AP Biology : Understanding Other Plant Evolution

Study concepts, example questions & explanations for AP Biology

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Example Questions

Example Question #3 : Plant Biology

What is a distinct feature of a C4 plant?

Possible Answers:

Light independent reactions

Closed stomata during the day

Carbon fixation

Bundle-sheath cells

Correct answer:

Bundle-sheath cells

Explanation:

Carbon fixation converts inorganic carbon dioxide into organic carbon compounds, such as glucose and cellulose. This is a characteristic function of both C3 and C4, and is a primary purpose of light independent reactions.

Closed stomata during the day is a characteristic of CAM plants, which allows for the conservation of water that is usually lost during photorespiration.

Bundle-sheath cells are a characteristic of C4 plants. The presence of bundle-sheath cells isolates rubisco, preventing rubisco from binding to oxygen during photorespiration.

Example Question #4 : Plant Biology

Which of the following refers to the principle of alternation of generations in plants?

Possible Answers:

Gamete-producing sporophytes

A life cycle that includes a multicellular haploid stage

The need for external pollinators

The differences between a tree and a seed

A life cycle which includes a unicellular haploid stage

Correct answer:

A life cycle that includes a multicellular haploid stage

Explanation:

Plants have a multicellular haploid stage called the gametophyte. Gametophytes () produce gametes () through mitosis, which combine to produce a zygote (). The zygote grows into a multicellular, diploid sporophyte (), which produces spores () through meiosis. Those spores give rise to multicellular gametophytes.

Example Question #4 : Plant Biology

How is it believed that plants first became photosynthetic?

Possible Answers:

The chloroplast was a cluster of synthesized proteins, which evolved over time

The origin of the chloroplast is still largely unknown

A vacuole became specialized for photosynthesis

An ancestor of modern plants internalized a photosynthetic prokaryote through phagocytosis

Correct answer:

An ancestor of modern plants internalized a photosynthetic prokaryote through phagocytosis

Explanation:

The chloroplast is believed to have evolved from photosynthetic bacteria that formed a mutualistic symbiotic relationship with an ancestor of plants through endosymbiosis. There is lots of evidence supporting the endosymbiotic theory, which is based on the principle of one organism phagocytosing another, resulting in mutualism.

Example Question #5 : Plant Biology

Mutualistic relationships between angiosperms and biotic pollinators foster which of the following types of evolution?

Possible Answers:

Speciation

Convergent evolution

Co-evolution

Divergent evolution

Correct answer:

Co-evolution

Explanation:

Biotic pollinators, such as bees and hummingbirds, share a mutualistic relationship with angiosperms. This leads to co-evolution, in which the selective pressure of one species impacts the genetic composition of another. In this case, the preferences of the pollinators impact the reproductive success of specific angiosperms.

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