Unit 7 Plants

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Unit 7 Plants

• Ch. 22 Plant Diversity

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What is a Plant?

• 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

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What Plants Need to Survive

• The lives of plants center on the need for light,
  water minerals, gas exchange, the transport
  of water nutrients throughout the plant body

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What Plants Need to Survive

• 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

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Early Plants

• For most of Earths history, plants did not exist
• The first plants evolved from an organism similar
  to the multicellular green algae living today

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Early Plants

• The oldest known fossils of plants are almost 450
  million years old, Cooksonia, a moss plant

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Overview of the Plant Kingdom

• The plant kingdom is divided into 4 groups based
  on 3 features water-conducting tissue, seeds,
  flowers

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Overview of the Plant Kingdom

• There are 235,000 flowering plant species, almost
  90 of all living species of plants

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Bryophytes

• Bryophytes - includesmosses, 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

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Groups of Bryophytes

• 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

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Groups of Bryophytes

• Liverworts are odd little plants that look like
  flat leaves attached to the ground, some species
  resemble the shape of a liver

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Groups of Bryophytes

• Hornworts are generally found in soil that is
  damp nearly year-round

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Human Use of Mosses

• 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 soils ability to
  retain water

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Seedless Vascular Plants

• Vascular tissue - specialized to conduct water
  nutrients throughout the plant

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Evolution of Vascular Tissue A Transport System

• 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

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Evolution of Vascular Tissue A Transport System

• 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

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Ferns Their Relatives

• 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

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Ferns Their Relatives

• Veins - vascular tissue (xylem phloem) gathered
  together
• Stems - supporting structures that connect roots
  leaves, carrying water nutrients between them

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Club Mosses

• Small plants that live in moist woodlands
• The most common club mosses look like miniature
  pine trees, called ground pines

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Horsetails

• Named because its stems look similar to
  horses tails
• During Colonial times, horsetails were
  commonly used to scour pots pans

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Ferns

• Ferns have true vascular tissues, strong roots,
  creeping underground stems (rhizomes), large
  leaves (fronds)

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Seed Plants

• 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

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Reproduction Free From Water

• 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

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Reproduction Free From Water

• Cones - the seed-bearing structures of
  gymnosperms
• Flowers - the seed-bearing structure of
  angiosperms

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Reproduction Free From Water

• Pollen grain - plant sperm
• Pollination - the transfer of pollen from male
  reproductive structure to female reproductive
  structure

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Reproduction Free From Water

• 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

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Reproduction Free From Water

• Seed coat - surrounds protects the embryo
  keeps the contents of the seed from drying out

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Gymnosperms - Cone Bearers

• Gymnosperms include gnetophytes, cycads,
  ginkgoes, conifers
• Gnetophytes only have 2 huge leathery leaves,
  which grow continuously spread across the ground

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Gymnosperms - Cone Bearers

• Cycads are palm-like plants that reproduce with
  large cones, typically found in tropical places

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Gymnosperms - Cone Bearers

• 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

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Gymnosperms - Cone Bearers

• 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

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Gymnosperms - Cone Bearers

• Today, conifers thrive in a wide variety of
  habitats in several biomes
• Most conifers are evergreens - they keep their
  leaves throughout the year

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Angiosperms - Flowering Plants

• Angiosperms develop unique reproductive organs
  known as flowers
• Flowers contain ovaries, which surround protect
  the seeds
• Fruit - a wall of tissue surrounding the seed

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Diversity of Angiosperms

• 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

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Characteristics of Monocots Dicots
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Diversity of Angiosperms

• There are 3 categories of plant life spans
  annual, biennial, perennial
• Annuals - flowering plants that complete a life
  cycle within one growing season

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Diversity of Angiosperms

• Biennials - angiosperms that complete their life
  cycle in 2 years
• Perennials - flowering plants that live for more
  than 2 years