly some ascomycetes, grow in soils of burnt areas. Such fungi are known as pyrophilous. Adaptations to Fire In frequent fire prone areas certain plants develop the following adaptations : 1- Certain trees, particularly conifers such as Pinus and Larix and dicots such as Quercus  develop fire resistant bark  with insulating effect against heat.  also have tall trunk with the crown restricted to upper zone only. This helps in escaping the destructions against surface and ground fires. 2. In some plants leaves are fire-resistant due to poor contents of such compounds such as resin or oil. 3. Some plants of Eucalyptus have adventitious or latent axillary buds which may develop into new branches. 4. Epilobium anguistifolium acts as a fire indicator species. It grows in patches and in dormant condition. In case of fire, these plants rapidly grow while other plants die due tofire. 5- Wind factor The strong moving current of air is called wind. It is an important ecological factor of the atmosphere affecting variously the plant life on flat plains, along sea coasts and at high altitudes in mountains. Wind is directly involved in transpiration, in causing several types of mechanical damage and in dissemination of pollen, seeds and fruits. Wind also modifies the water relations and light conditions of a particular area. The movement or velocity of wind is affected by such factors such as temperature, atmospheric pressure, geographical features (including topography), vegetation masses and position with respect to sea shores. Air moves from a region of high pressure to low pressure. The pressure differences are mainly due to differential heating of atmosphere. Winds result in various physical, anatomical and physiological effects on plants: 1. Physical effects such as breakage and uprooting; deformation; lodging or flattening of herbaceous plants such as wheat, maize, sugarcane, etc. erosion and deposition of soil around plant roots; plant injury due to salt spray along sea coasts 2. Anatomical and physiological effects Biotic Environmental factors organisms do not exist alone in nature but in a matrix of other organisms of many species. Many species in an area will be unaffected by the presence or absence of one another (This is often termed neutralism), but in some cases two or more species will interact. The evidence for such interaction is quite direct : populations of one species are different in the absence and in the presence of a second species. interspecific interactions The interactions between species may have positive or negative results. Following six general types of interactions have been described : A. Positive interactions 1. Mutualism ; 2. Commensalism ; 3. Protocooperation. B. Negative interactions 4. Exploitation ; (i) Social parasitism ; (ii) Parasitism ; (iii) Predation. 5. Amensalism and antibiosis ; 6. Competition. A. Positive interactions In case of positive interactions, populations help one another and either one or both the species are benefited. This benefit may be regarding the food, shelter, substratum or transport. Further, such an association may be continuous or transitory, obligate or facultative and the two partners may be in close contact (i.e., their tissues remain intermixed with each other) or one of them may live within a specific area of the other or attached to its surface. Positive interactions may be of the following types: 1- Mutualism Mutualism is an obligatory positive interspecific interaction that is strongly beneficial to both species. In past , it was termed symbiosis , Such mutually beneficial interactions are more common in the tropics than elsewhere. In this case, both of the species derive benefit.   Some common examples of mutualistic association are the following : 1. Pollination by animals 2. Lichens. They form the examples of mutualism where contact is close and permanent as well as obligatory. The body of lichens is made up of a matrix formed by a fungus, within the cells of which an alga is embedded (Fig. 5.1B). The fungus makes available the moisture and minerals to the algae, which prepare food by photosynthesis. In nature, neither of the two can grow alone dependently. Lichens tend to grow abundantly on bare rock surfaces.( Lichens = Algae + fungus ). 3. Symbiotic nitrogen fixation. Here a bacterium Rhizobium forms nodules in the roots of leguminous plants and lives symbiotically with the host. Bacteria get a protective space to live in and derive prepared food from the roots of higher plants and in return fix gaseous nitrogen, making it available to the plants. The leguminous plants use this nitrogen in the protein synthesis and 4. Mycorrhizae. In mycorrhizal associations, tree roots become infested with fungal hyphae. The fungi derive their food from the tree roots and in return their hyphae supply water and minerals that they absorb from the soil much like the root hairs of trees. It is believed that the fungus also regulates the pH and sugar level for a good growth of roots in acidic soils (e.g., conifers). Mycorrhizae may be on the surface of roots (ectotrophic) or inside between the cells of the roots (endotrophic). ( Mycorirhizae = plant+ fungus ). 5. Microorganisms and cellulose digestion Interspecific mutualism is nicely demonstrated by the flagellate protozoan, Trichonympha an obligate anaerobe in the gut of several species of woodeating termites where it digests cellulose. Trichonympha also occurs in the alimentary canal of woodeating roach Cryptocerus. The termite and roach reduce the wood to small fragments, passing them through the alimentary canal to hind gut, where the protozoans digest the cellulose, changing it into sugar. The host benefits the protozoa by removing harmful metabolic waste products and maintaining anaerobic conditions in the intestine. 2. Commensalism. Commensalism defines the coaction in which two or more species are associated and one species at least, derives benefit from the association, while the other associates are neither benefited nor harmed. The concept of commensalism has been broadened in recent years, to apply to coactions other than those centering on food; cover, support, protection, and locomotion are now frequently included.  Some common examples of commensalism are the following : 1- Lianas. These plants are common in tropical rain forests where light at ground level is scarce because of the dense and multistoreyed growth of vegetation. 2- Epiphytes. Epiphytes are the plants growing on other plants (Fig. 5.1F). They use other plants only as support and not for water or food supply. Epiphytes differ from the lianas in that they are not rooted into the soil. They may grow on trees, shrubs or larger submerged plants. 3. Epizoans. Some plants grow on the surfaces of animals. For example, some green algae grow on the long, grooved hair of sloth. ‫حيوان من اللبائن‬ 4. Epizoite. Likewise, ectocommensals or epizoite animals are associated with another animal , for the purpose of anchorage and protection , such as The remora fishes attach themselves to the bellies of sharks , and it usually feeds on the shark's leftovers. 