Chapter three
What is adaptation at the species level?

Physical adaptations that allow a species to survive in a given environment. For example, as a sled dog species’ year round thick coat of hair.

CHAPTER 3, p. 50

How is natural selection demonstrated?

When a species successfully produces a new generation.

CHAPTER 3, p. 50

What is natural selection at the population level?

The mechanism for evolutionary change in which environmental pressures (such as seasonal colder temperatures) cause certain genetic combinations in a population to become more abundant. For example, dogs that adapt to cold temperatures in the fall by growing thickened coats.

CHAPTER 3, p. 50

What is the zone of physiological stress?

The range along the environmental gradient for that factor (e.g., temperature), at which a species becomes infrequent as life becomes harder.

CHAPTER 3, p. 51

What are endemic species?

Habitat specialists that may occupy a very narrow niche.

CHAPTER 3, pp. 52&53; glossary, p. 381

What is the competitive exclusion principle?

No two species can occupy the same niche indefinitely.

CHAPTER 3, p. 53; Glossary, p. 380

What is speciation?

The process by which new species arise or develop.   

CHAPTER 3, p. 54; Glossary, p. 387

What is resource partitioning?

No two species can occupy the same ecological niche for long. The one that is more efficient in using available resources will exclude the other, reducing intraspecific competition.

CHAPTER 3, pp. 52, 53, & 57; Glossary, p. 386

What is Batesian mimicry?

Certain species that are harmless resemble poisonous or distasteful ones, gaining protection against predators who remember a bad experience with the actual toxic organism. For example, the monarch and viceroy butterflies.

Glossary, p. 379; CHAPTER 3, pp. 58&59

What is symbiosis?

The intimate living together of members of two species. For example, in lichens, a fungus and a photosynthetic partner (either an alga or a cyanobacterium) combine tissues to mutual benefit.

CHAPTER 3, p. 59; Glossary, p. 387

What is an invasive species?

A generalist or pioneering species that is moved into a new ecosystem. For example, the kudzu, water hyacinth, and walking catfish are all invasive species in the U.S.

CHAPTER 3, pp. 52&60; CHAPTER 5, p. 115; Glossary, p. 383

What are keystone species?

A keystone species plays has complex ties to the foundations of the ecosystem that is out of proportion to its abundance. For example, salmon in the Northwest.

CHAPTER 3, p. 60; Glossary, p. 383

When does a dieback or population crash occur?

When a population overshoots or exceeds the carrying capacity of its environment, resources become limited and death rates rise. If deaths exceed births, the growth rate becomes negative and the population may suddenly decrease, a change called a population crash or dieback.

CHAPTER 3, p. 61

What is a J curve?

The mathematical expression or graph of exponential population growth.

CHAPTER 3, pp. 61-62; Glossary, p. 383

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