Species, communities and ecosystems

Species

• Species are groups of organisms that can potentially interbreed to produce fertile offspring.

• Members of a species may be reproductively isolated in separate populations.

• Species have either an autotrophic or heterotrophic method of nutrition (a few species have both methods).

Consumers

Consumers are heterotrophs that feed on living organisms by ingestion.

 Detritivores are heterotrophs that obtain organic nutrients from detritus by internal digestion.

Saprotrophs or decomposers are heterotrophs that obtain organic nutrients from dead organisms by external digestion.

Ecosystems

• Autotrophs obtain inorganic nutrients from the abiotic environment.  Biotic and abiotic!
• The supply of inorganic nutrients is maintained by nutrient cycling.
• Ecosystems have the potential to be sustainable over long periods of time.

Community

• A community is formed by populations of different species living together and interacting with each other.   ALL biotic!

• A community forms an ecosystem by its interactions with the abiotic environment.

​Click below to learn about communities that exhibit mutualism, parasitism, and comensalism
Applications and skills:
• Skill: Classifying species as autotrophs, consumers, detritivores or saprotrophs (decomposers) from a knowledge of their mode of nutrition.

Make sure you can classify the following organisms to the right:
Skill: Setting up sealed mesocosms to try to establish sustainability. (Practical 5)
Mesocosms can be set up in open tanks, but sealed glass vessels are preferable because entry and exit of matter can be prevented but light can
enter and heat can leave. Aquatic systems can be set up also.  Here are examples of terrestrial ecosystems  Do your research before you set yours up! 

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Skill: Testing for association between two species using the chi-squared test with data obtained by quadrat sampling

Guidance:
• To obtain data for the chi-squared test, an ecosystem should be chosen in which one or more factors affecting the distribution of the chosen species varies. Sampling should be based on random numbers. In each quadrat the presence or absence of the chosen species should be recorded.

​Here is a quick review to get you thinking of what type of sampling you will want to do:
​• Skill: Recognizing and interpreting statistical significance.