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Angiosperms are the dominant terrestrial plants of the Cenozoic era. The synapomorphies of angiosperms include flowers, fruit, carpels, double fertilization, and endosperm. Most angiosperms also possess distinctive cells in the xylem and phloem. The largest angiosperm clades are the monocots and the eudicots.
learning outcomes
You should be able to:
Distinguish between the two different roles of sperm in angiosperm double fertilization.
Distinguish between pollination and fertilization.
Make inferences about the likely modes of seed dispersal based on the type of fruit the plant produces.
Compare the functions of flowers, fruits, and seeds.
What are the respective roles of the two sperm in double fertilization in angiosperms?
One sperm produces the diploid zygote, and another produces the (usually) triploid endosperm that will provide nourishment for the developing embryo.
Explain the difference between pollination and fertilization.
Pollination refers to the arrival of pollen on a stigma. After the pollen produces a pollen tube, it releases sperm to the megagametophyte, resulting in fertilization.
What are some of the differences between fruits that are dispersed by attracting animals to a food resource and those that are dispersed by attaching themselves to animals? Give examples of each.
Fruits that attract animals to a food resource often have a fleshy, edible ovary. Animals gather or eat the fruit, and the seeds may pass through the digestive tract alive and germinate after they are deposited in the animal’s stool. In some cases, such as tree nuts, the seeds are themselves edible, and the fruit serves as a hard, protective covering. Animals such as squirrels gather the nuts, eat some, and store others for later. Some of the stored nuts then germinate into new plants. In contrast, some seeds have sticky surfaces that adhere to animals that brush by the fruiting plant. If you have ever had to pull burrs off your clothes or your pet, you have pulled out fruits of plants that are being dispersed in this manner.
What are the different functions of flowers, fruits, and seeds?
Flowers are the site of pollination and fertilization and, in many species, serve to attract pollinators. Fruits may provide protection or means of dispersal for the seeds; often, the fruits are attractive to an animal that then disperses the seeds in its feces. The seeds protect the developing embryos until conditions are favorable for germination.
The remarkable diversity of the seed plants has been shaped by both biotic and abiotic components of the environments to which they have adapted. In turn, land plants—