Natural Selection

Guppies are small fish that live in South American rivers. They can have different-sized spots on their bodies. The river bottoms are covered in rocks. Guppies with spots that are the same size as the rocks on the bottom are harder for bigger fish to see and catch. The diagrams show three possible guppy populations. If their environment changes to have only large rocks, which of the following guppy populations will most likely survive?

• Only Population 2 will survive because it is the only population with variation.

• All the populations will survive because the guppies will change the size of their spots if they need to.

• Populations 1 and 2 will most likely survive.

• Populations 2 and 3 will most likely survive.

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Blue jays are birds that live in the forest. They can have beaks of different thicknesses. Blue jays use their beaks to get to the seeds they eat. Blue jays with thinner beaks can easily reach and eat the seeds inside pinecones. Blue jays with thicker beaks can easily open and eat seeds with hard shells. The diagrams below show three possible blue jay populations. If their environment changes to have only seeds in pinecones, which of the following blue jay populations will most likely survive?

• Populations 1 and 2 will most likely survive.

• Populations 2 and 3 will most likely survive.

• Only Population 2 will survive because it is the only population with variation.

• All the populations will survive because the blue jays will change the thickness of their beaks if they need to.

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How did the environment change between time 1 and time 2? How did the population change?

• You cannot tell how the environment changed. With each generation, more foxes passed on the gene for brown fur to their offspring.

• The environment became brown. Brown foxes are more likely to survive, so the white foxes changed to have brown fur.

• The environment became brown. Brown foxes are more likely to survive, so both kinds of foxes passed on the gene for brown fur to their offspring.

• The environment became brown. With each generation, more brown foxes survived long enough to pass on the gene for brown fur to their offspring.

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Survival of the Fittest and Evolution were proposed by what scientist?

• Charles Darwin

• Albert Einstein

• Steven Hawking

• Isaac Newton

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Since the 1800s humans have stopped burning coal, and the trees have returned to their original color. Which moth will be more successful in this environment?

• Dark moth

• Light moth

• Both will be equally successful

• Neither will be successful

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Which organisms are most likely to survive?

• the best adapted

• the fastest

• the strongest

• the most domesticated (tamed)

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The differences among a species, like different bird beaks, are called

• genes.

• variations.

• traits.

• theories.

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Darwin wrote that organisms with traits that are best suited to the environment will ________________

• increase in number
  

• become extinct
  

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Which term refers to the process by which individuals that are better suited to the environment survive and reproduce therefore passing down their genes to their offspring? 

• Evolution 

• Variation 

• Adaptation

• Natural Selection 

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What is another name for natural selection?

• survival of the smartest

• survival of the fastest

• survival of the biggest

• survival of the fittest

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