Transcript Photosynthesis - Sylmar High School

Chapter 24
Evolution and
Diversity of
Plants
Outline
Evolutionary History
Alternation of Generations
Nonvascular Plants
Vascular Plants
Seedless
Seed
Angiosperms
- Monocots and Eudicots
- Flowers
Evolution and
Diversity of Plants
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Evolution and
Diversity of Plants
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Evolutionary History of Plants
More than 98% of all biomass is plants
Multicellular photosynthetic eukaryotes
280,000 known species
Thought to have evolved from freshwater algae over 500
mya
Evolution of plants marked by four evolutionary events
associated with four major groups of plants
Nonvascular Plants
- Advent of nourishment of a multicellular embryo within the
body of the female plant
Representatives of the
Four Major Groups of Plants
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Evolution and
Diversity of Plants
Evolutionary History of Plants
Seedless vascular plants
 Advent of vascular tissue
Gymnosperms and angiosperms
Produce seeds
Flowering Plants
Attract pollinators that give rise to fruits
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Evolutionary History of Plants
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Alternation of Generations
Evolution and
Diversity of Plants
Life cycle involves alternation of generations
Multicellular 1n individuals (gametophytes) produce
multicellular 2n individuals (sporophytes)
Multicellular 2n individuals (sporophytes) produce
multicellular 1n individuals (gametophytes)
Sporophyte (2n):
Multicellular individual that produces spores by meiosis
Spore is haploid cell that will become the gametophyte
Gametophyte (1n):
Multicellular individual that produces gametes
Gametes fuse in fertilization to form zygote
Zygote is a diploid cell that will become the sporophyte
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Alternation of Generations
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Alternation of Generations
Evolution and
Diversity of Plants
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Appearance of generations varies widely
 In ferns, female portions are archegonia and are
fertilized by flagellated sperm
 In angiosperm, female gametophyte (embryo
sac), consists of an ovule
- Following fertilization, ovule becomes seed
 In seed plants, pollen grains are mature spermbearing male gametophytes
Reduction in the Size of the Gametophyte 10
Evolution and
Diversity of Plants
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Other Terrestrial Adaptations
Vascular tissue transports water and nutrients to
the body of the plant
Cuticle provides an effective barrier to water loss
Stomata bordered by guard cells that regulate
opening, and thus water loss
Protection of Eggs and Embryos
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Leaves of Vascular Plants
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Nonvascular Plants
Evolution and
Diversity of Plants
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Nonvascular plants (bryophytes)
Lack specialized means of transporting water and
organic nutrients
Do not have true roots, stems, and leaves
Gametophyte is dominant generation
Produces eggs in archegonia
Produces flagellated sperm in antheridia
Sperm swim to egg in film of water to make
zygote
Nonvascular Plants
Evolution and
Diversity of Plants
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Hornworts (phlym Anthocerophyta) have small
sporophytes that carry on photosynthesis
Liverworts (phylum Hepatophyta) have either
flattened thallus or leafy appearance
Mosses (phylum Bryophyta) usually have a leafy
shoot, although some are secondarily flattened
Can reproduce asexually by fragmentation
Dependent sporophyte consists of foot, stalk, and
sporangium
Hornwort
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Liverwort, Marchantia
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Moss (Polytrichum) Life Cycle
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Vascular Plants
Evolution and
Diversity of Plants
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Xylem conducts water and dissolved minerals up
from roots
Phloem conducts sucrose and other organic
compounds throughout the plant
Lignin strengthens walls of conducting cells in
xylem
Most seedless vascular plants are homosporous
Windblown spores are dispersal agents
All seed plants are heterosporous and have male
and female gametophytes
Seeds disperse offspring
Cooksonian Fossil
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Vascular Tissue
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Seedless Vascular Plants
Evolution and
Diversity of Plants
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Club Mosses (phylum Lycophyta)
Typically, branching rhizome sends up short
aerial stems
Leaves are microphylls (have only one strand of
vascular tissue)
Sporangia occur on surfaces of sporophylls
- Grouped into club-shaped strobili
Club Moss, Lycopodium
