What were the plants’ key adaptations for life on land?
- Seeds
- Pollens
- Microscopic gametophytes, due to appearance of the previous two traits
Define
Heterospory
The production of two kinds of spores: megasporangia (female gametophytes) and micro sporangia (male gametophytes)
Define
Integument
Layer of sporophyte tissue that protects the megasporangium
Define
Ovule
Whole structure of megasporangium (2n), megaspore (n) and integument (2n)
Define
Pollen grain
Male gametophyte enclosed within pollen wall, latter of which is composed of molecules secreted by sporophyte cells
Define
Pollination
Transfer of pollen to part of seed plant that contains the ovules
What are the clades of gymnosperms?
- Ginkgophyta (only ginkgo biloba, is tolerant to stressful conditions)
- Cycadophyta (palmlike leaves; endangered)
- Gnetophytes
- Coniferophyta (most are evergreens)
What are the reproductive adaptations of angiosperms?
- Flowers
- Fruits
- Double fertilization
Describe
Flowers
- Sepals: enclose flower
- M-Stamens: produce microspores that become pollen grains; composed of filament + anther, where the production occurs
- F-Carpels: makes megaspores; sticky stigma to receive pollen; style; ovary at base
- Petals: attract pollinators
Describe
Fruits
- Ovary walls thicken and matures into fruit
- Aid in seed dispersal, as the seeds are protected and transported by animals
Describe
Double fertilization
- Two sperm cells unite with two cells in female gametophyte
- One sperm + ovum = zygote
- One sperm + 2 nuclei = endosperm (3n)
Describe
Cross-pollination
- Transfer of pollen from anther of flower to anther of flower, both from different plants
- Enhance gentic variability
Opposite of autopollination