5- Some microorganisms such as bacterium Escherchia coli is found in human colon Lianas. Epiphytes 3- Protoocoperation. It is an association between individual of two species each of which is benefited by presence of other , but can live equailly well without association , ( not obligatory ). Predatory birds sitting on cattle are a protocooperation example as the bird eats ectoparasites such as leeches , etc. Relationship between sea anemones and hermit crabs. B. Negative Interactions In case of negative interactions, one or both species are harmed in any way during their life period. Some authors such as Clarke, 1954, prefer to call these types of interactions as antagonism. The negative interactions include the following three broad categories : 1. Exploitation. In exploitation, one species harm the other by making its direct or indirect use for support, shelter or food. It is of following types : (i) Social parasitism. Social parasitism describes the exploitation of one species by another, for various advantages. It is a kind of parasitism in which the parasite foists the rearing of its young into the host. Social parasitism in various stages of development is found among some higher vertebrates and insects. For example, there occurs an egg parasitism in two species of birds old world cuckoos and the brown headed cowbirds of North America, both of which do not build nests of their own, rather they deposit their eggs in nests of other species, abandoning eggs and young to the care of foster parents. (ii) Parasitism. Parasitism is a kind of harmful coaction (disoperation) between two species. It is the relation between two individuals wherein one individual called parasite receives benefit at the expense of other individual called host. Parasitism is mainly a food coaction, but the parasite derives shelter and protection from the host, as well. A parasite usually parasitizes a host which is larger in body size than it. Further, a parasite does not ordinarily kill its host, at least not until the parasite has completed its reproductive cycle. However, a host may die due to some secondary infection or suffer from stunted growth, emaciation, or sterility. parasitize may occur on the outside of the host (ectoparasites) or live within the body of the host (endoparasites). The endoparasites usually live in the alimentary tract, body cavities, various organs or blood or other tissues of host. Ectoparasites may be parasitic outside of body such as the blood sucking lice and flies, biting lice, mites, and ticks that occur on birds, mammals, and sometimes reptiles, and the monogenetic trematodes on fish. Further, endoparasites rely on various means of transport from one host to another so that their survival, range of distribution, and life cycle are unaffected. outside Lastly, parasites may be full-time (or permanent) parasites or part-time (or temporary) parasites. Mosquitoes and bugs that suck the blood of their hosts are temporary parasites. Some temporary parasites spend only a part of their life cycle as parasites. Permanent parasites, however, spend their life completely on other organisms. The common examples of permanent parasites are Plasmodium, Entamoeba histolytica, and other protozoan pathogens, , nematodes, arthropods, etc.  Q // compare between temporary and permanent parasites  The ectoparasites, and endoparasites have following parasitic adaptations : 1. In parasitic animals, a reduction of organs of special sense of nervous system, and of locomotory organs occur. 2. Most ectoparasites develop some clinging organs such as hooks, suckers, etc., to get attached with the body of their hosts. They also develop special piercing and sucking organs to suck the blood of animals or sap of plants. 3. Most endoparasites exhibit anaerobic respiration, high rate of reproduction, parthenogenesis, hermaphroditism, polyembryony, intermediate host and a complicated life-cycle. 4.Many parasites pass their entire existence in a single host; others require one, two, even three intermediate hosts. It is of ecological significance that both primary and intermediate hosts of a parasite occur in the same habitat or community. 5. Parasites are transferred from one host to another by active locomotion of the parasite itself;  by ingestion, as one animal sucks the blood of or eats another;  by ingestion as an animal takes in eggs, spores, or encysted stages of the parasite along with its food or drinking water; as a result of bodily contact between hosts;  Or by transportation from host by way of vectors. For example, the bacteria that cause tularemia in man are carried from rabbit to rabbit by ticks.( It is transmitted to humans by direct contact with infected animals or by vectors, such as ticks, mosquitos, and flies). Effects of parasite on the host : disease. Parasites may not cause immediate mortality but they cause damage to body structures, should it become excessive, may cause death. Because of these parasitically caused anatomical damages, the finely adjusted balance of different vital processes of host’s body become disturbed and host is said to be diseased Some of the common parasitic agents of disease and consequent mortality of animals are following : 1. Viruses are the potent agents of several disastrous diseases of plants and animals including man.. 2. Bacteria may produce localized inflamatory changes in tissue, enter the blood stream, or produce powerful poisons known as toxins.. 3. Fungus spores of Aspergillus may be drawn into the lungs of ground-feeding birds, where they germinate and grow, causing aspergillosis disease. 4. Protozoan parasites are especially important in the alimentary tract and in the blood. 5. Worm parasites, such as tapeworms, nematodes, and acanthocephalans may wander through the host’s body doing mechanical injury as well as destroying and consuming tissues. 6. External parasites such as ticks, fleas, lice, mites, and flies do not commonly produce serious mortality by themselves, but they are often vectors, transmitting protozoa, bacteria and viruses from one animal to another. 7. Nutritional deficiency in vitamins or minerals, or improper balance among carbohydrates, proteins, and fats may produce malformations, lack of vigour, or even death. 8. Food poisoning, botulism, occurs when certain food become contaminated with the toxins released by the bacterium Clostridium botulinum. Q// Numerate only the common parasitic agents of disease and consequent mortality of animals (iii) Predation. Predation occurs when members of one species eat those of another species. Often, but not always, this involves the killing of the prey. Most of the predatory organisms are animals, but there are some plants (carnivores) also. Four types of predation have been recognized :  Herbivores are animals that prey on green plants or their seeds or fruits; often the plants eaten are not killed but may be damaged.  Typical predation occur when carnivores prey on herbivores or on other carnivores.  