Plants! Ms. Klinkhachorn April 4, 2011 AP Biology

Land Plants Evolved From Green Algae This evolution occurred 500 million years ago Why is this specific event important to all of us?

Land Plants Evolved From Green Algae This evolution occurred 500 million years ago Why is this specific event important to all of us? –Plants allow other organisms to live on Earth –Provide oxygen and food

Evidence for this Evolution Lines of evidence 1. Produce cellulose (material of cell walls) in the same way 2. Peroxisomes have enzymes only found in green algae 3. Structure of sperm is closely related 4. Make cell plates similarly during division 5. Chloroplast and nuclear genes are similar

Sporopollenin A layer around zygotes that prevent them from drying out –Like a shell –How is this a trait that helps with evolution in this scenario?

Movement toward Land Advantages: –Increased sunlight –More CO2 than in water –Soil that is rich in nutrients compared to water –Fewer predators Challenges: –Lack of water –Dessication (dehydration) –Lack of support against gravity

Alternation of Generations Land plant life cycle is divided into 2 stages –Gametophyte –Sporophyte

Gametophyte and Sporophyte Produce gametes –Haploid These gametes come together during fertilization to form the diploid zygote, called the sporophyte

Fig. 29-5a Gametophyte (n) Gamete from another plant n n Mitosis Gamete FERTILIZATIONMEIOSIS Mitosis Spore n n 2n2n Zygote Mitosis Sporophyte (2n) Alternation of generations

Diversification of Plants Vascular vs nonvascular –Vascular tissue serves to transport water and nutrients in tubes through the plant (allows for bigger plants) –Nonvascular plants are called bryophytes

Vascular Tissue Xylem –Transports most water and minerals –Have extra structures in place to help with support against gravity First plants to grow tall Phloem –Distribute sugars, amino acids, and other organic products

Fig. 29-UN1 Nonvascular plants (bryophytes) Seedless vascular plants Gymnosperms Angiosperms

Diversification of Plants – Seed Plants Two Types –Gymnosperms (gymno = naked, sperm = seed) Seeds aren’t in chambers Pine trees –Angiosperms (angion = container) Seeds develop in ovaries and mature into fruits All flowering plants 90% of plants

End of Ch 29, Start of Ch 30

Seeds Seeds are an embryo and its food supply –Covered by a protective coat –A seed is analagous to a detachable and mobile version of a pregnant woman’s womb Dispersion through wind and other organisms

Adaptations of Seed Plants 1. Reduced gametophytes 2. Heterospory 3. Ovules and the production of eggs 4. Pollen and production of sperm 5. Seeds

Reduced Gametophytes Alternation of generation –Spend less time in the gametophyte stage –Gametophytes are small and are easier to protect against the environment

Heterospory Produce two types of different spores –Megaspore = Female gametophytes –Microspores = Male gametophytes Why is this useful?

22 Ovules and the production of eggs Ovule increases protection of the egg and the developing zygote –increases reproductive fitness 22

23 Pollen and Production of Sperm Pollen is a male gametophyte –pollen has a waterproof coat allows for wind transfer before pollen came about, had to transfer via water 23

24 Seeds Advantages over spores –multicellular –layers of protective tissue –stored energy 24

25 Angiosperms Major reproductive adaptation of the angiosperm is the flower –sepals –petals –stamens male reproductive organ produce microspores that develop into pollen –carpels female reproductive structure produce megaspores 25

26 Stamens and Carpels Stamens consist of the anther and the filament Carpels consist of the stigma, style, and ovary 26

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30 Two types of Angiosperms Monocots Eudicots 30

31 Fruits Disperse seeds Mature ovaries of the plants –a piece of fruit represents the thickening of the ovary wall 31

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