characteristics of plants: eukaryotic cells autotrophic and multicellular cell walls contain...
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CHARACTERISTICS OF PLANTS:Eukaryotic Cells
Autotrophic and Multicellular
Cell Walls Contain Cellulose
Alternation of Generation
Embryonic Development
• More than 280,000 species of plants inhabit Earth today.
Land plants (including the sea grasses) evolved from a certain green algae, called charophytes
Spirogyra, a
model chlorophyte
CHALLENGES FACED BY PLANTSFOR LIFE ON LAND•Obtaining enough water
•Transporting water and dissolved substances to other parts of the plant body and transporting the products of photosynthesis to other parts of the plant that don't conduct photosynthesis
•Preventing excessive loss of waterby evaporation
•Maintaining an extensive moist surface for gas exchange
•Supporting a large plant body againstgravity
•Carrying out reproduction when thereis little water
•Lastly, withstanding the extremefluctuations in temperature, humidity, wind, and light which are moderated in water due to its high heat capacity
Land Plants Evolved from GreenAlgae.
Common Characteristics:•Rose-shaped complexes for cellu-lose synthesis•Peroxisome enzymes•Structure of flagellated sperm•Formation of a phragmoplast
Charophyceans: Chara (top), Coleochaete orbicularis (bottom)
Several Features of Land Plants Differ From Those of Green Algae
Multicellular sex organs withan outer layer of jacket cellsCuticles on leaves
Derived Traits of Land Plants
(These traits are absent in the charophyceans – next four slides)
Apical Meristems of Plant Shoots and Roots
Alternation of Generations: a Generalized Scheme
Multicelllular Gametangia: Archegonium of Marchantia (left), Antheridium of a hornwort (right)
Multicellular Dependent Embryos: Marchantia (left), Shepherd's purse (right)
Walled Spores Produced In Sporangia
Cooksonia, a Vascular Plant of the Silurian Period
Leaves of Vascular Plants
• There are four main groups of land plants:
• Bryophytes • Pteridophytes • Gymnosperms • Angiosperms – 90% of all
plants
Representatives of theFour Major Groups of Plants
• There are four great episodes in the evolution of land plants:
–the origin of bryophytes from algal ancestors
–the origin and diversification of vascular plants
–the origin of seeds
–the evolution of flowers
p. 578
Some Highlights of Plant Evolution
475 mya
420 mya
360 mya
140 mya
Reduction in the Size of the Gametophyte
Hornwort
Liverwort Liverwort
Moss
Bryophytes
Moss with Sporophytes
Gametophytes
Liverwort, Marchantia Antheridia Archegonia
Hornwort – a Characteristic Bryophyte
Moss (Polytrichum) Life Cycle
The life cycle of Polytrichum, a moss
Pteridophytes
ClubMoss
Whisk Fern
Horsetail Fern
Whisk Fern, Psilotum
Club Moss
Club Moss in Olympic National Forest – WA State
Club Moss in Olympic National Forest
Club mosses (Lycopodium) have microphylls, with single veins
HorsetailHorsetails and the other seedless vascular plantshave highly branched vascularsystems calledmegaphylls.
Fern sporophyll, a leaf specialized for spore production
Fern Sori (clusters of sporangia)
• Sporophylls
–modified leaves with sporangia
• Most seedless vascular plants
–Are homosporous, producing one type of spore that develops into a bisexual gametophyte
sporangium > single > bisexual > eggs and sperm type of gametophyte spore
• All seed plants and some seedless vascular plants
–Are heterosporous, having two types of spores that give rise to male and female gametophytes
megaspore > female gametophyte > eggs
microspore > male gametophyte > sperm
Fern Life Cycle
The Life Cycle of a Fern
• The first seed plants evolved about 360 million years ago, near the end of the Devonian Period.
• A seed consists of a plant embryo packaged along with a food supply within a protective coat.
The Reduced Gametophyte of Seed Plants are Protected in Ovules and Pollen Grains
From Ovule to Seed
Phylum Ginkgophyta
The Gingko (biloba) treeis a “living fossil”and has been on the earth virtuallyunchanged for at least 150 million years. It produces “naked” seeds, as do all other gymnospernms.
Female Gingko
Seeds
The Ginkgo Tree
Male Female
Sago Palm or Cycad, a gymnosperm
Sago Palm or Cycad Cones
Figure 24.19
Phylum Gnetophyta: Welwitschia
Phylum Gnetophyta:
Ephedra
Ephedra
Figure 24.21
PhylumConiferophyta:
DouglasFir
These are male coneson a pine tree.
Male Pine Cones
Female Pine Cone
This picture was taken in Sequoia National Park in Central California.One sequoia tree, nicknamed the “GeneralSherman Tree” is the heaviest/largest tree in the world. It is over 2300 years old and weighsover 1300 tons.
This picture is of “The Lone Cypress”taken on the 17mile drive on the Monterey Peninsula.It is one of the most commonly photographed trees in the world.
This picture is of the Bristlecone Pine Tree which is the oldest tree in the world – over 4700 years old.
“Methusaleh” as the oldest tree is called is located in the White Mountains of California.
Pine Life Cycle
The Life Cycle of a Pine
• The great majority (90%) of modern-day plant species are flowering plants, or angiosperms.–Flowers evolved in the early
Cretaceous period, about 140 million years ago.
–A flower is a complex reproductive structure that bears seeds within protective chambers called ovaries.
Representatives of Major Angiosperm
Clades
Figure 30.18 Flower-pollinator relationships: Scottish broom flower and honeybee (left), hummingbird (top right), baobab tree and bat (bottom right)
Generalized Flower Structure
Angiosperm Life Cycle
The Life Cycle of an Angiosperm
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