Angiosperms Anthophyta More specialized xylem evolved. Tracheids seen in gymnosperms gave rise to vessel elements Xylem is reinforced by second cell wall, the fiber (also seen in conifers) Flower is the reproductive structure Coevolution is seen between flowers and animals

Pollination Wind pollination: <100 meters (vast majority); must be in groups 70% insect in angiosperms Yellow/blue flowers Moths flat flower, pale color, heavily scented Fly: may be scented like carrion Birds: red, orange, yellow; lack scent; lots of nectar Bats: bloom at night; dull/white petals; strong scent >30% fruits and veggies pollinated by bees

The Fruit What is a fruit? After fertilization the ovary becomes the fruit. It protects the seeds. Name three modifications that different fruits have for seed dispersal. Sweeten and turns colorful when ripe Have burrs that can sticks to animal’s fur Feathery like dandelions for wind dispersal of seeds

Sporophyte/Gametophytes Review the stages in plant alternation of generations! The life cycle of the angiosperms shows very reduced gametophyte generations. What is the male gametophyte? What is the female gametopyte? What is pollination? Bringing pollen to the stigma. How does self-incompatibility work?

Double Fertilization The pollen tube grows following pollination and leads to double fertilization. What is fertilized? Sperm + egg = zygote (2n) Sperm + 2 polar nuclei = endosperm (3n)

Pollen tube growth activity The epidermis of onions (that thin layer of cells that peels away between layers of onion bulb) was removed in strips and laid with inner side facing upwards on microscope slides. Pollen was dabbed onto the exposed inner surface of the onion epidermis and then a wet mount was made (water plus coverslip). The slides were placed and kept in a humid box lined with moist paper towel.

Seed Development Endosperm develops before embryo Endosperm provides food for developing embryo Embryo reaches a certain size and then enters dormancy until germination.

Germination How can seed dormancy be advantageous to a plant? Helps with dispersal Doesn’t leave dormancy until conditions are good What are some conditions for breaking dormancy? Desert – Only after good rainfall Chaparral – fire Others – coats weakened by digestive enzymes as they pass through animal’s digestive tract

Imbibation Hormone release …

Radicle emerges from seed Shoot tip breaks through the soil. Until this point how has the embryo received nutrients? Endosperm(food)and radicle (water).

Review the Evolution of Alternation of Generation in Plants

Pollen grain has 2 nuclei: Generative nucleus Tube nucleus