Gymnosperms (naked seeds)

Gymnosperms (naked seeds)• Diverged 150 mya, when Earth became warmer and drier and the

swamp forests declined. – no swimming for the sperm.

• Members of this group do not produce flowers and all are wind-pollinated.

• There are 4 distinct divisions: – Coniferophyta (cone-bearing trees and shrubs)– Ginkgophyta (flat fan-shaped leaves)– Cycadophyta (palm-like appearance) – Gnetophyta [3 distinct and unusual groups: gnetums, Welwitschia, and

Mormon tea (Ephedra)]

Coniferophyta

Includes pines and other cone-bearing trees and shrubs.

Ginkgophyta• Flat fan-shaped leaves• Native to Asia• Only one extant species,

Gingko biloba…. It’s a living fossil!

• It’s also an endangered species.

Cycadophyta• Palm-like appearance• Found primarily in tropical regions around

the world.• Some species are very endangered

Gnetophyta3 distinct groups:

Gnetum

Welwitschia

Ephedra

Pine Life Cycle• All gymnosperms are wind-pollinated trees or shrubs, but

insect pollination can happen too.

• Most are unisexual, with M and F reproductive structures on different parts of the same plant.

• They are heterosporous: male microspores develop into pollen, and female megaspores develop into the female gametophyte.

• The female gametophyte is not free-living, but retained within the megasporangium where it is nourished by the sporophyte parent plant.

Angiosperms• Phylum (division) Anthophyta Nope. • The carpel, a vessel in which the ovules are enclosed, is unique to

angiosperms.• After fertilization the ovule develops into a seed (like gymnosperms),

while the carpel matures into a fruit (unique to angiosperms)

Angiosperm flowers• Flowers are composed of both male and female reproductive

structures

• Many flowers are self-fertile, but cross-fertilization is important in maintaining genetic diversity.

• Pollinators, such as birds, insects, and mammals help transfer pollen from flower to flower. (~85% of it, actually)

2) Alternation of generations (Angiosperms)

Microsporangium

(anther)

Megasporangium

(carpel)

Pollen

Ovules

Ovary

Embryo

Fruit

Endosperm (3n)

GAMETOPHYTE (n)

SPOROPHYTE (2n)Seed

Coat (from mom)

Mature Sporophyte

Embryo

Endo.

Pollen Tube