LP-PartTwo - Warren`s Science Page

Download Report

Transcript LP-PartTwo - Warren`s Science Page

Gymnosperms: vascular seed bearing
plants with a naked seed coat
› No fruit around the seed
Conifers: seeds develop in a female
cone while male cones develop pollen
 Most are evergreens with needle or
scale-like leaves that have thick cuticles
 They make up the most abundant
(pines), tallest (redwoods), and oldest
(bristlecone pine) trees
Cycads: palm-like trees that flourished
during the Mesozoic era
› Only about 130 species still exist- confined to
tropics and subtropics
› They bear massive cone-shaped strobili that
produce either pollen (transferred by air
currents) or ovules
Ginkgos: reduced in
diversity from the
Mesozoic to only one
surviving species today
› Unusual in being
› Hardy, showing resistance
to insects, disease, and
air pollutants
Bonsai Ginkgos
Gnetophytes: most unusual
› Live in tropical and desert areas
The pine tree (sporophyte) produces two
kinds of cones
› Male cones produce sporangia that yield
microspores that develop into pollen grains
(male gametophyte)
› Female cones produce ovules that yield
megaspores (female gametophyte)
Pollination is the arrival of a pollen grain
on the female reproductive parts, after
which a pollen tube grows toward the
 Fertilization, which is delayed for up to a
year, results in zygote that develops into
an embryo within the conifer seed
Angiosperms: vascular seed plants that
make flowers and fruits
› After fertilization, the ovule becomes the
seed and the ovary becomes the fruit
Most angiosperms develop rapidly and
produce seeds quicker than
Development of the
flower lead to the
attraction of insects,
birds, and other
animals that helped
reproduction occur
› Lead to a great deal of
coevolution in flower
development and
When buffeted by severe environmental
challenges, the flowering plants did well
› Thanks to their protective seeds and help
from pollinators
Flowering plants arose from 3 lineages
and comprise a tremendous diversity
Three major groups:
1. Magnolids: include magnolias, avocados,
nutmeg and black pepper plants
2. Eudicots: include familiar shrubs, trees
(except conifers), and herbaceous plants
3. Monocots: include grasses, lilies, and major
food-crop grains
The female gametophyte forms the
 Pollen forms inside stamens
 Pollination leads to double fertilization:
one sperm fertilizes the egg, the second
sperm fertilizes a cell that becomes the
 Ovary tissue develops into the fruit that
covers the seeds
Table 23.1
 Table 23.2
 Page 388