Lab 7 – Bio 171

Plants 2 – Gymnosperms and Angiosperms

1A: Gymnosperms (naked seeds)• Diverged ~300 mya, when Earth became warmer and drier and the

swamp forests declined. – no swimming for the sperm. – During Carboniferous period.

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

• There are 4 distinct divisions/phyla: – 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

1B: 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• Diverged from gymnosperms 250-200 mya. First flowers

around 160 mya.• 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)

aka fruit!

2A: 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)

Pollinator coevolutionTricky orchid not entirely mutualistic

Competitive Exclusion – two species competing for the same resource cannot coexist

Coevolution allowed for adaptive radiation of insects

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

*note that arrows go counter-clockwise

Fruit!

2D: Fruits and dispersal

Mature ovule = fruit

Today

• Think about key derived characteristics• Can you think of possible adaptations that benefit

angiosperms in Montana?• Turn in your idea paragraph• Don’t forget: QHMs are required each week.• Next week: Spring Break!