Pteridophytes
During Carboniferous (354-290 mya), large amounts of carbon dioxide removed from the atmosphere by lycophytes and pteridophytes
Diverse phyla of gymnosperms dominated Earth’s vegetation through the Mesozoic ear (248-65 mya)
gymnosperm = new phyla of land plants
Cycads, ginkgos, and conifers*
- Reproduce using spores (like previous plant phyla) and seeds (like later to evolve angiosperms)
- Gymnosperms are seed plants
- Seeds protect and provide energy for young sporophyte
- “Naked seeds” meaning seeds are not enclosed by fruit
Phylum Coniferophyta = Conifers (cone bearers)
- Most common gymnosperms
- Pines, spruces, and firs
- Woody reproductive cones
- Most are evergreen (shed some but not all leaves each year)
- Needle leaves
- Many produce resin
Phylum Cycadophyta = Cycads
- Shrubby or treelike with palmlike leaves
- Some have large, cone-shaped strobili
- Restricted to warmer climates
Phylum Ginkophyta = Ginkgoes:
- One living species, Ginkgo biloba
- Fan-shaped leaves
homosporous
- one size of spore (haploid)
But some are heterosporous (of different sizes of spores)
the spore stays intact while the gametophyte grows inside
- gives an extra layer of protection for gametes and eventually the embryo
- naked seed plants
- sporophyte haploid spores retained in their reproductive structures
with the microspores, involved in pollen production
2n sporophyte generation produces haploid spores by meiosis
multicellular n gametophyte
non
transfer of pollen to female reproductive parts, with no water required
- an egg developing inside a gametophyte that is retained not only inside the spore wall but also inside integument and megasporangial tissues
- macrospore ends up as the ovule
the archegonium
single cell which is diploid zygote
yes
- Seeds are a key adaptation to reproduction in a land habitat
- Able to remain dormant in the soil – can wait for favourable conditions
- Adaptations to improve dispersal
- Can store considerable amounts of food
- Sperm can reach egg without having to swim through water
- Flowering plants with covered seeds
- Carpels (specialized leaves) protects ovules and seeds
- Flowers contain carpels at their centre
- Fruit structure nourishes and disperses seeds
- Major groups are monocots and eudicots
- Most ecologically diverse plants on Earth
- At least 260 000 species are known
Monocots and Eudicots
wheat, trillium, western wood lily
- twinflowers
angiosperms
- they have endoperms inside their seeds
endosperms: a triploid tissue
- Double fertilization
- One sperm fertilizes egg to become an embryo
- Other sperm fuses with different gametophyte tissue to form endosperm
- Ovule’s integument develops into a protective, hard and tough seed coat
- Seeds allow embryos access to food supplied by the older sporophyte generation
1. efficient transport
- vessel elements (more efficient than tracheids)
- more efficient phloem
2. double fertilization
- produces embryo and endosperm
3. ovary protects ovule
- develops from carpel, turns into fruit