524

AnnouncementQuiz 5: Material from Plant Nutrition through today’s lectureMake sure to start studying soon for the final!!!!Form and function is very important!!!!refer to your books or eCommons for diagrams!!!!!

3rd and Last Plant of the WeekBlue Gum Eucalyptis (Eucalyptus globulus)• Introduced to California (Exotic)• Bark sheds off in large flakey strips• Long slender green sickle shaped alternate leaves• Extremely common around Santa Cruz

Asexual ReproductionVegetative reproduction:Often the result of themodification of vegetative organSome maintain sexual andasexual reproduction

AsexualPLANT REPRODUCTIONVivipary (plantlets; modified leaves)Bulbs (modified leaves)Rhizomes (underground stems)Stolons (horiz. modified stems)all CLONAL

Apomictic seeds• Asexually Produced Seeds produced in the female gametophyte• Meiosis I w/o Meiosis II or,• Meiosis doesn’t occur• Gamete is diploid• Ovule develops into seed &Ovary develops into fruit

Advantage of Asexual Reproduction• Rapid colonization of favorable environment• No need to pollinate

Disadvantage to Vegetative Reproduction• Low genetic variation• Increased susceptibility to Disease• Loss of entire populationEx. Dutch Elm Disease on English Elm 1967 p.810

Plant Maturity• Annuals: 1 year life cycle• Biennials: 2 year life cycle; 2nd year reproductively mature• Perennials: 3+ years; reproductive maturity depends on the spp.(species)

Seed DispersalTransport of seeds away from parent plantMajor reasons for dispersal• Decrease competition w/ relatives• Avoid diseases• Increase the probability for future outcrossing

Intraspecific Competition: Competition between individuals of the same speciesIndividuals of the same spp.share similar resourcerequirementsDispersal decreasescompetition with closerelatives

Short distance dispersal• Annuals: Advantages • No competition with mom • Suitable conditions• Annuals: Disadvantages • Conditions can become unfavorable • Low genetic diversity for crossing over

Short distance dispersal• Perennials: Advantages • Suitable condition• Perennials: Disadvantages • Conditions can become unfavorable • Competition with mom • Low genetic diversity for crossing over

Janzen - Connell Hypothesis 1970Mechanism to explain high species diversity in te tropics• Genetically similar organism share similar pests and pathogensDensity Dependent Mortality

Density Dependent Mortality# of seeds Probability/ unit area of Seed Survival Distance from parent tree->

Fruits• Protect seed from damage byanimals and pathogens• Aid in seed dispersal• Fleshy or dry and inedible

5 modes of seed dispersal• Gravity• Wind• Ballistic• Water• Animals

Gravity Dispersal• Causes fruits to fall to the ground• Fruits can roll away and/or be consumes• Secondary Dispersal:Carried by water or animals at a later dateEx. Apples, nuts, acorns, etc.

Wind DispersalModified structures allowseeds float on breezes orfloat to the groundEx. Dandelion, Maple seeds

Ballistic DispersalSeeds are physicallyejected away from theparent plantNot very long distance,but secondary dispersalcan increase distanceEx. Geranium pratense

Water DispersalSeeds areadapted to survivebeing carried longdistance bywaterEx. Coconut

Animal Dispersal• Consumed and later defecatedin another place• Cached (buried) and forgotten• Carried inadvertently

Seed Dispersal: Summary The Private Life of Plants http://www.youtube.com/watch?v=zbQ1jWl3AOMMinute: 0935

The Evolution of AngiospermsGymnosperms: Most recent common ancestorWhat are Gymnosperms and how are they similar and different fromangiosperms?????

PLANT REPRODUCTION SexualFigure 28.5

Gymnosperm (“naked seed”Seeds not protected by an ovary or fruit tissue• Only 1,200 living spp.• Angiosperms est. 250k-400k spp.• Dominate the terrestrial environment 2nd to angiosperms• ALL SHOW SECONDARY GROWTH!!!!! ( all produce wood)

Gymnosperm (naked seed)• Cones are male and female reproductive structures• Tracheids for water conduct• ALL SHOW SECONDARY GROWTH

Major Groups of Gymnosperms• Cycads• Ginkgos• Gnetophytes• ConifersFig on p. 612 ch. 29

Cycads• Most ancestral• Found in tropics and sub tropics• Height up to 20m• ~300 spp.• Often confused for Palms

Ginkgos• Common during the Mesozoic era • 250- 65 MYA• Only one spp today Ginkgo biloba• Male and Female Trees• X and Y chromosomes distinguish males from females •Similar to humans, and unlike other plants

Gnetophytes• 90 spp. in 3 genera• Only exception in Gymnosperms • Contain Vessel Elements for xylem transportEx. Welwitschia

Conifers• Most abundant of all Gymnosperms (700 spp)• Forests make up largest terrestrial carbon sink• Most spp are evergreen

Ex. Conifers dominate the boreal forestsBoreal Forest Cover ~ 6 mil. sq.......

Major Synapomorphies of AngiospermsSynapomorphies: Shared derived traits of a group• Double Fertilization• Endosperm• Ovules and seeds enclosed in a carpel• Flowers• Phloem with companion cells• Reduced gametophytes

524

by Christina Pham on Jun 09, 2012

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524 Presentation Transcript