Evolution: It's a Thing - Crash Course Biology #20

A population evolves when

• a decision is made.

• a selective pressure changes the gene distribution of the population over time.

• it grows more fingers, as needed.

• it sticks to the plan.

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What do scientists mean when they use the term 'theory'?

• A theory is a hunch or a guess.

• A theory is a collection of fictional stories that, when added together, help shape the view of the natural world.

• Theories are ideas that explain natural phenomena.

• A theory just is an unproven law.

The fossil record suggests

• species never change.

• dinosaurs are not real.

• evolution did not occur in the time of the dinosaurs but picked up later in Earth's history.

• species change over time.

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The hind leg bone structures found in the skeletons of modern whales are examples of vestigial organs. Which of the following statements is true?

• Leg bones in whales are not proof of evolution.

• The most recent common ancestor of every species of whale did not have leg bones.

• The presence of leg bones in whales suggest whales evolved from a four-legged common ancestor.

• The leg bone structures will evolve into new fins someday.

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The bones found in a human hand and a bat's wing are examples of homologous structures. Which statement about the bones in a human hand and bat wing is true?

• The bones suggest humans and bats share a common ancestor.

• The bones might allow humans to fly and bats to write.

• The bones are formed from homozygous recessive genes.

• Homologous structures are the same as vestigial organs.

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What do all living things on Earth have in common?

• All species have homologous structures where hands are found.

• All species use RNA or DNA to carry their genetic informaiton.

• All species have some version of an appendix, a vestigial organ found in humans.

• All species photosynthesize or can evolve the ability to photosynthesize.

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Similarities between human genomes and those of other species like the chimpanzee, mouse, or fruit fly suggest

• every species' genome is about 96% similar.

• DNA will evolve into RNA.

• humans share a common ancestor with chimpanzees, mice, and fruit flies.

• humans evolved from chimpanzees, mice, and fruit flies.

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Darwin's finches are characterized by different sized beaks, the phenotypes of which were caused by different selective pressures like access to certain types of food. Darwin theorized that the finches

• evolved because they wanted to.

• evolved through unnatural selection.

• with medium-sized beaks are best adapted because nature tends to favor 'average' phenotypes.

• all share a common ancestor.

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Insect species can develop genetic resistance to pesticides like DDT over time. Which of the following statements is FALSE?

• Insecticide resistance is an example of evolution.

• The insecticide-resistance gene allows parents to survive long enough to pass it on to its offspring.

• Over time, the gene for insecticide resistance will increase in frequency among the gene pool.

• Insects are able to make a decision whether or not they want to adapt to the insecticide.

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