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LECTURE NOTES BY: DR. B. C. JOSHI, SAPKM, KICHHA ENVIRONMENTAL FACTORS 1 BIOTIC COMPONENT The biotic components of environment are the living components of environment like plants (producers of food), animals(consumers) including human beings and microorganisms. Biotic components form an important part of any ecosystem. PLANTS AS BIOTIC COMPONENTS OF ENVIRONMENT The green plants are the producers of food for all living beings in an ecosystem. The leaves and other green parts of the plant contain chlorophyll which help in synthesizing food and releases oxygen through photosynthesis. The process of photosynthesis needs sunlight and it manufactures food with the help of water absorbed from the soil and harmful carbon dioxide from the atmosphere. ANIMALS AS BIOTIC COMPONENTS OF ENVIRONMENT They are known as the consumers of an ecosystem. They depend on plants for their survival. Animals like earthworm and wood lice help in running of nutrient cycles by providing food to decomposers. Certain animals like jackals, crows, vultures etc. act as scavengers and consume the dead and decayed bodies of animals. MICROORGANISMS AS BIOTIC COMPONENTS OF ENVIRONMENT The microorganisms are also known as the decomposers of an ecosystem. The microorganisms form a very large group of biotic components. They are found in all types of habitats and climatic conditions. They are members of bacteria, viruses and fungi group. Nitrogen fixing bacteria converts atmospheric nitrogen to a form in which it can be used by living organisms. Some bacteria such as cyanobacteria engage in plantlike photosynthesis in producing food. A cyanobacteria, Spirulina is used as rich source of protein and used as food in humans. Bacteria also play an important role in production of human food like cheese, curd, etc. Microorganisms play vital role in recycling of nutrients. INTERLINKING BETWEEN BIOTIC COMPONENTS Thus, all the three components of the biotic environment are closely interlinked to each other. The plants are producers which provide food and oxygen. The animals are consumers which fully depend on the plants for their survival. Microorganisms though a separate components of the biotic environment but help in various ways in the maintenance of the environment 2 ABIOTIC COMPONENT Abiotic factors are the non-living factors in an ecosystem that affect the survival of organisms in that ecosystem. They include: water availability sunlight temperature range 1 LECTURE NOTES BY: DR. B. C. JOSHI, SAPKM, KICHHA substrate - rock type or sand geographical terrain oxygen availability exposure 3 EDAPHIC FACTORS These include Soil and substrate Soil profile Topography Minerals pH Fire Range of tolerance SOIL The word soil is derived from the Latin word solum meaning earthy material in which plants grow. The science which deals with the study of soil is called Soil Science, Pedology (pedos = earth) or edaphology (edaphos = soil). The process of formation of soil is called pedogenesis. A soil complex is formed of 5 categories of components namely mineral matter, organic matter or humus, soil water, soil air and living organisms. The quality of soil is due to its fertility, texture, structure, organic contents and air - water relationship. SOIL PROFILE The vertical layered structure of soil is called the soil profile. There are 4 main horizons in a soil profile. O - horizon is the organic layer composed of dead organic residues. A - horizon is the top soil, the upper most layer which contains roots. B - horizon is the sub soil. C - horizon is the less weathered parent material. 2 LECTURE NOTES BY: DR. B. C. JOSHI, SAPKM, KICHHA 3 Comparison of soil profile (a) temperate deciduous forests (b) tropical rain-forests The organic matter in the soil is of 2 types. 1. Freshly dead and partially decomposed plant and animal material called litter or detritus 2. Colloidal, amorphous and dark coloured humus. Soil helps in providing water and minerals to the land plants It acts as a substratum for a variety of organisms like bacteria, fungi, many kinds of animals and plants. It is the site for decomposition of plants and animals. It provides water, minerals and fossil fuels to man. LECTURE NOTES BY: DR. B. C. JOSHI, SAPKM, KICHHA The type of soil (clayey, sand and loamy) and its water retention aeration and mineral contents determine the nature of plants and animals. On the basis of these characters of soil, the plants are divided into 5 ecological categories. Halophytes - plants found on saline soil Psammophytes - plants found on sandy soil Lithophytes - plants found on rocky surface Chasmophtyes - plants found in rock - crevices Oxylophytes - Plants found on acid soils The ground dwelling animals which may be cursorial (running) such as ostrich, rhea, ungulates, wolves, cats, bears, hyaenas etc, saltatory (jumping) such as rodents, rabbits, wallabies, kangaroos or graviportal (heavy) such as turtles armadillos, elephants etc exhibit different kinds of adaptations for different kinds of soil. For E.g., if the soil is firm and hard, the large animals inhabiting the ecosystem tend to have small hooves or paws. If the soil is wet and spongy, they tend to have broad hooves or paws. TOPOGRAPHY Topography includes the physical features of the earth like altitude, slope, exposure, mountain chains, valleys, plains, etc. Marked variations in temperature at different altitudes result in the division of earths vegetation into different zones such as equatorial, tropical rain forests, desert or grasslands, deciduous forests, coniferous forests, tundra, ice and snow of poles. 