Name ________________________________
Populations and Ecosystems Study Guide
You are responsible for knowing and being able to apply the following terms and
concepts on the exam. You should know the definition and how the key terms relate
to one another for each section of Chapter 21. Please study – your grade depends on
it.!
Section 1: pages 704-9
Key terms
Organism
Habitat
Biotic factor
Abiotic factor
Species
Community
Ecology
Population
Ecosystem
Photosynthesis
What is a habitat? What basic needs are provided by an organism’s habitat?
Why do different organisms live in different habitats?
What might happen to an organism if its habitat could not meet one of its needs?
What are biotic factors?
What are abiotic factors?
Why are water and sunlight important to most organisms?
What are the levels of an ecosystem? Know what happens at each level.
What is an ecosystem?
Would all the different kinds of organisms in a forest be considered a population or
community? Explain.
How might a change in one population affect other populations in a community?
Section 2: pages 711-18
Key terms
Estimate
immigration
limiting factor
birth rate
emigration
carrying capacity
death rate
population density
What are the different methods ecologists use to determine population size? When
would an ecologist use these methods?
How do populations change in size?
What happens when either the birth rate or death rate increases in a population?
What is the population statement and what does it mean?
What is immigration, and when does it occur?
What is emigration, and when does it occur?
Be able to read, understand and explain a graph showing changes in populations
What is population density and how is it calculated?
What are limiting factors? List all and explain how they impact populations
Section 3: pages 722-29
Key terms
Natural selection
Competition
Prey
Commensalism
host
adaptations
predation
symbiosis
parasitism
niche
predator
mutualism
parasite
What is natural selection?
What are adaptations?
How are a snake’s sharp fangs an adaptation that helps it survive in the saguaro
community?
Explain how natural selection in snakes might have led to adaptations such as sharp
fangs.
What is a niche?
Why can’t two species occupy the same niche?
What are three main ways in which organisms interact?
Give an example of each type of interaction – is there a winner/loser?
What are the three types of symbiotic relationships?
For each type of symbiotic relationship, explain how the two organisms are affected.
What are the different types of defense strategies used by organisms?
Section 4: pages 730-33
Key terms
Succession
Secondary succession
primary succession
pioneer species
What is succession?
What are primary and secondary succession, and how do they differ?
What are some pioneer species?
What are some natural events that can disturb an ecosystem?
Grass poking through a crack in a sidewalk is an example of succession. Is it primary
or secondary succession? Explain.
Also study the review and assessment on pages 735-737.