Ecology is a study about interaction between organisms and their environment

Introduction to ecology lesson consists of several ecological theories and principles

1. 3/27/2024 1 PRINCIPLES OF ECOLOGY

2. 3/27/2024 2 PRINCIPLES OF ECOLOGY

3. INTRODUCTION TO ECOLOGY UNIT ONE 3 3/27/2024

4. Definition of Ecology What is ecology? Ecology is the scientific study of the distribution and abundance of organisms and how these properties are affected by interactions between the organisms and their living and non-living environments. Ecology is a branch of biology that studies living organisms. Organisms can be studied at many different levels i.e. Biosphere, Biome, Ecosystem, Community, Population and species level. Living things depend upon each other and on the non-living components of the environment for their reproduction, growth, survival, etc. 4 3/27/2024

5. Con’t…. Ecology is the study of the relationship of living organisms among themselves and with the non-living components of the environment. Ecology deals with the biology of organisms, populations, communities, ecosystems, etc. and their functional processes in their natural environment. Hilaire (1859) proposed the term Ethology: …..for the study of the relation of the organisms with in the family and society in the aggregate and in the community Mivart (1894)-Hexicology: the study of the relations which exist between the organisms and their environment Ecology is the Greek word, Oikos, which means house. It is the study of the households of the planet earth. 5 3/27/2024

6. Con’t… Who coined the term ecology first? Ernst Haeckel (1866)….. the knowledge of the sum of the relation of organism to the surrounding outer world. Different authors defined ecology in different ways. Odum , ecology is the study of structure and function of Nature or the study of ecosystems. Krebs , Ecology is the scientific study of interactions which determine distribution and abundance of organisms. 6 3/27/2024

7. Con’t…. Charles Elton of England defined ecology as the study of scientific natural history. Andrewarths of Australia defined it as the study concerned with the distribution of organisms. Clematis (1905) defined ecology as a science of community. Begon, Harper & Townsend (1986) jointly defined ecology as the description, explanation and prediction of individuals, populations, and communities in space and time. Ecology deals with organisms, populations, communities, ecosystems and the biosphere. 7 3/27/2024

8. Terminology of ecology Biosphere: The zone of air, land and water at the surface of the earth that is occupied by organisms. Environment: The combination of all the external conditions and the potential effect of the inner environment ( heteromosaic of abiotic conditions). Biome: Large, ecological unit composed of similar types of climax communities on a global scale, arising as a result of complex interactions of climate, other physical factors, and biotic factors (e.g., rainforest, tundra, grassland....) Ecosystem: All of the organisms of a given area and the encompassing physical environment. Community: The species that occur together in space and time 8 3/27/2024

9. Con’t… Population: Any group of individuals, usually of a single species, occupying a given area at the same time; groups of organisms with homologue (same) alleles. Organism (individual): Any individual living creature, either unicellular or multicellular Habitat: The environment of an organism; the place where it is usually found. Niche: The role played by (occupation or profession) and the address of a particular species in its ecosystem Competition: Interaction between members of the same population or of two or more populations to obtain a resource that both require and which is available in limited supply. 9 3/27/2024

10. Con’t… Food chain: A sequence of organisms through which energy captured from sunlight by photosynthesis is transferred from one consumer (or trophic level) to the next; each organism in the chain eats the preceding and is eaten by the following member of the sequence; there are seldom more than six links in a chain, with autotrophs at the bottom and the largest carnivores at the top. Food web: Representation of feeding relationships in a community that includes all the links revealed by dietary analysis; it depends upon the number of species involved and their connectiveness , i.e. number of connections Biotic: Living; usually applied to the biological aspects of an organism’s environment, i.e. the influence of other organisms (opposite of abiotic). 10 3/27/2024

11. Main sub division of Ecology Ecological studies may be conducted at different levels of organism, habitat or taxonomic affinities. 1. Division based on taxonomic affinities Plant ecology Animal ecology 2. Division based on habitat Aquatic Terrestrial 3. Division based on level of organization Autecology Synecology 11 3/27/2024