Insect parasitism is another form of predation in which the insect parasite lays eggs on or near the host insect, which is subsequently killed and eaten.  Finally, cannibalism is a special form of predation in which the predator and prey are from the same species. Like the predators, the prey has its certain defensive specializations. The prey risk is determined by density of prey population, availability of food and protective cover (concealment place), movement, activity, habits, size, age, strength and escape reactions of prey. Besides these striking morphological features, Prey often develop the following two antipredator defence strategies : aposematic colouration and group living.  Aposematic colouration. Many animals have evolved distastefulness as a means of predator defence. Toxins may be obtained from food or synthesized by the prey species. Many of these toxic prey species feature bright colours, termed aposematic colouration and these colours are usually regarded as a signal to predators.  Group living. Group living is normally not advantageous for the individuals. Then why do birds form blocks and ungulates go about in herds ? One possible reason for living in groups is to reduce predation losses. Q // What are the antipredator defence strategies  There are three main advantages a prey organism can obtain by living in a group. First, early detection of predators may be facilitated if many eyes are looking. Prey in groups may, thus, be able to spend more time feeding and less time looking for potential predators. Second, if the prey are not too much smaller than the predator ( prey larger than predator ), several of them acting together may be able to deter the predator from attacking. One possible example of this is mobbing in birds (e.g., crow). Third, if the predator is still able to attack a group, it must select one individual in the group to capture. By fleeing in confusion, the prey may confuse the predator,who may not be able to concentrate on any one individual. Alternatively, by being in the centre of a group, an individual may reduce its chances of being eaten.. A prudent predator would not eat prey individuals in their peak reproductive ages because that type of mortality would reduce the productivity of the prey population. Prudence dictates eating of those individuals that would die in the normal course and which contribute little to productivity. Often these are the oldest and the youngest individuals in a prey population which are hunted by the predator. Old individuals may be post-reproductive, and young individuals often have a high death rate due to othercause. 2. Amensalism. Amensalism is a comprehensive term in biotic interactions to denote the adverse or depressing effect of one of the competing population or species while the other, remains stable. Thus, amensalism is a situation in which one population definitely inhibits the other while remaining unaffected itself. By so modifying the environment, the organism improves its own chance of survival.  allelochemic. The inhibitor substance may be inorganic chemicals such as acids or bases which are produced by pioneering organisms (inhibitor species) and which reduce the competition for nutrients, light, and space, between the amensal species and inhibitor species. ( allelochemic will be discussed in more detail later in Chapter Four).  The production of relatively simple organic toxins is another source of chemical inhibitors. These toxins inhibit seedling growth in the vicinity. This may affect succession of plant species, especially important in the early stages.  A third type of inhibitor chemical is the antibiotic–a potent antimicrobial agent. It is a substance produced by an organism, which, in low concentrations, can inhibit or kill the growth of another organism.  Juglans nigra commonly called the black walnut tree secretes a chemical Juglone from its roots. This chemical kills the plants that are around the black walnut tree.  Another example of amensalism is small plants that grow under big trees. These big trees hinder the amount of available sunlight and obstruct the required sunlight to the small plants under them. When the leaves or fruits fall on the ground, juglone is released to soil, where it is oxidized to a substance that inhibits the growth of certain under story species and garden plants such as heaths and broad-leaf herbs, and favours others such as bluegrass and blackberries. The term antibiosis generally refers to the complete or partial inhibition or death of one organism by another through the production of some substance or environmental conditions as a result of metabolic pathway. These substances and/or conditions are harmful (antagonistic) to other organisms. Antibiosis is more commonly referred to secretions by microorganisms that check the growth of others. Production of chemicals that are antagonistic to microbes the antibiotics is well known. Antibiotics produced by bacteria, fungi, actinomycetes, and lichens are widespread in nature and may be one of the reasons why bacteria pathogenic to man cannot multiply well in soils. Penicillium, a fungus found in soil produces antibiotic substances that check the growth of a large variety of bacteria. A number of antibiotics such as penicillin, have been used extensively in human medicine.  Q / What do you mean by the following : Antibiosis , Allelochemic, Antibiotic , Juglone 3. Competition. The presence of other organisms may limit the distribution of some species through competition. Such competition can occur between any two species that use the same sorts of places. Note that two species do not need to be closely related to be involved in competition. For example, birds, rodents and ants may compete for seeds in desert environments. Competition among animals is often over food, water and mates. Animals may also do competition for space, i.e., nesting sites, wintering sites, safer sites from predators. Plants can compete for light, water, nutrients, or even for pollinators and/or attachment sites. Competition is an important process affecting the distribution and abundance of plants and animals. There are two different types of competition, defined as follows : (a) Resource competition (also called scramble competition) occurs when a number of organisms (of the same or of different species) utilise common resources that are in short supply. (b) Interference competition (also called contest competition) occurs when the organisms seeking a resource harm one another in the process, even if the resource is not in short supply. Note that the competition may be interspecific (between two or more different species) or intraspecific (between members of the same species). Q/ What are the two different types of competition Q/ What is the difference between intraspecific competition and interspecific competition? Answer / Interspecific competition occurs between individuals of different species. Intraspecific competition occurs between individuals of the same species OR  Intraspecific competition occurs between members of the same species. For example, two male birds of the same species might compete for mates in the same area....  