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)
– Haploid spores
created by
meiosis
– Gametophyte
grows from spore
– Gametophyte
has sperm & egg
cells
General Plant Life Cycle
• Sporophyte (diploid)
– Diploid zygote
created from
sperm & egg
– Zygote grows
into a mature
sporophyte
– Sporophyte
creates haploid
spores by
meiosis
• Gametophyte grows
from spore (cycle
restarts)
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)
• Gametophyte phase
– Dominant stage
– Carpet of moss growing
near ground
• Female gametophyte:
produces egg
• Male gametophyte :
produces sperm
– Sperm swims through
water to fertilize egg
(zygote created)
• Sporophyte phase
– Sporophyte stalk grows
up from the zygote
– Sporangia contain
haploid spores
– Haploid spores land
• Gametophyte stage
restarts
Moss Life Cycle
Ferns
• Seedless, vascular plants
– Vascular: allows taller growth
• Rhizoids: underground stems draw nutrients
• Fronds: leaves uncurl
– sporangia on underside
Fern Life Cycle
• Sporophyte phase
– Dominant stage
– Sporangia produces
haploid spores
– Spores released into air
• Gametophyte phase
– Spores land & grows into
prothallus
• Female gametophyte:
produces egg
• Male gametophyte :
produces 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 mature tree
– Female cones: contains
megaspores (female
gametophyte)
– Male cones: contains
microspores (male
gametophyte)
• Microspores released &
stick to female cones
• Pollen tube grows towards
egg
• Sperm travels down pollen
tube (zygote/seed created)
• Sporophyte stage restarts
female
male