AP Biology : Plant Evolution

Study concepts, example questions & explanations for AP Biology

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Example Questions

Example Question #1 : Understanding The Water Land Transition

Which is of the following is not an adaptation/modification that enabled plants to move from aquatic to terrestrial environments as they evolved?

Possible Answers:

Cutin

Thylakoid membranes

Roots and root hairs

Stomata

Correct answer:

Thylakoid membranes

Explanation:

Thylakoid membranes are found within chloroplasts, which are used for photosynthesis. Plants found in both aquatic and terrestrial environments photosynthesize, so these membranes cannot be considered adaptations uniquely benefiting terrestrial plants.

Comparatively, cutin is a waxy coating found on various parts of plants that helps prevent water loss when exposed to air. Stomata are tiny openings in the epidermis of plants that allow for the exchange of carbon dioxide and oxygen while minimizing water loss. Roots and root hairs allow plants to absorb nutrients and water from the soil. Water loss was the primary challenge plants faced when moving from aquatic to terrestrial environments; cutin, stomata, roots, and root hairs all help terrestrial plants absorb and conserve water.

Example Question #2 : Understanding The Water Land Transition

Which structures did not evolve after plants emerged onto land?

Possible Answers:

Vascular transport

Seeds

Waxy cuticles

Stomata

Cell walls

Correct answer:

Cell walls

Explanation:

Cell walls were present in plant cells before the transition to land. Seeds, stomata, waxy cuticles, and vascular transport all evolved to reduce water loss and circulate water to all areas of the plant. Water loss and circulation were not an issue before the transition to land; plants were forced to adapt these traits in order to survive in a terrestrial environment.

Example Question #3 : Understanding The Water Land Transition

As plants moved from water to land, they developed structures and lifestyles better suited to life in their new environment. Which of the following is not an example of these adaptations?

Possible Answers:

Cuticle

Decrease in rigidity 

Increase in vertical height

Roots

Vascular tissue

Correct answer:

Decrease in rigidity 

Explanation:

Plants developed more rigid structures to help maintain their growth on land as opposed to water.

Waxy cuticles developed to help reduce water loss/desiccation. Roots allowed plants greater access to water, as well as provided anchoring to the ground; this allowed plants to grow taller. Vascular tissue facilitated transport of water and nutrients to all parts of the plant. Stomata helped with gas exchange.

Example Question #1 : Plant Evolution

What is a distinct feature of a C4 plant?

Possible Answers:

Carbon fixation

Bundle-sheath cells

Closed stomata during the day

Light independent reactions

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 #1 : Understanding Alternation Of Generations

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

Possible Answers:

Gamete-producing sporophytes

The need for external pollinators

A life cycle that includes a multicellular haploid stage

A life cycle which includes a unicellular haploid stage

The differences between a tree and a seed

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 #3 : Plant Evolution

How is it believed that plants first became photosynthetic?

Possible Answers:

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

A vacuole became specialized for photosynthesis

An ancestor of modern plants internalized a photosynthetic prokaryote through phagocytosis

The origin of the chloroplast is still largely unknown

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 #4 : Plant Evolution

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

Possible Answers:

Convergent evolution

Divergent evolution

Speciation

Co-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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