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15 Cards in this Set
- Front
- Back
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How do seeds form in Angiosperms?
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After fertilization, the plant embryo grows & develops
Once meristems and cotyledons (seed leaves) differentiate, development stops (or, the embryo becomes dormant) Outer layers of the ovule develop into a relatively impermeable seed coat, enclosing the dormant embryo and endosperm (stored food) Mature seeds contain between 5% - 20% water |
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Adaptive Importance of Seeds
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Postpone development until favorable conditions are present
Afford maximum protection to the young plant at its most vulnerable stage of development Contain stored food permitting development before photosynthesis starts (Endosperm) Have specific dispersal mechanisms, facilitating migration of alleles into new gene pools |
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Cotyledons
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seed leaves
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Male reprodutive site
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stamen
sperm are made in anther |
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Female reproductive site
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pistel which contains ovary
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How do fruits form?
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Fruits are mature ovaries
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Dry fruits
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follicles, legumes, samaras, nuts, grains
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Fleshy fruits
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drupes, berries, hesperidia, pomes, pepos
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Aggregate fruits
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develop from many ovaries of a single flower
strawberries, blackberries |
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Multiple fruits
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develop from a cluster of flowers
pineapple, mullberry |
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Methods of Seed dispersal via fruit (w/ example)
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Birds – fruits with fleshy coverings, usually shiny black, blue, or red
Mammals - fruits with hooked spines that attach to fur - fruits buried by squirrels or other mammals (nuts) Wind – maples, elms, dandelions, cottonwoods, etc. Water – beach plants (like coconuts) |
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Germination: Definition
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The resumption of growth and development by a spore or seed
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Germination: Conditions Necessary
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Only occurs when water is absorbed, which breaks the seed coat
Sufficient oxygen must be present for development to continue Thus very few types of seeds can germinate under water |
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Germination: Process at start
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Cellular respiration resumes, using oxygen & food stored in seed
Roots emerge first, then cotyledons |
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Hypocotyl
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connects root system to cotyledons
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