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Topic 5: Ecology & Evolution Miss Friedman

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1 Topic 5: Ecology & Evolution Miss Friedman
5.1: Communities Topic 5: Ecology & Evolution Miss Friedman

2 5.1.1: Definitions Ecology The study of the relationship between living organisms and between those organisms and their environment Ecosystem A community and its abiotic environment Population A group of organisms of the same species who live in the same area at the same time

3 5.1.1: Definitions Community
Populations of different species in the same area which are interacting Species A group of organisms which can interbreed and produce fertile offspring Habitat Location within which a species normally lives

4 5.1.2: Autotrophs & heterotrophs
Producer An organism that synthesises its organic molecules from simple inorganic molecules Heterotroph consumer Obtains organic molecules from other organisms

5 5.1.3: Consumers, detritivores, saprophytes
An organism that ingests other organic matter that is living or recently dead Detritivores An organism that ingests non-living organic matter Saprophytes An organism that lives on or in non-living organic matter, secreting digestive enzymes into and absorbing the products of digestion

6 5.1.4: Food chains Food chains show a simple linear flow of “who eats who” Therefore shows the energy flowing through the links in the chain Questions to consider! How is energy lost in the chain? Why are big, dangerous predators so rare?


8 5.1.5: Food webs A diagram that shows how food chains are linked together into more complex feeding relationships Advantages over food chain Shows much more complex interactions between species within a community/ecosystem More than one producer supports a community A single producer is a food source for many primary consumers A consumer might have a number of different food sources on the same/different trophic levels A consumer can be an omnivore, feeding as a primary consumer but also as a consumer at higher tropic levels


10 5.1.6: Trophic level The tropic level of an organism defines the feeding relationship of that organism to other organisms in a food web Autotraph Producer Tropic level 1 Hetertroph Primary consumer Tropic level 2 Secondary consumer Trophic level 3 heterotroph Tertiary consumer Trophic level 4

11 5.1.7: Determining tropic levels in food chains/webs
Assign tropic levels to the food web on the right!

12 5.1.8: Constructing a food web
Producers are usually shown at the bottom Use full name of organisms Arrows show the movement of matter & energy

13 5.1.9:Light & food chains Sunlight is the source of energy for most communities, both aquatic and terrestrial Very few communities deep in the ocean use geothermal energy

14 5.1.10: Energy flow in Food chain
a) Not all solar energy will come into contact with chlorophyll and will therefore not be trapped in the synthesis of organic compounds b) Photosynthesis c) Consumers feeding and passing on energy in the food d) Loss of energy as heat from respiration e) death and the consumption of dead organisms by detritivores. Or as food not assimilated because of incomplete digestion. Energy Loss loss of energy in undigested food which will then be used by saprophytes/ decomposers loss of heat energy in the reactions of respiration ultimately all energy will be lost has heat

15 5.1.11: Efficiency of energy transformations
When energy is changed from one form into another, it is never 100% efficient Approximately only 10-20% of the energy on one trophic level will be assimilated at the next higher trophic level

16 5.1.12: Shape of energy pyramids
A pyramid of energy is a graphical representation of the amount of energy of each trophic level in a food chain The units are kJ/m2/yr The narrowing shape illustrates the gradual loss of energy processing along the links of a food chain to higher trophic levels

17 5.1.13: Energy and matter in ecosystems
Energy is NOT recycled through the ecosystem Energy is constantly received from the sun and constantly radiates out in the form of light & heat Matter IS recycled The process of recycling nutrients requires energy

18 5.1.14: Decomposers Two main groups are detritivores (e.g. earthworms, dung beetles) and saprotrophs (e.g. fungi, bacteria) Decomposition is a complex process and serves many functions; formation of soil, recycling of nutrients, reduction of high energy carbon compounds Organic molecules are oxidized to release nitrogen in the form of nitrate, nitrite, and ammonia Oxidation of organic compounds provides energy for saprophyte but returns matter to abiotic environment

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