Interspecific competition occurs between members of different species. For example, predators of different species might compete for the same prey.  Chapter three Behavioral Ecology  1 inheritance influences Behavior Behavior encompasses any action that can be observed and described. For example we described the aggressive behavior of male mountain bluebirds toward other males during mating. In the same manner, scientists pose the question of whether genetics can determine the behavior an animal is capable of performing. The “nature versus nurture” question asks to what extent our genes (nature) and the environment (nurture) influence behavior. We would expect that genes, which control the development of neural and hormonal mechanisms, also influence thebehavior of an animal. The results of experiments done to discover the degree to which genetics controls behavior support the hypothesis that most behaviors have, at least in part, a genetic basis. A- Experiments that suggest Behavior Has a genetic Basis Among the many animal behavior studies, studies of lovebirds and garter snakes suggest that behavior has a genetic basis, and one type of study in human's attempts to evaluate nature versus nurture. 1- Nest Building in Lovebirds Lovebirds are small, green-and-pink African parrots that nest in tree hollows. Several closely related species of lovebirds in the genus Agapornis build their nests differently. - Fischer lovebirds cut large leaves (or in the laboratory, pieces of paper) into long strips with their bills. They use their bills to carry only one of the longer strips at a time to the nest to make a deep cup. - Peach-faced lovebirds cut somewhat shorter strips and carry them to the nest in a very unusual manner. They pick up several of these short strips with each trip to the nest in their bills and then insert them into their feathers. Researchers hypothesized that if the behavior for obtaining and carrying nesting material is inherited, then hybrids might show intermediate behavior. When the two species of birds were mated, the hybrid birds were observed to have difficulty carrying nesting materials. They cut strips of intermediate length and then attempted to tuck the strips into their rump feathers. They did not push thestrips far enough into the feathers, however, and when they walked or flew, the strips always came out. Hybrid birds eventually learned, after about 3 years, to carry the cut strips in their beaks, but they still briefly turned their heads towardtheir rump before flying off. These studies support the hypothesis that behavior has a genetic basis. 2- Food Choice in Garter Snakes A variety of experiments have been conducted to determine if food preference in garter snakes has a genetic basis. There are two types of garter snake populations in California. Inland populations are aquatic and commonly feed under water on frogs and fish. Coastal populations are terrestrial and feed mainly on slugs.‫الرخوي ات‬ The experimental results of matings between snakes (inland and coastal) show that their newborns have a partial preference for slugs when feeding. Differences between slug acceptors and slug rejecters appear to be inherited. Experiments were able to determine the physiological difference between the two populations. When snakes eat, their tongues carry chemicals to an odor receptor in the roof of the mouth. They use tongue flicks to recognize their prey. Even newborns will flick their tongues at cotton swabs dipped in fluids of their prey. Swabs were dipped in slug extract, and the number of tongue flicks were counted for newborn inland snakes and newborn coastal snakes. Coastal snakes had a higher number of tongue flicks than did inland snakes.Apparently, inland snakes do not eat slugs because they cannot detect their smell as easily as coastal snakes can. A genetic difference between the two populations of snakes results in a physiological difference in their nervous systems. Although hybrids showed a great deal of variation in the number of tongue flicks, they tended to average between the number performed by coastal and inland snakes, as predicted by the genetic hypothesis.  3- Twin Studies in Humans On occasion, human twins have been separated at birth and raised under different environmental conditions. Studies of these twins have shown that they have similar food preferences and activity patterns, and they even select mates with similar characteristics. This type of study lends support to the hypothesis that at least certain behaviors are primarily influenced by nature (genes). B- Animal studies that Demonstrate Behavior Has a genetic Basis The nervous and endocrine systems are both responsible for the overall coordination of body systems. Studies have shown that the endocrine system plays a role in determining behavior. 1- Egg-Laying Behavior in Marine Snails The egg-laying behavior in the marine snail Aplysia involves a specific sequence of movements. Following copulation, the animal extrudes long strings of more than a million egg cases. The animal takes the egg case string in its mouth, covers it with mucus, waves its head back and forth to wind the string into an irregular mass, and attaches the mass to a solid object, such as a rock. Several years ago, scientists isolated and analyzed an egg laying hormone (ELH) that causes the snail to lay eggs, even if it has not mated. ELH was found to be a small protein of 36 amino acids that diffuses into the circulatory system and excites the smooth muscle cells of the reproductive duct, causing them to contract and expel the egg string. 2- Nurturing Behavior in Mice In another study, investigators found that maternal behavior in mice was dependent on the presence of a gene called fosB. Normally, when mothers first inspect their newborns, various sensory information from their eyes, ears, nose, and touch receptors travel to the hypothalamus. This incoming information causes fosB alleles to be activated, and a particular protein is produced. The protein begins a process during which cellular enzymes and other genes are activated. The end result is a change in the neural circuitry within the hypothalamus, which manifests itself in maternal nurturing behavior toward the young. Mice that do not engage in nurturing behavior were found to lack fosB alleles, and the hypothalamus failed to make any of the products or to activate any of the enzymes and other genes that lead to maternal nurturing behavior. Female mice with fosB alleles tended to retrieve their young and bring them back to them after they became separated. 