Organisms and Populations PDF

ANMOLSHARMALIVE Ecology is the study of interactions among organisms and between the organism and its physical (abiotic) environment. Ecology is concerned with 4 levels of biological organization: Organisms, Populations, Communities & Biomes. ORGANISM AND ITS ENVIRO...

ANMOLSHARMALIVE Ecology is the study of interactions among organisms and between the organism and its physical (abiotic) environment. Ecology is concerned with 4 levels of biological organization: Organisms, Populations, Communities & Biomes. ORGANISM AND ITS ENVIRONMENT - Physiological ecology (Ecology at the organismic level) is § Stenothermal: They can tolerate only a narrow range of the study of adaptation of an organism to environments in temperatures. terms of survival and reproduction. b. Water - The rotation of earth and the tilt of its axis cause annual - It is the second most important factor. variations in temperature & seasons. Major biomes (desert, - Desert organisms have special adaptations to limited water. rain forest, tundra etc.) are formed due to these variations & - Productivity & distribution of plants is dependent on water. precipitation (rain & snow). - For aquatic organisms, water quality (pH, chemical composition) is important. The salt concentration (salinity in parts per thousand) is less than 5 in inland waters, 30-35 in the sea and > 100 in some hypersaline lagoons. - Based on the tolerance to salinity, organisms are 2 types: § Euryhaline: Tolerate a wide range of salinities. § Stenohaline: Tolerate only a narrow range of salinity. Many freshwater animals cannot live for long in sea water and vice versa because of the osmotic problems. c. Light - Plants need sunlight for photosynthesis. - Small forest plants (herbs & shrubs) are adapted to photosynthesize optimally under very low light because - Regional and local variations within a biome lead to the they are overshadowed by tall, canopied trees. formation of different habitats. - Many plants depend on sunlight for photoperiodism (e.g. - Life exists even in extreme & harsh habitats. E.g. Rajasthan flowering). desert, rain-soaked Meghalaya forests, deep ocean trenches, torrential streams, permafrost (snow laden) polar regions, - Many animals use diurnal and seasonal variations in light intensity and photoperiod for timing their foraging, high mountain tops, thermal springs & compost pits. reproductive & migratory activities. Our intestine is a habitat for many microbes. - Sun is the ultimate source for light & temperature on land. - The physico-chemical (abiotic) components (water, Deep (> 500m) in the oceans, the environment is dark and light, temperature, soil etc.) & biotic components there is no energy available from sun. (pathogens, parasites, predators, competitors etc.) lead to variation of different habitats. - The spectral quality of solar radiation is also important for life. The UV spectrum is harmful to many organisms. Not - The distinct role and position of an organism in its all the colour components of the visible spectrum are environment is called its niche. By this, each organism tolerates various conditions, utilises various resources etc. available for marine plants. d. Soil Abiotic Factors - Nature & properties of soil is differed due to climate, a. Temperature weathering, sedimentation, method of soil development etc. - The most ecologically relevant environmental factor. - Soil composition, grain size & aggregation determine the - Temperature on land varies seasonally. It gradually percolation and water holding capacity of the soils. decreases from equator to the poles and from plains to - These characteristics and parameters like pH, mineral mountain tops. It ranges from subzero levels (in polar areas composition & topography determine the vegetation and & high altitudes) to >500C (in tropical deserts). animals in an area. - Average temperature in thermal springs & deep-sea - In aquatic environment, the sediment-characteristics hydrothermal vents is above 1000 C. determine the type of benthic animals. - Mango trees cannot grow in temperate countries (Canada, Responses to Abiotic Factors Germany etc.). There is no Snow leopard in Kerala forests. - Organisms maintain a stable internal environment Tuna fishes are rare beyond tropical latitudes in the ocean. (homeostasis) despite varying external environmental - Temperature affects kinetics of enzymes, basal metabolism conditions. This is possible by following processes. and other physiological functions of the organism. - Based on range of thermal tolerance, organisms are 2 types: a. Regulate § Eurythermal: They can tolerate a wide range of - It is the maintenance of homeostasis by physiological & temperatures. behavioural means. It ensures constant body temperature 1 ANMOLSHARMALIVE (thermoregulation), constant osmotic concentration Diapause (a stage of suspended development) of many (osmoregulation) etc. E.g. All birds & mammals, very few zooplanktons in lakes & ponds. lower vertebrates and invertebrates. Adaptations - Thermoregulation in mammals: The success of - Adaptation is the morphological, physiological & mammals is mainly due to their ability to maintain a behavioural attribute that enables an organism to survive constant body temperature. and reproduce in its habitat. In summer, when outside temperature is more than body - Many adaptations have evolved over a long evolutionary temperature (370C), sweating occurs. This results in time and are genetically fixed. evaporative cooling and brings