Ch 13 organism and population || Class 12 ||

ORGANISM AND POPULATION || BIOLOGY || CLASS 12 ||

1. Chapter 13 ORGANISM AND POPULATION

2. Ecology : Ecology is the branch of science that studies the relationship between organisms and their physical & biological environment . Level of Organization in ecology:

3. Organisms : Organisms form the basic unit of study in ecology . Species : Organisms with similar features and the potential to interbreed among themselves and produce fertile offspring, constitute a species. Populations : Population is a group of individuals of the same species, inhabiting in a given area. Biological Community : Biological community is constituted by an assemblage of the populations of all different species that live in an area and interact with each other. A biotic community has a distinct species composition and structure . Ecosystem : Is a biological system in nature and composed of a biotic community integrated with its physical (abiotic) environment through the exchange of energy and recycling of the nutrients .

4. Habitat : Habitat is the place where an organism lives . Biomes : Biomes is a very large unit, constituting of a major vegetation type and associate fauna found is a specialized zone. Niche : The ecological niche of an organism represents the range of conditions that it can tolerate the resources it utilizes and its functional role in the ecological system. Each species occupies a distinct niche and no two species occupy the same niche. Biosphere : It is the sum total of all the biomes on the earth . Environment : Environment is a sum total of all biotic and abiotic factors that surround and potentially influence an organism. Temperature, water, light and soil are the major abiotic factors.

5. BIOMES Large ecosystem are called Biome. Each Biome is identified by its climax community. Altitude and latitude determine the boundary of Biome. Annual variations in the intensity and duration of temperature and precipitation are responsible for the formation of major biomes .

6. S. No. Biome Location Vegetation 1. TUNDRA Tundra region Lichen, Moss, Grass 2. NORTHERN CONIFEROUS South to tundra Pine, Deodar, Cypress 3. TEMPERATE DECIDOUS Centrally located Oak 4. TROPICAL DECIDOUS Plains and low hilly areas Sal, Teak, Tendu 5. TROPICAL RAIN FOREST Equatorial region Hopea 6. MEDITERRANEAN FOREST Pacific coast of America and Australia Small trees and Shrubs 7. TROPICAL SAVANNA South America and south Australia Coarse grasses. Large trees 8. GRASS LAND 9. DESERT Asia, North Africa

7. Name of Grassland Place Prairies North America Pampas South America Steppes Europe and Asia Tussocks New Zealand Veldts Africa MAJOR GRASSLANDS

8. FACTORS EFFECTING ECOLOGY

9. ABIOTIC FACTORS 1. Temperature : The physiological functions and geographical distribution of organisms is governed by temperature. Temperature affects the kinetics of enzymes, BMR (Basic Metabolic Rate) and other physiological actions in organisms . On the basis of temperature organisms are classified into 2 categories- A. Eurythermal: A few organisms which can tolerate wide range of temperatures are called eurythermal organisms . B. Stenothermal: Many organisms which can tolerate narrow range of temperatures are called stenothermal organisms . C. Ectotherms / Poikilotherms / Cold blooded animals D. Endotherms / Warm blooded animals

10. HOMEOSTASIS – The process by which organism maintain constant internal environment with respect to outside environment. Temperature effect a no. of morphological characters in various organism Bergman rule – Birds and mammals attain greater body size in colder regions and lesser in warmer regions. Allen's rule – Animals from colder climate generally have shorter ears and limbs to minimise heat loss. Jorden’s rule – Fishes occurring in cold water have more vertebra than those found in warmer water.

11. D. Gloger’s rule – Animals of tropic region are more darker in colour and heavily pigmented than those in arctic region. E. Rensch’s rule – Birds of colder region have narrow wings than those found in warmer region.

12. THERMAL STRATIFICATION IN LAKES 3 layer on the basis of temperature. Epi - limnion – Top most layer exposed to solar radiation Meta- limnion - transition zone; max temp. change Hypo- limnion - basal region ; low temperature

13. 2. Soil : Nature and properties of soil depends on climate, weathering process . The process of soil formation by breaking of rocks is called Peadogenesis The physical and chemical properties of soil determine the type of plants that can grow in a particular habitat. The characteristics of the bottom sediments of aquatic environment determine type of benthic animals that can live there.