2 The Environment influences Behavior Even though genetic inheritance serves as a basis for behavior, it is possible that environmental influences (nurture) also affect behavior. For example, behaviorists originally believed that some behaviors were unchanging behavioral responses known as fixed action patterns (FAP).An FAP is elicited by a sign stimulus—a particular trigger in the environment. For example, male stickleback fish aggressively defend a territory against other males. In laboratory studies, the male reacts more aggressively to any model that has a red belly like he has, rather than to a model that looks like a female stickleback fish. In this instance, the color red is a sign stimulus that triggers the aggressive behavior. Investigators discovered that many behaviors that were originally thought to be FAPs could improve with practice due to the organism’s learning. In this context, learning is defined as a durable change in behavior brought about by experience. Learning can be brought about by a wide variety of experiences. Habituation is a form of learning in which an animal no longer responds to a particular stimulus due to experience. Deer grazing on the side of a busy highway, ignoring traffic, is an example of habituation.  1- instinct and learning Laughing gull chicks’ begging behavior appears to be an FAP, because it is always performed the same way in response to the parent’s red bill (the sign stimulus). A chick directs a pecking motion toward the parent’s bill, grasps it, and strokes it downward.Parents can bring about the begging behavior by swinging their bill gently from side to side. After the chick responds, the parent regurgitates food onto the floor of the nest. If need be, the parent then encourages the chick to eat. This interaction between the chicks and their parents suggests that the begging behavior involves learning. To test this hypothesis, diagrammatic pictures of gull heads were painted on small cards, and then eggs were collected from nests in the field. The eggs were hatched in a dark incubator to eliminate visual stimuli before the test. On the day of hatching, each chick was allowed to make about a dozen pecks at the model. The chicks were returned to the nest, and then each was retested. The tests showed that, on average, only one-third of the pecks by a newly hatched chick strike the model. But 1 day after hatching, more than half the pecks are accurate, and 2 days after hatching, the accuracy reaches a level of more than 75%. Investigators concluded that improvement in motor skills and learning can help improve the development of instinctive behaviors. 2- Imprinting Imprinting, a form of learning, occurs when a young animal forms an association with the first moving object it sees. Konrad Lorenz was one of the first individuals to study imprinting in birds. He observed chicks, ducklings, and goslings following the first moving object they saw after hatching, typically their mother. Imprinting in the wild has survival value and leads to reproductive success. This behavior enables an individual to recognize its own species and thus eventually to find an appropriate mate. In the laboratory, however, investigators found that birds can seemingly be imprinted on any object even a human or a red ball if it is the first moving object they see during a sensitive period of 2 to 3 days after hatching. The term sensitive period means the period of time in which a particular behavior develops. A chick imprinted on a red ball follows it around and chirps whenever the ball is moved out of sight. Social interactions between parent and offspring during the sensitive period seem to be a key to normal imprinting. For example, female mallards cluck the entire time that imprinting is occurring. It might be that vocalization before and after hatching is necessary to normal imprinting. 3- Social interactions and learning White-crowned sparrows sing a species-specific song, but males of a particular region have their own dialect. Birds were caged in order to test the hypothesis that young white-crowned sparrows learn how to sing from older members of their species. Three groups of birds were tested. Birds in the first group heard no songs at all. When grown, these birds sang a song that had a slight resemblance to the adult song. Birds in the second group heard tapes of white-crowns singing. When grown, they sang in that dialect, as long as the tapes had been played during a sensitive period, about age 10–50 days. White-crowned sparrows’ dialects (or other species’ songs) played before or after this sensitive period had no effect on the birds. Birds in a third group did not hear tapes and instead were given an adult tutor. No matter when the tutoring began, these birds sang the song of the tutor species. Results like these show that social interactions apparently assist learning in birds. 4- Associative learning A change in behavior that involves an association between two events is termed associative learning. For example, birds that get sick after eating a monarch butterfly no longer prey on monarch butterflies, even though they may be readily available. The smell of freshly baked bread may entice you to have a piece, even though you may have just eaten. If so, perhaps you associate the taste of bread with a pleasant memory, such as being at home. Two examples of associative learning are classical conditioning and operant conditioning. 4.1 Classical Conditioning Classical conditioning is a method of modifying behavior by pairing two different types of stimuli (at the same time), causing an animal to form an association between them. The best-known laboratory example of classical conditioning is that of an experiment by the Russian psychologist Ivan Pavlov. First, Pavlov observed that dogs salivate when presented with food, so he began to ring a bell whenever the dogs were fed. Eventually, the dogs salivated excessively whenever the bell was rung, regardless of whether food was present. The dogs had come to associate the ringing of the bell with being fed. Classical conditioning suggests that an organism can be trained—that is, conditioned—to associate a response with a specific stimulus. Unconditioned responses occur naturally, as when salivation follows the presentation of food. Conditioned responses are learned, as when a dog learns to salivate when it hears a bell. #Advertisements attempt to use classical conditioning to sell products. Commercials often pair attractive people with a product being advertised in the hope that viewers will associate attractiveness with the product. This pleasant association may cause them to buy the product. #Some types of classical conditioning can be helpful when trying to increase beneficial behaviors. For example, it has been suggested that you hold a child on your lap when reading to him or her. The hope is that the child will associate a pleasant feeling with reading. 