Transcript General Plant Life Cycle

Plant Life Cycles
Plant Evolution
• Descendants from green
algae (~450mya)
– Contain cellulose in cell
walls
– Contain chlorophyll
– Starch stored
• Land Plants Must Overcome
– Drying out
– Gas exchange
– Nutrient transport system
– Support
Land adaptations
• Cuticle: Waxy coating
prevents water loss
• Stomata: pores that
open/close to permit gas
exchange
• Roots & Stems: support
• Vascular system: tissue
that transports nutrients
– Nutrients & water go up
plant
– Sugars go down the
plant
General Plant Life Cycle
• Alternation of
generations
• Gametophyte
(haploid)
– Begins with spores
created by meiosis
– Mature
gametophyte
grows by mitosis
– Male & female
organs
– Sperm & egg
created
General Plant Life Cycle
• Sporophyte
(diploid)
– Begins when
sperm fertilizes
egg (zygote)
– Zygote divide by
mitosis to create
a mature
sporophyte
– Meiosis
produces
haploid cells
Mosses
• Nonvascular,
seedless
• Grow low to ground
to retain moisture
• Lack true leaves
– Leaf-like structures
only 1 cell thick
• Rhizoids anchor into
soil
• Early inhabitant of
new ecosystems
(succession)
Moss Life Cycle
• Gametophyte phase
– Dominant stage
– Carpet of moss
growing near ground
– Male sperm & female
egg created
– Sperm swims through
water to fertilize egg
• Sporophyte phase
– Stalk grows up from
the gametophyte
– Sporangia houses
haploid spores
– Spores land and new
gametophyte grows
Ferns
• Seedless, vascular plants
– Vascular: allows taller growth
• Rhizoids: underground stems draw nutrients
• Fronds: leaves uncurl
– sporangia on underside
• Sori: sporangia
Fern Life Cycle
• Sporophyte phase
– Dominant stage
– Sporangia produces
haploid spores
– Spores released into air
• Gametophyte phase
– Spore grows into
prothallus
• Archegonium: produces
female egg
• Antheridium: produces male
sperm
– Sperm swims to egg
– Zygote begins sporophyte
stage
Conifers
• Seed advantages
– Don’t depend on
water
– Protects & nourishes
embryo
– Allow plants to grow in
new locations
• Conifers: woody cone
houses seeds
– Male cones: produce
pollen
– Female cones:
produce egg
• Pines, redwoods,
spruce, cedar
Conifer Life Cycle
• Sporophyte phase
– Cones grow on tree
– Female cones
• Megaspores inside
(gametophyte)
• Male pollen lands
– Male cones
• Microspores (gametophyte)
released & sticks to
archegonium
• Pollen tube grows from
pollen
• Sperm travels down pollen
tube
female
male