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Plant Diversity and Life Cycles

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Presentation on theme: "Plant Diversity and Life Cycles"— Presentation transcript:

1 Plant Diversity and Life Cycles

2 5 derived characteristics in land plants (not in ancestors)
Apical meristems – localized areas of cell division in shoot & tips Alternation of generations – separate slide Walled spores produced in sporangia tough wall resists drying 2n spore mother cells go through meiosis to produce 4 haploid spores Multicellular gametangia Archegonium – (female) produces haploid egg & keeps it Antheridium – (male) produces & releases sperm Multicellular, dependent embryos develop w/in archegonium from zygote Derive nutrition from female parent tissue with specialized placenta- like cells

3 2 more traits that evolved in many plant groups
Cuticle Made of waxes on surface of epidermal cells Protection Secondary compounds Repel herbivores & parasites Absorb UV radiation Attract symbionts

4 Basic Life Cycle of Plants – Alternation of Generations

5 4 Major Plant Phyla Bryophytes Pterophytes Gymnosperms Angiosperms
nonvascular plants Bryophytes (mosses) Land plants vascular plants Seedless Pterophytes (ferns, etc) Seed plants Naked seeds – Gymnosperms Coniferophyta Enclosed seeeds – Angiosperms Anthyophyta

6 Bryophytes Non-vascular – whole body can absorb water
Gametophyte is larger (dominant) stage Sporophyte dependent on gametophyte No true leaves Flagellated sperm Mosses require water for fertilization. Why?

7 Moss Life Cycle – p. 581

8 Pterophytes Seedless vascular plants Ex – ferns
Sporophyte larger stage True roots & leaves w/ horizontal stem Sporangia on leaves called sporophylls Homosporous – one kind of spore (bisexual gamete – egg & sperm) Heterosporous female spore (megaspore) female gametophyte egg Male spore (microspore) male gametophyte sperm

9 Fern Life Cycle – p. 585

10 Vascular Seed Plants Common traits Seeds Integument – seed coat
Female gametophyte – food supply Embryo sporophyte – baby plant Advantage of seeds Consists of embryo and food supply contained in protective coat Better resist harsh environments Disperse offspring more widely

11 Ovules – contains female gametophytes
Reduced gametophytes – spores retained in sporangia, develop into gametophytes Heterospory – Megasporangium produce one megaspore & female gametophyte Microsporangium produce many microspores & male gametophytes Ovules – contains female gametophytes Pollen – contain male gametophytes – transferred to female part of plant and will germinate into a pollen tube that finds the ovule and egg

12 Gymnosperms Bear “naked” cones – seeds are exposed on modified leaves that usually form cones Pollen cones – produce pollen Ovulate cones – produce eggs Coniferophyta – pines, firs, redwoods

13 Pine Life Cycle – p. 597

14 Angiosperms Anthophyta - Flowering plants used for sexual reproduction
Megasporangium megaspore megagametophyte in ovule (all enclosed in ovary of flower) Microsporangium microspore microgametophyte in anther of flower Fruits - mature ovary – seed develops from ovules after fertilization, the wall of the ovary thickens Ex – tomato, grapefruit, nectarine, milkweed, walnut Pollination required for transfer of pollen from flower to the female sex organs of another flower

15 Double Fertilzation One sperm fertilizes the egg cell and the other sperm combines with the two polar nuclei of the large central cell of the embryo sac. Result - One sperm nucleus unites with the egg to form the diploid zygote, from which the embryo develops, and the other unites with two polar nuclei to form the triploid, primary endosperm nucleus (nutrition).

16 Flower anatomy

17 Angiosperms

18 Seeds – monocots & dicots

19 Germination Imbibation – taking in H2O
ABA decreases (plant soluble hormone that causes dormancy) Embryo responds and releases gibberellin (stimulates release of amylase) Amylase breaks down starch for nutrition which allows for growth Root extends downward while shoot extends upward

20 Factors affecting germination – HOW?
Water Oxygen Temperature Light


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