Biology 2 /SL Review Book Topic G.1 Community Ecology
Name _________________________
Review Book Topic G: Ecology and Conservation
Topic G1 Review Book: Community Ecology
Assessment Statements
G.1.1
Outline the factors that affect the distribution of plant species, including temperature, water, light, soil
pH, salinity and mineral nutrients.
G.1.2
Explain the factors that affect the distribution of animal species, including temperature, water, breeding
sites, food supply and territory.
G.1.3
Describe one method of random sampling, based on quadrat methods, that is used to compare the
population size of two plant or two animal species.
G.1.4
Outline the use of a transect to correlate the distribution of plant or animal species with an abiotic
variable.
G.1.5
Explain what is meant by the niche concept, including an organism’s spatial habitat, its feeding activities
and its interactions with other species.
G.1.6
Outline the following interactions between species, giving two examples of each: competition,
herbivory, predation, parasitism and mutualism.
G.1.7
Explain the principle of competitive exclusion.
G.1.8
Distinguish between fundamental and realized niches.
G.1.9
Define biomass.
G.1.10
Describe one method for the measurement of biomass of different trophic levels in an ecosystem.
Key facts
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A community is a group of populations living together and interacting with one another in an area.
A community might be named by an environmental feature (e.g., pond community) or by the dominant plant
species (e.g., an oak community).
The distribution of organisms in a community is affected by both abiotic and biotic features.
The biosphere means all parts of the Earth where organisms live, and is divided into seven biomes, each
defined by its particular vegetation and animal life.
Factors that affect the distribution of plant species include temperature, water, light, soil pH, salinity, and
mineral nutrients. TWLPSM, Tom will leave Paris Saturday morning.
Factors affecting the distribution of animal species include temperature, water, breeding sites, food supply,
and territory. TWBFT
Random sampling enables ecologists to more easily determine the size of a population.
Quadrat sampling involves selecting a square of a certain size (larger squares for larger areas), mapping them
onto a sampling area, numbering the quadrats, then randomly selecting quadrants to sample. The average
numbers of organisms counted per quadrat is then multiplied by the total number of quadrats in the mapped
area.
Transect sampling involves laying out a line across a sampling area, setting out a quadrat at right angles to the
line at regular intervals, counting the species of interest in each quadrat, measuring abiotic features of interest
in each quadrat, and looking for relationships between the features and populations.
Every organism in an ecosystem has a particular role in that ecosystem, the organism’s niche. Niche includes
where the organism lives (spatial habitat), what and how it eats, and interactions with other species.
Interactions between species include competition (for resources), herbivory (consumption of plants),
predation, parasitism, and mutualism.
A parasite is an organism that lives on or in a host and depend on the host for at least part of its life cycle.
Two species living together where both organisms benefit from the relationship is termed mutalism. clownfish
and sea anemones are an example of a mutualistic relationship.
The principle of competitive exclusion states that no two species in a community can occupy the same niche.
When two species have a need for the same resources, one will be excluded.
Biology 2 /SL Review Book Topic G.1 Community Ecology
Name _________________________
15. The fundamental niche of an organism is the complete range of biological and physical conditions under which
an organism can live. The realized niche of a species is the actual mode of existence, which results from
adaptations and competition with other species.
16. Biomass is the total mass of organic matter (carbon compounds). To measure biomass, samples have to be
dried to remove water (inorganic). It’s expressed a g m-2 yr-1 (grams per meter squared per year). Ecologists
have developed techniques for calculating biomass in an area, including techniques for animal biomass and
plant biomass.
Further notes
Complete the following.
1. What are the six main abiotic factors that can affect the distribution of plant species?
2.
What are the five main factors that can affect the distribution of animal species?
3.
Explain how each of the five factors listed in question 2 above affect the distribution of animal species.
4.
Outline how you would use random sampling (using quadrats) to compare the population of maple trees to
the population of oak trees in Alapocas Woods.
Biology 2 /SL Review Book Topic G.1 Community Ecology
Name _________________________
5.
Outline how you would use a transect to correlate the distribution of pillbugs with soil temperature in
Alapocas Woods.
6.
Explain the niche concept using green frogs in Indiana as an example, include spatial habitat, feeding activities,
and interactions with other species.
7.
Why can’t two different species occupy the same niche? Use foxes and coyotes as an example in your
explanation.
Biology 2 /SL Review Book Topic G.1 Community Ecology
8.
Compare and contrast fundamental niche and realized niche.
9.
How would you measure the biomass of Alapocas Woods?
Name _________________________