Evolution of Plants

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Evolution of Plants

• Land plants evolved from green algae.

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Evolution of Plants

• Seedless, Nonvascular Plants
• They grow close to the ground or on surfaces
  where they can absorb water and nutrients and
  also rely on free-standing water for
  reproduction.
• Examples liverworts, hornworts, and mosses

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Evolution of Plants

• Seedless, Vascular Plants
• They depend on water for reproduction.
• A vascular system allows these plants to grow
  higher above the ground and still get materials
  they need from the soil.
• Examples club mosses, whisk ferns, horsetails,
  and ferns

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Evolution of Plants

• Seed-bearing, Vascular Plants
• From an evolutionary viewpoint, seed plants have
  several great advantages over their ancestors.
• Seed plants can reproduce without free-standing
  water. They instead rely on the process of
  pollination.
• Seeds nourish and protect plant embryos.
• Seeds allow plants to disperse to new places.

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Evolution of Plants

• Two basic types of seed-bearing plants
• Cone-bearing Plants
• A gymnosperm is a seed plant whose seeds are not
  enclosed in fruit.
• A cone is the reproductive structure of most
  gymnosperms. It contains hard protective scales.
• Examples cycads, ginkgo, and conifers (pines,
  redwood, spruce, cedar, fir, and juniper)

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Evolution of Plants

• Flowering Plants
• An angiosperm or a flowering plant is a seed
  plant that has seeds enclosed in some type of
  fruit.

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Classification of Plants

• Classification by Seeds
• A cotyledon is an embryonic leaf inside a seed.
• Monocots
• Characteristics
• one cotyledon
• have parallel veins in long, narrow leaves
• flower parts usually occur in multiples of three
• bundles of vascular tissues are scattered
  throughout the stem.
• Examples corn, wheat, rice, grasses, irises,
  and lilies

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Classification of Plants

• Dicots
• Characteristics
• two cotyledons
• have leaves with netlike veins
• flower usually occur in multiples of four or five
• bundles of vascular tissue are arranged in rings
• Examples most deciduous trees and peanuts are
  also dicots

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Classification of Plants

• Classification by Stems
• Woody Stems
• Wood is a fibrous material made up of dead cells
  that are part of the vascular system of some
  plants. Examples Trees, shrubs, and most vines
• Herbaceous
• Do not have stems made of wood.
• Examples cucumbers, cacti, and marigolds.

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Classification of Plants

• Classification by Lifespan
• Annual Flowering
• Plants that mature from seeds, produce flowers,
  and die all in one year are called annuals.
• Examples Corn and lettuce are common annuals,
  as are some garden flowers such as zinnias.
• Biennial Flowering
• Plants that take two years to complete their life
  cycle are called biennials.
• Example Carrots
• Perennial
• Any flowering plant that lives for more than two
  years is a perennial.
• Examples Most woody plants, some grasses and
  dandelions.

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Anatomy of Plants

• Plant tissues are made of three basic cell types.
• Parenchyma Cells
• Stores starch, oils, and water for the plant.
• Help heal wounds of the plant.
• Have thin flexible walls.

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Anatomy of Plants

• Collenchyma Cells
• Provide support to a growing plant.
• Strong and flexible.

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Anatomy of Plants

• Sclerenchyma Cells
• Sclerenchyma cells are the strongest.
• These cells have a second cell wall made of
  lignin, which makes these cells very tough and
  durable, but rigid.
• Die when they reach maturity.

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Anatomy of Plants

• Plant organs are made of three tissue systems.
• Dermal Tissue System
• Covers the outside of a plant
• protects the plant
• secretes cuticle of leaves
• forms outer bark of trees

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Anatomy of Plants

• Ground Tissue System
• Ground tissue provides support and stores
  materials in roots and stems.
• In leaves, ground tissue is packed with
  chloroplasts, where photosynthesis makes food for
  the plant.

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Anatomy of Plants

• Vascular Tissue System
• The system of vascular tissue transports water,
  mineral nutrients, and organic compounds to all
  parts of the plant.

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Anatomy of Plants

• Made up of two networks of hollow tubes.
• Xylemcarries water and dissolved mineral
  nutrients.
• The cohesion-tension theory proposes that the
  physical properties of water allow the rise of
  water through a plant.