12. Con’t… Autecology: A study of the individual species in relation to their environments. It includes the study of its geographical distribution, taxonomic position, morphological characters, reproduction, life cycle and behavior with reference to ecological factors that might influences these activities. Synecology: A study of the groups of organisms in relation to their environments It comprises population ecology, community ecology, and the study of the ecosystems. 12 3/27/2024

13. Con’t… Depending up on the condition exist Synecology may deals the following Population ecology: it deals with the growth, size and regulation of the population. Studies in terms of size, growth…… Community ecology: it deals with the ecology of different populations in the same habitat and same environmental conditions. Studies in terms of why is this community of a particular diverse, why does a particular community occurs at a given location and how community interact and change through time? Ecosystem ecology: biological productivity of an ecosystem or nature and how it can best serve the mankind encompasses ecosystem ecology. Studies in terms of how much and what rates are energy and nutrients being stored and transferred between components of the environment. 13 3/27/2024

14. Con’t… The principle of ecology is applied to solve many environmental problems. The terms like palaeoecology, conservation ecology, resource ecology, pollution ecology, chemical ecology etc. are recently emerged branches of ecology. Conservation ecology : - deals with the application of ecological principles to the proper management of resources leading to sustainable yield of resources for human welfare. It also studies how to reduce the risk of species extinction. Resources ecology : - deals with renewable and non renewable resources and their management. Pollution ecology : - studies problems associated with the movement of pollutants in the environment. 14 3/27/2024

15. Con’t… Chemical ecology: it is concerned with the chemical affinity or preferences shown by different organisms Taxonomic ecology: it is concerned with the ecology of different taxonomic group, viz. microbial ecology, mammalian ecology, insect ecology and so on Habitat ecology: it includes the study of animal and plants in different habitat. According to habitat it can be further divided into aquatic and terrestrial habitat Human ecology: it deals with the effects of human activities on environment and vise versa Applied ecology: it deals with the application of ecological concept to human needs including wild life management, biological control, forestry and conservation of natural resources 15 3/27/2024

16. Con’t… Physiological ecology (Eco-physiology): physiological adaptation according to ecological conditions Palaeo-ecology: it deals with the environmental condition and life of the past ages. Evolutionary ecology: it deals with the evolutionary problems like speciation and segregation Genecology (ecological genetics): relation of environment with genetic variability Eco-geography: it studies the geographical distribution of plants and animals in different environments 16 3/27/2024

17. Con’t… Pedology: it deals with the study of soil and refers to its nature like acidity, alkality, humus contents, mineral contents, soil types Ethology: it is the study of animal behavior in different environments under their natural conditions Sociology: when ecology and Ethology are combined it be comes sociology System ecology: when the structure and function of an ecosystem is analyzed using applied mathematics, statistics or computer. 17 3/27/2024

18. Con’t… SCOPE OF ECOLOGY (COVERAGE) Ecology has a wide scope of coverage and is significant in many fields such as range, forest and managements; agriculture – livestock raising; fish culture; conservation of land and its products (minerals, soil, vegetation, water); space ecology; problems of increasing population; pollution; urbanization; town planning; disaster mitigation. 18 3/27/2024

19. ENVIRONMENTAL FACTORS UNIT TWO 19 3/27/2024

20. Introduction Living organisms interact with their biotic and abiotic environments. These living and non-living components of the environment having direct or indirect influence on the organisms are said to be environmental factors . It includes the interaction between organisms and organisms , organisms and non-living components . The environmental factors such as temperature, light, water, gasses, soil, altitude, etc. are the abiotic factors . The interaction between living things is referred to as biotic factors . 20 3/27/2024

