1. Chapter 24 Reproduction in Plants

2. Alternation of Generations All plants have a life cycle in which a diploid sporophyte generation alternates with a haploid gametophyte generation - Sperm and eggs represent the haploid gametophyte - zygotes produced from fertilization create diploid sporophyte In seed plants we recognize the sporophyte as the plant Where are the gametophytes found?

3. Gymnosperms Cones are the where we find the gametophytes for seed plants Two cone types: 1. Pollen cones – contain pollen grains and represent the male gametophyte (sperm) 2. Seed cones – contain 2 ovules that develop into large egg cells or the female gametophyte (egg) Pollination – cycle begins in the spring when male cone releases large amounts of pollen grains; female is fertilized when pollen is caught and contacts ovule – Mainly wind blown to reach other plants

4. Pollen vs Seed Cones

5. Alterations of Generations

6. Structure of Flowers Angiosperms or flowering plants contain the gametophytes within the structures of the flower 4 kinds of specialized parts of flower: 1. Sepals – outer leaf-like covering for the bud 2. Petals – attract pollinators with bright colors 3. Stamen – contains male gametophyte anther- oval sac where meiosis takes place for production of pollen grains filament –supports anther 4. Carpels – contains female gametophyte Ovary – produces eggs Stigma – female receptacle surface where pollen is caught Style – narrow stalk that supports stigma

7. Flower Anatomy

8. Angiosperms Pollination with angiosperms is mainly by animals - bees, birds, bats, and other insects carry pollen to each flower some is wind-blown, but less efficient Fertilization – pollen grain lands on stigma forms pollen tube fusing one sperm with an egg – Second fertilization takes place that forms an endosperm (3n) food rich cell that nourishes seedling during development – Double fertilization is believed to explain the evolutionary success of angiosperms

9. Alterations of Generations

10. Seed and Fruit Development Seeds provide a protective and nutritional covering for embryos - as they mature ovary walls thicken to form fruit around seeds Ex: apple Seed dispersal is necessary for continuation of species - can occur by eliminated waste from animals - can be spread by wind and water

11. Seed and Fruit Development Seed dormancy – period when the embryo is alive but not growing - occurs in order to grow during optimal conditions - can allow for long distance dispersal - environmental conditions like temperature and moisture can end dormancy Seed Germination – early growth stage of embryo - absorbs water, swells food storing tissues - cracks open seed coat - young root emerges and grows