Plant Reproduction Sexual Reproduction Sexual reproduction requires fusion

Plant Reproduction

Sexual Reproduction • Sexual reproduction requires fusion of male cells in the pollen grain with female cells in the ovule. • List some advantages and drawbacks to sexual reproduction.

Terms to know: • Haploid: having a single set of chromosomes in each cell. • Diploid: having two sets of chromosomes in each cell. • Mitosis: cell division, which produces two genetically identical cells. • Meiosis: reduction division, which produces four haploid reproductive cells.

Plant Life Cycle

Alternation of Generations

Alternation of Generations • Plants have a double life cycle with two distinct forms: • Sporophyte: diploid, produce haploid spores by meiosis. • Gametophyte: haploid, produce gametes by mitosis.

Non-flowering plants • Mosses, ferns, and related plants have motile, swimming sperm. • What kind of environmental conditions would be required for reproduction in these plants? • What kinds of limits does external reproduction impose on these plants?

Moss Life Cycle

Fern Life Cycle

Gymnosperms • Gymnosperms have reduced gametophytes. • Male gametophyte is contained in a dry pollen grain. • Female gametophyte is a few cells inside of the structures that become the seed.

Gymnosperms

Conifer pollination • Conifers are wind-pollinated plants. • Chance allows some pollen to land on the scales of female cones. • Pollen germinates, grows a pollen tube into the egg to allow sperm to fertilize the egg. • What are some advantages and disadvantages to wind pollination?

Flowers

Pollen go-betweens • Showy flowers are the result of selection for more efficient pollination strategies. • Flower parts are modified leaves. Those that were brightly colored attracted insects in search of pollen. • Why would insects search for pollen? What other rewards do flowers offer? • What are advantages and disadvantages to relying on insects as pollinators?

Flower Parts PISTIL

Angiosperm Life Cycle

Double Fertilization

Flower to Fruit

Ovule to Seed

Seed Anatomy

Seed Germination

W O R K • Use what you have learned about plant life cycles to explain why most mosses and ferns live in moist environments, but flowering plants can live just about anywhere. T O G E T H E R