21. Abiotic Factors (Physical Factors) Abiotic factors are the non-living components, aspects or factors of the ecosystem . They could be nutrients, minerals, gases, rocks, soils, temperature, weather etc. These environmental factors control the geographical distribution and abundance of biological organisms on earth . Living things need certain abiotic factors in order to live such as oxygen, water, shelter. Abiotic factors can be broken down into physical resources and physical factors 21 3/27/2024

22. Con’t… Plants need sunlight, water, carbon dioxide, nutrients and soil as physical resources. Animals need physical resources such as oxygen, water and nutrients . If plants and animals do not get these physical resources they die . They are absolute factors. Physical factors are those abiotic factors which limit the quality of life of an organism. Abiotic factors like pH of water, degree of salinity and temperature etc. are said to be physical factors. These are said to be limiting factors when they determine the presence or absence of a species in an environment . 22 3/27/2024

23. Con’t… Two scientists, Justus von Liebig and Victor Shelfold developed the Law of the minimum in 1840 and the Law of tolerance in 1913, respectively. Law of the minimum states that even if the organism gets several abiotic factors, only one of these factors limits the optimization of the organism’s growth . This factor is said to be the limiting factor . The law of tolerance developed by Shelford states that the amount of the physical factors that the organism requires has upper and lower tolerance limits (see Fig 2.1). The most obvious example is temperature . No organism can live below zero , and no organism can live above 100 oc (extreme examples). 23 3/27/2024

24. Con’t… Fig 2.1:- Tolerance limits 24 3/27/2024

25. 1. Climatic factors a. Temperature Temperature exerts a profound influence on the physiological activities of organisms. There are maximum and minimum temperature limits which the organism can tolerate. Temperature affects animal performance, microbial activities and photosynthesis in plants. Temperature extremes affect the activity of enzymes . Photosynthesis is one of the most fundamental characteristics of plants i.e. conversion of light energy into chemical energy of organic molecules . 25 3/27/2024

26. Con't… Photosynthesis is the basis for the life of plants (their growth, reproduction) and it is also the ultimate source of energy for most heterotrophic organisms . Extreme temperatures generally reduce the rate of photosynthesis by plants (Link) Two different organisms perform photosynthesis actively at different temperatures . Fig 2.2:- Pleurozium schreberi and a desert shrub, Atriplex lentiformis This shows that two different plants have different optimal temperature for their effective photosynthesis. 26 3/27/2024

27. Con’t… This range of temperatures is therefore; called the biokinetic zone. Based on temperature tolerance, animals are classified as eurythermal (wide temperature tolerance) or stenothermal (narrow temperature tolerance). The distribution of plants and animals is greatly influenced by extremes in temperature. The following are examples of temperature effects with ecosystems: The opening of the flowers of various plants during the day and night is often due to temperature difference between the day and night; The seed of some plants (biennials) normally germinate in the spring or summer; this phenomenon is well observed in carrots and is called vernalization ; 27 3/27/2024

28. Con’t… Some fruit trees such as the peach require a cold period each year so that it can blossom in the spring; Deciduous trees lose their leaves in winter and enter into a state of dormancy, where the buds are covered for protection against the cold; The seeds of many plants , e.g. peach and plum, must be exposed to a cold period before they germinate ; this chilling ensures that seeds don't germinate during autumn, but after winter, when the seedlings have better chances to survive; In animals, a distinction is made between ectothermic ("cold-blooded" or poikilothermic) animals and endothermic ("warm-blooded" or homothermic ) animals although the difference is not clear cut; In desert conditions are a greater temperature variation between day and night and organisms have distinct periods of activity , for e.g. many cacti flower at night and are pollinated by nocturnal insects; 28 3/27/2024

29. Con’t… b. Sunlight Light is another abiotic environment that affects living things directly or indirectly . It is the ultimate source of energy for the biological world. Without sunlight all life on earth excluding some microorganisms which are chemosynthetic , die out . Light induce greater elongation and development of plant tissue. Duration of light exposure also affects plant growth. The photoperiod which is the difference in the relative duration of day light and darkness , influences stem elongation , flowering, fruit growth and other physiological processes in plants and animals. 29 3/27/2024