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Anatomy of Plants

• Phloem carries minerals and sugars out of the
  leaves to stems and roots.

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Anatomy of Plants

• Parts of Plants
• Roots
• Roots support the plant and absorb, transport,
  and store nutrients.
• root cap covers the tip
• apical meristem is an area of growth
• vascular cylinder contains xylem and phloem

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• There are two main types of roots.

• Fibrous root systems have fine branches.

• Taproot systems have one main root.

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• Stems have many functions.
• support leaves and flowers
• house most of the vascular system
• store water
• Grow underground for storage
• Form new plants

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• Primary growth increases a plants length.

• Secondary growth increases a plants width.

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Anatomy of Plants

• Tree Rings
• Tree rings form due to uneven growth over the
  seasons. In spring, if water is plentiful, new
  xylem cells are wide and have thin walls. These
  cells appear light in color. When water becomes
  more limited in the following months, xylem cells
  are smaller and have thicker walls, so they
  appear darker in color. These two growth together
  make up one ring. The age of a tree can be
  determined by counting these annual rings.

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Anatomy of Plants

• Leaves
• The blade is usually broad and flat, and it
  collects the sunlight for the plant.
• The blade connects to the stem by a thin stalk
  called the petiole.

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Anatomy of Plants
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Anatomy of Plants

• The dermal tissue of many leaves is covered a
  cuticle, a waxy, waterproof layer that helps hold
  in moisture.
• In most plants, the top and undersides of leaves
  have different functions.
• The upper portion of the leaf has most of the
  chloroplasts and is where most photosynthesis
  takes place.
• The underside portion of a leaf has tiny holes in
  the cuticle, called stomata. Guard cells allow
  stomata to close to prevent water loss, or to
  open to allow air to move in and out. Without
  stomata, the movement of air would be prevented
  by the cuticle.

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Plant Reproduction

• Plants complete their life cycle by alternating
  between two phases.
• Diploid Phase plant produces spores.
• Haploid Phase plant produces gametes.

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Plant Reproduction

• Life cycle phases look different among various
  plant groups.
• Life Cycle of Nonvascular Plants Moss
• Nonvascular plants have a dominant gametophyte
  (haploid) phase is dominant and require water to
  reproduce.

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Plant Reproduction
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Plant Reproduction

• Life Cycle of Seedless Vascular Plants Ferns
• The sporophyte (diploid) phase is dominant phase.
• Sori are clusters of sporangia (spore-producing
  sacs) that are found on the underside of the fern
  leaf.
• A mature sporophyte is called a fiddle head.

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Plant Reproduction
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Plant Reproduction

• Life Cycle of Seed Plants Conifers
• The sporophyte (diploid phase) is the dominant
  phase.
• Produce two types of spores that develop into
  male and female gametophytes (pollen is produced
  in male cones, while eggs are produced in female
  cones).
• Pollination occurs in a cone-bearing plant when a
  pollen grain reaches the small opening of an
  ovule in the female cone. After pollination, eggs
  are produced inside the ovule and a pollen tube
  begins

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Plant Reproduction
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Plant Reproduction

• Life Cycle of Seed Plants Flowering Plants
• Flowers contain reproductive organs protected by
  specialized leaves.
• The outermost layer of a flower is made up of
  sepals. Sepals are modified leaves that protect
  the developing flower.

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Plant Reproduction

• Petals are the modified leaves inside of sepals.
  Their bright colors often help to attract animal
  pollinators.

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Plant Reproduction

• Flowers can be a single sex or contain both.
• A stamen is the male structure of a flower.
• The stamen includes
• filament (holds up anther)
• anther (produce pollen)

anther
stamen
filament
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Plant Reproduction

• The female structure is called a carpel.
• Flowers can have several carpels fused together
  called a pistil.
• Structure of pistil
• stigma (sticky where pollen lands)
• style (tube that leads to ovary)
• ovary (female reproductive structure)

stigma
style
pistil
ovary
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Plant Reproduction

• Flowers allow for more efficient pollination than
  occurs in most gymnosperms, which rely on wind
  for pollination.
• Insects and other animals feed on pollen or
  nectar and transfer pollen when feeding.

