Unit 2 Life Cycles

Fern Life Cycle

Sporophyte (2n) — Dominant, leafy fern plant. Produces haploid spores by meiosis.

Sporangia — Structures on fern leaves where spores are produced by meiosis.

Spores (n) — Haploid cells that grow into the gametophyte through mitosis.

Gametophyte (n) — Small, haploid structure that produces sperm and eggs by mitosis.

Fertilization — Sperm swims through water to reach the egg, forming a diploid zygote.

Zygote (2n) — Develops through mitosis into a new fern sporophyte.

Fern Life Cycle — Sporophyte → meiosis → spores → gametophyte → gametes → fertilization → zygote → sporophyte.

Gymnosperm Life Cycle

Sporophyte (2n) — Dominant plant, such as a pine tree. Produces spores through meiosis.

Male Cone — Produces microspores that develop into pollen grains.

Pollen (Male Gametophyte) — Produces sperm and is carried to the female reproductive structure.

Megaspore (n) — Develops into the female gametophyte inside an ovule.

Female Gametophyte (n) — Produces the egg inside the ovule.

Pollination — Pollen reaches the female reproductive structure, usually by wind.

Fertilization — Sperm reaches and fertilizes the egg, forming a diploid zygote.

Seed — Contains the embryo. Gymnosperm seeds are “naked” because they are not enclosed in fruit.

Gymnosperm Life Cycle — Sporophyte → meiosis → spores → gametophytes → pollination → fertilization → zygote → seed → sporophyte.

Angiosperm Life Cycle

Sporophyte (2n) — Dominant generation; the flowering plant you see. Produces spores through meiosis.

Flower — Reproductive structure containing the male and female parts of the plant.

Pollen (Male Gametophyte) — Develops from a microspore and produces sperm.

Embryo Sac (Female Gametophyte) — Develops inside the ovule and contains the egg.

Pollination — Pollen moves from the anther to the stigma.

Double Fertilization — One sperm fertilizes the egg to form a diploid zygote; another sperm forms triploid endosperm (3n) for nutrition.

Seed — Develops from the ovule and contains the embryo.

Fruit — Develops from the ovary and protects/disperses the seeds.

Angiosperm Life Cycle — Sporophyte → meiosis → spores → gametophytes → pollination → double fertilization → seed/fruit → sporophyte.

Biggest differnces

Fern: Spores, no seeds, sperm needs water.

Gymnosperm: Naked seeds, cones, pollen, no fruit.

Angiosperm: Flowers, enclosed seeds, fruit, double fertilization.