4.2 Operant Conditioning Operant conditioning is a method of modifying behavior in which a stimulus-response connection is strengthened. Most people know that it is helpful to give an animal a reward, such as food or affection, when teaching it a trick. It is quite obvious that animal trainers use operant conditioning. They present a stimulus to the animal—say, a hoop—and then give a reward (food) for the proper response (jumping through the hoop). Sometimes, the reward does not need to be immediate; in latent operant conditioning, an animal makes an association without the immediate reward, as when squirrels make a mental map of where they have hidden nuts. B. F. Skinner #was well known for studying this type of learning in the laboratory. In the simplest type of experiment he performed, a caged rat inadvertently pressed a lever and was rewarded with sugar pellets, which it avidly consumed. Thereafter, the rat regularly pressed the lever whenever it wanted a sugar pellet. In more sophisticated experiments, Skinner #even taught pigeons to play Ping-Pong by reinforcing the desired responses to stimuli. #In child rearing, it has been suggested that parents who give a positive reinforcement for good behavior will be more successful than parents who punish behaviors they believe are undesirable. Orientation and migratory Behavior Migration is long-distance travel from one location to another. Loggerhead sea turtles hatch on a Florida beach and then travel across the Atlantic Ocean to the Mediterranean Sea, which offers an abundance of food. After several years, pregnant females return to the same beaches to lay their eggs. Every year, monarch butterflies fly from North America to Mexico, where they overwinter, and then return in the spring to breed. At the very least, migration requires orientation, the ability to travel in a particular direction, such as south in the winter and north in the spring. Most of the research studying orientation has been done in birds. Many birds can use the sun during the day or the stars at night to orient themselves. The sun moves across the sky during the day, but the birds are able to compensate for this, because they have a sense of time. They are presumed to have a biological clock that allows them to know where the sun will be in relation to the direction they should be going anytime of the day. Experienced birds can also navigate, which is the ability to change direction in response to environmental clues. These clues are apt to come from the Earth’s magnetic field. A study that was done with starlings, which typically migrate from the Baltics to Great Britain and return. Test starlings were captured in Holland and transported to Switzerland. Experienced birds corrected their flight pattern and still got to Great Britain. Young, inexperienced birds ended up in Spain instead of Great Britain. Migratory behavior has a proximate cause and an ultimate cause. The proximate cause consists of environmental stimuli that tell the birds it is time to travel. The ultimate cause is the possibility of reaching a more favorable environment for survival and reproduction. Is the benefit worth the cost—the dangers of the journey? It must be, or the behavior would not persist. Cognitive learning In addition to the modes of learning already discussed, animals may learn through observation, imitation, and insight. For example, Japanese macaques learn to wash sweet potatoes before eating them by imitating others. Insight learning occurs when an animal solves a problem without having any prior experience with the situation. The animal appears to call upon prior experience with other circumstances to solve the problem. For example, chimpanzees have been observed stacking boxes to reach bananas in laboratory settings. Other animals, too, aside from primates, seem to be able to reason things out. In one experiment, ravens were offered meat that was attached to string hanging from a branch in a confined aviary. The ravens were accustomed to eating meat, but they had no knowledge of how strings work. It took several hours, but eventually one raven flew to the branch, reached down, grabbed the string with its beak, and pulled the string up over and over again, each time securing the string with its foot. Eventually, the meat was within reach, and the raven was able to grab the meat with its beak. Other ravens were then also able to perform this behavior. It seems that animals are capable of planning ahead. A sea otter will save a particular rock to act as a hard surface against which to bash open clams. A chimpanzee strips leaves off a twig, which it then uses to secure termites from a termite nest. If animals can think, many people wonder if they have emotions. This, too, is an unexplored area that is now of interest. 3 animal communication Communicative Behavior Communication is an action by a sender that may influence the behavior of a receiver. The communication can be purposeful, but it does not have to be. Bats send out a series of sound pulses and listen for the corresponding echoes to find their way through dark caves and locate food at night. Some moths have an ability to hear these sound pulses, and they begin evasive tactics when they sense that a bat is near. Bats are not purposefully communicating with the moths. The bat sounds are simply a cue to the moths that danger is near. 1- Chemical Communication Chemical signals have the communicative advantage of being effective both night and day. A pheromone is a chemical signal in low concentration that is passed between members of the same species. Some animals are capable of secreting different pheromones, each with a different meaning. Female moths secrete chemicals from abdominal glands, which are detected downwind by receptors on male antennae. The antennae are especially sensitive, and this ensures that only male moths of the correct species (and not predators) will be able to detect them. Ants and termites mark their trails with pheromones. Cheetahs and other cats mark their territories by depositing urine, feces, and anal gland secretions at the boundaries. Klipspringers ‫(الظباء الصغيرة‬small antelope) use secretions from a gland below the eye to mark the twigs and grasses of their territory. Pheromones are known to control the behavior of social insects, as when worker bees slavishly care for the offspring produced by a queen. Researchers are trying to determine to what degree pheromones, along with hormones, affect the behavior of animals. Researchers are trying to determine if pheromones are responsible for whether the animal will carry out parental care, become aggressive, or engage in courtship behavior. Some researchers also maintain that human behavior is influenced by pheromones wafting through the air—pheromones that are not perceived consciously. They have discovered that like mice, humans have an organ in the nose, called the vomero nasal organ (VNO) that can detect not only odors but also pheromones. The neurons from this organ lead to the hypothalamus, the part of the brain that controls the release of many hormones in the body.  2- Auditory Communication Auditory communication is communication through sound. It has some advantages over other kinds of communication. #It is faster than chemical communication, and unlike visual communication, #it is effective both night and day. Further, auditory communication# can be modified not only by loudness but also by pattern, duration, and repetition. In an experiment with rats, a researcher discovered that an intruder