Transcript Introduction to Plants - Clark Pleasant Community School Corp

Introduction to Plants
AP Biology
Invading Land
• Conditions to
overcome: buoyancy
of water is missing, no
longer bathed in a
nutrient solution, air
dries things out
Invading Land
• Those adverse
conditions favored
evolution of:
structures that support,
vessels that transport,
and structures that
conserve water
• See handout
Three major groups
• Bryophytes: small nonvascular plants
– Mosses, liverworts
• Seedless, vascular plants –ferns, horsetails
• Seed bearing plants
– Usually divided into two classes:
– Gymnosperms (“naked seeds”) and
Angiosperms (flowering plants)
What is vascular tissue?
• Tissues that conduct
water and food
throughout the plant
• Equivalent of blood
vessels in higher
animals
• Xylem conducts water
• Phloem conducts food
How do bryophytes survive
without vascular tissue?
• Must remain small
• Must have water for
reproduction
• Must live in moist
areas
• Rely on diffusion and
primitive rootlike
structures to absorb
water
moss
hornwort
liverwort
Seedless, Vascular
Whisk
ferns
ferns
horsetails
Invading Land
• Evolutionary order:
bryophytes first—410
million years ago
• Ferns—by 360 million
years ago
• Conifers—by 290
million years ago
• Angiosperms—138
million years ago
Bryophytes
• Mosses, liverworts,
hornworts
• 18,600 species
• Small
• Moist environments
• No vascular tissue (no
xylem or phloem)
• Rhizoids are rootlike
Bryophytes
• “Alternation of
generations” means a
gametophyte plant
produces a sporophyte
plant, which then
produces a
gametophyte
• Sporophyte remains
attached to the
gametophyte
Bryophytes
Sporophyte
capsules
• The stages are named
after what they
produce
• A sporophyte produces
spores
• A gametophyte
produces gametes
Bryophytes
• Sperm must swim to
the egg, so water must
be available
• Also need water
because they do not
have true roots or
vascular tissue
archegonium
antheridium
Bryophytes
Ferns
•
•
•
•
12,000 species
Mostly tropical
Very diverse
Range is size from 1
cm to 25 meters tall
• Have vascular tissue,
but do not produce
seeds
Ferns
• Dominant stage is the
sporophyte (2n)
• Alternation of
generations
• Sporophyte produces
haploid spores (n)
which grows into a
gametophye
Sori contain spores
sorus
Ferns
• Germinating spores
develop into small
gametophyes, the
plant’s stage which
produces gametes
• The gameotyphyte
plant is very small and
hard to notice
• Heart shaped: called a
prothallus
Tiny gametophyte
sporophyte
gametophyte
Fern gamete producing structures
archegonia
antheridia
Gametophyte
• Antheridia are sperm producing structures
• Archegonia are egg producing structures
• Fertilization forms a zygote (2n), which
develops into a sporophyte plant (2n)
• The sporophyte develops into the leafy fern
we recognize, and will go on to produce
haploid spores
Gymnosperms : Naked Seeds
(not enclosed in a fruit)
• 4 Major groups:
• Cycads: mostly tropical or subtropical
regions
• Gingkoes: native to Southeastern China
• Conifers: cone bearing
• Gnetales: resemble angiosperms, but no
flower
Cycads
Most common in
equatorial
regions, some
subtropical areas
Cycad Distribution
Gingkoes
Fruit has a foul
odor; some cities
have removed all
female trees
Gnetales
• Small leaves that
resemble angiosperm
leaves
• No flowers
• Cones may be fleshy
and brightly colored
• Some consider them to
be a “bridge” to
angiosperms
Conifers
• Trees and shrubs that
have needles or scale
like leaves
• Bear seeds on exposed
cone scales
• Most are evergreen
• Examples: pine, fir,
cypress, redwood,
pacific yew
Coniferous Forest
Why are they typically in colder climates?
Conifers
• Both male and female
cones are produced
• Male cones produce
pollen, which drifts
and lands on ovules of
female cones
• Pollen sprouts a tube
which grows to the
eggs inside the ovule
Conifers
• After fertilization, the
zygote develops into a
seed.
• The seed becomes a
mature sporophyte (2n),
producing male and
female cones
• The cones produce
haploid spores which
become pollen and eggs
Conifers
• Slow to reproduce
• After pollen lands,
may be a year before
fertilization occurs
• This is a competitive
disadvantage
Angiosperms
• Flowering plants
• The flower is the
reproductive structure
• Sporophyte is the
dominant generation
• Gametophyte generation is
small (microscopic) ; this
offers protection and
nutrition, and is a
competitive advantage.
Angiosperms
• Coevolved with
pollinators
• Birds
• Insects: bees,
butterflies, moths, etc.
• Bats
• Mutually beneficial
Flower parts
Stamen (male) produces
pollen; Pistil (female)
produces egg
Stamen and Pistil
Angiosperms
• Zygote (embryo)
forms in the base of
the female ovary in an
ovule
• Each ovule becomes a
seed; the whole ovary
becomes the fruit, or
part of the fruit
Seed
Each ovule may
produce a seed
Ovary
Receptacle