Study Guide

Plant Evolution and Diversity Questions

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Plant Evolution and Diversity Questions

1. What structures did early land plants evolve? How did these help them live on land instead of water?

2. Knowing that convergent evolution can cause plants to be similar, what do you predict would have a better chance of becoming invasive in the desert: a plant from Arizona, or a plant from Maine?

3. Why can’t we just split angiosperms into monocots and dicots like people used to do?

4. Lycophytes were tall trees during the Carboniferous period. Today, the only lycophytes that exist are small, herbaceous plants. What happened?

5. What is the advantage of having flowers?

Plant Evolution and Diversity Answers

1. Answer: Early land plants evolved cuticles, which are waxy layers that keep water from evaporating. Since air is not as wet as water, plants that had a mechanism for keeping water in were well-situated to live on land. The earliest land plants were still limited in their growth because they did not have well-developed roots or leaves. Later, seedless vascular plants evolved roots that anchored them and helped them draw nutrients from the soil. Big leaves offered the plants more area to intercept the Sun’s rays and make sugars from photosynthesis.

2. Answer: Although we can never predict what a plant will do in a new environment or predict invasions, the plant from Arizona has a better chance of becoming invasive. In fact, it has a better chance of surviving period, since it is probably already adapted to desert conditions.

3. Answer: The past division of the angiosperms into monocots and dicots was based on the number of cotyledons plants have, but it was also believed to be an evolutionary split of those two types of plants. We know now that some of the plants with two cotyledons, the Magnoliids, are actually more primitive than the monocots and belong in a different group.

4. Answer: The Carboniferous period was characterized by a warm and wet climate. Toward the end of the period, the Earth’s climate cooled. The tall lycophytes died out. We can only guess why, but for some reason, they couldn’t survive being tall in a dry climate. The smaller lycophytes were more resilient to the climate change, and their descendants are today’s lycophytes.

5. Answer: Flowers attract animals with their colors, scents, and nectar. These animals inadvertently take some of the flower’s pollen as they drink nectar and transfer pollen to other flowers in the same species when they travel around looking for more nectar. Animal pollinators can efficiently take pollen from one plant to another and improve the odds of successful fertilization. Successful fertilization leads to seeds, and seeds lead to plants, so flowering plants were able to spread all over the world.

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