Ch 30 Seed Evolution in Gymnosperms Flashcards
(31 cards)
Seed
Consists of an embryo and nutrients
What surrounds the seed?
A protective seed coat
Why are plant seeds an advance in the evolution of life on land?
They enabled the plants that possessed them to become the dominant producers in most terrestrial ecosystems
In addition to seeds, the following are common to all seed plants:
1) Reduced gametophyte
2) Heterospory
3) Ovules
4) Pollen
In nonvascular plants, what is the dominant free-living stage?
The gametophyte
In seedless vascular plants, what is the dominant free-living stage?
The sporophyte
What is true of the gametophytes of seed plants?
They develop within the walls of the spores and are retained within tissues of the sporophyte
The ancestors of seed plants were likely homosporous or heterosporous?
Homosporous
Homosporous
Possessing one type of sporangia
Seed plants are homosporous or heterosporous?
Heterosporous
Heterosporous
Possessing male and female sporangia
Megasporangia
Produce megaspores
Megaspores
Give rise to the female gametophyte (produces eggs)
Microsporangia
Produce microscopes
Microspores
Give rise to the male gametophyte (pollen grains)
An ovule consists of:
1) Megasporangium
2) Megaspore
3) One or more protective integuments
What occurs once a pollen grain reaches the ovule?
It extends a pollen tube that discharges sperm into the female gametophyte within the ovule
Advantages of seeds over spores:
1) Can remain dormant for days to years until conditions are favorable for germination
2) Have supply of stored food
3) May be transported long distances by wind or animals
Two groups of seed plants:
1) Gymnosperms
2) Angiosperms
Gymnosperms
Seeds are exposed on groups of sporangia that form cones
Angiosperms
Flowering plants with seeds within fruits
Four phyla of gymnosperms
1) Cycadophyta
2) Ginkophyta
3) Gnetophyta
4) Coniferophyta
Phylum Cycadophyta
Cycads
Phylum Ginkophyta
One living species, Ginko biloba
