Week 2 - Alternating Genomes & Reproduction

Gametophyte

Haploid sexual generation

Sporophyte

Diploid asexual generation

Plant generations for the first 100m years

Sporophyte stage became larger & more complex, gametophyte stage became smaller & enclosed in sporophyte

Large gametophyte, small sporophyte

Bryophytes, parasitic sporophyte relies on gametophyte for nutrients & carbon

Small gametophyte, large sporophyte

Ferns & horsetails, sporophyte is dominant

Female gametophyte

Enclosed in sporophyte

Male gametophyte

Dispersed as pollen grain

Parasitic

Gametophytes are ______ on sporophytes

Mutations in adult somatic cells

Animals - not passed onto next generation

Plants - passed onto offspring

Deleterious mutations

Removed from population because gametophytes will not develop

3 major groups of angiosperms

Magnoliids, Eudicots/dicots, monocots

Magnoliids

Earliest evolved angiosperms

Tulip trees, magnolias

Eudicots/dicots

75% of flowering plant diversity

Basal & derived

Basal eudicots

Earlier evolved

Poppies & buttercups

Derived eudicots

More recent evolution

Rosid & asterid groups

Flowers

Do not fossilize well, difficult to see transitional forms in fossil record

Unique to angiosperms

Flowers

Seeds have endosperm

Good food source for embryo

Xylem vessels (plant plumbing)

Rosid dicots

Separate petals

Roses, apple trees

Asterid dicots

Fused petals

Purple asters, Canada goldenrod

Non-showy flower monocots

Mostly grasses

Cover 20-30% of land surface

Food crops

Petaloid monocots

More showy flowers

Lilies, asparagus, orchids

Dicot seedlings

Two cotyledons

Net arrangement of leaf veins

Cotyledon

Seed leaf, two on dicots, one on monocots

Monocot seedings

One seed leaf

Parallel arrangement of leaf veins

Angiosperms

> 50% of extant plant species

Dominate most habitats