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Plant Reproduction

• Fertilization takes place within the flower.
• Pollination
• One cell in the pollen grain grows into a pollen
  tube that extends toward the ovule.
• The other cell in the pollen grain divides by
  mitosis, producing two sperm that travel down the
  pollen tube. One fertilizes the egg.
• The other sperm combines with the polar nuclei to
  become a cell with a triploid (3n) nucleus that
  will become the endosperm, a food supply for the
  developing plant embryo.
• The process is called double fertilization which
  only happens in flowering plants.

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Plant Reproduction

• Fruits and Seed Dispersal
• The function of fruit in flowering plants is to
  help disperse seeds to eliminate competition with
  parents.
• Animals, wind, and water can spread seeds.
• Examples
• Bird eats a blackberry and defecates out the seed
  away from the bush.
• Dog gets burr in fur and scratches it off in a
  new location.
• Dandelion fluff is actually a fruit with a seed
  attached and is spread by the wind.
• Coconuts float thousands of miles across oceans
  and arrive on different islands.

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Plant Reproduction

• Seeds will not grow until conditions are
  favorable. This period before growth is called
  dormancy.
• Examples Strawberry seeds remain dormant until
  their seed coats are weakened in the digestive
  tract of an animal. Other seeds have waterproof
  seed coats that can only be cracked by winter ice.

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Plant Reproduction

• When a seed begins to grow it is called
  germination.
• Embryo takes up water and breaks out of seed
  coat.
• Seedling growth begins.
• Enzymes are activated inside the seed to help
  digest the endosperm.

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Plant Reproduction

• Plants can reproduce asexually with from a
  fragment of a stem, leaf, or root.
• Example prickly pear cactus

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Plant Reproduction

• Vegetative reproduction is a type of asexual
  reproduction in which stems, leaves, or roots
  attached to the parent plant produce new
  individuals.
• Example aspen trees

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Plant Hormones

• A hormone is a chemical messenger produced in one
  part of an organism that stimulates or suppresses
  the activity of cells in another part. When a
  hormone meets the right receptor, it triggers a
  response.
• Gibberellins are plant hormones that produce
  dramatic increases in size.
• Ethylene a plant hormone that causes ripening and
  is naturally produced by fruits.
• Auxins are plant hormones involved in the
  lengthening of plant cells.

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Plant Response

• Plants can respond to light, touch, gravity, and
  seasonal changes. These responses are called
  tropisms.
• Phototropism is the tendency of a plant to grow
  toward light.

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Plant Response

• Thigmotropism is the response of plants to touch.

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Plant Response

• Gravitropism is the response to Earths
  gravitational pull.

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Plant Response

• Plants take signals from the changing lengths of
  day and night throughout the year, in a response
  called photoperiodism.
• Shorter days and longer nights during the fall
  help trigger the leaves of many deciduous trees
  to change color. This response is part of the
  preparation for winter, when these trees enter a
  stage of dormancy.

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Plant Adaptations

• Mutualisms
• A mutualism is an interaction between two species
  in which both species benefit.
• Examples
• plant roots and fungi (mycorrhizae)
• plant roots and bacteria (legumes)
• plants and pollinators (orchid and moth).
• Commensalism
• Symbiosis where 1 species benefits.

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Plant Adaptations

• Plant-Herbivore Interactions
• Plants have a variety of adaptations that
  discourage animals from eating them.
• spines (cacti, roses)
• defensive chemicals (poison ivy, natural
  pesticides).

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Plant Adaptations

• Leaf Adaptations
• In desert climates leaves are adapted to minimize
  water loss.
• Cacti leaves are actually the sharp spines that
  protect them from predators and help minimize
  water loss due to transpiration.
• Agave plants store water in their leaves.

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Plant Adaptations

• In cold, dry climates, leaves are minimized to
  prevent damage from the cold.
• Pine needles are leaves with a small surface area
  and a thick, waxy epidermis that protects them
  from cold damage.

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Plant Adaptations

• In aquatic environments, plant leaves are adapted
  for gas exchange or movement of water.
• The water lily has stomata on the upper surface
  of its leaves.
• Many aquatic plants also have flexible petioles
  adapted to wave action.

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Plant Adaptations

• In tropical climates, plants leaves are adapted
  to combat the competition for light, space, and
  nutrients.
• Many tropical plants have very large, broad
  leaves to allow for more photosynthesis.

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Plant Adaptations

• A few plants are actually predators to supplement
  nitrogen in low nutrient environments.