The 14 species of finches on the Galapagos Islands evolved from a single species
ID: 55959 • Letter: T
Question
The 14 species of finches on the Galapagos Islands evolved from a single species that migrated to the islands several million years ago. Different finch species live on different islands. A major difference among finch species is in their beaks: both size and shape vary greatly.
Assume that a population of one of these finch species is undergoing evolution by natural selection with respect to beak size and shape. What changes occur gradually over time that indicate the population is evolving?
Within their lifetimes, some individual finches' beaks change in size or shape.
The proportions of finches having different beak sizes/shapes change across generations.
Each finch's learned ability to use its beak is automatically passed on to its offspring.
All finches in each new generation develop the same new, improved beak size and shape.
DDT is an insecticide that was used extensively in the mid-1900s to kill mosquitoes. It was very effective at first, but after a few decades DDT became less effective at killing mosquitoes because many populations had evolved resistance to DDT. Which of the following conditions would biologists say was required for the evolution of DDT resistance in a population?
A few mosquitoes in the population were resistant to DDT before it was ever used.
Mosquitoes in the population learned to adapt to the high levels of DDT in the environment.
The mosquito population needed to evolve DDT resistance in order to avoid extinction.
Exposure to DDT caused specific, nonrandom mutations for DDT resistance within the population.
Ducks are aquatic birds. Their feet are webbed and this trait makes them fast swimmers. Biologists believe that ducks evolved from land birds that did not have webbed feet. The amount of webbing on a duck's feet is a heritable trait. Consider the following hypothetical scenario: An ancestral species of duck had a varied diet that included aquatic plants and terrestrial plants and insects. These ducks spent time on both land and water. Individuals of this species varied in the amount of webbing in their feet, with some individuals having more webbing and some having less. As many years went by, the environment changed such that the aquatic food sources were much more plentiful than those on land. Many generations later, almost all ducks had more webbing on their feet. How is this best explained?
Ducks with less webbing worked harder than ducks with more webbing to eat aquatic plants. The more they used their feet, the more webbed their feet became, so they got enough food to survive and reproduce.
Due to chance mutations, all the ducks' feet in the next generation had more webbing. They were therefore able to eat aquatic plants and get enough food to survive and reproduce.
Ducks with more webbing were better at eating aquatic plants than ducks with less webbing, so the ducks with more webbing survived and reproduced better than ducks with less webbing.
Ducks with less webbing needed to grow more webbing in their feet in order to improve their access to aquatic plants, which allowed them to survive better and reproduce more.
Use the following passage and graphs to answer the last question.
Horned lizards use their horns to defend against predatory birds. A researcher observed that lizards living in areas with predatory birds have longer horns than those in areas with no predatory birds. This observation led her to hypothesize that longer horns offer more protection against predation than do shorter horns. To test this hypothesis, the researcher tagged 20 lizards with long horns and 20 lizards with short horns in each of two locations: Desert Valley, where there are no predatory birds, and Cactus Corner, where there are predatory birds. She returned every week for 12 weeks to measure survival of tagged lizards. The graphs below represent her findings.
Lizard graphs
Q41. What can you conclude from the researcher's results?
The hypothesis that longer horns offer greater protection against predation is supported.
The hypothesis that longer horns offer greater protection against predation is NOT supported.
The experiment is well designed, but the data is inconclusive about the hypothesis.
The experiment is not well designed to test the hypothesis.
Explanation / Answer
Answer
1.
Species undergo evolution due to natural selection so that become highly adapted to their environment which will ultimately result in their survival. With respect to beak size and shape, the finches undergo natural selection so that they get adapted to different food sources in the future. Finches with smaller and blunt beaks cannot crack open harder seeds and due to this fact, they starve and die. Finches with pointy and bigger beaks can crack open both soft, and harder seeds resulting in their survival.
Therefore, the correct answer is option (b). The proportions of finches having different beak sizes/shapes change across generations.
2.
It was thought that a few mosquitoes had mutations that will produce resistance against DDT. When DDT was administered, the mosquitoes that do not have the mutation died and these mutant mosquitoes survived and reproduced similar kind of offsprings. Therefore, the correct answer is option (a). A few mosquitoes in the population were resistant to DDT before it was ever used.
3.
The ancestral ducks with more amount of webbing in their feet were in the evolution phase and since webbing is a heritable trait, these ducks had higher survival rates when compared to the ducks with less webbing. Thus, the less webbed ducks died during the course of evolution and the ducks with more webbing survived better as they had better food sources and produced more offspring.
Therefore, the correct answer is option (c). Ducks with more webbing were better at eating aquatic plants than ducks with less webbing, so the ducks with more webbing survived and reproduced better than ducks with less webbing.
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