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Seedless Vascular Plants
Evolution and
Diversity of Plants
Ferns and Allies
Horsetails (phylum Sphenophyta)
- Rhizome produces tall aerial stems
- Contains whorls of slender, green branches
- Small, scalelike leaves also form whorls at the
joints
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Horsetail, Equisetum
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Ferns
Evolution and
Diversity of Plants
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Whisk Ferns (phylum Psilotophyta)
Branched rhizome has rhizoids
Mutualistic mycorrhizal fungus helps gather
nutrients
Ferns (phylum Pterophyta)
Large conspicuous fronds
- Divided into leaflets
- Dominant sporophyte produces windblown spores
Whisk fern, Psilotum
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Diversity of ferns
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Fern Life Cycle
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Seed Plants
Evolution and
Diversity of Plants
Seed plants are the most plentiful plants in the
biosphere
Seed coat and stored food allow an embryo to
survive harsh conditions during long period of
dormancy
Heterosporous
- Drought-resistant pollen grains
- Ovule develops into seed
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Seed Plants
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Gymnosperms
Evolution and
Diversity of Plants
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Gymnosperms have ovules and seeds exposed
on the surface of sporophylls
Confiers
Cycads
Ginkgoes
Gnetophytes
Conifers
Evolution and
Diversity of Plants
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Conifers, as well as other gymnosperm phyla,
bear cones
Tough, needlelike leaves of pines conserve water
with a thick cuticle and recessed stomata
- Considered a “soft” wood because it consists
primarily of xylem tissue
Pine Life Cycle
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Cycads
Evolution and
Diversity of Plants
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Cycads (phylum Cycadophyta)
Large, finely divided leaves that grow in clusters
at the top of the stem
Pollen and seed cones on separate plants
Pollinated by insects
Cycad Cones
Figure 24.19
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Ginkgoes
Evolution and
Diversity of Plants
Ginkgoes (phylum Ginkgophyta)
Dioecious
Some trees producing seeds
Others producing pollen
One surviving species (Gingko biloba)
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The Ginkgo Tree
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Ephedra
Figure 24.21
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Welwitschia miribilis
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Gnetophytes
Evolution and
Diversity of Plants
Gnetophytes (phylum Gnetophyta)
Have similarly structured xylem
None have archegonia
Strobili have similar construction
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Angiosperms
Evolution and
Diversity of Plants
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Angiosperms (phylum Anthophyta)
An exceptionally large and successful group of
plants
Ovules are always enclosed within diploid tissues
Became dominant group of plants in the late
Cretaceous and early Paleocene periods
Amborella trichopoda
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Monocots and Eudicots
Two classes of flowering plants
Monocotyledones (Monocots)
- One cotyledon in seed
Eudicotyledones (Dicots)
- Two cotyledons in seed
Evolution and
Diversity of Plants
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Flower Diversity
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The Flower
Evolution and
Diversity of Plants
Peduncle (flower stalk) expands at tip into a
receptacle
Bears sepals, petals, stamens, and carpels, all
attached to receptacle in whorls
Calyx (collection of sepals) protect flower bud
before it opens
Corolla (collection of petals)
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The Flower
Evolution and
Diversity of Plants
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Each stamen consists of an anther and a filament
(stalk)
Carpel has three major regions
Ovary - Swollen base
- Fruit
Style - Elevates stigma
Stigma - Sticky receptor of pollen grains
Generalized Flower
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Flowering plant life cycle
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Flowers and Diversification
Evolution and
Diversity of Plants
Wind-pollinated flowers are usually not showy
Bird-pollinated flowers are often colorful
Night-blooming flowers attract nocturnal
mammals or insects
Usually white or cream-colored
Fruits of flowers protect and aid in dispersal
Utilize wind, gravity, water, and animals for
dispersal
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Review
Evolutionary History
Alternation of Generations
Nonvascular Plants
Vascular Plants
Seedless
Seed
Angiosperms
- Monocots and Eudicots
- Flowers
Evolution and
Diversity of Plants
51
Ending Slide Chapter 24
Evolution and
Diversity of
Plants