4 LECTURE NOTES BY: DR. B. C. JOSHI, SAPKM, KICHHA Height above sea level forms the altitude. At high altitudes, the velocity of wind remains high, temperature and air pressure decrease, humidity as well as intensity of light increases. Due to these factors, vegetation at different altitudes is different showing distinct zonation. The directions of mountain chains or ranges and high mountains act as wind barriers and affect the climate and rainfall and other factors which have a significant effect on the growth of vegetation and the distribution of animals. Slope is the characteristic feature of mountains. The steepness of a slope has a distinct effect on the climate of the area, namely the incidence of solar radiations, rainfall, wind velocity and the temperature of the region. Steepness of the slope decides the rapidity with which water flows away from the surface and determines the characteristic of the soil. A slope remains exposed to the sun and wind and this affects greatly the kind of plants growing there. MINERALS Minerals are also called as biogenic materials and are essential for the proper growth of organisms. So the type and distribution of plants and animals are determined by specific distribution of minerals. Deficiency or absence or excess of minerals results in abnormal growth or even death of organisms. To derive the required nutrients, organisms are adapted differently. Examples: a) Plants found in nitrogen - deficient bog soil have either nitrogen fixing bacteria or become insectivorous. b) Snails occur in soils rich in calcium content to form their shell. c) Halophytes and many marine animals have salt secreting glands. d) Leguminous plants like pea, gram methi show symbiosis with nitrogen fixing bacteria in their root nodules. High concentration of minerals generally limits the distribution of animals. Example: Dead sea is devoid of vegetation because of high salt content. pH pH is the relative acidity or alkalinity of medium. Every organism needs a specific pH called optimum pH for its optimum growth. Some organisms prefer alkaline medium (more than pH 7). For example prtozoans and molluscs, where as some organisms prefer acidic (less than pH 7). For example euglena and other pyhtoflagellates flourish in water having pH 2.8. Still other forms can survive in a wide range of pH. For example tapeworm (pH range from 4 to 11). FIRE Fire has important effects on the environment. Fire removes plant cover, burns litter on the soil surface and causes loss of nutrients. Due to forest fires a variety of animals groups die. 5 LECTURE NOTES BY: DR. B. C. JOSHI, SAPKM, KICHHA RANGE OF TOLERANCE Plants and animals show a range of tolerance to environmental factors. The factor, which is present in least amount may become limiting. For example water availability limits plant growth in deserts. But, not only “too little” of something is a limiting factor, even “too much” may be the limiting factor. The response of an organism to a range or gradient of an environmental factor The organisms are abundant in the central optimum range. In the zone of stress, only a few organisms survive and in the zone of intolerance, organisms are absent. If the organism has wide range of tolerance, it is usually distributed and if its tolerance range is narrow it is restricted. The gradual adjustment of an organism to slowly changing new environmental condition is called as Acclimatisation. 6 LECTURE NOTES BY: DR. B. C. JOSHI, SAPKM, KICHHA BIOTIC FACTORS & TROPHIC LEVELS • The term 'biotic factors" refers to all living organisms in an ecosystem. • Depending on how the living organisms in an ecosystem obtain, store and utilize release energy, they are categorized into three main trophic levels, (a) producers (b) consumers and (c) decomposers or detritivores. Producers: Life cannot exist without energy. The ultimate source of energy for the functioning of an ecosystem is teh sun. They can starch by the process of photosynthesis utilizing radiant energy, C02 water and minerals. The producers occupy the first trophic level in a food chain. Certain bacteria such as sulphur bacteira obtain energy by breaking down chemical substances. These are described as chemoautotrophs. The producers occupy the first trophic level in an ecosystem are described as chemoautotrophs.The producers occupy the first trophic level in an ecosystem. The plants and their products containing stored energy form the source of energy for the animals, which directly feed on them, (herbivores), the producers occupy the first tropic level in an ecosystem. Consumers: Animals feed on autotrophs or their products either directly or indirectly. They