Plant Reproduction AP Biology Unit 5

Bryophyte (Moss) Life Cycle Nonvascular Plant The gametophyte is the dominant form – Dominant form = the “plant” we think of as a bryophyte Gametophyte is anchored to the ground by rhizoids (H 2 O absorbing filaments). Mosses require water for reproduction - the sperm will swim to the egg by following a trail of chemicals.

Question… What times of year or environmental conditions would favor moss reproduction? –Wet, rainy

Reproductive Organs Archegonium –Female sex organ  produces egg Antheridium –Male sex organ  produces sperm

Sperm and Egg are produced from spores through MITOSIS Sperm have to be splashed to a nearby archegonium

Sporophyte is attached to and nutritionally dependent on the gametophyte

Vascular Plants: Homosporous vs. Heterosporous Vascular plants have sporophylls –modified leaves that produce sporangia (which become spores) Homosporous plants –Most ferns Heterosporous plants –All seed plants (angiosperms and gymnospems) and some seedless plants

Pterophyte (Fern) Life Cycle The dominant form is the sporophyte Like mosses, water is necessary for reproduction Sori are clusters of sporangia on the underside of leaves Homosporous plants Gametophyte is a tiny plant anchored in the soil by rhizoids

Gametophyte/Sporophyte Relationships 3 different possibilities –Larger gametophyte, sporophyte is dependent on it –Larger sporophyte, gametophyte is independent –Larger sporophyte, gametophyte is dependent

Gymnosperm Life Cycle Sporophyte is the dominant form Heterosporous Have “naked” seeds – nothing around the seed Cones are either male (contain pollen) or female (contain ovule)

Gymnosperm cones Cells on the Ovulate cone will form megasporangium  form female gametophyte Cells on the Pollen cone will form microsporangium  form male gametophyte (pollen grain)

Micropyle = opening that pollen tube enters through While the pollen tube is being extended, sperm are produced through MITOSIS, megaspore is produced through MEIOSIS male gametophyte (pollen grain) lands on the ovulate cone and extends a pollen tube (digests it way) towards the female gametophyte