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 leve l

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

19. Q. Outline the process of decomposition by saprotrophs
Decomposition is a biological process begins with the secretion of extra-cellular digestive enzymes. These enzymes are produced by the saprophytic bacteria and fungi were they secrete the enzymes onto the dead organism and the enzymes hydrolyse the biological molecules of which the dead organism is composed into soluble molecules that will then be absorbed by the fungi or the bacteria.