occupy different trophic levels and accordingly ihey are divided into three types. Primary consumers: Feed on producers directly. These are also called herbivores. The primary consumers constitute the second trophic level in an ecosystem. Ex: Protozoans, crustaceans, molluscs etc. On land the primary consumers include animals such as cows, deer, rabbits, grasshoppers, snails etc. In the aquatic environment the herbivores include some protists, crustaceans, molluscs etc. The microscopic free-floating zooplankton constitutes the primary consumers. The primary consumers from the second trophic level in an ecosystem. Secondary consumers: • Feed on the primary consumers. They constitute the third trophic level. Ex.: Frogs, dogs, foxes etc.Wolves of the terrestrial eco-system and fishes of the aquatic ecosystem. • Approximately 50 % of light energy that falls on the plants is absorbed. Of this 1% is converted into chemical energy. Tertiary consumers: Feed on secondary consumers and also on primary consumers, these are also called as 'Climax consumers'. Ex: Hawks, vultures, lions, tigers etc. Decomposers: 7 LECTURE NOTES BY: DR. B. C. JOSHI, SAPKM, KICHHA • When organisms die their bodies and the waste materials passed from the bodies of living organisms form a source of energy and nutrients for other organisms. • Decomposers are also called microconsumers, saprotrophs or osmotrophs etc. Eg: Fungi and bacteria. • Producers and consumers can not survive without decomposers, because decomposers play an important role in an ecosystem by breaking down complex molecules of dead organisms into simple molecules. These are converted into nutrients which are available for the producers to prepare food material. • An Ecosystem has two functional aspects (a) Biogeochemical cycles and (b) Energy flow. • Recycling of the inorganic nutrients is brought about by the decomposers (Bacteria and fungi) which breakdown the compiex molecules of deed organisms and waste materials. The nutrients are utilized by producers to store energy. These activities form the "Biogeochemical cycles". Decomposion of organic matter includes 3 stages i. Particulate detritus formation by saprophytes ii. Conversion of detritus into humus by saprophytes and detrivores iii. Slower mineralization of humus Characaters of a biotic community • The kinds of organisms present in biotic community are called - Species composition. • A few species which are dominant in terms of number and biomass are referred to as Dominant species • The species which greatly influence biotic community relative to their abundance in biomass or number are said to be - Keystone species • Species like Mycorhizal sps absorb nutients from soil and organic residue and are called Link species. • Insects, as they are useful in pollination referred to as- Critical link species. The transition zone between two biotic communities is called - Ecotone • Dominant species are - Pine trees in taiga and grass in grass lands • Keystone species are - Fig trees in tropical forests (as they produce large number of fruits ) • Ecosystem is seriously, influenced by - Removal of either keystone species (or) dominant species Example of ecotone is the zone between forest and grass land. • The increase in the number of organisms and diversity of organisms in ecotone is called Edge effect. • The species in ecotone are called - Edge specie; 8 LECTURE NOTES BY: DR. B. C. JOSHI, SAPKM, KICHHA Interactions • Lemna gibba dominates Spirodela polyrhiza and is called Competetive exclusion. • When in a same medium Competitive exclusion is observed between aquatic aroids called duckweed or Spirodela and Lemna (Acquatic aroids) Lemma gibba excludes Spiro dela polyrhiza • Chemical inhibition of one species by another is called Allelopathy • Different species interacting with one another and live together intimately and is called – Symbiosis • Association between two organisms which and metabolically dependent on each other and both are benefited is called – Mutualism • Association in which one gets benefitted and the other one is unaffected is called Commensalism • Association in which one is living at the expense o the other is called - Parasitism • In commensalism one is harmed and other is Uneffectuated • Interaction in which one organism is killing the other for the food is called – Predation • predation helps for the transfer of energy in a food chain. Population size of the prey is limited by- predation. • Important adaptations in animals to avoid predator are - camouflage, venomous nature, spiniscence mimicry, warning coloration etc. • Two species resembling each other to escape from predators is called - Mimicry • The type of protection in defenceless organism is to mimic. • Mimicking other organism with defence is called - Batesian mimicry. • The process in which the mimics share the same defence mechanism as model is Mullerian mimicry ECOLOGICAL SUCESSION • The process of occurance of gradual, orderly and predictable changes in the composition of communities towards a climax type is called Ecological succession • The succession which begins on an area which is not in