Summary

These notes cover fundamental concepts in ecology, such as life organization, environment, ecosystem structure and function. The text defines key terms and discusses factors impacting populations and ecosystems.

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1 Life Organization Organism : a dynamic biological unit influenced by fluctuating environment. Environment consists of microenvironment and macroenvironment. Microenvironment : local surrounding of the organism. Macroenvironment : sum. Of total physical and bi...

1 Life Organization Organism : a dynamic biological unit influenced by fluctuating environment. Environment consists of microenvironment and macroenvironment. Microenvironment : local surrounding of the organism. Macroenvironment : sum. Of total physical and biotic condition existing external to the organism. Ecosphere or Biosphere : Thin veil of living material around the globe (part of the earth in which life exist). World : single vast ecosystem. Habitat : the place in which each kind of organisms is normally found. Biosphere : entire place occupied by living organisms. Biotope : basic unit in biosphere. Biotopes: are grouped together to form ……… (bio cycles - biospheres - bio chores) Bio chores: are grouped together to form ………. (bio cycles - biospheres - bio chores) The ecosystem : unit which include living organisms and non-living substances. The biosphere is divided into three habitats (biocycles or realms) 1. Marine (halobiotic) 2. Fresh water (lymnobiotic0 3. terrestrial (geobiotic) Structure aspects of ecosystem: 1. description of the arrangement. 2. types and numbers of species. Functional aspects of ecosystem: 1. Flow of energy. 2. cycling of nutrients. The non-living part of the ecosystem includes different kind of habitats. Biologist 2 1. Water : habitat for aquatic organisms. 2. Land : habitat for terrestrial organisms. 3. Soil habitat : habitat for microbes and plants. Biomes : distinct large area of earth with relatively homogenous climatic factors, fauna and flora. Abiotic factors of the ecosystem: 1- climatic: a. Solar radiation, temp. and wind b. rain fall 2- physical: a. Light and pressure b. fire 3- chemical : a. Acidity b. salinity ━ Biotic factors of the ecosystem are the all living organisms. 1. Competition 2. Neutralism 3. Commensalism 4. Parasitism& Predation 5. Amensalism Limiting factor: any factor acting to alter the growth and survival of a population. Liebig's law of the minimum : ━ Growth of plant is dependent on the amount of food stuff which is presented to it in minimum quantity. ━ Example : crop production is not dependent on nutrition's needed in large quantities. ━ e.g Co2 and H2o not dependent on some raw materials as boron which is needed in minute quantities. Population : group of individuals of the same species live at the same area. Community : group of different population live in the same area and is interact with each other. Biologist 3 Two principles must be added to the law : 1-application of law under steady(constant) condition. 2-factor interaction : the action of some factors other than the minimum one may modify the rate of growth. Biotic potential & environmental resistance & balance of nature 1. Biotic potential : power of a population to increase in number when all environmental conditions are optimal. 2. Environmental resistance : the sum. Of the physical and biological factors which prevent a species from reproducing at its maximum rate. 3. Balance of nature : the interaction between the environmental resistance and biotic potential. ━ environmental resistance is low when species is first introduced into a new area, so it increases in number but after words, the environmental resistance to it increases. Shelford's law of tolerance : Organisms have an ecological minimum and maximum limiting factor between them this is a range which represents limits of tolerance. To express the degree of tolerance, we use : Steno → narrow range Eury → wide range Examples : 1-steno thermal - eurythermal → refers to temp. 2- stenohydric - euryhydric → refers to water. 3- stenohaline - euryhaline → refers to salinity. 4- stenophagic - euryphagic → refers to food. 5- stenoecious - euryecious → refers to habitat. Comparison between tolerance limits of stenothermal and eurythermal Biologist 4 Example : Trout eggs develop between OoC → 12oC with optimum at 4oC Frog eggs develop between OoC → 30oC with optimum at 22oC So trout eggs → stenothermal Frog eggs → eurythermal Subsidiary principles to the law : 1. organism may have wide range of tolerance for one factor and narrow range for another. 2. when conditions are not optimum → the limits of tolerance may be reduced. 3. organism with wide ranges of tolerance for all factors are widely distributed. 4. organisms in nature are not living at the optimum range due to physical factors (particular ). 