1. ECOSYSTEMS

2. C ONCEPT OF AN ECOSYSTEM Ecology can be defined as the study of relationships between organisms and their environment An ecosystem is a group of plant and animals, along with the physical environment with which it interacts The abiotic and the biotic components of an ecosystem forms an interdependent ecological system An ecosystem can be large or small depending on the number of species present in it

3. S TRUCTURE AND FUNCTION OF AN ECOSYSTEM Ecology examines the life histories, distribution and behaviour of individual species, as well as the structure and function of a natural system in terms of populations, communities, ecosystems and landscapes Examples of ecosystems- rain forests, grasslands, lakes, oceans Within each ecosystems, there is interdependence between species However, ecosystems are controlled by climate

4. Every organism is a chemical factory that captures matter and energy from its environment and transforms them into structures and processes that makes life possible Matter and energy are essential constituents of both universe and living organisms

5. PRODUCERS Plants convert carbon dioxide and water into energy rich compounds by the use of sunlight, a chemical process known as photosynthesis Green plants have additional capacity to synthesis higher organic compounds including sugars, starch, lipids, proteins and vitamins which contains five fundamental elements namely carbon, oxygen, hydrogen, nitrogen and phosphorous

6. CONSUMERS Organisms which are not capable of undergoing photosynthetic process are called consumers, because they get nutrients and energy by ingesting other organisms Herbivores: which feed directly on the plants Carnivores: these are secondary consumers and consume animal feed Omnivores: those living organisms that consumes both plants and animals as food Scavengers: which feed upon dead and decaying plants and animal matter

7. DECOMPOSERS If the world only had producers and consumers, the flow of matter would be only in one direction For returning compounds to elemental forms and for recycling and used again in the food chain, decomposers are required Bacteria and fungi play this role They act on plant and animals and release basic elements into environment

8. E NERGY FLOW IN ECOSYSTEMS Most organisms depend on the sun for the energy needed to create structures and carry out the process required to sustain life Most of the dangerous short wave radiation is filtered out by top layer of the atmosphere The remaining energy provides the two critical factors essential for life, heat and light The solar energy drives photosynthesis in green plants Photosynthesis converts radiant energy into useful chemical energy The energy captured by photosynthesis supports all life on earth

9. The chemical energy stored in plants is subsequently transferred to consumers through food chain and food web by eating and being eaten process The behaviour of energy in an ecosystem can be termed as energy flow The flow of energy is always unidirectional

11. F OOD CHAIN Transfer of food energy from the source in plants through series of organisms that consumes and are consumed is called food chain In each transfer some energy is lost Shorter the food chain, greater the energy available to that population Food chains are of two basic types The grazing food chain: which starts from a green plant base, goes to grazing herbivore and on carnivore The detritus food chain: which goes from non-living organic matter into microorganism and then to detritus feeding organisms and their predators

12. F OOD WEB Individual food chains interconnect to form a food web For example, the food web of a tropic forest is highly complex and includes tens of thousands of species

13. E COLOGICAL PYRAMIDS Most ecosystems have a huge number of primary producers supporting a smaller number of herbivores, which in turn supports an even smaller number of secondary consumers

14. E COLOGICAL SUCCESSION Biological community have a history in a landscape The process by which organisms occupy a site and gradually change environmental conditions by creating soil, shade, shelter or increasing humidity is called ecological succession or development Can be classified as primary succession secondary succession

15. P RIMARY SUCCESSION This occurs when a community begins to develop on a site previously unoccupied by living organisms such as island, sand, body of water In primary succession, the following is observed The new site is first colonised by a few hardy pioneer species, often microbes, lichens that can withstand conditions and lack of resources Their body creates patches of organic matter Debris accumulates in packets, providing soil in which seeds become lodged and grow

16. S ECONDARY SUCCESSION Secondary succession occurs when an existing community is disrupted and a new one subsequently develops at that site. The disruption may be caused by natural forces or by human activity such as deforestation Organism modify environment in ways that allows one species to replace another

17. BIOMES The earth has many different combinations of environmental conditions that support the amazing range of organisms around us which results in biodiversity These can be classified into few broad groups 1.Forest ecosystems 2.Grasslands 3.Deserts 4.Aquatic ecosystems

18. F OREST ECOSYSTEMS Plants have been dominating the earth for about 3 billion years They have unique art of manufacturing their own food by photosynthesis from nature and rest of the world depends on them for food and sustenance Plants constitute 99% of the earth’s living species If this ratio(99:1) is distributed by deforestation, then natural balance will be lost and entire living world will suffer the most Forests are renewable resource and have a key role in improving the quality of environment Forests also contribute much to the economic development of the country by providing goods and services to people and industry They are treasure house of valuable plants and animal genes and medicinal plants

19. Some forest types are Coniferous forests Deciduous and evergreen forests Tropical moist forests

20. C ONIFEROUS FORESTS These consists of cone bearing trees Thin needle like leaves have smaller surface area and thick waxy coating that help trees minimise moisture loss These occurs where moisture is limited by sandy soil, low precipitation These can survive harsh winters or extended droughts Among the dominant conifers are pine, hemlock, spruce, cedar and fir

21. D ECIDUOUS AND EVERGREEN FORESTS Forests of broad leaved trees occur throughout the world where rainfall is plentiful When water is scarce, they shed their leaves to conserve water Temperate deciduous forests contain rich and varied association of oak, birch, elm trees If the climate is warm year round, forests are dominated by broad leaf evergreen trees These forests provide good habitat for tigers, bears and other endangered species

22. T ROPICAL MOIST FORESTS The humid tropical regions of South and Central America, Africa, southeast Asia and some of the pacific islands support one of the most complex and biologically rich biome type in the world Occur when rainfall is abundant and temperatures are warm to hot year round It has been estimated that around one half to two thirds of all species of terrestrial plants and insects live in tropical forests

23. GRASSLANDS

24. D ESERTS Deserts are dry with precipitation that is both infrequent and unpredictable from year to year Deserts with less than 2.5 cm of measurable precipitation supports almost no vegetation Many desert animal avoid drying sun by feeding at night and most acquire water from seeds and vegetation they eat Some of the deserts are located in southwest of America, north and south Africa, small part of China, India France etc.

25. A QUATIC ECOSYSTEMS Approximately 71% of earth’s surface is covered by ocean Only 2.7% of the total water is fresh water Out of this only 1% water on earth is usable These are mainly classified into 1.Freshwater ecosystem 2.Marine ecosystem

26. F RESHWATER ECOSYSTEM They include Ponds Lakes Rivers Streams Freshwater ecosystems are influenced by local climate, soil and surrounding terrestrial ecosystems

27. WETLANDS Wetlands are ecosystems in which land surface is saturated or covered with standing water at least part of the year There are many kinds of wetlands and they can be classified as Swamps Marshes Bogs and fens Swamps are wetlands with trees, marshes are wetlands without trees, and bogs and fens are waterlogged area saturated by ground water or rainwater

28. U SES OF WETLANDS Wetlands are valued as major breeding, nesting ground for migratory birds Wetlands also provide unique ecological service in storing and purifying water Wetlands also improve water quality by acting as natural water purification system by absorbing nutrients and toxins They prevent salt water intrusion flow of ground water Coastal wetlands helps in stabilize shore lines and reduce storm damage

29. C OASTAL MARINE ECOSYSTEMS Include rocky coasts, sandy beaches, offshore barrier islands They are generally rich in life forms Offshore erosion due to human activity, destructive fishing practices, offshore drilling or mining are some of the problem faced by these ecosystems