Honors and AP Biology Homework Chapter 17: Eukaryotes Plants
Textbook assignment: Chapter 17: The Evolution of Plant and Fungal Diversity, sections 1-13.
- 17.1 Differences between plants and algae are apparent in adaptations (structures or characteristics) that allow plants to live on dry land. These include methods to retrieve nutrients from the soil and air, structures to support the body of the plant without the additional support of water, methods of reproduction that do not depend on a water environment, and ways of retaining water in dry climates. Consider: if plants had to develop all of these new structures to survive on land, what advantages did a land habitat offer?
- 17.2 Plants are grouped into two major types based on internal methods of water and nutritional transport: non-vascular plants such as mosses and bryophytes, which have no internal veins, leaves or roots; vascular plants, which have leaves and roots. Seedless vascular plants include ferns and horsetails. Seed plants include gymnosperms (seeds without coats) and angiosperms (coated seeds). Angiosperms are considered the most "successful" group since they account for over 90% of the nearly 300 000 plant species alive now. The phylogenetic tree for plants branches on four characteristics:
- Dependent embryos
- Lignified vascular tissues
- 17.3 Each group of plants is distinguished as well by the way its haploid and diploid generations alternate. Every plant produces spores (diploid cells) that form gametophytes; these structures produce egg and sperm gametes that fuse (fertilization) to form zygotes that grow into sporophytes, the structures that produce the spores, and the cycle starts over. The dominant generation is the generation that produces the largest or most enduring structure of the plant. In mosses, the gametophyte is the bigger part of the plant; the spore producing structure is small in comparison to the rest of the plant. In mosses, the gametophyte is the bigger part of the plant; the spore producing structure is small in comparison to the rest of the plant. Mosses are dependent on reproduction since their flagellated sperm must swim to find ova.
- 17.4 All other plants have dominant sporophytes: the spore-producing part of the plant is large, while the gamete-producing part is small or temporary. This is true of ferns, which "die back" each year to a small thalmus gametophyte. Current carbon-bearing coal deposits are cited as evidence that large fern forests once dominated plant life during a wet period (Carboniferous period), which gave way in the Mesozoic era to domination by gymnosperms. Coal-burning since the industrial revolution began has returned CO2 to the atmosphere, and may be the cause of a global warming trend.
- 17.5 Seedbearing plants include gymnosperms and angiosperms. In gymnosperms, the gametophyte structures lie in the scales of the ovulate cones. Pollen released from pollen cones on the same or neighboring trees fertilizes individual scales, which then form seeds that can develop into a new plant.
- 17.6 Angiosperms bear flowers as their gametophyte generations. The structure of the flower provides both egg gametes (ovule) and pollen (anthers) which transfer sperm to the stigma. Flowers may be self-pollinating (a flower can pollinate its own ova), or foster various combinations of cross-pollination from other flowers on the same plant, or from other flowers on plants of the same species.
- 17.7 As with all other plants, the alternation of generation provides both haploid gametes (sperm and ova) through meiosis, and a diploid seed or zygote.
- 17.8 The ovary of a flower ripens and becomes a fruit, which attract animals to eat the fruit. The animals become vectors for the plant, carrying seeds far from their origins.
- 17.9 Angiosperms account for most agricultural food plants. Flowers allow not only for collection and storage of seeds, but for cross-breeding.
- 17.10 About 90% of angiosperm species depend on animals, particularly insects but also birds and bats, for pollination processes and seed dispersal. Flowers use color and scent to attract different types of animals.
- 17.11 Plant diversity is essential to our food supply. Destruction of plant habitats decreases plant diversity and endangers the current environment and ecosystem balances.
Read the following weblecture before chat: Plants and Plant Phyla
Take notes on any questions you have, and be prepared to discuss the lecture in chat.
Perform the study activity below:
To get a better sense of the sporophyte vs gametophyte life cycles of planes, Check out the Fern Life Cycle. Click on each secion of the diagram for information about each phase in the plant's growth and development.
Chat Preparation Activities
- Essay question: The Moodle forum for the session will assign a specific study question for you to prepare for chat. You need to read this question and post your answer before chat starts for this session.
- Mastery Exercise: The Moodle Mastery exercise for the chapter will contain sections related to our chat topic. Try to complete these before the chat starts, so that you can ask questions.
- No quiz yet: the Chapter Quiz opens when we finish the chapter.
Read through the lab for this week; bring questions to chat on any aspect of the lab, whether you intend not perform it or not. If you decide to perform the lab, be sure to submit your report by the posted due date.
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