Download Chapter 30 Plant Diversity II: The Evolution of Seed Plants seed

Chapter 30
Plant Diversity II: The Evolution of Seed Plants
seed plants
- 3 modifications:
reduction of gametophyte
 retained in moist reproductive tissue of sporophyte generation
origin of seed  zygotes developed into embryos packaged with a food
supply within a protective seed coat (seed replaced spore)
evolution of pollen
 plants no longer ties to water
seed development
ovule: consists of nucellus and egg-containing gametophytes
gametophyte develop here and are nourished by nucellus
gametophyte develops into a sporophyte embryo if fertilized by a sperm cell
sporophyte-containing ovule develops into a seed
pollen - vehicle for sperm cells
- microspores develop into pollen grains which mature to form male gametophytes
- carried by wind or animals
- sperm cells sometimes flagellated
gymnosperms - vascular plant bearing naked seeds not enclosed in a special chamber
- 4 groups:
cycads
ginkgo
gnetophytes
conifers
- largest division
- most are evergreens (pines, firs, spruces, larches, yews, junipers, cedars,
cypresses, and redwoods)
- wood used for most lumber and paper
- needle-shaped leaves with thick cuticles
- multicellular sporophyte is most conspicuous stage
(pine tree is a sporophyte)
- cones - contain sporangia (has haploid spores)
angiosperms
- flowering plants
flower - reproductive structure
- parts: sepals - enclose bud
petals - attract pollinators
stamen - produce pollen
carpel: stigma - sticky, receives pollen
ovary - protects ovule (which develops into seed)
fruit
- ripened ovary that protects dormant seed and aids dispersal
aggregate fruits - several ovaries (raspberries)
multiple fruits - develops from several flowers (pineapple)
fruit modifications that aid dispersal:
fruits shaped like kites, propellers
burr-like fruits cling to fur
edible fruit eaten then dispersed
pollen grains
- immature male gametophytes
- develop in anthers of stamen
female gametophytes
life cycle:
seed
- within ovule
- contains embryo sac with haploid egg and other haploid cells
pollen lands on stigma
pollen grows a pollen tube down style to ovary
pollen discharges 2 sperm cells into embryo sac
double fertilization occurs (egg fertilized to form zygote; endosperm (3n) formed)
- mature ovule
- contains:
embryo - develops from zygote with 1 or 2 seed leaves
monocots
- have 1 seed leaf
dicots
- have 2 seed leaves
endosperm
- rich in starch and other food
seed coat
- protects