5. the limits of tolerance for reproductive individuals are narrow than non-reproducing adult plants or animals. The Ecological Niche It's the functional role of an organism in the community as : a) its trophic position. b) its position in environmental gradients of temp, moisture ,ph. ,soil,.. Types of ecological niche: 1. hypervolume niche (multi-dimensional niche). ━ The position of organism in environmental gradients of temp., moisture, ph., soil and interpositions of existence. 2- habitat niche(spatial niche). Several species live in the same general habitat but each species has its own microhabitat. 3-trophic niche: Two species live in the same habitat but they occupy different trophic niche. Biologist 5 e.g. : two aquatic bugs live in the same pond but: a)first bug(notonecta) → feeds on other animals b)second bug(corixa) → feeds on decaying vegetation. Overlapping niches and niche separation : Competitive exclusion → no two species can persist in the same niche, either one or both become extinct. Example: Two species of plants that are able to grow in saline water ━ Species A → grow successfully in the salinity of soil solution 0-2% ━ Species B → grow successfully in the salinity of soil solution 1-3% 1- individuals lie in the area of overlap → a) adapted to survive under salination 1-2% b) in direct competition. 2- individuals lie in areas of nonoverlap → a) show greater survivorship b)reproduce successfully c) not in inter specific Biologist 6 Character displacement: Allopatry → species occur in different geographic regions. Sympatry → species occur in the same area (not necessary in the same niche). By character displacement : Differences in closely related species : a)diverge in sympatry b)converge in allopatry character displacement has two adaptive values: 1- reduce competition 2- prevent hybridization Example: Two species of nuthatches (1&2) 1-two species → are very similar in allopatry 2-two species →diverge in bill size and facial pigmentation Difference in bill size → reduce food niche overlap Difference in facial pigmentation → facilitate species recognition and prevent Ecological Data Rule 1 → not everything will be measured a-collect useful data b-ecological theory and your ecological insight will give you what data you will measure. N.B → it's mistake to think that statistical analysis by itself will give you what data you should collect. Biologist 7 Rule2 → find problem and state your objectives. Problem → once solved will help us to conserve our resources. Objectives → will answer a question to test an ecological hypothesis. Rule3 → collect data that will achieve your objectives : a-achieve your objectives b-answer your question c-ignore statistician Rule4 → some ecological question is impossible to answer at the present time Ex. To map the movement of the all killer whales on the pacific coast → is impossible financially or technically at this time Rule5 → with continuous data, save time and money Ex. The number of locusts per square meter and rate of food per individual per day will give us an estimate of the total food consumption of a locust population. Rule6 → measure the possible error to every ecological estimate. Statistical population are not biological populations (change in space and time). Ex. If you count rabbits in one year then remove foxes and count the rabbits in the second year → you may find that rabbit number increased → this may due to : Reduced fox predation disease or parasites or reduction in better food to rabbits.(variables not measured). Rule7 → never confuse statistical significance with biological significance. Statistical significance → achieved by statistical (mechanical). Biological significance → not mechanical concept but refers to particular set of measurements. For example, a difference in survival rate of 3% per year between males and females of a seabird population → may be very significant biologically but not statistically significant. Rule8 → code all your ecological data and enter it on a computer. Rule9 → garbage in, garbage out: Poor data → due to lack how to take field measurements Biologist 8 Good data → due to repeated measurements. N.B : Ecological data may be useless for several reasons : 1-not collect data at right season 2-not repeated 3-not related to the problem Anthill → important soil modification Introduction to soils Four basic components of most soils are : Elevation → the movement of fine mineral particles out of an upper layer of soil. Illuviation → the deposition of fine mineral particles in lower soil layer. Organic activity → true soil is influenced by living organisms that aid in development of soil through addition of organic matter. Humus → 1- organic matter decomposition by fungi, bacteria ,earthworm, insects into semi soluble chemical substances. 2- make up the upper layer of the soil. 3- redistributed within minerals by large soil organisms like earthworm, beetles and termites. 4- bind with larger minerals and organic matter so it's difficult to be seen in isolation. 