14. On the basis of agents involved in formation of soil it is of following types : Alluvial soil- make through water Colluvial soil- make through gravity . Galacial soil – make through ice . Eolian – make through wind.

15. SOIL PROFILE Vertical section of soil representing its morphological appearance. Consist of 5 layers – O-layer : humus content A-layer : minerals particles B-layer : big soil particles C-layer : weathered rocks R-layer : parental rocks

16. SOIL ORGANIC MATTER The dead organic matter present in the soil is called humus which is formed by the decomposition of plant and animal remains. Freshly fallen plant and animal material is called Detritus or Litter Partially decomposes litter is called Duff Fully decomposed litter is called Humus.

17. Decomposition : Breakdown of complex organic matter into simpler organic substances is called decomposition. Steps in Decomposition – Fragmentation – Breakdown of detritus into smaller particles. Leaching – movement of water soluble inorganic nutrients into the soil. Catabolism – degradation of detritus into simpler organic substance with the help of bacterial and fungal enzymes. Humification – accumulation of dark coloured substance called humus. Mineralisatio n – release of inorganic nutrients.

18. 3. Light : It is a complex physical environmental factor. light is important abiotic factor bec. the autotrophs prepares its food by photosynthesis. Sciophytes : Small herbaceous plants and some shrubs live under the canopy forest trees are adapted to photosynthesis under very low light intensities. Animal use the seasonal variations in the light intensity and photoperiod as cues for timing of forage, reproduction and migration. The distribution of red, green and brown algae at difference depths of water depends on the light, red algae can live in very deep water .

19. Solar constant – solar radiation before entering the atmosphere carries energy at a constant rate of 2 cal known as solar constant. UV radiation is distinguished in UV-C : 100-280 nm UV-B : 280-320 nm UV-A : 320-400 nm AL-BIDO VALUE- The ability of a surface to reflect the incoming radiation is called albido value. It is 80% for fresh snow, 20-30% for sand and 5-10% for forest  

20. 4. Water Important factor influence the life of organisms . The productivity and distribution depends on water. For aquatic organisms, chemical composition , pH, salinity and temperature of water are important. Euryhaline : The organisms which can tolerate wide range of salinity are called euryhaline organisms. Stenohaline : The organisms which can tolerate narrow range of salinity stenohaline organisms.

21. Response to Abiotic Factors Regulators : Some organisms are able to maintain homeostasis by physiological (Some times behavioral) means which ensures body temperature , constant osmotic concentration. All birds and mammals, a very few lower vertebrates and invertebrates are regulators (Thermoregulation and osmoregulation ). For example, human beings maintain their body temperature by sweating in summer and shivering during winter season. Plants do not have such mechanisms to maintain internal temperatures.

22. 2. Conformers : Majority of animals and nearly all plants cannot maintain a constant internal environment. Their body temperature changes with the ambient temperature. In a quatic animals the osmotic concentration of the body fluids change with that of the ambient water and osmotic concentration. Some species have evolved the ability to regulate, but only over a limited range of environmental conditions, beyond which they simply conform . Thermoregulation is energy-expensive process. Heat loss or gain is a function of surface area. Therefore small animals are not found in polar region.

23. 3. Partial regulators : Hairs on the body acts as heat insulator. In smaller organisms the surface area is large as compared to the volume. But in large animal this ratio is small. So, the larger animals effectively controls the body temperature . 4. Migration : The organisms can move away temporarily from the stressful habitat to a more comfortable area and return when stressful period is over . 5. Suspension : Organisms that cannot migrate , suspend their metabolic functions during stressful period. It is called suspension . E.g . Hibernation, aestivation, Diapause.

24. • Hibernation: Hibernation is a process by which the animals avoid the stress and become inactive during winter. Ex : Polar bear, Frogs, Lizards • Aestivation: Aestivation is a process by which the animals avoid the stress and summer related problems and become inactive during summer. Ex : snails and fishes • Diapause: It is a stage of suspended development seen in many zooplanktons to avoid unfavorable conditions.

