Creating the next generation
Plant Reproduction Creating the next generation Asexual Reproduction Asexual reproduction is natural cloning.Parts of the plant, such as leaves orstems, produce roots and become anindependent plant. List some benefits and some drawbacksto asexual reproduction. Fast, no mate required. Beneficial for plants that must compete for scarce resources. However, all individuals are genetically identical. Sexual Reproduction Sexual reproduction requires fusion ofmale cells in the pollen grain with femalecells in the ovule. List some advantages and drawbacks tosexual reproduction. Fusion of egg and sperm cells. May be limited to a certain season. Slower than asexual reproduction. Allows genetic mixing, increasing variability in a population. Terms to know: Haploid: having a single set ofchromosomes in each cell. Diploid: having two sets ofchromosomes in each cell. Mitosis: cell division, which producestwo genetically identical cells. Meiosis: reduction division, whichproduces four haploid reproductive cells. Plant Life Cycle Alternation of Generations
Plants have a double life cycle with twodistinct forms: Sporophyte: diploid, produce haploidspores by meiosis (reduction division). Gametophyte: haploid, producegametes by mitosis (simple celldivision). Non-flowering plants Mosses, ferns, and related plants havemotile, swimming sperm. What kind of environmental conditionswould be required for reproduction inthese plants? What kinds of limits does externalreproduction impose on these plants? Reproduction in these plants requires wet conditions, and requires having male and female parts close together. Living conditions, plant size, and genetic mixing is limited. Moss Life Cycle Fern Life Cycle Conifers Conifers (also non-flowering plants) havereduced gametophytes. Male gametophyte is contained in a drypollen grain. Female gametophyte is a few cellsinside of the structures that becomethe seed. Conifer life cycle Conifer pollination Conifers are wind-pollinated plants.
Chance allows some pollen to land onthe scales of female cones. Pollen germinates, grows a pollen tubeinto the egg to allow sperm to fertilize theegg. What are some advantages anddisadvantages to wind pollination? Animals vs. Plants Plant Reproduction Animal Reproduction Life cycle
Alternation of generations No alternation of generations Gametes Haploid gametes Spores Haploid spores No spores Gametes made by Haploid gametophyte, by mitosis Diploid organism, by meiosis Spores made by Diploid sporophyte, by meiosis Flowers Pollen go-betweens Showy flowers are the result of selectionfor more efficient pollination strategies. Flower parts are modified leaves. Thosethat were brightly colored attractedinsects in search of pollen. Why would insects search for pollen?What other rewards do flowers offer? What are advantages and disadvantagesto relying on insects as pollinators? Pollen itself is a protein-rich food for insects. Some plants offer other rewards, such as nectar. Flower Parts Incomplete flowers Flowers are complete if they have allparts, and perfect if they have both maleand female parts. Grass flowers: incomplete, usuallyimperfect (separate male and femaleflowers) A tulip is complete (though the sepalsare the same color as the petals) andperfect. Imperfect flowers Angiosperm Life Cycle Gametogenesis: Male Gametogenesis: Female Double Fertilization Fruits From ovary to fruit The ovary of the flower contains the ovules.
As fertilized ovules develop into seeds,the ovary wall develops into the fruit. In science, the term fruit refers to amature ovary that contains seeds. Flower to Fruit Types of dry fruits Capsule (Poppy) Legume (Bean pod) Achene
(Sunflower) Follicle (Columbine) Silique (Money Plant) Nut (Hazelnut) Types of fleshy fruits Drupe (Peach) Pome (Apple) Pepo (Cucumber)
Berry (Tomato) Aggregate (Strawberry) Multiple (Pineapple) Seeds Ovule to seed Seed Anatomy Seed anatomy Seed dormancy Seeds can remain dormant in the soil forlong periods of time. Dormancy helpsensure that seeds only germinate whenconditions are right. When we weed or cultivate a bare patchof soil, the weeds that sprout upimmediately usually come from the seedbank already in the soil. Breaking dormancy Seeds require moisture and the righttemperature to germinate. In addition, some seeds germinate onlyafter certain environmental signals: Drying Temperature (period of cold or heat) Disruption of the seed coat Seed Germination