Plant Reproduction Thinking Question: • Is a seed alive? Is a fruit alive? Answer as completely as you can on your own paper. (Hang on to your paper until the end of class.) Asexual Reproduction • Asexual reproduction is natural “cloning.” Parts of the plant, such as leaves or stems, produce roots and become an independent plant. • List some benefits and some drawbacks to asexual 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 Animals vs. Plants Plant Reproduction Animal Reproduction Alternation of No alternation of Life cycle generations generations Gametes Haploid gametes Haploid gametes Spores Haploid spores No spores Gametes made Haploid gametophyte, Diploid organism, by by by mitosis meiosis Spores made Diploid sporophyte, by No spores by meiosis 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 Conifers • Conifers (also non-flowering plants) 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. Conifer life cycle 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? 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? Flowers Flower Parts Incomplete flowers • Flowers are complete if they have all parts, and perfect if they have both male and female parts. • Grass flowers: incomplete, usually imperfect (separate male and female flowers) • A tulip is complete (though the sepals are the same color as the petals) and perfect. Imperfect flowers Gametogenesis: Male Gametogenesis: Female Double Fertilization Angiosperm Life Cycle Thinking question • 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.