Transcript Chapter 22

Chapter 22
Plant Diversity
1
22–1 Introduction to Plants
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Objectives
• Explain what a plant is
• Describe what plants need to
survive
• Describe how plants first evolved
3
What Is a Plant?
• Plants are members of the
kingdom Plantae
• Plants are multicellular
eukaryotes that have cell walls
made of cellulose. They develop
from multicellular embryos and
carry out photosynthesis using
the green pigments chlorophyll a
and b
4
The Plant Life Cycle
• Plants have life cycles that are
characterized by alternation of
generations
• the two generations are the
haploid (N) gametophyte, or
gamete-producing plant, and the
diploid (2N) sporophyte, or sporeproducing plant.
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What Plants Need to Survive
1.
2.
3.
4.
Sunlight
Water and Minerals
Gas Exchange
Movement of water and nutrients
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Early Plants
• The first plants evolved
from an organism
much like the
multicellular green
algae living today.
10
The First Plants
• The first true plants were still
dependent on water to complete
their life cycles, similar to today’s
mosses in that they were simple
in structure and grew close to the
ground.
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• From these plant pioneers,
several major groups of plants
evolved.
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Mosses
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Ferns
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Cone Bearing Plant
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Flowering plant
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Overview of the Plant Kingdom
• Botanists divide the plant
kingdom into four groups based
on three important features:
1. Water conducting tissues
2. Seeds
3. Flowers
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22 – 2 Bryophytes a.k.a
(Non-vascular plants)
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Objectives
• Describe the adaptations of
Bryophytes
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bryophytes
• Type of early plant with no
vascular tissue that draw water in
their cells by osmosis.
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Moss
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Liverwort
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Hornwort
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• During at least one stage of their
life cycle, bryophytes produce
sperm that must swim through
water to reach eggs of other
individuals.
• Therefore, they must live in
places where there is rainfall or
dew for at least part of the year
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Asexual
Reproductive
Part
Sexual
Reproductive/
Photosynthetic
Part
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22–3 Seedless
Vascular Plants
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Objectives
• Explain how vascular tissue is
important to ferns and their
relatives
• Describe the three phyla of sporebearing plants
• Identify the stages in the cycle of
ferns
29
• In just a few million years, plants
grew to a whole new scale on the
landscape.
Q: What caused this increase in
size?
A: Vascular Tissue
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Vascular tissue
• A type of tissue that is specialized
to conduct water and nutrients
through the body of the plant
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Evolution of Vascular Tissue
• Both forms of vascular tissue—
xylem and phloem—can move
fluids throughout the plant body,
even against the force of gravity.
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Xylem
• Carry water upwards from the
roots to every part of the plant
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Phloem
• Transports nutrients and
carbohydrates produced by
photosynthesis from the leaves
down to the roots
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• Vascular plants also evolved the
ability to produce lignin, a
substance that makes cell walls
rigid.
• The presence of lignin allows
vascular plants to grow upright
and tall
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Ferns and Their Relatives
• Seedless vascular plants include
club mosses, horsetails, and
ferns.
• Like other vascular plants, ferns
and their relatives have true roots,
leaves, and stems.
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Roots
• Absorb water
and minerals
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Leaves
• Collect light for photosynthesis
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Veins
• Made of xylem and phloem
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Stems
• Used for
support,
connect roots
and leaves,
carry water
between
them
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Club Mosses
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Horsetails
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Ferns
Underground Stem
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22 – 4 Seed Plants
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Objectives
• Describe the reproductive
adaptations of seed plants
• Describe the evolution of seed
plants
• Identify the four groups of
gymnosperms
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• Over millions of years, plants with
a single trait—the ability to form
seeds—became the most
dominant group of photosynthetic
organisms on land.
• Seed plants are divided into two
groups:
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Gymnosperms
• Cone plants
• Bear their seeds directly on the
surfaces of cones
Ex.) conifers, pines, spruces,
cycads, ancient ginkgoes and
gnetophytes
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Angiosperms
• Flowering plants
• Bear their seeds within a layer of
tissue that protects the seed
Ex.) grasses, flowering trees
shrubs, wild flowers
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Reproduction Free From Water
• Unlike mosses and ferns, however,
seed plants do not require water for
fertilization of gametes.
Q: Why was this an advantage?
A: They could live further away from
water
• Adaptations that allow seed plants to
reproduce without water include
flowers or cones, the transfer of
sperm by pollination, and the
protection of embryos in seeds.
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Cones and Flowers
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Cones
• Seed bearing structures of
gymnosperms
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Flowers
• Seed bearing
structures of
angiosperms
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Pollen
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Pollen grain
• Contains the male gamete
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Pollination
• The transfer of pollen from the
male gametophyte to the female
gametophyte
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Seeds
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seed
• An embryo of a plant that is
encased in a protective covering
and surrounded by a food supply
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embryo
• Early development stage of a
sporophyte plant
• The seed’s food supply provides
nutrients to the embryo as it
grows
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Seed Coat
• Surrounds and protects the
embryo and keeps the contents of
the seed from drying out
• Can be specialized for dispersal
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Evolution of Seed Plants
• Over a period of millions of years,
continents became much drier,
making it harder for seedless plants
to survive and reproduce.
• For that reason, many moss and fern
species became extinct. They were
replaced by seed plants with
adaptations that equipped them to
deal with drier conditions.
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Gymnosperms—Cone
Bearers
• The most ancient surviving seed
plants are the gymnosperms.
• Gymnosperms include:
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Gnetophytes
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Cycads
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Ginkgos
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Conifers
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22–5 Angiosperms Flowering Plants
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Objectives
• Identify the characteristics of
angiosperms
• Explain what monocots and dicots
are
• Describe the three different life
spans of angiosperms
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• Flowering plants originated on
land and quickly came to
dominate Earth’s plant life.
• The vast majority of living plant
species reproduce with flowers.
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Flowers and Fruits
• Angiosperms have unique
reproductive organs known as
flowers.
Q: Why are flowers evolutionary
adaptations?
A: they attract animals that
pollinate them
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• Flowers contain ovaries, which
surround and protect the seeds
• After pollination, the ovary
develops into a fruit, which
protects the seed and aids in its
dispersal.
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Fruit
• Ripened ovary, thick wall of tissue
that surrounds the seed
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Diversity of Angiosperms
• The angiosperms are an
incredibly diverse group. Not
surprisingly, there are many
different ways of categorizing
these plants.
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Monocots and Dicots
• Monocots and dicots are named
for the number of seed leaves, or
cotyledons, in the plant embryo.
Monocots have one seed leaf,
and dicots have two seed leafs
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Woody and Herbaceous Plants
• Woody plants – Have woody
stems
Ex.) trees, shrubs, vines
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Herbaceous Plants
• Plant stems that are smooth and
nonwoody
Ex.) dandelions, petunias, and
sunflowers
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Annuals, Biennials,
and Perennials
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Annuals
• Angiosperms that complete a life
cycle within one growing season
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Biennials
• Angiosperms that complete their
life cycle in two years
• In the first year, biennials
germinate and grow roots, stems,
leaves
• During their second year,
biennials grow new stems and
leaves and then produce flowers
and seeds
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Perennials
• Flowering plants that live for more
than two years
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