Evolution of Plants:
Unicellular multicellular multicellular Fern
autotrophic ----> aquatic ----> terrestrial -----> vascular
aquatic autotrophic Moss gymnosperms/angiosperms
- Many angiosperms reproduce sexually and asexually. (Flowers have both parts) Example: lily
- Diploid (2n) sporophytes produces spores by meiosis; these grow into haploid (n) gametophytes.
- Gametophytes produce haploid (n) gametes by mitosis; fertilization of gametes prodices a sporophyte.
- In angiosperms, the sporophyte is the dominant generations, the large plant that we see.
- Tropisms: phototropism = seed plant will grow toward light and gravitropism = if a seed plant seed is planted upside down it will still grow the corect way due to gravity.
- Flowers consist of 4 floral organs: sepals, petals, stamens, and carpels.
- A stamen (male) consists of a filament topped by an anther with pollen sacs that produce pollen (male).
- A carpel has a long style with a stigma on which pollen may land.
- At the base of the style is an ovary containing one or more ovules.
- A single carpel or group of fused carpels is called a pistol.
- Complete flower contains all 4 floral organs.
- Incomplete flowers lack 1 or more floral organs, for example: stamens or carpels.
- Double Fertilization results from the discharge of 2 sperm from the pollen tube into the embryo sac.
- One sperm fertilizes the egg, and the other combines with the polar nuclei; giving rise to the triploid (3n) food storing endosperm.
- After double fertilization, each ovule developes in to a seed.
- The ovary developes into the fruit enclosing the seeds.
- Angiosperm = closed seed
- A fruit developes from an ovary.
- It protects the enclosed seeds and aids in seed dispersal by wind or animals.
- A fruit maybe classified as dry, if the ovary dries out at maturity, or fleshy, if the ovary becomes thich, soft, and sweet at maturity.
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