Ecosystems and communities

1. Ecosystems and communities Ms.TRS

2. Organisation of life on Earth • Single specific organism of a species. Eg: Rabbit ( A speciesis a group of similar organisms that can interbreed to produce fertile offspring) • Population: a group of organisms of the same species in a given area at a given time. Eg: A group of rabbits in a grassland • (Habitat: the physical area in which an organism of a certain species can be usually found.) • Community: a group of different populations of different types of organism in a given area at a given time. Eg: The group of rabbits living with the deer, ants and mosquitoes in the grass land. • Ecosystem: Community of organisms and their interaction with the abiotic factors of the environment. Eg: animals and plants in the grass land along with air, water, soil and light . • Biome: A large geographical area with characteristic climate, landforms, plants, and animals. • Biosphere: Total of all areas on Earth where life can be found. It extends into the atmosphere, the bottom of the ocean, and thousands of feet below the Earth’s surface.

3. Autotroph: An organism that synthesises its organic molecules from simple inorganic molecules. Eg. Grass Heterotroph: An organism that obtains its organic molecules from other, simpler organisms. Eg. A wolf, hawk, human, shark etc. Consumer: An organism which ingests other organic matter which is living or recently dead. Eg. A wolf, hawk, human, shark etc. Detrivore: An organism that ingests non-living matter. Eg. Snails, crabs, worms, maggots etc. Saprotroph: An organism which lives on or in non-living organic matter, secreting digestive enzymes into it and absorbing the products of digestion. Example: Mushrooms

4. A food chain shows a simple, linear flow of 'who eats who' and therefore the energy and matter that is transferred through the links.The arrow always points in the direction of the energy flow! Example: carrot plant  carrot fly  fly catcher  sparrow hawk What is a food chain?

5. A food web is a diagram that shows how food chains are linked together into more complex feeding relationships. What is a food web?

6. - They demonstrate much more complex interactions between species within a community or ecosystem.- They demonstrate that there is more than one producer supporting a community.- They show that a single producer is a food source for many consumers.- Demonstrates that a consumer can have many different food sources either on the same or different trophic levels.- Demonstrates that a consumer can be an omnivore, feeding as a primary consumer and as a consumer at higher trophic levels. Food webs are better than food chains

7. The trophic level of an organism defines the feeding relationship of an organism to other organisms in a food.Eg.Producer > Trophic Level 1Primary Consumer > Trophic Level 2Secondary Consumer > Trophic Level 3Tertiary Consumer > Trophic Level 4 Trophic levels

8. - Light is the initial energy source for almost all communities.- This is because to maintain food webs, food chains, community and all their reactions require energy. - This energy is mainly sourced from the sun. - The principle trap of sunlight energy is the protein molecule chlorophyll found in the chloroplasts of producers cells. Sunlight is the initial energy source for almost all communities.

9. Energy flow in a food chain Some energy is transferred from one trophic level to the next. Energy lost between trophic levels include -material not consumed -material not assimilated -heat lost through cell respiration

10. Energy transfers are never 100% efficient • The transfer of energy from one trophic level to the next is inefficient • Approx 10-20 % of the energy on one trophic level will be assimilated at the next higher trophic level • Energy at trophic levels is measured as energy per unit area per unit time (kJ m-2yr-1).

11. Trophic Pyramids or Energy Pyramids Quaternary Consumer 0.1 KJ 10% Hawk Tertiary Consumer 1 KJ Snake 10% Secondary Consumer Frog 10 KJ 10% Primary Consumer 100 KJ Grasshopper 10% Producers Grass 1000 KJ Sunlight: Only 5% is actually harnessed by photosynthesis!

12. Energy flow is one way where as the nutrients passed through the food chains are recycled. New matter is not created.Producers (autotrophs) take inorganic molecules like carbon dioxide, water and nitrates and convert them to organic compounds. Consumers feed at different trophic levels taking in organic matter and using it for their own growth. The activity of decomposers return these materials to the environment.

13. Saprotrophic bacteria and fungi recycle the nutrient (organic molecules) of dead organisms. • Decomposition is a biological process begins with the secretion of extra-cellular digestive enzymes • These enzymes are produced by the saprophytic bacteria and fungi • They secrete the enzymes onto the dead organism • The enzymes hydrolyse the biological molecules of which the dead organism is composed • The hydrolysed molecules are soluble and will then be absorbed by the fungi or the bacteria • Organic molecules are oxidised to release carbon dioxide back to the atmosphere • Organic molecule are oxidised to release nitrogen in form of nitrate, nitrite and ammonium. • The oxidation of these organic compounds produces energy for the saprophyte but returns the various forms of matter to the abiotic environment.