25. Adaptation Adaptation is any changes of the organism (morphological, physiological, and behavioral) that enables it to survive and reproduce in its habitat. Adaptations have evolved over a long period of time and are genetically controlled. Examples: Desert Plants : have thick cuticle on leaf surface. Sunken stomata. leaves modified into spines. Due to CAM pathway photosynthesis the stomata remain closed during the day. Ex: Opuntia , cactus etc.

26. Aquatic Plants : Have evolved aerenchyma for buoyancy and floating. leaves have waxy covering . Desert animal : Kangaroo rat living in the desert of North America never drink water. The water requirement is by internal fat oxidation (in which water is the by product ). It is also able to concentrate its urine so that the minimal volume of water is lost during excretion

27. || POPULATIONS ECOLOGY ||

28. Population Attributes Population is a group of individual living in a particular geographical area . A population has certain attributes that an individual does not possesses . Important characteristics of a population are : Population density : Population density of a species is the number of individuals of a species per unit area or volume Population density =  

29. 2. Birth rate or Natality Rate : It is expressed as the number of births per thousand individuals of a population per year. 3. Death rate or Mortality rate : It is expressed as the number of deaths per thousand individual of a populations during a given period . 4. Sex ratio : It is expressed as the number of females per 1000 males of a population in given time.

30. Age pyramid A population at any given time is composed of individuals of different age group.- 1. Pre-reproductive (0-14 years) 2. Reproductive (14-44 Years) 3. Post- reproductive (45 and above) If the age distribution is plotted for the population , the resulting structure is called as age pyramid. For human population, the age pyramids show the age distribution of males and females in a combined diagram. The shape of pyramids reflects the growth status of the population i.e. an expanding/ growing population, a stable population, a declining population.

31. Population Growth The size of population keeps changes with the time, depending on the factors like: Food available Weather predator pressure Competition. The density of a population in a given habitat during a given period changes due to four basic - Natality (N), Mortality (M), Immigration (I) and Emigration (E ). Immigration : Number of individuals of the same species that have come into the habitat from elsewhere during a given period . Emigration : Number of individuals of the population who have left the habitat and gone elsewhere during a given time period.

32. The natality and immigration contribute to increase in the size and density of a population . Mortality and emigration contribute to a decrease in population. If ‘N’ is the population density at time t’ then, the equation for the population growth is: Nt = N0+[(B+I)- (D+E )] • Nt = Population density at time. • N0 = Population in beginning. • B = Birth rate. • I = Immigration. • D = death rate. • E = emigration.

33. Population Growth Models 1. Exponential Growth Model When the resources availability is unlimited in the habitat, the population grows in an exponential or geometric fashion , Exponential Growth Equation is = Where , = Population density after time t = Population density at time zero r = intrinsic rate of natural increase e = the base of natural logarithms (2.71828 ) Exponential growth : ‘J’ shape curve is obtained. When resources are not limiting the growth. Any species growth exponentially under unlimited resources conditions can reach enormous population densities in a short time. Growth is not so realistic  

34. 2. Logistic growth model A population growing in a habitat with limited resources (food and space) shows logistic growth : Verhulst -Pearl Logistic Growth is described by the following equations : dN/ dt = rN (K-N / K ) Where, N = Population density at time t r = Intrinsic rate of natural increase K = Carrying capacity Logistic Growth (Sigmoid curve is obtained) When resources are limiting the Growth. Resources for growth for most animal populations are finite and become limiting. The logistic growth model is a more realistic one.

35. Population Interactions Living organisms interact in various ways to form biological communities. Interspecific interactions: It is the interactions of population of two different species. Intraspecific interactions: It is the interactions of individuals of the same species. Interaction are of following types – Predation Competition Parasitism Commensalism Ammensalism . Mutualism.

36. Predation : Interaction between species involving killing and consumption of prey is called predation. The species which eats the other is called the predator and the one consumed is termed as the prey. The predator keeps check on prey population . The reduction in predator population may lead to increase in prey population . Predators play important roles in ecosystem : (a) Transfer of energy across trophic levels. (b) Keep prey population under control : The invasive prickly pear cactus was brought under control by introduction of a cactus-feeding predator (moth ) in Australia . Biological pest control methods : Used in agricultural are based on the ability of predator to regulate prey population.