5- importance of humus: a-enhance a soil's ability to hold and store moisture b-reduce the eluviation of soluble nutrients from the soil c-improves soil structure Biologist 9 Translocation → the complete chemical removal of the substances from the soil. N.B → water → downward in the soil → mechanical and chemical translocation of materials. Pathway of leached substances → end in ground water zone then travel into water bodies like lakes and rivers Soil texture → refers to the size and distributions of the mineral particles in the soil. Particles are grouped into three main classes: according to size Particle Size sand 2-0.06mm silt 0.06-0.002mm clay Less than 0.002mm N.B → clay particles are the most important particles in the soil because : 1-clay has large surface area→a-highly reactive b-has the ability to attract and hold +ve charged nutrient ions. 2- clay is flexible → absorb H2o and other substances at its surface. Soil Ph : 1-maximum soil fertility occurs in ph. 6 to 7.2 2-soil ph. is controlled by the conc. Of free H+ (hydrogen ion in the soil )that is available to the soil by H2o → H+ + OH- (dissociation by activity of plants, roots, chemical reaction). 3-soil with H+ conc. → tend to be acidic Soil with low H+ conc →tend to be alkaline 4-ph lower than 5.5 → nutrients become very soluble Ph high → nutrients become soluble so ph. influencing reactions and fertility in the soil through solubility of many nutrients. Soil profile → sequence of horizontal layer result from eluviation into lower soil horizons then illuviation in the lower soil horizons. N.B → illuviation means movement of particles Illuviation : means accumulation of particles Biologist 10 Soil horizons are up to five : 1- 0 Horizon → topmost layer composed of plants and humus 2-A Horizon → composed of primarily minerals has two important characteristics : a- zone of translocation b- mixing of humus and organic matter with mineral particles. N.B → A horizon differentiated into a dark upper horizon or organic accumulation and lower horizon showing loss of material by eluviation 3-B Horizon → 1- mineral soil layer which is strongly influenced by illuviation 2-with higher bulk density than A horizon due to its enrichment of clay 3- colored by iron oxides or by calcium carbonate illuviated from A horizons. 4- C Horizon → composed of weathered parent material. 5-R Horizon → composed of unweather bed rock. Soil colour : 1- soil or tropics → red or yellow due to oxidation of Fe+ or Al+ 2- temperate grassland → black due to large addition of humus 3-forest soil → grey due to heavy leaching of iron 4- soil with high water body → greenish or grey blue due to iron reduction N.B : organic matter → colours soil black while iron oxides + organic matter → colours soil brown Nature of the soil is an important factor influencing the productivity of ecosystem. Explain ? Soils provide vascular plants with 1- medium for growth 2- nutritional requirements So nutrient status in soil limit :1-plant growth 2-productivity of consumer Organism so down the food chain. Biologist 11 Soil Biology The study of microbial and faunal activity and ecology in the soil. Soil life, Soil biota, Soil fauna or edaphon→ collective term that includes all organisms that spend a signification portion of their life cycle within a soil profile. Soil invertebrates are classified according to their size: 1-microfauna 2-mesofauna 3-macrofauna 4-megafauna Body size: Body size: Body size: Body size: 20mm-200mm 200mm-2mm 2mm-20mm 20mm Ex.Protozoa. Ex.Microarthropods Ex. certain Ex. like mites and earthworms, Earth worms, springtails. gastropods and small rodents, isopods. reptiles and amphibians. Microflora → bacteria, actinomycetes and fungi. Soil fauna are classified according to morphological adaptations and the ecological functions into : 1-Temporary inactive geophilic →a- are organisms that live in the soil for only certain phases of their life, such as to overwinter. b- Have weak influence on the ecological function of the soil (prey for other organisms). 2-Temporary active geophilic → organisms live in the soil in a stable manar for a large part of tier life (for one or more developmental stages and emerges from the soil as adult). Ex. Organisms having larvae(important for soil ecology act as predators) and pupae(play minor role in the soil). 3-Periodical geophilic → organisms that spend a part of their life cycle in the soil, generally as larvae but occasionally go back to the soil to perform various activities such as laying eggs. Ex. Several coleopteran such as scarabaeus : a- spend their larval stages in the upper soil layers. b-when adult, use the soil as food source. 