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Evolution and ecology
6 MDCAT Biology questions with answers and explanations.
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The theory of evolution by natural selection was proposed by Alfred Wallace and:
- 1 Gregor Mendel
- 2 Charles Darwin
- 3 Louis Pasteur
- 4 Robert Hooke
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Correct answer: Charles Darwin
Darwin and Wallace presented the idea together in 1858. Darwin set it out in full in On the Origin of Species.
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Roughly what percentage of energy is passed on from one trophic level to the next?
- 1 1%
- 2 10%
- 3 50%
- 4 90%
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Correct answer: 10%
Most energy is lost as heat and in life processes, so only about 10% reaches the next level.
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The human arm and a whale's flipper are examples of:
- 1 Analogous structures
- 2 Vestigial structures
- 3 Homologous structures
- 4 Convergent traits
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Correct answer: Homologous structures
They have the same basic bone plan from a common ancestor but do different jobs, which makes them homologous.
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In a population in Hardy-Weinberg equilibrium, q squared is 0.04. What is the frequency of heterozygotes (2pq)?
- 1 0.16
- 2 0.32
- 3 0.64
- 4 0.96
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Correct answer: 0.32
q = 0.2, so p = 0.8. Then 2pq = 2 x 0.8 x 0.2 = 0.32.
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Nitrogen-fixing bacteria in the root nodules of legumes belong to the genus:
- 1 Rhizobium
- 2 Nitrosomonas
- 3 Escherichia
- 4 Streptococcus
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Correct answer: Rhizobium
Rhizobium lives in root nodules and turns nitrogen gas into ammonia that the plant can use.
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Which of these is a producer in a food chain?
- 1 Grass
- 2 Rabbit
- 3 Fungus
- 4 Hawk
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Correct answer: Grass
Producers make their own food by photosynthesis. Grass is a producer, while rabbits and hawks are consumers and fungi are decomposers.