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Plant Diversity
Chapter 22
What is a Plant?
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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
Life Cycle
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Haploid (N)-Gametophyte; gamete-producing
Diploid (2N)-Sporophyte; spore-producing
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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)
Generalized Plant Life Cycle
Section 22-1
Haploid
Diploid
MEIOSIS
Spores
(N)
Sperm
(N)
Eggs
(N)
FERTILIZATION
Go to
Section:
Plant Survival
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Sunlight
Water and Minerals
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Movement of Water/Nutrients
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Taken up through the roots
Make food in their leaves
Water and nutrients carried upward through tissue
from soil
Gas Exchange
Early Plants
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Evolved from multicellular green algae
First plants were dependent on water
Similar to today’s mosses in structure and
growth close to the ground
Evolved different adaptations for terrestrial
environments
Section 22-1
Cladogram of Plant
Groups
Cone-bearing
plants
Ferns and
their relatives
Seeds
Water-Conducting
(Vascular) Tissue
Go to
Section:
Overview of the Plant Kingdom
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Divided into four groups based on waterconducting tissues, seeds and flowers
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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
The Diversity of Plants
Section 22-1
Cone-bearing plants
760 species
Ferns and
their relatives
11,000 species
Mosses and
their relatives
15,600 species
Go to
Section:
Flowering
plants
235,000 species
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
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Water needed for reproduction
Act as natural sponge and form peat moss
Bryophytes
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Mosses
Liverworts
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http://www.ghettodriveby.com/hornworts/
Hornworts
Seedless Vascular Plants
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Vascular tissue-Specialized to conduct water
and nutrients thought he body of the plant
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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
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Formed by cell division in thin layers inside bark
Width of the bands indicate environmental conditions
for each year (Ex. Drought conditions)
Ferns
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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
Seed Plants
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Gymnosperms-Seeds on cone surfaces
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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
Section 22-4
The Structure of a
Seed
Seed coat
Seed
Embryo
B
Stored
food supply
A
Go to
Section:
Reproduction without Water
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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
A Bee With Pollen On It’s Leg
Gymnosperms
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1)
Cone Bearers / “naked seed”
Gnetophytes:
a) Ex. Welwitschia-Namibian desert with large,
leathery leaves; spread across the ground
2)
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
Welwitschia mirabilis,
a Gnetophyte. And Zamia pseudoparasitica,
a Cycad.
http://www.conifers.org/pinophyta.htm
Gymnosperms
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Ginkgoes-Only Ginkgo biloba currently exists
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Conifers-(Coniferophyta)
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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
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
Ginkgo and Pseudotsuga menziesii,
a Conifer.
http://www.conifers.org/pinophyta.htm
Angiosperms
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Phylum Anthophyta “enclosed seed”
Cretaceous Period (135 million years ago)
arrival
Dominate Earth’s 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
Seed Dispersal By Wind And
General Flower Structure
http://science.kennesaw.edu/biophys/biodiversity/plants/plpix5.htm
Monocots and Dicots
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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
Comparison of
Monocots and Dicots
Section 22-5
Monocots
Go to
Section:
Dicots
Seeds
Single
cotyledon
Two
cotyledons
Leaves
Parallel
veins
Branched
veins
Flowers
Floral parts
often in
multiples of 3
Floral parts often
in multiples
of 4 or 5
Stems
Vascular
bundles
scattered
throughout stem
Vascular
bundles
arranged in
a ring
Roots
Fibrous roots
Taproot
Monocots and Dicots
http://www.emc.maricopa.edu/faculty/farabee/biobk/BioBookPLANTANATII.html
Diversity of Angiosperms
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Wood plants made of cells with thick cell walls
(Trees, shrubs and vines)
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(Ex. Grapes and Ivy vines)
(Ex. Blueberries and rose bushes)
Herbaceous plants-No wood production as
they grow (Ex. Dandelions, zinnias,
sunflowers and petunias)
Rose Bush, Grape Vine, Zinnias and
Petunias
http://www.flowers.vg/flowers/petunia01.htm
Diversity of Angiosperms
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Annuals-Complete a life-cycle within one growing
season
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Biennials-Complete their life cycle in 2 years
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(Ex. Marigolds, petunias, pansies, zinnias, wheat and
cucumbers)
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
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(Ex. Asparagus, grasses-herbaceous stems)
(Ex. Maple trees-wood stem)
Primrose, Marigolds, Ornamental
Grasses
http://landscaping.about.com/cs/designexamples1/l/bllandscaping10.htm