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Plant Reproduction. W O R K T O G E T H E R. 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.

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Plant Reproduction

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Plant Reproduction


W

O

R

K

T

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E

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H

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R

  • 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


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


Angiosperm Life Cycle


Gametogenesis: Male


Gametogenesis: Female


Double Fertilization


Flower to Fruit


Ovule to Seed


Seed Anatomy


Seed Germination


W

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  • 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.


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