down body temperature. In winter, when the temperature is below 370C, shivering Adaptations of kangaroo rat in North American deserts: occurs. It produces heat and raises the body temperature. § Internal fat oxidation gives water as byproduct if there is - Most of the organisms are not regulators or are partial no external source of water. regulators because thermoregulation is energetically § Ability to concentrate urine so that minimal volume of expensive especially for small animals (shrews, humming water is used to remove excretory products. birds etc.). They have a larger surface area relative to their Adaptations of desert plants: volume. So they lose body heat very fast when it is cold § Presence of thick cuticle on leaf surfaces. outside. Then they have to expend much energy to generate § Sunken stomata minimise water loss due to transpiration. body heat. So, very small animals are rare in Polar Regions. § CAM photosynthetic pathway enables their stomata to remain closed during day time. b. Conform § Desert plants like Opuntia have no leaves (they are - 99% of animals and nearly all plants cannot maintain a reduced to spines). Photosynthesis is done by stems. constant internal environment. Their body temperature or osmotic concentration Adaptations of mammals: change with the surrounding § Mammals from colder climates have shorter ears and conditions. They are called limbs to reduce heat loss. This is called Allen’s Rule. conformers. § Aquatic mammals like seals have a thick layer of fat - In aquatic animals, osmotic (blubber) below their skin that acts as an insulator and concentration of body fluids reduces loss of body heat. changes with that of the Physiological and biochemical adaptations: ambient osmotic concentration. § Archaebacteria are found in hot springs & deep-sea c. Migrate hydrothermal vents where temperature is >1000C. Many fish thrive in Antarctic waters (temperature is below 00C). - Many animals like birds move away temporarily from § Many marine invertebrates & fishes live at great depths in stressful habitat to a more hospitable area and return when the ocean where the pressure is >100 times the normal stressful period is over. atmospheric pressure. - E.g. During winter, Keolado National Park (Bhartpur, § At a high-altitude place (>3,500 m) we feel altitude Rajasthan) hosts migratory birds coming from Siberia and sickness. Its symptoms are nausea, heart palpitations & other extremely cold northern regions. fatigue. This is due to low atmospheric pressure. So the d. Suspend body does not get enough O2. Gradually, we acclimatize the - In bacteria, fungi & lower plants, thick walled spores help situation and the body compensates low O2 availability by to survive unfavourable conditions. Under suitable increasing RBC & breathing rate and decreasing the conditions, they germinate. binding capacity of hemoglobin. - In higher plants, seeds and some vegetative reproductive Behavioural adaptations: structures serve to tide over periods of stress by reducing § Desert lizards bask in the sun and absorb heat when their their metabolic activity. They germinate under favourable body temperature is low, but move into shade when the moisture and temperature. ambient temperature starts increasing. In animals: Examples are § Some species burrow into the soil to hide and escape from Hibernation of bears during winter. the above-ground heat. Aestivation of some snails and fishes during summer. POPULATIONS - A population is a group of individuals of same species that - Population ecology is an important area of ecology as it live in a given geographical area, share or compete for links ecology to population genetics & evolution. similar resources and potentially reproduce. Population Attributes - E.g. All the cormorants in a wetland, rats in an abandoned Birth rates: Refer to per capita births. dwelling, teakwood trees in a forest tract, bacteria in a E.g. In a pond, there are 20 lotus plants last year and culture plate and lotus plants in a pond etc. through reproduction 8 new plants are added. 2 ANMOLSHARMALIVE Hence, the current population = 28 The birth rate = 8/20 = 0.4 offspring per lotus per year. Death rates: Refer to per capita deaths. E.g. 4 individuals in a laboratory population of 40 fruit flies died during a week. Hence, the death rate = 4/40 = 0.1 individuals per fruit fly per week. Sex ratio: A population has a sex ratio. E.g. 60% of the population is females and 40% males. - If N is the population density at time t, then its density at Age pyramid: It is the structure obtained when the age time t +1 is distribution (% individuals of a given age or age group) is Nt+1 = Nt + [(B + I) – (D + E)] plotted for the population. Population density increases if B+I is more than D+E. For human population, age pyramids generally show age Otherwise it will decrease. distribution of males and females in a combined diagram. - Under normal conditions, births & deaths are important factors influencing population density. Other 2 factors have importance only under special conditions. E.g. for a new colonizing habitat, immigration may be more significant to population growth than birth rates. Representation of age pyramids for human population Growth Models Population size or population density (N): It is the a. Exponential growth number of individuals of a species per unit area or volume. - Resources (food & space) are essential for the unimpeded E.g. population density of Siberian cranes at Bharatpur population growth. wetlands in any year is