Topic 5.1

1. Topic 5.1 Communities and populations

2. 5.1.1- Definitions – Ecology • Ecology- the study of the relationship between living organisms and those organisms and their environment.

3. Definitions

4. 5.1.2- autotrophs and heterotrophs • An autotroph is an organism that synthesizes its organic molecules from simple in organic molecules. • A heterotroph is an organism that obtains organic molecules from other organisms.

5. 5.1.3 - Consumers, Detritivores and Saprotrophs • Saprotrophs • An organism that lives on or in non-living organic matter secreting secreting digestive enzymes into and absorbing the p products of digestion. • Detritivores • An organism that ingests non-living organic matter • Consumers • An organism that ingests other living organic matter or recently killed recently killed organic matter.

6. Food Chains - a simple linear flow of' who eats who' and therefore the energy and matter flowing through the links in the chain ( 5.1.4)

7. Food web - a diagram that shows how food chains are linked together into more complex feeding relationships.(5.1.5) • Shows the much more complex interactions between species within a community/ ecosystem • More than one producer supporting a community • A single producer being a food source for a number of primary consumers • That a consumer may have a number of different food sources on the same or different trophic levels • That a consumer can be an omnivore, feeding as a primary consumer and as a consumer at higher trophic levels

8. Trophic Level - The trophic level of an organism defines the feeding relationship of that organism to other organisms in a food.(5.1.6)

9. Distinguishing between trophic levels by looking at a food chain or web. (5.1.7)

10. 5.1.8 – constructing a food web

11. 5.1.9 - light is the initial source of energy for almost all food chains and webs • To maintain food chains, food webs, communities and all their interactions requires energy. • Sunlight is the source of this energy for most communities both aquatic and terrestrial. • The principle trap of sunlight energy is the protein molecule chlophil found in the chloroplasts of producers cells

12. 5.1.10 – Energy flow in a food chain • 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. • 100% 10% 1% 0.1%

13. 5.1.11 – Transfer of energy is 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. • 100% energy from the sun tertiary consumer 0.1% energy • Producers

14. 5.1.12 – the shape of energy pyramids The narrowing shape illustrates the gradual loss of energy progressing along the links of a food chain to higher tropic levels (see above for detail). The base of this pyramid would have a scale = energy/ area/unit time e.g. kJ m-2 yr-1 Unlike pyramids of number a pyramid of energy cannot invert due to the second law of thermodynamics,'energy cannot be created nor destroyed' .

15. 5.1.13 – Energy stays but nutrients are recycled • Energy flows: this diagram is a simple version of the pyramids of energy. At each trophic level energy is lost as heat. At the top of the pyramid of energy it tapers to a point showing how all energy is ultimately radiated to space as heat. • Matter cycles: new matter is not created, no new carbon, hydrogen or oxygen. Producers take inorganic molecules and convert them to organic compounds. Consumers feed at different trophic levels taking in organic matter and using it for their own growth. This cycling of matter is the subject of the carbon, nitrogen and water cycle.

16. 5.1.14 – how saprotrophic bacteria and fungi recycle nutrients • Decomposition is a complex process and serves many functions, including the formation of soil, the recycling of nutrients stored in the organic materials, and the reduction of high energy carbon compounds. • 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.