1 Jan 298:44 AM Ch. 30 Plant Diversity II The Evolution of Seed plants ancient squash seed
1Jan 298:44 AM
Ch. 30 Plant Diversity II
The Evolution of Seed plants
ancient squash seed
2Jan 298:48 AM
Essential Question:
How did the emergence of seed plants change the course of evolution?
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Common traits of all seed plants
1. gametophyte reduction in size
2. heterospory
3. Ovules and production of eggs
4. Pollen and production of sperm
5. Seeds
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Common traits of all seed plants:
1. reduced gametophytes can be microscopic
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advantages of reduced gametophyte
a. protection of female gametophytes from environmental changes
b. help prevent drought
c. protect from UV radiation
d.can obtain nutrients from sporophytes
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2. Heterospory
• each megasporangia produces 1 megaspore (spore from a heterosporous plant species that develops into a female gametophyte)
• each microsporangia produces many microspores (a spore from a hetersporous plant species that develops into a male gametophyte)
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3. Ovules and production of eggslayers of integument enclose megasporegymnosperms 1 integumentangiosperms two integumentswhole structure = ovule
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4. Pollen and production of sperm• microspores become pollen grains (male gametophytes)• protected by sporopollenin (tough coat polymer)• carried by wind, animals for pollination• Purpose: reproduction over long distances• advantages: long distance, no motility needed
yellow iris pollen
http://www.microscopyuk.org.uk/mag/indexmag.html?http://www.microscopyuk.org.uk/mag/artjul99/pollen.html
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5. Evolution of seeds
Advantages:• multicellular layer of tissue (seed coat) extra protection for embryo can resist harsh conditions
• Supply of food within can remain dormant for years
• disperse widely
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Gymnosperms = plants that have naked seedsnot enclosed in ovaries
evolution of gymnosperms360 million years ago, became extinctCarboniferous period started, then Permian period (more dry
so favored gymnosperms)needle shaped leaves, thick cuticles helped with water conservation
dominate the Mesozoic Era
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Phylum Cycadophyta
http://www.ucmp.berkeley.edu/seedplants/cycadophyta/cycads.html
Have large cones and palmlike leaves
most prevalent duringMesozoic era
~130 species today
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Phylum Ginkophyta
Ginkgo biloba
fanlike leaves that turn gold in autumn
ornamental tree
seeds smell rancid when decay
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Phylum Gnetophyta
Welwitschia SW Africa
Gnetum subtropical Africa/Asia
some tropical and desert species
3 genera
Ephedra Desert shrubsproduce ephedrine (decongestant)
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Phylum Coniferophyta
SequoiaDouglas Fir
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Largest of gymnosperm phyla
600 species
most are evergreens
bristlecone pineoldest living tree4,600 years old
Pacific yew source of taxolovarian cancer drug
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Life Cycleof a pine
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male pollen cone
female cones
http://oregonstate.edu/trees/con/spp/big/lppbg064.GIF
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Angiosperms Flowering plants
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Angiosperms are seed plants that produce reproductive structures called flowers or fruits
Evolution140 million years ago late Mesozoic
hypothesis of carpel from early reproductive leaf
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flower specialized for sexual reproduction
sepals enclose flower before it opens
petals aid to attract pollinators
stamen produce microsporesthat develop pollen grains
carpels make megaspores which make female gametophytes
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Fruits= mature ovary
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Types of fruit:
fleshy = wall of ovary is soft during ripeningEx. oranges, plums, grapes
Dry fruits = wall is hard during ripeningEx. beans nuts, grains
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fleshy fruit
dry fruit
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Pollinator relationships
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adaptations for dispersal:
• parachutes/propellers dandelions, maples
• water dispersal coconuts
• barbs so animals carry them
• animals eating seeds come out in feces
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Life cycle of angiosperm
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double fertilization
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Angiosperm Diversity
Monocots species with on cotyledon
Eudicots species with two cotyledons
Basal Angiosperms three lineages, formerly grouped with dicots; oldest lineages
Magnoliids evolved later; more closely related to eudicots and monocots
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Basal Angiosperms
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magnoliids
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Monocots Dicots
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Monocots Dicots
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Monocots
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Dicots
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Products from seed plants for Humans
1. food
2. tea, coffee
3. spices (ex. cloves, saffron, vanilla, black pepper)
4. sources of wood
5. medicinesex. atropine (pupil dilator) belladonna plant menthol (cough medicines) eucalyptus tree
morphine (pain reliver) Opium poppydigitalin (heart medication) Fox glove
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How did the emergence of seed plants change the course of evolution?
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