Transcript (Vascular) Tissue

Chapter 22
Plant Diversity
22-1 Introduction to Plants
• What is a plant?
Multicellular
Eukaryotes
Cell walls made of cellulose
Carry out photosynthesis using chlorophyll a
and b
o Develop from multicellular embryos
o
o
o
o
 Can think of them like stationary animals that eat
sunlight!!
The Plant Life
Cycle: Alternation
of Generations
• Gametophyte =
haploid (N), gameteproducing plant
• Sporophyte = diploid
(2N), sporeproducing plant
• Gametes are
produced by meiosis;
spores are produced
by mitosis
Plant Reproduction
• Alternation of Generations
• 2 stages
o Gametophyte
Stage—haploid (n)
 makes gametes
 gametes join to start sporophyte
o Sporophyte
Stage—diploid (2n)
 produces spores which grow into gametophyte
 undergoes meiosis
• What Plants Need to Survive
o
Sunlight—to carry out
photosynthesis
 leaves are adapted to be broad and flat
for maximum absorption
o
Water and Minerals—for
photosynthesis too!
 lose water through transpiration
through stomata in leaves; evolved a
waxy cuticle to minimize water loss
o
o
Gas Exchange—CO2 and O2
Movement of Water and Nutrients
 take up water through roots, has
specialized tissues to help move it
through the entire plant
 xylem- moves water and nutrients
upward
 phloem- moves sugar down toward
roots
• Early Plants
In Water
First plants evolved
from something like
our multicellular green
algae
o dependent on water
for reproduction; no
vascular tissue (xylem
and phloem) so plants
needed to be close to
ground;
o was moss-like and
evolved slightly to
resist water loss
o
o
Vascular Tissue
• A transport system in plants specialized to
conduct water and nutrients throughout
the plant
• Allowed plants to grow, reach new heights
• 2 types of vascular tissue: xylem &
phloem
o
o
Xylem: carries water upward
Phloem: carries nutrients (food)
• For millions of years, plants didn't grow
larger, but 420 mil. yrs ago, vascular
tissue appeared
• The first plants on land were trailblazers!
had to learn to acquire, transport, and conserve
water
o Without plants, we humans/animals could not
be here!
o
• Evolved other characteristics such as
flowers to attract insects, seeds , roots,
stems, leaves.
Kingdom Plantae
Divided by: Waterconducting tissue, seeds,
and flowers
• 1. mosses/bryophytes
(nonvascular)
• 2. seedless vascular plants
• 3. Gymnosperms
• 4. Angiosperms (flowering
plants) 235,000 species
(90% of all living plants)
Flowering
plants
Cone-bearing
plants
Ferns and
their relatives
Flowers; Seeds
Enclosed in Fruit
Mosses and
their relatives
Seeds
Water-Conducting
(Vascular) Tissue
Green algae
ancestor
22-2 Bryophytes
• Mosses and their relatives are
BRYOPHYTES- nonvascular plants
• Grow in moist, shaded areas!!
• Depend on water for reproduction,
lack vascular tissue
• Land adaptations: grow in very
moist environments; draw up water
by osmosis; very low to the ground
• Groups of
Bryophytes
• Mosses
(Bryophyta)
o
o
Found in swamps,
bogs, near
streams,
rainforests,
POLAR regions!
Have rhizoidslong, thin cells
strung out to
absorb water and
nutrients- pg. 557
• Liverworts
(Hepaticophyta)
Liver-shaped, need
damp soil year-round
o Gametophytes—broad
and thin—use soil for
moisture
o produce “umbrellas”
asexually
o Gemmae—
multicellular spheres
that have many
haploid cells
o
• Hornworts (Anthocerophyta)
Need damp soil year-round
Gametophytes- same type as
liverworts
o Sporophytes- looks like a tiny,
green horn
o
o
• Life Cycle of Bryophytes
o
o
o
o
o
GAMETOPHYTE stage
is dominant and carries
out most of
photosynthesis
Fertilization in these
plants requires the sperm
to swim- need water!
Protonema—a young
mass of filaments
produced by a spore
Sperm: antheridia
Egg: archegonia these
can be on the same or
different plants
• Human Uses
Sphagnum- giant
sponge
o Peat- burned as fuel
o Peat moss- holds
water in garden soil,
increases acidity of soil
o
22-3 Seedless Vascular Plants
• Evolution of Vascular Tissue
o
o
o
Specialized to conduct water and
nutrients.
Tracheids- hollow cells with thick
cell walls that resist pressure.
 Connected end to end
 Allow water to move through a
plant more efficiently than by
diffusion alone.
Tracheids are the key cells in
xylem
 Carries water upward from roots
to every part of plant
• Phloem
Second type of vascular
tissue.
o Transports solutions of
nutrients and carbs.
o Main cells are long and
specialized.
o
• Both xylem and phloem
can move fluids against
gravity.
