Plant Diversity Chapter 22

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Plant DiversityChapter 22
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What is a Plant?

• Plants are the base for the food chain on land.
• Provide shade, shelter and oxygen
• Evolved more than 470 million years ago
• Multicellular, Eukaryotes
• Cell walls made of cellulose
• Photosynthesis using chlorophyll a and b
• Most are autotrophs few parasites saprobes
• Ex. Trees, shrubs, grasses, mosses and ferns

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Life Cycle

• Haploid (N)-Gametophyte gamete-producing
• Diploid (2N)-Sporophyte spore-producing
• Produce a new individual by mitosis
• All plants have both phases, but in different
  forms
• Can reproduce independently of water
• Some also reproduce asexually (vegetative)

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Generalized Plant Life Cycle
Section 22-1
Spores(N)
Sperm(N)
Eggs(N)
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Plant Survival

• Sunlight
• Water and Minerals
• Taken up through the roots
• Movement of Water/Nutrients
• Make food in their leaves
• Water and nutrients carried upward through tissue
  from soil
• Gas Exchange

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Early Plants

• Evolved from multicellular green algae
• First plants were dependent on water
• Similar to todays mosses in structure and growth
  close to the ground
• Evolved different adaptations for terrestrial
  environments

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Cladogram of Plant Groups
Section 22-1
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Overview of the Plant Kingdom

• Divided into four groups based on
  water-conducting tissues, seeds and flowers
• Reproductive structures and body plan are also
  considered
• Compare DNA sequences of various species
• Deep Green (1994)-Evidence that first plants
  evolved from green algae that lived in fresh water

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The Diversity of Plants
Section 22-1
Cone-bearing plants760 species
Floweringplants235,000 species
Ferns andtheir relatives11,000 species
Mosses andtheir relatives15,600 species
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Bryophytes

• Nonvascular plants
• 1) Mosses (in swamps)
• Can live in harsh environments
• Rhizoid-long, thin cells absorb water and
  minerals and anchor them to the ground
• 2) Liverworts and 3) hornworts
• Use osmosis to draw up water
• Water needed for reproduction
• Act as natural sponge and form peat moss

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Bryophytes

• Mosses Liverworts Hornworts
• http//www.ghettodriveby.com/hornworts/

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Seedless Vascular Plants

• Vascular tissue-Specialized to conduct water and
  nutrients thought he body of the plant
• Xylem-form of vascular tissue that carries water
  upward from the roots to every part of the plant
• Phloem-transports solutions of nutrients and
  carbohydrates from photosynthesis
• Tree rings in the lower trunk indicate the tree
  age
• Formed by cell division in thin layers inside
  bark
• Width of the bands indicate environmental
  conditions for each year (Ex. Drought conditions)

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Ferns

• Evolved 350 million years ago
• Roots-Underground organs to absorb water and
  minerals with water-conducting tissue
• Leaves-Photosynthetic organ that contain bundles
  of vascular tissue
• Veins-Made of xylem and phloem
• Stems-Connect roots and leaves

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Seed Plants

• Gymnosperms-Seeds on cone surfaces
• Conifers, Cycads, Ginkgoes and gnetophytes
• Angiosperms-Flowering plants with seeds in tissue
  layers
• Flowers or cones transfer sperm by pollination
  and protect embryos in seeds
• Life cycle alternates between gametophytes and
  sporophyte

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The Structure of a Seed
Section 22-4
B
A
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Reproduction without Water

• Cones-sporophyte structures which are seeding
  bearing for gymnosperms
• Flowers-Seed-bearing structure of angiosperms
• Pollen Grains-Contain male gametophytes
• Seeds-Embryo of seed plant with seed coat and
  food supply
• Eaten and dispersed by animals or stick to their
  fur
• Fossils from 30 million years ago

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A Bee With Pollen On Its Leg
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Gymnosperms

• Cone Bearers / naked seed
• Gnetophytes
• a) Ex. Welwitschia-Namibian desert with large,
  leathery leaves spread across the ground
• Cycads- (Cycadophyta)
• a) Palm-link plants with large cones
• b) Appeared during Triassic Period (225 million
  years ago)
• c) Grow in tropical and subtropical places

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Welwitschia mirabilis,a Gnetophyte. And Zamia
pseudoparasitica,a Cycad. http//www.conifers.or
g/pinophyta.htm
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Gymnosperms

• Ginkgoes-Only Ginkgo biloba currently exists
• One of the oldest seed plant species alive today
• Cultivated in China and planted around temples
• Often planted in urban settings in U.S. due to
  resistance to air pollution
• Conifers-(Coniferophyta)
• Ex. Pines, spruces, firs, cedars, sequoias,
  redwoods
• Long, thin leaves (Ex. Pine needles)-reduces
  surface area, waxy layer
• Most are evergreens with cycling of needles

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Ginkgo and Pseudotsuga menziesii,a Conifer.
http//www.conifers.org/pinophyta.htm
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Angiosperms

• Phylum Anthophyta enclosed seed
• Cretaceous Period (135 million years ago) arrival
• Dominate Earths plant life
• Reproduce with flowers or fruits
• Ovary develops into fruits to protect seed and
  for dispersal
• Fruit-thick wall of tissue surrounding the seed

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Seed Dispersal By Wind And General Flower
Structurehttp//science.kennesaw.edu/biophys/biod
iversity/plants/plpix5.htm
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Monocots and Dicots

• Cotyledons-Seed leaves in the plant embryo
• Monocots-One seed leaf, parallel veins, multiples
  of 3 floral parts, vascular bundles scattered and
  fibrous roots
• Dicots-Two seed leaves, branched veins, multiples
  of 4 or 5 floral parts, vascular bundles in a
  ring and a taproot

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Comparison ofMonocots and Dicots
Section 22-5
Monocots
Dicots
Seeds
Leaves
Flowers
Stems
Roots
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Monocots and Dicotshttp//www.emc.maricopa.edu/fa
culty/farabee/biobk/BioBookPLANTANATII.html
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Diversity of Angiosperms

• Wood plants made of cells with thick cell walls
  (Trees, shrubs and vines)
• (Ex. Grapes and Ivy vines)
• (Ex. Blueberries and rose bushes)
• Herbaceous plants-No wood production as they grow
  (Ex. Dandelions, zinnias, sunflowers and petunias)

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Rose Bush, Grape Vine, Zinnias and
Petuniashttp//www.flowers.vg/flowers/petunia01.h
tm
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Diversity of Angiosperms

• Annuals-Complete a life-cycle within one growing
  season
• (Ex. Marigolds, petunias, pansies, zinnias, wheat
  and cucumbers)
• Biennials-Complete their life cycle in 2 years
• Year 1-germinate and grow roots very short
  stems
• Year 2-Grow new stems and leaves and produce
  flowers and seeds
• (Ex. Primrose, parsley, celery)
• Perennials-Live for more than 2 years
• (Ex. Asparagus, grasses-herbaceous stems)
• (Ex. Maple trees-wood stem)

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Primrose, Marigolds, Ornamental
Grasseshttp//landscaping.about.com/cs/designexam
ples1/l/bllandscaping10.htm