BIOL 112 Lab 4
« previous | Wednesday, September 19, 2012 | next »
Modified Objectives:
- Alternation of Generations (haploid / diploid)
- Evolutionary trend of gametophytes
- Flower structure
- 15 Microscope Slides
- Pollination vs. Fertilization (double fertilization)
- Visually distinguish among the following plant types:
- Algae
- Bryophyte (moss)
- Ferns
- Gymnosperms
- Angiosperms
Supergroup Archaeplastida
Red algae, green algae, land plants
descended from an ancient protist that engulfed a photosynthetic cyanobacterium
Green Algae: relatives of land plants 2 Groups of green algae: chlorophyta and charophyta
Green algae show two adaptations for land environments:
- Increased cellular organization and specialization
- Shift from isogamous [vocab 1] to oogamous [vocab 2] sexual reproduction: egg is large and stationary, sperm are small and motile.
Group Chlorophyta
Asexual reproduction under favorable conditions, but sexually form a zygote to survive harsh conditions.
- Individuals are haploid; zygote is diploid, but undergoes meiosis to form spores that germinate into algae
Representative individuals:
| Chlamydomonas | Spirogyra | Volvox | Ulva | |
|---|---|---|---|---|
| Organization | Single-celled | Filamentous (attached end-to-end) | Colonial (primary and daughter) | Multicellular "blades" w. specialized structures |
| Asexual Reproduction | mitosis | mitosis and fragmentation [vocab 3] | mitosis — forms inner daughter colony | |
| Gametes (Sexual Reproduction) | Isogamous | Isogamous (zygospores formed internally prior to conjugation) | Oogamous (zygospores formed inside colony and released when colony disintegrates) | Isogametes; isogamous (true alternation of generations w. distinct haploid/gametophyte and diploid/sporophyte stages) |
| Flagella | Two | Flagellated gametes | Many, synchronized; flagellated sperm | Flagellated isogametes |
| Dominant Stage | Haploid (reduced diploid stage) | Haploid (reduced diploid stage) | Haploid (reduced diploid stage) | Split betw. haploid and diploid thallus |
Group Charophyta
stoneworts
closest-living algae with algal and plant-like characteristics
Alternation of Generations
- haploid gametophyte produces haploid gametes by mitosis
- gametes merge to form diploid zygote
- zygote undergoes mitosis and grows into a diploid sporophyte
- sporophyte produces haploid spores by meiosis
- spores undergo mitosis to form a gametophyte (cycle starts over)
Group Bryophyta
Mosses, liverworts, and hornworts
- homospory
- male and female spores look identical
- heterospory
- male gametophytes come from microspores
- female gametophytes come from macrospores
- Lack vascular tissues (no true roots, stems, or leaves)
- Flagellated sperm require moist environment
- Dominant haploid gametophyte thallus and reduced diploid sporophyte
Dioecious plants (separate "male" and "female" plants):
- Females have archegonia
- Males have antheridia
Group Pterophyta
Ferns; seedless vascular plants
Development of vascular tissues (carry water and nutrients throughout plants)
- Stem is called stolon
- Roots are called Rhizomes
Still depend on water to transport flagellated sperm to egg
Dominant form is the diploid sporophyte; diminished haploid gametophyte prothallus that can be monoecious (male and female parts—antheridia and archegonia—on same structure).
Zygote develops attached to gametophyte
Vascular Plants
- gymnosperms
- "naked" (gymno-) "seed" (-sperm)
- cone-bearing
- angiosperms
- seed enclosed in fruit
- flowering plants
Seeds allow for following adaptations:
- survive harsher conditions (cold, drought)
- small multicellular sporophyte can remain dormant
- embryo protected by seed coat and surrounded by food supply
- facilitated dispersal
- female gametophyte protected inside diploid sporangium
Gymnosperms
Cycads (dioecious)
Heterosporous:
- microspores made on microstrobilus (cone)
- macrospores made on macrostrobilus
Ginkgophyta (also dioecious) do not have macrostrobiili, but two bare ovules
Coniferophyta (monoecious): Female macrostrobli grow at top of tree, while male microstrobili grow on bottom (prevents self-pollination)
Pollination v. Fertilization
- Pollination
- when pollen lands on a female gametophyte
- Fertilization
- when sperm contained within pollen reaches egg and fuses
Angiosperms
Ovary located deep inside flower