Plants
Table of Contents Plants ..................................................................................................................................... 2 Major autotrophic groups ........................................................................................................ 2 Alternation of generations ...................................................................................................... 2 Plasticity ........................................................................................................................................ 3 Monocot v Eudicot ...................................................................................................................... 5 Internal architecture ................................................................................................................. 5 Water movement ........................................................................................................................ 7 Angiosperm reproduction ....................................................................................................... 7 Tropisms ........................................................................................................................................ 8 Hormones ...................................................................................................................................... 9 Animals ................................................................................................................................. 9 Invertebrates ............................................................................................................................... 9 Inferring evolutionary relationships ................................................................................ 10 Vertebrates ................................................................................................................................ 11 Animal structure ...................................................................................................................... 11 Histology ..................................................................................................................................... 14 Nervous system ........................................................................................................................ 15 Sensory perception ................................................................................................................. 15
Plants Major autotrophic groups • •
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Algae, bryophytes, ferns, gymnosperms, angiosperms o Not fungi as they don’t photosynthesise Algae: unicellular or multicellular, contain chlorophyll a, ‘seaweed’ in large numbers, marine environment. No vascular tissue, embryo, flowers. 4% of plant species o Rhodophyta (red seaweed): colour from accessory pigments (red= phycoerythrin, blue= phycocyanin). CaCO3 in cell walls à coral reefs, tides and water currents used to move gametes à fertilisation o Phaeophyta (brown seaweed): mannitol and laminarin (glucose polymer) as food stores, align in cell walls. Blades help floatation and are site of photosynthesis. Holdfast at one end of stipe, meristem with blades at the other o Chlorophyta (green algae): chlorophyll a and b present as well as “true” starch for storage eg. sea lettuce. Undergo both sexual (gametes, fertilisation, zygote…) and asexual (clones form à zoospores) reproduction Bryophytes: mosses – flat (thalloid) or with leafy shoots, no roots, seeds, flowers or vascular tissue. Approximately 8% of plant species o Eggs, sperm enclosed by protective organs (archegonia, antheridia), embryo develops in archegonia, occurs in head of gametophyte o Gametophyte with rhizoids, stalk and leaves; sporophyte with stalk, operculum and capsule at top Ferns, fern allies: vascular plants, no seeds, spores born in sporangia, large leaf-like fronds are common o About 3% of plant species o Sporophyte is the dominant plant stage (has roots and fronds so better suited to life) Gymnosperms (conifers, cycads) – form secondary xylem (wood), produce ‘naked’ seeds (not produced in fruit) exposed on cone scales o Pollen forms in male cones (small), released into wind, attach to eggs in female cone scales o Autumn of second year: ones release seeds à young saplings o Sperm nucleus discharged into egg = fertilisation à sporophyte embryo, food resources are in seed coat, for development Angiosperms (flowering plants): account for 85% of plant species, seeds are produced in fruit o Flower, fruit, endosperm (rich in starch and food reserves), vessels and sieve tubes (phloem) o Fruit= beneficial because animals consume it à long distance dispersal
Alternation of generations •
Halpoid (n, gametophyte) and diploid (2n, sporophyte) phases in one life cycle (named by what is produced in phase)
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Particularly evident in ferns, in bryophytes they exist simultaneously
Plasticity •
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Modular fashion of shoot development in all angiosperms o Structural stem produced from apical meristem (may be protected by unfurled young leaves) à terminal bud o Nodes: have tissue with potential to be leaves, make apical meristems (at apical buds) o Internodes sit between nodes Stem systems are subject to different morphologies (especially with respect to nodes) Atypical function of module elements adds to plasticity eg. apical meristem produces a flower/inflorescence (group of flowers), not a stem Leaf arrangements + phyllotaxis: o Only about 10% of light penetrates a leaf
Plants Major autotrophic groups • •
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•
•
•
Algae, bryophytes, ferns, gymnosperms, angiosperms o Not fungi as they don’t photosynthesise Algae: unicellular or multicellular, contain chlorophyll a, ‘seaweed’ in large numbers, marine environment. No vascular tissue, embryo, flowers. 4% of plant species o Rhodophyta (red seaweed): colour from accessory pigments (red= phycoerythrin, blue= phycocyanin). CaCO3 in cell walls à coral reefs, tides and water currents used to move gametes à fertilisation o Phaeophyta (brown seaweed): mannitol and laminarin (glucose polymer) as food stores, align in cell walls. Blades help floatation and are site of photosynthesis. Holdfast at one end of stipe, meristem with blades at the other o Chlorophyta (green algae): chlorophyll a and b present as well as “true” starch for storage eg. sea lettuce. Undergo both sexual (gametes, fertilisation, zygote…) and asexual (clones form à zoospores) reproduction Bryophytes: mosses – flat (thalloid) or with leafy shoots, no roots, seeds, flowers or vascular tissue. Approximately 8% of plant species o Eggs, sperm enclosed by protective organs (archegonia, antheridia), embryo develops in archegonia, occurs in head of gametophyte o Gametophyte with rhizoids, stalk and leaves; sporophyte with stalk, operculum and capsule at top Ferns, fern allies: vascular plants, no seeds, spores born in sporangia, large leaf-like fronds are common o About 3% of plant species o Sporophyte is the dominant plant stage (has roots and fronds so better suited to life) Gymnosperms (conifers, cycads) – form secondary xylem (wood), produce ‘naked’ seeds (not produced in fruit) exposed on cone scales o Pollen forms in male cones (small), released into wind, attach to eggs in female cone scales o Autumn of second year: ones release seeds à young saplings o Sperm nucleus discharged into egg = fertilisation à sporophyte embryo, food resources are in seed coat, for development Angiosperms (flowering plants): account for 85% of plant species, seeds are produced in fruit o Flower, fruit, endosperm (rich in starch and food reserves), vessels and sieve tubes (phloem) o Fruit= beneficial because animals consume it à long distance dispersal
Alternation of generations •
Halpoid (n, gametophyte) and diploid (2n, sporophyte) phases in one life cycle (named by what is produced in phase)
•
Particularly evident in ferns, in bryophytes they exist simultaneously
Plasticity •
•
•
•
Modular fashion of shoot development in all angiosperms o Structural stem produced from apical meristem (may be protected by unfurled young leaves) à terminal bud o Nodes: have tissue with potential to be leaves, make apical meristems (at apical buds) o Internodes sit between nodes Stem systems are subject to different morphologies (especially with respect to nodes) Atypical function of module elements adds to plasticity eg. apical meristem produces a flower/inflorescence (group of flowers), not a stem Leaf arrangements + phyllotaxis: o Only about 10% of light penetrates a leaf