30. Con’t… Depending up on the day length required for the induction of flowering plants are divided into three groups . 1. Short day plants :-These plants flower if the light exposure is for less than a critical duration of about 14 hours and the dark period continuous. Examples are Nicotiana, Chrysanthemum and Xanthium. 2. Long day plants :-These plants flower if they experience nights which are shorter than a certain critical length. Spinach, wheat, barley, clover and radish are examples of long day plants. 3. Day-neutral plants :-These are not sensitive to day-length and bloom regardless of the photoperiod. 30 3/27/2024

31. Con’t… Intense light promote a high rate of transpiration and may cause dehydration of protoplasm. The length of light period also affects the structure of vegetative organs, growth, germination, pigmentation, nutrition requirement and even susceptibility to parasites. Light period also affects animals . breed during the winter whereas others are summer breeders developmental process in many fish and in silk worms locomotion in some aquatic organisms 31 3/27/2024

32. Con’t… The intensity and quality of light determine the distribution of photosynthetic organisms in the aquatic environment . Light quality, intensity and the length of the light period are very important factors in the normal functioning of an ecosystem . Quality of light The light coming from the sun is a mixture of different colors or colors of different wave lengths. Of these colors plants absorb blue and red portion of the light for photosynthesis. In aquatic ecosystem the quality of light is one of the limiting factors for photosynthesis. 32 3/27/2024

33. Con’t… Light intensity The intensity of light that reaches the earth surface varies according to the latitude and season of the year. The source of light also affects the growth and movement of organisms in a given ecosystem. The followings are the responses of plants to light source. Phototropism Phototropism is the directional growth of plants in response to light where the direction of the stimulus determines the direction of growth ; stems demonstrate positive phototropism i.e. they grow towards the light source while roots are negative phototropic (grows away from the direction of light source. 33 3/27/2024

34. Con’t… Phototaxis Phototaxis is the movement of the whole organism in response to a unilateral light source, where the stimulus determines the direction of movement. Photokinesis Variation in intensity of locomotory activity of animals which is dependent on the intensity of light stimulation , and not the direction, is called photokinesis. Photonasty Photonasty is the movement of parts of a plant in response to a light source , but the direction of the stimulus does not determine the direction of the movement of the plant. 34 3/27/2024

35. Con’t… c. Water Plants and animals are distributed from the entirely aquatic environments to the dry deserts. Animals in aquatic environment have the problem of regulating the water balance of their body while terrestrial animals face the problem of desiccation . Plants can be classified into 3 groups based on their water requirements. Hydrophytes are those plants which grow in water and water logged areas Mesophytes grow in areas with moderate water requirements . Xerophytes are plant which grows in deserts or dry areas where the water source is a serious problem. 35 3/27/2024

36. Con’t… Water requirements of animals Water scarcity also affects terrestrial animals and the animals are exposed to desiccation. To cope up with the water shortage the animals developed just a few interesting adaptations The body covering of organisms limits water loss E.g. Chitinous body covering of insects, the scales of reptiles, the feathers of birds and the hair of mammals Some mammals have few or no sweat glands and use other cooling devices . E.g. a camel able to absorb water in the form of water vapor directly from the atmosphere . E.g. the dew from the coastal fog is an important source of moisture for insects of the Namib. 36 3/27/2024

37. Con’t… d. Gases Oxygen, carbon dioxide and nitrogen are the most important gases used by plants and animals. All aerobic organisms use oxygen during respiration to liberate energy from food. Carbon dioxide is used by green plants during photosynthesis in which plants make their own food. Plants get nitrogen through the action of certain bacteria, algae and the action of lighting. e. Wind Winds carry water vapor which may condense and fall in the form of rain and snow. 37 3/27/2024

38. Con’t… It also play role in flower pollination and seed dispersal of some plants. Wind can also cause erosion of soil which removes and redistribute top soil from degraded areas. It can also amplify the effects of temperature by increasing heat loss by evaporation and convection. It also increases the evaporation rate of animals and transpiration rate of plants resulting in more rapid water loss. 38 3/27/2024

