Plant Reproduction and Plant Diversity II
Seed plants –
3 adaptations that seed plants have:
Gametophytes of seed plants almost invisible.
Gametophytes still exist –
Seed - sporophyte embryo packaged with
Seed plants produce 2 different types of sporangia - produce 2 different types of spores:
Gametophytes stay in sporophyte as it develops.
Ovule –
Female gametophyte develops inside megaspore; produces 1 + egg cells.
Fertilized egg develops into sporophyte embryo.
Whole ovule develops
Microspores (pollen) – light, carried through air.
Pollen will create pollen tube
2 groups of seed plants:
Gymnosperms
4 phyla of gymnosperms still around.
Phylum Ginkgophyta
Phylum Cycadophyta - cycads Phylum Gnetophyta –
Phylum Coniferophyta
Conifers
Conifers are evergreen - keep leaves all year long.
Needles help in dry conditions.
Conifers include pines, firs, spruces, larches, yews, junipers, cedars, cypresses, and
redwoods.
Life cycle of gymnosperms
Conifers - heterosporous
Produce
During pollination, pollen falls on ovule.
Creates pollen tube that digests through megaspore.
Megaspore, now fertilized, goes through meiosis
1 cell turns into female gametophyte, others (archegonia) will develop within gametophyte.
Angiosperms
Angiosperms Phylum Anthophyta - all angiosperms.
Divided into 2 groups:
Monocots -
Angiosperms - long tracheids –
Most angiosperms rely on pollination through animals; grasses Flower - specialized shoot –
Sepals - base of flower –
Petals lie inside ring of sepals
Male organ - stamen
Anther –
Female organ - pistil Stigma –
Style connects stigma to ovary at base of pistil which allows
Entire structure –
Ovule contains.
Fruit –
As seeds develop from ovules after fertilization Fruit helps protect
Some fruits, dandelion,
Burrs that stick to animals
Fruit develops after pollination triggers hormonal changes
Wall of ovary becomes pericarp
If flower not pollinated 3 different types of fruits.
Simple fruits come from
Aggregate fruit (blackberry) –
Multiple fruit (pineapple)
Ovules - contain
Angiosperm life cycle starts with mature flower on
Anthers of flower produce
Ovules produce megaspores that form
After its release from anther,
Plants can self-pollinate;
Pollen grain begins growing from stigma toward ovary.
Discharges 2 sperm cells into female gametophyte.
1 sperm fuses with egg nucleus to form diploid zygote.
Develops into embryo.
Embryo has rudimentary root; one (in monocots) or two seed leaves (in dicots), cotyledons.
Other sperm nucleus fuses with 2 polar bodies to form endosperm, (triploid or 3n) in
monocots.
Dicots - nutrition goes directly to cotyledons.
As ovules develop into seeds, ovary develops into fruit.
Conditions favorable - germination occurs (seed coat ruptures, embryo emerges as seedling)
Seedling uses food stored in either endosperm
The fruit
Ovary of flower develops into fruit,
Wall of ovary becomes pericarp,
Apples
As seed develops - enters dormancy –
1st organ to emerge from germinating seed -
Asexual reproduction
Plants can clone –
Fragmentation –
Scientists use this process to
Co-evolution
Certain animals only eat certain plants Plants evolved special fragrances –
Plants and human welfare
All fruit and vegetable crops Corn, rice, wheat Use plants for medicinal purposes;