plant reproduction and life cycle

plant reproduction and life cycle

The life cycle of a plant is very different from the life cycle of an animal. Humans are made entirely of diploid cells (cells with two sets of chromosomes, referred to as 2n). Our only cells that are haploid cells (cells with one set of chromosomes, n) are sperm and egg cells. Plants, however, can live when they are are at the stage of having haploid cells or diploid cells. If a plant has a haploid chromosome number of 20, what is the diploid chromosome number? If the diploid chromosome number is 20, what is the haploid number? Plants alternate between diploid-cell plants and haploid-cell plants. This is called alternation of generations, because the plant type alternates from generation to generation. In alternation of generations, the plant alternates between a sporophyte that has diploid cells and a gametophyte that has haploid cells. Alternation of generations can be summarized in the following four steps: follow along in the Figure 1.1 as you read through the steps. 1. The haploid gametophyte produces the gametes, or sperm and egg, by mitosis. Remember, gametes are haploid, having one set of chromosomes. 2. Then, the sperm fertilizes the egg, producing a diploid zygote that develops into the sporophyte, which of course, is diploid. 3. The diploid sporophyte produces haploid spores by meiosis. 4. The haploid spores go through mitosis, developing into the haploid gametophyte. As we will see in additional Plants concepts, the generation in which the plant spends most of its life cycle is different between various plants. In the plants that first evolved, the gametophyte takes up the majority of the life cycle of the plant. During the course of evolution, the sporophyte became the major stage of the life cycle of the plant. In ferns, the sporophyte is dominant and produces spores that germinate into a heart-shaped gametophyte.

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instructional diagrams

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questions

all plants produce seeds.

a. true

-->  b. false

like humans, eukaryotic multicellular plants are made entirely of diploid cells.

a. true

-->  b. false

in plants, what structure produces gametes? what process produces gametes?

a) the sporophyte produces gametes by mitosis.

b) the sporophyte produces gametes by meiosis.

-->  c) the gametophyte produces the gametes by mitosis.

d) the gametophyte produces gametes by meiosis.

in an alternation of generations life cycle, the gametophyte is part of which generation?

a) the diploid generation

-->  b) the haploid generation

c) both generations

d) the gamete generation

in an alternation of generations life cycle, a diploid zygote develops into

-->  a) the sporophyte.

b) the gametophyte.

c) mature spores.

d) none of the above

in a plant, if an egg cell has 20 chromosomes, how many chromosomes will be in the sporophyte?

a) 10

b) 20

c) 30

-->  d) 40

in an alternation of generations life cycle, spores develop into

a) the sporophyte.

-->  b) the gametophyte.

c) the gametes.

d) the zygote.

diagram questions

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