39. Con’t… 2. Soil (edaphic factors) These factors include soil texture, aeration, soil temperature, soil water, soil solution and pH , together with soil organisms and decaying matter Fig 2. 3:- Soil characteristics 39 3/27/2024

40. Con’t… Soil texture The size of soil particles varies from microscopic particles called clay to larger particles called sand. Loam soil is a mixture of sand and clay particles. Sandy soils are suitable for growing plants because they are well aerated, excess water drains away quickly, they warm up quickly during the day and is easy to cultivate . Sandy soils do not retain much water and soon dry out and contain few soil nutrients required for plant growth. Clay soils hold large amount of water and are rich in mineral nutrients . They are unsuitable in that they are badly aerated, soon become waterlogged and is difficult to cultivate ; it is also cold during winter. Loam soils possess desirable properties of both sand and clay - it has a high water retaining capacity, good aeration, and good nutrient content and is easily cultivated . 40 3/27/2024

41. Con’t… Soil air Soil air is found in those spaces between the soil particles that are not filled with soil water. The amount of air in soil depends on how firmly the soil is compacted . In well-aerated soil at least 20% of its volume is made up of air. Soil temperature Soil temperature is an important ecological factor. It has been found that the temperature of soil below a depth of about 30cm is almost constant during the day but seasonal temperature differences do occur . At low temperature, there is little decay by decay-causing microorganisms. 41 3/27/2024

42. Con’t… Soil water Soil water can be classified into three types Hygroscopic water occurs as a thin film of water around each soil particle . Capillary water is that water held in the small spaces between the soil particles . Gravitational water is the water which drains downwards through the soil . Soil solution Soil solution is the decaying remains of plants and animals , together with animal excretory products and faeces , form humus. This increases the fertility of the soil . 42 3/27/2024

43. Con’t… pH Acidity or alkalinity of soil (the pH of the soil) influences the biological activity in soil and the availability of certain minerals . Thus the pH of soil has a greater influence on the growth and development of plants. Some plants e.g. Azaleas, Ericas, ferns and many protea species grow best in acid soils ( soils with a pH below 7), while lucerne and many xerophytes grow better in alkaline soils (soils with a pH above 7). 43 3/27/2024

44. Con’t… 3. Physiographic factors (topographic factors) The physiographic factors include factors such as altitude, slope of land and the position of the area in relation to the sun or rain-bearing winds . This affects the distribution of organisms . Altitude affects the distribution of vegetation through its effect on temperature, rainfall, and insulation. The rise in altitude reduces the absorption of solar radiation. The air temperature also drops as the altitude increases and this is true in soil temperature too. The fall in temperature of soil affects the activity of plant roots and reduces the absorption of water and mineral from the soil. Wind is also strong at higher altitude . 44 3/27/2024

45. Con’t… 4. Periodic disturbances Catastrophic disturbances such as fire, hurricanes, typhoons , and volcanic eruptions can devastate biological communities. The area is re-colonized by organisms or repopulated by the survivors , but the structure of the community undergoes succession of changes . 45 3/27/2024

46. Biotic Factors (Biological factors) An ecosystem is a community of organisms that interact with each other and with the abiotic and biotic factors in their environment . Biotic means living and biotic factors are the other, living parts of the ecosystem with which an organism must interact. The biotic factors with which an organism interacts depend on whether it is a producer, a consumer, or a decomposer . Producers are also known as autotrophs or self-feeders . Producers manufacture the organic compounds that they use as sources of energy and nutrients. Most producers are green plants or algae that make organic compounds through photosynthesis. 46 3/27/2024

