4.1 Species, communities and ecosystems

IB Syllabus Statements

Understandings:

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 are heterotrophs that feed on living organisms by ingestion.
Detritivores are heterotrophs that obtain organic nutrients from detritus by internal digestion.
Saprotrophs are heterotrophs that obtain organic nutrients from dead organisms by external digestion.
A community is formed by populations of different species living together and interacting with each other.
A community forms an ecosystem by its interactions with the abiotic environment.
Autotrophs obtain inorganic nutrients from the abiotic environment.
The supply of inorganic nutrients is maintained by nutrient cycling.
Ecosystems have the potential to be sustainable over long periods of time.

Applications and skills:

Skill: Classifying species as autotrophs, consumers, detritivores or saprotrophs from a knowledge of their mode of nutrition.
Skill: Setting up sealed mesocosms to try to establish sustainability. (Practical 5)
Skill: Testing for association between two species using the chi-squared test with data obtained by quadrat sampling.
Skill: Recognizing and interpreting statistical significance.

Understandings:

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 are heterotrophs that feed on living organisms by ingestion.
Detritivores are heterotrophs that obtain organic nutrients from detritus by internal digestion.
Saprotrophs are heterotrophs that obtain organic nutrients from dead organisms by external digestion.
A community is formed by populations of different species living together and interacting with each other.
A community forms an ecosystem by its interactions with the abiotic environment.
Autotrophs obtain inorganic nutrients from the abiotic environment.
The supply of inorganic nutrients is maintained by nutrient cycling.
Ecosystems have the potential to be sustainable over long periods of time.

Applications and skills:

Skill: Classifying species as autotrophs, consumers, detritivores or saprotrophs from a knowledge of their mode of nutrition.
Skill: Setting up sealed mesocosms to try to establish sustainability. (Practical 5)
Skill: Testing for association between two species using the chi-squared test with data obtained by quadrat sampling.
Skill: Recognizing and interpreting statistical significance.

Define what makes a group of organisms a species.
Members of a species may be reproductively isolated in separate populations. Explain what this means.
Distinguish between autotrophic and heterotrophic methods of nutrition.
Consumers, detritovores, and saprotrophs are all considered heterotrophs. Explain how they are different.
Define a community.
A community forms an ecosystem by its interactions with the non-living environment. What is another term for this non-living part of the environment?
Outline how autotrophs obtain energy and nutrients.
What is meant by a nutrient cycle. Use a specific example in your answer.
Explain why ecosystems have the potential to be sustainable over long periods of time.
Most plants and algae are autotrophic, but some are not. Give an example of a plant that obtains its nutrition by heterotrophic means.
You encounter an unknown organism. How would you determine if it would classified as an autotroph, consumer, detritovore or saprotroph?
Explain the purpose of setting up a mesocosm.
Outline how an association between two species could be tested for using the chi-squared test and quadrat sampling. Note: an ecosystem should be chosen in which one or more factors varies; in each quadrat the presence or absence of the chosen species should be recorded
Explain the meaning of statistical significance.
Explain how human life depends on sustainable communities.