habited by any biotic community to establish a climax community is - Primary Succession • The succession that begins in an area from which a community was removed to establish a climax community is called Secondary Succession • An inorgamic environment which get: predominated by autotrophs is called Autotrophic Succession • Polluted areas with more decomposed matter get: dominated by heterotrophs is called Heterotrophic Succession • The first community that is established either in primary or secondary succession is called Pioneer Community • Climax community is established after the Stabilization of environment 9 LECTURE NOTES BY: DR. B. C. JOSHI, SAPKM, KICHHA • Climax community can not be replaced • The ecological succession that starts on barren Rocks or in places where there is 10 extreme deficiency of water is said to be -Xerosere • The ecological succession that starts in the habitat which is rich in water is called Hydrosere • The ecological succession in the habitat which i: moderate in water is called Mesosere • In ecological succession finally - Climax stage, woodland stage is established FOOD CHAINS • The transfer of food-energy from plants to animals and then to other animals by successive stages of feeding is called food chain. • The cyclic interdependence of one trophic level over the others forms a food chain. • In an ecosystem energy is transfered through a series of organisms, each feeding on the preceding organisms and providing raw materials and energy for the next organisms. • Each stage of the food chain is known as trophic level. • The first trophic level is occupied by the autotrophic organisms, so they are called producers. • The organisms of the second trophic level are called primary consumers or herbivores. 20% - 30% of net primary production is consumed by the herbivores. • The organisms of the third trophic level are called secondary consumers or primary carnivores. • The organisms of the fourth trophic level are called tertiary consumers or secondary carnivores. • The final carnivore of a food chain is not eaten by other animals, so it is known as climax carnivore. • The grazing food chains are linear and are usually with 4 to 5 trophic leves in the chain. • The grazing food chain starts from a green plant base, goes to grazing herbivores and onto carnivores, (predator food chain and parasitic food chain). • In predator food chain one animal captures and devours (eats) another animal. • An animal that eats another animal is called a predator. • The animal consumed by the predator is called prey. • A predator that consumes members of its species is known as cannibalistic. • An animal that eats dead animal is referred to as scavenger. • The plants and animals of a grazing food chain are infected by parasites. The parasites derive their energy from their hosts. Thus a parasitic food chain is formed within a grazing food chain. • The detritus food chain starts from dead organic matter and ends in inorganic compounds. LECTURE NOTES BY: DR. B. C. JOSHI, SAPKM, KICHHA • The organic waste materials and the dead bodies of producers, consumers of a 11 grazing food chain form detritus. • The organisms which feed exclusively on the dead bodies of animals and plants and organic waste materials are known as detrivores (algae, fungi, bacteria, insects worms, nematodes, centipedes). • Detritus ecosystem develops on organic debris, living producers may be absent, sunlight is not directly essential. • The cross-linking of many food chains in an ecosystem is called food web. • Stability of the ecosystem is maintained by Food web. • A direct linking between prey and predator without any branching is called Iota link • A branching link in which a predator feeding on more than one type of organisms is Lamda link • A branching link in which one prey organism is predated by more than one predator is Gamma Link • The number, biomass and energy of organisms gradually decrease from producer level to the consumer level. This can be represented in the form of a pyramid called ecological pyramid • Ecological pyramid is the graphic representation of the number, biomass and energy of the successive trophic levels of an ecosystem. • The concepts of ecological pyramid was first described by Charles Elton. Ecological pyramids represent the trophic structure (feeding relationships) and trophic function (efficiency of energy transfer through biotic components) of an ecosystem. • Pyramid of numbers depicts the number of individual organisms at different trophic levels of food chain. • The total weight of living matter per unit area present in the ecosystem is called biomass. • Pyramid of biomass depicts the amount of biomass at different trophic levels of food chain. • Pyramid of energy depicts the amount of energy at different trophic levels of food chain. • Ecological pyramids are always upright, ie. the apex is pointed upwards. • In some ecosystems the number and biomass of producers are less and those of consumers are more. So the apex is directed dowards. This type of pyramid is called inverted pyramid. • Inverted pyramid of numbers is found in parasitic food chain. Inverted