47. Con’t… A few producers, including specialized bacteria , can extract inorganic compounds from the environment and convert them to organic nutrients in the absence of sunlight. This process is called chemosynthesis. Only producers can make their own food. They also provide food for the consumers and decomposers . The producers are the source of the energy that drives the entire ecosystem. Organisms that get their energy by feeding on other organisms are called heterotrophs, or other-feeders. Some consumers feed on living plants and animals . Others get their energy from dead plant and animal matter , called detritus. 47 3/27/2024

48. Con’t… The detrivores are further divided into detritus feeders and decomposers. The detritus feeders consume dead organisms and organic wastes directly . Decomposers break the complex organic compounds into simpler molecules , harvesting the energy in the process. The survival of any individual organism in an ecosystem depends on how matter and energy flow through the system and through the body of the organism . The other organisms (biotic factors) can include predators, parasites, prey, symbionts, or competitors. 48 3/27/2024

49. Con't…. A predator regards the organism as a source of energy and matter to be recycled . A parasite is a type of consumer organism . As a consumer, it does not make its own food . It gets its food ( energy and matter to be recycled ) from its host . The organism's prey is a source of energy and matter . A symbiont is a factor that does not provide energy to the organism , but some how aids the organism in obtaining energy or matter from the ecosystem . Finally, a competitor reduces the organism's ability to harvest energy or matter to be recycled . The distribution and abundance of an organism will be affected by its interrelationships with the biotic environment. 49 3/27/2024

50. Con’t… Humans are omnivores, consuming both producers and other consumers . Humans can also adjust the length of the food chain as needed . E.g. humans who must deal with shortages of food resources usually alter their eating habits to be closer to the energy source. Humans are also biotic factors in ecosystems. Other organisms are affected by human actions. 50 3/27/2024

51. Con’t… Periodicity Means day and night changes . At dawn the dominance of dark over light fails and animals like birds, beetles, bees, butterflies etc become active. At dusk the opposite happens and the dark takes its dominance over the light and organisms like water lilies fold their flowers, animals which are active at night appear. Moths, Foxes, owls etc. take over the niche occupied by the day time active organisms. The change of seasons also brings conspicuous changes in the activities of animals and plants. E.g. During the season of spring , migratory birds start to migrate and the reproductive cycles of many animals and plants are initiated . 51 3/27/2024

52. Con’t… Continuous vs. seasonal reproduction Environmental factors affect reproduction in animals and plants . Plants do not produce flowers during the dry season and they need the coming of rain . Ephemerals are short lived desert plants which germinate, grow and flower within a short period of time after short rains. Light is another important environmental condition affecting reproduction in plants . Based on the light requirement plants are grouped into three -long day plants, short day plants and day neutral plants. The plants bloom based on the length of light period they need. Short day plants produce flowers when the length of time period is shorter than certain critical time while the long day plants need the light period longer than certain critical time. 52 3/27/2024

53. Con’t… Both short day and long day plants produce flowers based on seasons . Long day plants flower in the season they get light for longer period and the short day plants bloom in the season they get shorter light period . Thus, their reproduction is seasonal. The day neutral plants produce flowers regardless of the length of the light period . This shows that day neutral plants are not affected by seasons of short or long light period . Seasonal reproduction is also observed in animals . Light is one of the environmental factors that trigger seasonal reproduction in animals. E.g. if you take ewes in the northern hemisphere they start cycling in late summer and continue sexual behavior through mid winter . During the spring and summer , under the influence of increasing day length , most ewes undergo a period of low to non-existent ovulatory and estrous activity known as seasonal anestrus. 53 3/27/2024

54. Con’t… Circadian rhythms The term circadian was derived from the Latin word circa which means about and dies meaning day. Circadian rhythm refers to the rhythmic activities of 24 hours. The period of the circadian rhythm, the number of hours from the beginning of activity on one day to the beginning of activity on the next is referred to as free-running. Many plants and animals are influenced by two periodicities. One is the internal circadian rhythm of approximately 24 hours and the second is the external environmental rhythms , usually precisely 24 hours. Light and temperature are the most important time setter to adjust the internal and the environmental rhythms. 54 3/27/2024