37. Examples : (i) Biological control methods to control pests (ii) Carnivorous animals like tiger eating deers, snake eating frog (iii) Insectivorous plants like Nepenthes, Drosera, Utricularia Prey species have evolved various defence mechanisms to reduce the impact of predation – Certain insect species and frogs have camouflage (Cryptic coloration ). Monarch Butterfly is very distasteful to its prey bird. It has a special chemical in its body. This chemical is produced during its caterpillar stage by feeding on poisonous weeds . The problem of predation is more severe for plants than animals as they cannot move . Plants have developed certain morphological and chemical defense mechanism against herbivores.

38. 2. Competition: • Competition is an interaction among the individuals of same species (Intraspecific ) or between individuals of different species (Interspecific ). • Competition between the individuals of same species is for same resources that are limited . • In some case, resources need not be limiting for competition to occur, the feeding efficiency of one species might be reduced due to the interfering of the other species . E.g . Abingdon tortoise in Galapagos Island became extinct within a decade after goats were introduced into the island. It was due to the fact that the goats had greater browsing efficiency than the tortoise.

39. Unrelated species also compete for same resources. Ex :- flamingo & fish compete for zooplankton Competitive release : • "A species, whose distribution is restricted to a small geographical area because of the presence of a competitively superior species is called competitive release . • These species is found to expand its distributional range dramatically when the competing species is experimentally removed. Gause’s Competitive Exclusion Principle : It states, ‘that two closely related species competing for the same resources cannot exist together and the competitively inferior will be eliminated by superior ’.

40. Resource Partitioning: It is the mechanism meant for coexistence of species to face competition . According to this, if two species compete for the same resource , they could avoid competition by choosing different times for feeding or different foraging patterns . Ex. MacArthur showed that five closely related species of Warbles living on the same tree were able to coexist and avoid competition by having behavioral differences in their foraging( hunting) activities.

41. 3. Parasitism: • Parasitism is the interspecific interaction where one of the species (Parasite) depends the other species (Host)for food and shelter . • Host gets harmed and parasite gets benefitted . • Parasites are host-specific and parasite and its host tend to co-evolve. Co-evolve : It means that if the host evolves a special mechanism to reject or resist the parasite, the parasite has to evolve the mechanisms to neutralize them . Parasitism also involves shelter, in addition to food obtained by a parasite. Parasites may be ectoparasites or endoparasites . Ectoparasites live on the surface of their host while endoparasites live inside the body of the host .

42. Parasites adaptations: • Parasite tends to co-evolve. • It may loss of sense organs. • Presence of suckers or hooks. • Loss of digestive system. • High reproductive capacity . Examples ( i) Cuscuta growing on shoe Flower plant (ii) Head lice and humans (iii) Ascaris , Taenia , Plasmodium causing diseases in humans Example of Brood parasitism (i) Koel laying its eggs in crow’s nest.

43. 4. Commensalism: • It is the interspecific interaction in which one species benefits and the other is neither harmed nor benefitted . Ex : Epiphytes i.e Orchids growing on a tree branch . Barnacles growing on the back of whales. Association between Egret and grazing cattle. Egrets always forage close to cattle are grazing because they easily get insects. The Clown fish living along with sea anemones. Clown fish get protection from predators. Sucker fish on the back of shark Sea anemone on the shell of hermit crab

44. 5. Mutualism : It is the interspecific interaction in which Both the species interact gets benefit . E.g . Lichens are relationship between Fungus and Algae/ Cyanobacteria. Mycorrhiza – an association of Fungus with roots of higher plants. Fungi help to absorb nutrients from the rocks and plants provide energy yielding carbohydrates to fungi. Plants depend on insects for pollination and in return they give them nectar or pollens to eat. Animals help the plants in seed dispersal and in return they give fruits to animals as food . fig tree and pollinator species of wasp. Fig species can be pollinated by its partner wasp only . Rhizobium in root nodules of legumes

45. 6. Amensalism : It is the interspecific interaction in which one is harmed and the other is neither benefited nor harmed . • E.g : Penicillium secretes chemical penicillin kills bacteria.

46. Interaction Species A Species B Predation + - Competition - - Parasitism + - Commensalism + Ammensalism - Mutualism + + Population Interactions

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