pyramid of biomass is occur in pond and lake ecosystems. • The pyramid of energy is always upright (never inverted). Functional aspects of an ecosystem • Energy that enters the ecosystem is- Light energy LECTURE NOTES BY: DR. B. C. JOSHI, SAPKM, KICHHA • Light energy is converted to chemical/potentia energy by the process Photosynthesis 12 • Potential energy is converted to- Kinetic energy • Biological systems get closed if there is no continuous entry of - Solar energy • Regarding the energy flow, the earth is considered as an Open system • Regarding the flow of elements in an ecosystem the earth is considered as Closed system • Cycling of elements occurs endlessly in an ecosystem between -Biotic & abiotic factors • The elements whose non-supply tend to limit biological activity are called nutrients Biogeochemical Cycles: • The pathway by which a chemical element or molecule moves through both biotic and abiotic components of an ecosystem is called -Biogeochemical cycles • All biogeochemical cycles are closed systems. The place where chemicals are held for long period: of time at one place in biogeochemical cycle is called -Reservoir • The place where chemicals are held for short periods are called Exchange pools • Reservoirs & Exchange pools are generally Abiotic & Biotic factors respectively. • The period of time a chemical is held in one place is called its Residence time is called its -Residence time. • Reservoir of gaseous cycles like Nitrogen, Carbon etc is –Atmosphere • Reservoir of sedimentary cycles like sulphur, phosphorus etc are -Sedimentary rocks Nitrogen cycle • The very important element of proteins, DNA & RNA, Nucleic acids is - Nitrogen • Nitrogen is fixed in the form of Nitrates • Nitrogen is fixed in soil by Azatobacter Nitrogen is fixed in the roots of legumes by Rhizobium • In water cyanobacteria act as Nitrogen fixing bacteria • Nitrogen is changed into ammonia by ammonifying bacteria Nitrosomonas (Nitrite bacteria) present in the soil converts Aminonia into nitrite Nitrobactor (Nitrate bacteria) converts Nitrites to nitrates Pseudomonas & Clostridium (denitrifying bacteria) convert Nitrates into nitrogen. Phosphorus Cycle • Atmosphere does not play a role in the movement of phosphorus, because they are present as solids On the earth • Phosphate normally occurs in nature as part of a Phosphate ion • Most of the phosphates are found in –Ocean • Sediments or in rocks Phosphates are carried back to the oceans by weathering of rocks and from soil as runoff Phosphorus occurs in nature as Orthophosphate (P04)3 LECTURE NOTES BY: DR. B. C. JOSHI, SAPKM, KICHHA • Geological process which brings ocean sediment on to land are - Geological up heavals 13 Energy Flow • The study of the laws of energy and its transformation is called- Energetics • The standard international unit of energy is the joule • Energy flow in an ecosystem is -Unidirectional • The weight or quantity of organisms in an area at a given moment is called-Standing crop • The total amount of organic material produced by living organisms of a particular area within a set period of time is called - Productivity • The rate at which biomass is produced by organisms which convert inorganic substrates into complex organic substrates is called -Primary productivity • Organisms like bacteria convert chemical energy to biomass by —Chemosynthesis • The total primary productivity is known as -Gross Primary productivity (GPP) • Energy stoted in plant tissues is considered as Net Primary productivity • Net primary production = Gross primary production- energy utilised for respiration-NPP = GPP - R • The rate at which consumers of an ecosystem convert the chemical energy of their ingested food material into their own body substance (biomass) is called -Secondary productivity • The percentage of production of one trophic leve that is ingested by the next higher trophic level is called Exploitation efficiency • The percentage of energy ingested that is actuall) absorbed across the wall of gut is called Assimilation efficiency • Assimilation efficiency of herbivores is less than that of carnivores due to the presence of relatively indigestible cellulose in their food material Exploitation efficiency food ingested / total food available for ingestion X 100 Assimilation efficiency food digested / total food ingested x 100 • The total plant material ingested by herbivore - the materials lost as faces is called Gross secondary production (GSP) • Energy stored in the tissues of consumers is - Ne secondary production (NSP) • Percentage of energy lost in the transformation of absorbed solar energy to chemical energy by producers is as high as 99% • The efficiency of transfer of energy from one trophic level to the higher trophic level is 10% • The rule that states that only 10% of net energy ii transferred to next higher trohic level in an ecosystem is referred to as -10% rule (Lindermann's trophic efficiency rule) LECTURE NOTES BY: DR. B. C. JOSHI, SAPKM, KICHHA • Percentage of net primary production that i^ converted to net secondary production in herbivore: is called - Trophic efficiency of herbivores. 14