55. Plant Nutrients Sixteen chemical elements  are known to be important to a plant's growth and survival. The sixteen chemical elements are divided into two main groups:  non-mineral  and  mineral .   1. Non-Mineral Nutrients The Non-Mineral Nutrients   are  hydrogen (H), oxygen (O),  &  carbon (C ). These nutrients are found in the air and water.  2. Mineral Nutrients The  13 mineral nutrients , which come from the soil, are dissolved in water and absorbed through a plant's roots. There are not always enough of these nutrients in the soil for a plant to grow healthy. This is why many farmers and gardeners use fertilizers to add the nutrients to the soil.  55 3/27/2024

56. Con’t… The mineral nutrients are divided into two groups: macronutrients and  m icronutrients . Macronutrients    Macronutrients can be broken into two more groups:   primary and     secondary nutrients .  T he   primary nutrients  are  nitrogen (N) ,  phosphorus (P) , and potassium  (K) . These major nutrients usually are lacking from the soil first because plants use large amounts for their growth and survival.  The s econdary nutrients  are  calcium (Ca) ,  magnesium (Mg) , and sulfur  (S) . There are usually enough of these nutrients in the soil so fertilization is not always needed. 56 3/27/2024

57. Con’t… Micronutrients   Micronutrients  are those elements essential for plant growth which are needed in only very small (micro) quantities . These elements are sometimes called minor elements or trace elements. The micronutrients are boron(B), copper (Cu), iron (Fe), chloride ( Cl ), manganese  (Mn), molybdenum (Mo)  and  zinc (Zn) . Recycling organic matter such as grass clippings and tree leaves is an excellent way of providing micronutrients (as well as macronutrients) to growing plants. 57 3/27/2024

58. Con’t… I. Arnon and R. Stout (1939) used the following three criteria to determine essentiality of minerals The plant will not complete its life cycle in the absence of that particular element The element should not be replaceable The element should play direct role in the metabolism of the plant. Mineral elements are utilized by the plants in four basic ways The elements may form part of structural unit. E.g. C in cellulose or N in protein Elements may be incorporated in to organic molecules in metabolism. E.g. Mg in chlorophyll molecules or P in ATP Elements may function as enzymatic activators i.e. act as catalyst Elements in ionic form help to maintain osmotic balance. E.g. K in guard cells 58 3/27/2024

59. Con’t… Seasonal availability of Nutrients and food for plants and Animals Seasonal changes affect the availability of food both in the aquatic and terrestrial ecosystems. For the herbivores (grazers and browsers) in the terrestrial habitat food availability is high during the rainy seasons. Dry seasons are the period when the terrestrial animals suffer from the scarcity of food and water. In pelagic herbivores , the growth of plant material and grazing by zooplankton are closely related events in space. With benthic filter feeders , however, the quantity of food seasonally available must depend on the amount reaching the bottom through the water column 59 3/27/2024

60. Con’t… The available nutrients for organisms , especially microbes, fungi and plants plays a key role in determining the types of organisms and their abundance as well as the success of communities depending on these organisms. Seasonal fluctuations of materials determine the availability of nutrients . When one compares the nutrient inputs into the aquatic habitat during the dry season and the rainy season , it is obvious that the input will be high during the rainy season . The underlying reason is that during the rainy season the nutrients are washed by the surface runoff from the surrounding agricultural lands in to the water bodies . Industrial and municipal wastes are also the source of nutrients such as organic carbon, inorganic nitrogen and phosphate input into the water bodies. This can lead to Eutrophication (depletion of oxygen in water) and alteration of aquatic species distribution and diversity. 60 3/27/2024

61. Con’t… The availability of nutrients in soil may vary both in time and space. Among the bacterial activities that have significant implications for ecosystem health and stability, the nitrogen cycle is recognized as being of fundamental importance. Environmental conditions, such as temperature and nutrients , vary considerably with season. 61 3/27/2024

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