• Also evolved lignin,
substance that makes
cells walls rigid.
o
Allow plants to grow
upright and reach great
heights.
• Ferns and Their
Relatives
o 3 groups of
seedless vascular
plants:
o Club mosses
o Horsetails
o Ferns
 True vascular
tissues
 Underground
stems (rhizomes)
Large leaves
(fronds)
Plant Vocabulary
Roots - underground organs that absorb water and
minerals
Leaves -photosynthetic organs that contain one or more
bundles of vascular tissue
Vein - cluster of vascular tissue in leaves (xylem and
phloem)
Stems - supporting structures that connect roots & leaves,
carrying water & nutrients between them
Club Mosses
• Today, club mosses
are small plants that
live in moist
wetlands
• Fossilized club
mosses form today's
coal
Ferns: Most Numerous Type of
Seedless Vascular Plant
• More than 11,000
species today
• Ferns reproduce by
producing spores!
• Fronds = large leaves
• Rhizome =
underground stems
Life Cycle of Ferns
Fern Reproduction (By Spores!)
Ferns and other vascular plants have a life cycle in which
the diploid sporophyte is the dominant stage. The
sporophyte produces spores by meiosis!
sporangia - containers on fronds holding spores
sori - clusters of sporangia
When spores germinate, they turn into haploid
gametophytes. The small gametophyte grows rhizoids
(long rootlike cells) and becomes the mature
gametophyte. It produces sperm and egg cells, which
unite in fertilization to produce a sporophyte embryo, which
grows into the mature sporophyte fern.
22-4 Seed Plants
• Can be divided into
two groups:
• Gymnosperms
o
Conifers (pines and
spruces), cycads,
ginkgoes, gnetophytes
• Angiosperms
o
Grasses, flowering
trees and shrubs,
wildflowers, cultivated
flowers.
• Reproduction Free From Water
o Adaptations
allow seed plants to
reproduce without standing water
Flowers or cones
Transfer of sperm by pollination
protection of embryos in seeds
o Seed plants do not require water for
fertilization of gametes
so seed plants can live almost
anywhere!
• Cones and Flowers
o Cones- seed-bearing structures of
gymnosperms
o Flowers- seed-bearing structures of
angiosperms
o gametophyte structure lives inside
cone/flower!
• Pollen grain
o Contains male gametophyte
o Spern is carried by wind, insects, birds,
small animals, or bats
o Pollination is the transfer of pollen from
the male reproductive structure to the
female structure.
Seeds
Seeds
• Embryo in a protective covering (seed coat),
surrounded by a food supply.
• Embryo = organism in its early stage of
development
• seed coat = structure that surrounds and protects
plant embryo and prevents it from drying out
• Evolution of Seed Plants
o
o
After Carboniferous and Devonian, Earth became drier, many
mosses and ferns died out.
Replaced by seed plants that could deal with drier conditions (fossils
from 360 mil. yrs ago)
• Gymnosperms- Cone
Bearers
o
o
o
o
“naked seeds”
Gnetophytes
Cycads
Ginkgoes
• Conifers
o
o
Most common gymnosperms
P. Coniferophyta- pines, spruces,
firs, cedars, sequoias, redwoods,
and yews.
• Ecology of Conifers
Wide variety of habitats:
mountains, sandy soil, and cool,
moist areas.
o Adaptations
o
 Long, thin leaves, reduces
surface area
 Thick, waxy layer
 Openings for gas exchange
located below surface of leaf in
cavity
 Most are “evergreens”
The Pine Cone
Temperate rain forest outside Seattle, WA
22-5 Angiosperms- Flowering Plants
• Flowers and Fruits
Flowers are reproductive organs- attract animals
which transport pollen, more efficient than wind
pollination.
 Flowers contain ovaries: surround and
protect seed
o Fruit is the thick tissue wall surrounding the seed,
animals transport to distant locations via the
digestive system.
o
• Diversity of
Angiosperms
o
Monocots and
Dicots
 Named for the
number of
seed leaves
(cotyledons) in
plant embryo.
 Mono- one
 Di- two
• Woody and
Herbaceous Plants
Woody plants- thick
cell walls that support
the plant body.
 Trees, shrubs,
some vines (ex.
Roses)
o Herbaceous- stems
are smooth and nonwoody.
 Dandelions,
sunflowers, etc.
o
• Annuals, Biennials, Perennials
o Annual - completes a life cycle in one growing season
o Biennial - completes life cycle in two years
 1st year: germinate and grow roots, very short stems, sometimes
leaves.
 2nd year: grow new stems and leaves, then flowers and seeds.
o
Perennial - lives for more than two years.