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9 Cards in this Set
- Front
- Back
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how does an organism increase their chance of survival |
by respnding to chages in the environment |
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describe kineses |
-non directional response to stimulus -the animal does not move toward or away from the stimulus -rate of movement changes until more favourable conditions are found -example: woodlice |
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describe taxes |
-more advanced response -movement is directly towards or way from the stimulus -direction of movement changes -example: maggots |
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describe tropisms |
-ressponse to directional stimuli that can maintain th roots and shoots of flowering plants in a favourable environment - a tropism is the movement of a part of aa plant in response to and directed by an external stimulus -the movement is by growth so is slow - positve= towards stimulus -negative= away from stimulus |
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how many types of tropism are there |
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how do plants respond to different stimuli |
-plants respond to change using plant hormones often called plant growth factors -they are made in tissuesall over the plant -they may be used where the are made or transported within the plant via the phloem |
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what are the effects of plant growth factors |
-cell divison -cell elongation -cell differentiation |
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describe IAA |
-indoleacetic acid (IAA) is made in the tips of the shoots and roots -it can move by diffusion from cell to cell or can be transported by the phloem -it is invlved in the regulation of the cell elongation -IAA stimulates cell elongation in shoots but inhibits cell elongation in roots -IAA belongs to a group of plant growth facrors known as auxins |
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describe photoreceptors |
-structures or pigments that are sensitive to the light -phototropins are a group of photoreceptors primarily responsible for triggering phototropisms -when light of the right wavelrngth is present changes in thee phototropin molecules trigger a cascade of reactions in the cell, this ultimately results in redistribution of auxin so that ther is more on the shaded side of the plant. |
