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.