Chapter 22: Plant Diversity
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Chapter 22: Plant Diversity
Comparison of Water and Land as Habitats for Plants
WATER LAND
Water Close to each cell Under land surface, evaporates quickly above surface
Minerals Close to each cell On or under land surface
Gases Dissolved at low concentrations Plentiful in the air
Support Provides buoyancy, support Much less support for parts in air
Light Cuts out some wavelengths and lowers intensity
Much light available
Temperature Little fluctuations, slow change Changes more rapid, wider extremes
Reproduction Motile gametes swim Water seldom available for swimming gametes
Dispersal Water carries offspring to new locations
Water seldom available to carry offspring to new locations
Adaptations of Land Plants to Terrestrial Environments
PROBLEM ADAPTATION
1. Obtaining water and mineral nutrients when they no longer surround entire plant
Rhizoids or roots
2. Transporting water within the plant Xylem
3 Transporting food from sites of manufacture to sites of use Phloem
4. Preventing evaporation from surfaces exposed to air Cuticle
5. Obtaining gases for photosynthesis and respiration Stomata
6. Obtaining sunlight for photosynthesis Leaves
7. Supporting body in medium lacking buoyancy Xylem
8. Coordinating plant growth and plant response to changes in the environment
Hormones
9. Getting gametes to together without reliable supply of water for sperm
Pollen
10. Dispersing new individuals to suitable locations Airborne spores, then seeds
Differences Between Bryophyta and Tracheophyta
BRYOPHYTA TRACHEOPHYTA
1. No vascular tissue Vascular tissue present in sporophytes
2. No true roots, stems, leaves; rootlike rhizoids anchor plant and absorb water
Most modern forms have roots, stems, and leaves in sporophyte generation
3. Not more than a few cm tall Usually more than a few cm high
4. Sporophyte dependent on gametophyte generation
Sporophyte independent, self-sufficient
5. Gametophyte generation dominant Sporophyte generation dominant
6. Gametophyte independent, self-sufficient
Gametophyte independent (“lower” vascular plants) or dependent on sporophyte (gymnosperms and angiosperms
7. Water needed for swimming sperm during sexual reproduction
Water needed for swimming sperm except in angiosperms and higher gymnosperms
8. Lack of vascular tissue restricts to moist envs
Wide range of habitats
A. Metaphyta: Plant Kingdom
1. Bryophyta (Phylum) • Simpler plants; lack vascular system (transport
tubes such as xylem & phloem)• Depend on H2O to a greater extent than
vascular plantsEx: mosses & liverworts
Moss
2. Tracheophyta (Phylum) • Higher plants• 3 main groups possess water vascular system, so LESS
DEPENDENT ON H2O mosses (evolutionary advantage)1. P. Pterophyta (ferns) sperm require water for fertilization2. Gymnosperms/ conifers (cone-bearing) most ancient seed plants - POLLEN TUBE carries sperm- adaptation for terrestrial life3. Angiosperms/ flowering plants POLLEN TUBE carries sperm - Adaptation for terrestrial life/ *life cycle
Tracheids
B. Processes Essential to Sexual Reproduction
1. Meiotic Cell Division reduces species chromosome number by ½ haploid gametes2. Fertilization restores species chromosome number (egg & sperm nuclei fuse- forms zygote)
• Haploid (n) – cell has one member of each pair of chromosomes
• Diploid (2n) – cell has both members of each chromosome pair
C. Reproduction in Mosses & Ferns
1. Alternation of Generations life cycle in which a spore producing plant (sporophyte) alternates with a gamete producing plant (gametophyte)a. Sexual reproduction by a gametophyte alternates with… b. Asexual reproduction by a sporophyte
2. Mosses common moss plant is the gametophyte3. Ferns common fern plant is the sporophyte
NOTE: * Review life cycles handout * Life cycles dependent upon water for fertilization * Habitat restricted/limited by water
Plant Life Cycle• Have 2 alternating phases
known as “Alternation of Generations”1. diploid phase (2N) sporophyte / spore-producing plant2. haploid phase (N) gametophyte/ gamete-producing plant)
Moss Life Cycle
Fern Life CycleProthallus- gametophyte
D. Alternation of Generations (Plant Reproduction)
1. What are the generations?
SPOROPHYTE GAMETOPHYTE
Ferns Leaf-like frond(dominant)
Heart-shaped
Mosses Stalk/capsule Short leafy shoot(dominant)
Flowers Entire plant(dominant)
Pollen grain/ ovule
Cont. Alternation of Generations
2. Which plants have ONLY ONE kind of gametophyte and which plants have TWO KINDS of gametophytes Can you tell why???
• FERNS ONE gametophyte --- Has both antheridia AND archegonia
• MOSS TWO gametophytes --- Antheridia and archegonium on separate leaf-like stalks
• FLOWERS TWO gametophytes --- Microscopic pollen and ovule
Cont. Alternation of Generations
3. What alternates?• Processes Mitosis/ meiosis/ fertilization• Nutrition Dependent (hetertrophic)/
independent (autotrophic)• Chromosome # Diploid/ haploid• Size Dominant (large/ conspicuous)/
not dominant (smaller/ inconspicuous)• Duration Most of life cycle/ short time
period• Sex Asexual (spores)/ sexual (gametes)
4. In plant reproduction, what stage is between the diploid parent plant and the diploid young offspring plant?
• Haploid gametophyte stage5.In plant reproduction, what cell division
process is used to make the gametes?• Mitosis- gametophytes are haploid
SUMMARY OF MAJOR PLANT CHARACTERISTICS (METAPHYTA)(Autotrophic, multicellular, cell wall of cellulose
COMMON NAME PHYLUM NAME VASCULARTISSUE
ORGANS LIFE CYCLE HABITAT
MossesLiverworts
Bryophyta Absent No true roots, stems, leaves
Need water for
Gametophyte dominant, fusion of egg & sperm
fertilization!
Moist areas
Ferns(Felicineae)
Tracheophyta(Pterophyta)
Present/ xylem& phloem
True roots, leaves, develop from rhizome (underground stems) Need water for
Sporophyte dominant, distinct multicellulargametophyte(prothallium)
fertilization!
Moist areas
Conifers(Gymnospermae)- Wind-pollinated
Tracheophyta(Coniferophyta)
Present/ xylem& phloem
True roots, stems, leaves Pollen tube
Sporophyte dominant, seeds & cones
carries sperms
Wide-spread
Flowering Plants(Angiospermae)-Most evolutionary advanced plants- Wind/ animal-pollinated
Tracheophyta(Anthophyta)
Present/ xylem& phloem
True roots, stems, leaves
Pollen tube
Sporophyte dominant,floweres & seeds
carries sperms
Wide-spread
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