1. Plant Evolution
Chapters 29 & 30

2. Main Points Evidence that land plants have evolved from green algae
Disadvantages and advantages of life on land
The major evolutionary characteristics of bryophytes and seedless vascular plants
Plants have a unique life cycle termed alternation of generations with a gametophyte generation and a sporophyte generation
The typical life cycle pattern of plants, as demonstrated by ferns
The evolutionary significance of seeds and pollen as key adaptations to life on land
The evolutionary significance of flowers and fruits in angiosperm reproduction

3. I. Land plants evolved from green algae
A. Approximately 500 million yeas ago
B. Enabled other life-forms to survive on land
Advantages
Challenges
Increased sunlight (not filtered by water)
Lack of water
More carbon dioxide available
Desiccation (drying out)
Soil rich in nutrients
Structural support against gravity
Fewer predators

4. C. Alternation of generations
1. Composed of two multicellular stages
Gametophyte – haploid, produces gametes
Sporophyte – diploid, makes spores by meiosis

5. II. Bryophytes A. 3 phyla – mosses, liverworts, hornworts
B. Non-vascular – no xylem or phloem
1. Must be small
C. Gametophyte stage dominant
1. Require water for sperm to meet egg
2. Smallest, simplest sporophytes of all plant groups – must absorb water, sugar, nutrients from parental gametophytes

6. III. Seedless Vascular Plants
A. Ferns, club mosses, horsetails
B. Evolution of vascular tissue allowed plants to grow taller and gain more access to sunlight
C. Still require a film of water for sperm to reach egg
D. Diploid sporophyte stage dominant
E. Formed forests of tall plants in the Carboniferous period, formed deposits of coal (now used as fuel)

8. Advantages over spores
IV. Seed Plants
A. Seeds – plant embryos packaged with a food supply in a protective coat
Dispersed from parents by wind, animals, etc.
Pollen - male gametophyte, contains 2 sperm nuclei, waterproof coating
Advantages over spores
Layers of protective tissue around embryo
Contain a supply of stored energy
Can wait for conditions to be good before germinating
Sperm doesn’t require water to reach egg

9. B. Gymnosperms – naked seeds (no fruit, often cones)
1. Four phyla, largest is the conifers – pines, spruces, firs, and redwoods

10. C. Angiosperms – flowers and fruits
About 90% of all plant species
Flowers – specialized for sexual reproduction – improves the efficiency of pollination
a. Don’t have to rely on wind, attract birds and insects which transfer pollen anthers (male parts) to carpels (female parts) of other flowers
b. Grasses – don’t attract pollinators but produce huge quantities of wind-borne pollen

11. 3. Fruits – mature ovaries
Thicken as seeds develop from ovules after fertilization
Help disperse seeds

12. 4. Monocots and eudicots (dicots)
a. Monocots – about 70,000 species, have one cotyledon in the seed, parallel leaf venation, flowering parts in multiples of 3
b. Eudicots – about 170,000 species, two cotyledons in seed, net leaf venation, flowering parts usually in multiples of 4s or 5s