can avoid attack by increasing the frequency with which it makes an appeasement sound. Male crickets have calls, and male birds have songs for a variety of occasions. For example, birds may have one song for distress, another for courting, and still another for marking territories. Sailors have long heard the songs of humpback whales transmitted through the hulls of ships. Bottlenose dolphins have one of the most complex languages in the animal kingdom. Language is the ultimate auditory communication. Humans can produce a large numberof different sounds and put them together in many ways. Nonhuman primates have different vocalizations, each having a definite meaning, as when vervet monkeys give alarm calls. Although chimpanzees can be taught to use an artificial language, they do not progress beyond the capability level of a 2-year-old human child. It has also been difficult to prove that chimps understand the concept of grammar or can use their language to reason. It still seems as though humans possess a communication ability greater than that of other animals. 3- Visual Communication Visual signals are most often used by species that are active during the day. Contests between males often make use of threat postures that possibly prevent outright fighting. A male baboon displaying full threat is an awesome sight that establishes his dominance and keeps peace within the baboon troop. Hippopotamuses perform territorial displays that include mouth opening. Many animals use complex courtship behaviors and displays. The plumage of a male Raggiana Bird of Paradise allows him to put on a spectacular courtship dance to attract a female, giving her a basis on which to select a mate. Defense and courtship displays are exaggerated and always performed in the same way, so that their meaning is clear. Fireflies use a flash pattern to signal females of the same species. The body language of students during a lectureprovides an example. Students who are leaning forward in their seats and making eye contact with the instructor appear interested and engaged with the material. Students who are leaning back in their chairs and gazing aroundthe room or doodling are indicating that they have lost interest. Instructors can use students’ body language to determine whether they are effectively presenting the material and make changes accordingly. The hairstyle and dress of a person, or the way he or she walks and talks, are also ways to send messages. People who dress in black, moveslowly, fail to make eye contact, and sit alone may be telling others that they are unhappy, or simply that they do not wantto be socially engaged. Psychologists have long tried to understand how visual clues can be used to better understand human emotions and behavior. Similarly, researchers are evaluating body language in animals to determine whether theyalso have emotions. 4- Tactile Communication Tactile communication occurs when information is passed from one animal to another by touch. For example, recall that laughing gull chicks peck at the parent’s bill to induce the parent to feed them. In primates, grooming—one animal cleaning the coat and skin of another helps cement social bonds within a group. Honeybees use a combination of communication methods, but especially tactile ones, to impart information about the environment. When a foraging bee returns to the hive, it performs a “waggle dance,” which indicates the distance and direction of a Bees can use the sun as a compass to locate food because they have a biological clock, an internal means of telling time, which allows them to compensate for the sun’s movement in the sky. Today, we know that the timing of the clock, in both insects and mammals (including humans), requires alterations in the expression of a gene called period.  Chapter four Ecological biochemistry  Ecological Biochemistry: Allelopathy and Defense Against Herbivores 1. Introduction Plants contain a vast array of compounds referred to as secondary metabolites that play no role in primary catabolic or biosynthetic pathways. Many of these metabolites influence important ecological interactions (e.g., deterring herbivores, protection against pathogens, allelopathy, symbiotic associations, seed germination of parasites, or interactions with pollinators). Others provide protection against ultraviolet radiation or high temperatures. This chapter discusses the role of secondary compounds in allelopathic and plant—herbivore interactions. 2. Allelopathy (Interference Competition) Some plants harm the growth or development of surrounding plants by the release of chemical compounds: allelopathic compounds or allelochemicals. These allelopathic effects are invariably negative, and the compounds may come from living roots or leaves or from decomposing plant remains (Fig. 1). Other released compounds may have positive effects, such as the carboxylates that solubilize phosphate in the rhizosphere or chelate Al metals and avoid Al toxicity ). These positive effects are not referred to as interference competition or allelopathy [the word allelopathy is derived from two Greek words: allelon (of each other) and pathos (to suffer)]. The chemicals involved in positive interactions, however, may still be referred to as allelochemicals. (Fig. 1) Some species, e.g., Lupinus sericeus(silky lupine) and Gaillardia grandiflora (blanketflower) are resistant to the allelochemical [(þ)-catechin] released by Centaurea maculosa, because they release increased amounts of oxalate upon exposure to catechin. Oxalate blocks generation of reactive oxygen species and reduces oxidative damage generated in response to catechin. Genotypes of one species, e.g., Triticum aestivum (wheat) differ substantially in the rate at which they release allelochemical phenolics. This characteristic has potential in integrated weed management, because the wheat genotypes that release most phenolics tend to have the greatest capacity to suppress the weedy grass Lolium rigidum (annual ryegrass. Benzoxazinoids (cyclic hydroxamic acids) are common allelochemicals in root exudates from Triticum aestivum (wheat), Zea mays (corn), and Secale cereale (rye). In soil, the exudates may be converted into other benzoxazinoids, many with a similar phytotoxic effect. Allelopathic compounds may have originally evolved as compounds that deter pathogens or herbivores and subsequently become involved in interactions between higher plants. Secretory glands were well developed in the early gymnosperms and angiosperms of the Paleozoic before there were terrestrial herbivores, but after the evolution of terrestrial fungi which suggests that early defense systems may have been directed at pathogens. The mode of action of most allelopathic compounds is unknown. Many phenolic compounds inhibit seed germination of grasses and herbs, and they may inhibit ion uptake or respiration. Volatile terpenoids can inhibit cell division. Potentially allelopathic compounds can be detoxified by some species through mechanisms. The allelopathic effects of Juglans nigra (black