TLS Online TPP Program

#Question id: 7113


In flies, frogs, and chicks, gradients of morphogens determine the future antero-posterior and dorso-ventral axes of the developing embryo. How is the antero-posterior axis determined in C. elegans?

#Unit 5. Developmental Biology
  1. bicoid protein is translated in the anterior of the fertilized egg, leading to a gradient that determines the antero-posterior axis
  2. nodal triggers formation of an organizer that will determine the dorsal, and hence the anterior, side of the embryo
  3. beta-catenin becomes localized to the nucleus in the future anterior cells after fertilization
  4. sperm entry leads to a reorganization of the cytoskeleton and redistribution of maternally packaged PAR proteins, which in turn determine the antero-posterior axis
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TLS Online TPP Program

#Question id: 4635

#Unit 11. Evolution and Behavior

Which statement about natural selection is most correct?

TLS Online TPP Program

#Question id: 4636

#Unit 11. Evolution and Behavior

Given a population that contains genetic variation, what is the correct sequence of the following events, under the influence of natural selection?

1. Well-adapted individuals leave more offspring than do poorly adapted individuals.

2. A change occurs in the environment.

3. Genetic frequencies within the population change.

4. Poorly adapted individuals have decreased survivorship.

TLS Online TPP Program

#Question id: 4637

#Unit 11. Evolution and Behavior

A biologist studied a population of squirrels for 15 years. During that time, the population was never fewer than 30 squirrels and never more than 45. Her data showed that over half of the squirrels born did not survive to reproduce, because of competition for food and predation. In a single generation, 90% of the squirrels that were born lived to reproduce, and the population increased to 80. Which inference(s) about this population might be true?

A) The amount of available food may have increased.

B) The number of predators may have decreased.

C) The squirrels of subsequent generations should show greater levels of genetic variation than previous generations, because squirrels that would not have survived in the past will now survive.

Choose correct combination,

TLS Online TPP Program

#Question id: 4639

#Unit 11. Evolution and Behavior

If the HMS Beagle had completely bypassed the Galapagos Islands, Darwin would have had a much poorer understanding of the

TLS Online TPP Program

#Question id: 4640

#Unit 11. Evolution and Behavior

During drought years on the Galapagos, small, easily eaten seeds become rare, leaving mostly large, hard-cased seeds that only birds with large beaks can eat. If a drought persists for several years, what should one expect to result from natural selection?

TLS Online TPP Program

#Question id: 4641

#Unit 11. Evolution and Behavior

Which of the following statements is an inference of natural selection?