Transcript Ch.22 - Jamestown School District

Unit 7 Plants
Ch. 22 Plant Diversity
What is a Plant?
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Plants are multicellular eukaryotes that have
cell walls made of cellulose
They develop from multicellular embryos &
carry out photosynthesis using the green
pigments chlorophyll a & b
What Plants Need to Survive
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The lives of plants center on the need for light,
water & minerals, gas exchange, & the
transport of water & nutrients throughout the
plant body
What Plants Need to Survive
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Plants use the energy from the sun to carry out
photosynthesis
All cells require a constant supply of water, so
plants must obtain & deliver water to their
cells
Plants require oxygen for cellular respiration,
& carbon dioxide for photosynthesis
Early Plants
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For most of Earth’s history, plants did not exist
The first plants evolved from an organism
similar to the multicellular green algae living
today
Early Plants
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The oldest known fossils of plants are almost
450 million years old, Cooksonia, a moss plant
Overview of the Plant Kingdom
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The plant kingdom is divided into 4 groups
based on 3 features: water-conducting tissue,
seeds, & flowers
Overview of the Plant Kingdom
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There are 235,000 flowering plant species,
almost 90% of all living species of plants
Bryophytes
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Bryophytes - includes:mosses, liverworts, &
hornworts, nonvascular plants
Bryophytes have life cycles that depend on
water for reproduction
Lacking vascular tissue, they can draw up
water by osmosis only a few centimeters above
ground
Groups of Bryophytes
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Mosses are the most common, & grow in areas
of water: swamps & bogs, etc.
They lack vascular tissue, which means they
do not have true roots
Rhizoids - long, thin cells that
anchor them in the ground &
absorb water & minerals from
surrounding soil
Groups of Bryophytes
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Liverworts are odd little plants that look like
flat leaves attached to the ground, some
species resemble the shape of a liver
Groups of Bryophytes
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Hornworts are generally found in soil that is
damp nearly year-round
Human Use of Mosses
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In certain environments, dead sphagnum moss
forms thick deposits of peat
Peat can be cut from the ground & burned as
fuel, or used in
gardening because
it can improve the
soil’s ability to
retain water
Seedless Vascular Plants
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Vascular tissue - specialized to conduct water
& nutrients throughout the plant
Evolution of Vascular Tissue: A
Transport System
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Tracheids - thick cells that resist pressure, key
cells in xylem
Xylem - transport system that
carries water from roots to
every part of a plant
Phloem - transports solutions
of nutrients & carbs produced
by photosynthesis
Evolution of Vascular Tissue: A
Transport System
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Both forms of vascular tissue (xylem &
phloem) can move fluids through the plant
body, even against the force of gravity
Lignin - makes cell walls rigid, enables
vascular plants to grow upright & reach great
heights
Ferns & Their Relatives
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Seedless vascular plants that include: club
mosses, horsetails, & ferns
Ferns have true roots, leaves, & stems
Roots - underground organs that absorb water
& minerals
Leaves - photosynthetic organs that have 1 or
more bundles of vascular tissue
Ferns & Their Relatives
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Veins - vascular tissue (xylem & phloem)
gathered together
Stems - supporting structures that connect
roots & leaves, carrying water & nutrients
between them
Club Mosses
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Small plants that live in moist woodlands
The most common club mosses look like
miniature pine trees, called “ground pines”
Horsetails
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Named because its stems look
similar to horses’ tails
During Colonial times,
horsetails were commonly used
to scour pots & pans
Ferns
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Ferns have true vascular tissues, strong roots,
creeping underground stems (rhizomes), &
large leaves (fronds)
Seed Plants
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Seed plants are divided into 2 groups:
gymnosperms & angiosperms
Gymnosperms - have their seeds directly on
the surfaces of cones
Angiosperms - (flowering plants) - have their
seeds within a layer of tissue that protects the
seed
Reproduction Free From Water
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Adaptations that allow seed plants to
reproduce without water include flowers or
cones, the transfer of sperm by pollination, &
the protection of embryos in seeds
Reproduction Free From Water
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Cones - the seed-bearing structures of
gymnosperms
Flowers - the seed-bearing structure of
angiosperms
Reproduction Free From Water
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Pollen grain - plant sperm
Pollination - the transfer of pollen from male
reproductive structure to female reproductive
structure
Reproduction Free From Water
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Seed - an embryo of a plant that is encased in a
protective covering & surrounded by a food
supply
Embryo - an organism in its
early stage of development
Reproduction Free From Water
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Seed coat - surrounds & protects the embryo &
keeps the contents of the seed from drying out
Gymnosperms - Cone Bearers
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Gymnosperms include: gnetophytes, cycads,
ginkgoes, & conifers
Gnetophytes only have 2 huge leathery leaves,
which grow continuously & spread across the
ground
Gymnosperms - Cone Bearers
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Cycads are palm-like plants that reproduce
with large cones, typically found in tropical
places
Gymnosperms - Cone Bearers
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Ginkgo may be one of the oldest seed plant
species alive today
Often planted around temples in China
Today, they are planted in urban areas where
their toughness &
resistance to air pollution
make them popular shade
trees
Gymnosperms - Cone Bearers
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Some conifers like the
bristlecone pine tree can live
for more than 400 years
Others like the giant redwoods,
can grow to more than 100m
in height
Gymnosperms - Cone Bearers
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Today, conifers thrive in a wide variety of
habitats in several biomes
Most conifers are “evergreens” - they keep
their leaves throughout the year
Angiosperms - Flowering Plants
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Angiosperms develop unique reproductive
organs known as flowers
Flowers contain ovaries, which surround &
protect the seeds
Fruit - a wall of tissue surrounding the seed
Diversity of Angiosperms
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Monocots & dicots are the 2 classes of
angiosperms
They are named for the # of seed leaves, or
cotyledons, in the plant embryo
Monocots - 1 seed leaf
Dicots - 2 seed leaves
Cotyledon - the first leaf or first pair of leaves
produced by the embryo of a seed plant
Characteristics of Monocots &
Dicots
Diversity of Angiosperms
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There are 3 categories of plant life spans:
annual, biennial, & perennial
Annuals - flowering plants that complete a life
cycle within one growing season
Diversity of Angiosperms
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Biennials - angiosperms that complete their
life cycle in 2 years
Perennials - flowering plants that live for more
than 2 years