walnut) illustrate the multiplicity of ecological effects. In a zone up to 27 m from the tree trunk, many plants [e.g., Solanum lycopersicum (tomato), Medicago sativa (alfalfa)] die. The toxic effects are due to the leaching from the leaves, stems, branches, and roots of a bound phenolic compound, which undergoes hydrolysis and oxidation in the soil. The bound compound, which is nontoxic itself, is the 4- glucoside of 1,4,5-trihydroxy-naphthalene. It is converted to the toxic compound juglone (5-hydroxynaphtoquinone). Some species are resistant to juglone [e.g., Poa pratensis (Kentucky bluegrass)], probably because they detoxify this allelochemical. Juglone severely inhibits the relative growth rate, photosynthesis, stomatal conductance, and respiratation of Zea mays (corn) and Glycine max (soybean), when applied at a concentration of 10 mM or more. This concentration can be found in soil under black walnut when it is used in alley cropping. Allelopathic interactions also appear to play a major role in desert plants [e.g., between Encelia farinosa (brittlebush) and its surrounding plants in the Mojave desert in California, USA]. In many of these plants, a simple benzene derivative is produced, primarily in the leaves (Fig. 3). It is released when the leaves fall to the ground and decompose. An example of growth inhibition by a toxin produced in roots, rather than leaves, is that of the rubber plant guayule (Parthenium argentatum). The aromatic compound (Fig. 3), remarkably, causes inhibition of plants of the same species (autotoxicity). Similar examples of autotoxicity have been found for cultivars of Triticum aestivum (wheat) in bioassays under laboratory conditions. In several cucurbit crops [e.g., Citrullus lanatus (watermelon), Cucumis melo (melon), and Cucumis sativus (cucumber)], autotoxicity contributes to ‘‘soil sickness’’; that is, a reduction in yield when crops are grown on the same plot without rotation (Yu et al. 2000). Cinnamic acid is one of the autotoxic compounds in cucumber; it induces formation of reactive oxygen species (ROS). Allelopathic and autotoxic effects probably play a role in many environments; however, it is hard to estimate their ecological significance. Some of the released compounds are probably decomposed rather rapidly by microorganisms, thus diminishing their potential effects. Other allelopathic compounds decompose rather slowly, including a group of phenolic compounds mostly referred to as tannins. Allelochemicals may also affect soil microorganisms and thus indirectly affect surrounding plants. For example, monoterpenes from Picea abies (Norway spruce) inhibit nitrification, either directly or indirectly due to immobilization of mineral nitrogen. Exudates released by some plants, e.g., Eragrostis curvula (weeping lovegrass) are antagonistic against plant—parasitic nematodes. These nematicidal compounds such as glucosinolates,. Detoxification of Xenobiotics by Plants: Phytoremediation Plants, like any other organisms in the environment,are continually exposed to potentially toxic chemicals: xenobiotics. These xenobiotics may be natural secondary plant chemicals, which we discussed in this chapter, industrial pollutants, or agrochemicals.Many xenobiotics are lipophilic; they are therefore readily absorbed and accumulate to toxic levels within the plant, unless effective means of detoxification are present. if plants have pathways to produce and cope with a vast array of natural secondary chemicals, can they also be put to use to clean up environmental pollutants. In this section we discuss the capacity of some plants to detoxify organic pollutants. The cellular detoxification systems of plants dispose of the xenobiotics by two sequential processes. 1. Chemical modification 2. Compartmentation The reactions responsible for chemical modification of lipophilic xenobiotics involve hydrolysis or oxidation that makes the chemicals more hydrophilic and creates reactive sites by the addition or exposure of functional groups (e.g., hydroxyl or carboxyl groups) (step I); the modified chemicals may still be toxic. If the xenobiotic already has a functional group that is suitable for conjugation, then there is no need for step I. The next step is the conjugation of the modified xenobiotic (phase II), followed by export from the cytosol (step III). Hydrolysis of the xenobiotics in phase I is catalyzed by various esterases and amidases, but the major reactions are oxidations catalyzed by the cytochrome P-450 system , which involves mono-oxygenases that insert one atom of oxygen into inert hydrophobic molecules to make them more reactive and water- soluble. The rates of chemical transformation and the types of metabolites that are formed depend on plant geno type and accounts for variation in herbicide resistance and tolerance to pollutants. In phase II, the (modified) xenobiotic is deactivated by covalent linkage to endogenous hydrophilic molecules (e.g., glucose, malonate, or glutathione) which produces a water-soluble nontoxic conjugate. Export of the conjugates from the cytosol to the vacuole or apoplast (phase III) occurs by membrane-located transport proteins. This detoxification pathway shares many features with the pathway used by plants for the vacuolar deposition of secondary metabolites (e.g., anthocyanins).  One important detoxification mechanism is chemical modification of the xenobiotic by covalent linkage to tripeptides like glutathione (Fig. 24). Conjugation with xenobiotics may take place spontaneously or may require catalysis by glutathione-S-transferase. Glutathione is an important plant metabolite that acts both as a reducing agent that protects the cell against oxidative stress and guards against chemical toxicity via the modification reactions of phase II. Glutathione conjugates that are deposited in the vacuole can undergo further metabolism. For example, the glycine residue of the glutathione moiety may be removed enzymatically which is sometimes followed by enzymatic removal of the glutamic acid residue (Fig. 25).The glutathione- mediated and related detoxification systems probably evolved for the metabolism and compartmentation of natural substrates. For example, a glutathione-S-transferase is required for the synthesis of anthocyanins; it produces a glutathione conjugate that can be transported to the vacuole. Cytochrome P-450 is, similarly, involved in anthocyanin biosynthesis. Therefore, the selective mechanisms that led to the catalytic proteins of the pathway that has an apparent specificity for industrial chemicals are probably associated with the metabolism of natural secondary plant products,including allelochemicals and pigments. Higher plants, unlike microorganisms and animals, are unable to catabolize xenobiotics; instead, detoxification mechanisms have evolved that lead to the formation of water-soluble conjugates that are compartmented in the vacuole or deposited in the apoplast. The residues may persist in plant tissues for a considerable time, and may affect consumers of the plant tissues. A thoro