4-Geobionts → are organisms that are well adapted to the life in the soil and can't leave this environment. Biologist 12 Ex. Collembolan, Dipluran and Proturan. N.B : soil contamination occurs → soil with : a- high geobiont b- low temporary inactive geophilic. The degree of interaction between soil organisms and the soil itself depends on the part of the life cycle that spent in the soil. Explain? N.B : Depending on the available food sources many soil fauna are able to change their feeding strategies for example → carnivorous species able to feed on dead organic matter in time of low food availability. N.B : it's difficult to provide average abundance for soil invertebrates because of : a-high variability in both time and space. b-differences in sampling methods. Importance of soil fauna : 1-key components of soil food web. 2-recycling of organic matter, energy and nutrients. Microarthropods: a- gp1→originated in epigeous habitat (above the soil) ex.coleoptera, chilopoda,diplopoda,diptera. b-gp2→originated directly in the soil. Ex. Protura,Diptra. c-gp3→don't have forms in epigeous or aquatic habitat. Ex. Palpigrada. Characteristics that allow microarthropods to survive within the soil habitat : 1-reduction of visual organs. 2-reduction of body length (miniaturization). 3-reduction of appendages. 4-loss of pigmentation. 5-distribution of chemo and hygroreceptors not only on oral region but also on other body structures. N.B : Collembola → the most importance gp of soil microarthropods because of : 1-their number of species. Biologist 13 2-their number of individuals. 3-it's useful as indicators of soil quality. According to an ecological and functional classification, its possible to identify three groups of earthworms that differ in size, burrowing capability, type of food and habitat. charecter epigeic endogeic anecic 1-size 0.5 to 5 cm 1 to 8 cm Excess of 5 cm 2-burrowing Poorly burrowers Burrowers→make Excellent capability horizontal burrowers tunnels →make vertical tunnels 3-type of food litter Humus and dead litter roots 4-habitat Superficial in the first few In mineral layer organic layer cm of mineral soil but rise to the surface at night 5-colour red Not pigmented Reddish brown 6-ph Good tolerant to Below 5 restricts ……………. low ph their activity Diversity of soil fauna Usually two groups of organisms are recognized in the soil: 1-Euedaphons → organisms that live in the strip mineral soil. 2-Hemiedaphons → organisms that live in the strip of organic soil. 3-Epiedaphons → (epigeons) → organisms that live in the surface of the soil. 4-Hyperedaphons → organisms that extend to the herbaceous of the soil. The moisture content and ph. of the soil have the greatest influence on distribution of soil organisms. Example → Hemi edaphon spring tails were subdivided into three categories according to humidity: 1-Hydrophilic → living on the surface of free H2o 2-Mesophilic → living in damp organic litter Biologist 14 3- Xerophilic → living in dry areas N.B : The greatest diversity is observed in system with equilibrium between the productivity level and the perturbation rate. Two factors influence the soil community: 1-the nutrient resource availability. 2-diversity of microhabitats. The role of soil fauna in soil ecosystem process: 1-Decomposition of organic matter 2-Distribution of organic matter within soil horizons 3-Soil aeration 4-Formation of humus 5-nutrients cycling 6-springtails that feed on fungi can spread fungal spores N.B → basic component in hypogea food chain is detritus → refers to animal and plant decompositions in the soil. Principal factors affecting the loss of soil fauna diversity : 1-agriculture activities such as applications of pesticides, fertilizers and sewage 2-human activities can alter physical, chemical and biological properties of the soil 3-urbanization process 4-land use factors such as tillage 5-habitat destruction Using soil fauna to improve soil health: By 1-decreasing bulk density 2-increase soil pore-space 3-soil horizon mixing 4-litter decomposition 5-increase water holding capacity Biologist 15 6-increase aeration Ex. Protozoa, nematode, termites and earth worms( excrete castings(casts) ) → provide nutrients to plants. Castings → mixture of soil and partially digested plants. Use of soil invertebrates in soil biodiversity assessment and as soil biological quality indices : Indicators of soil quality should fulfil the following criteria : 1-sensitivity to variations of soil management 2-good correlation with the beneficial soil functions 3-helpfulness in revealing ecosystem processes 4-comprehensibility and utility for land managers 5-easy to measure Ex. Collembolan and proturan are good indicators in the soil due to : a- their limited mobility b-lack capacity to leave soil soil quality → refers to the capacity of a specific kind of soil to function within natural ecosystem bundries to : a-sustain plant and animal productivity b-enhance water and air quality c-support human health Edaphic fauna → super organisms that assumes a crucial significance due to the chemical-physical and biological processes that are rooted in the soil. Biologist 16 Biologist

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