Unit 5: Plants Flashcards
Early plants
- within archaeplastida (as well as red and green algae)
- only green algae contains chlorophyll A & B like plants
early plants adaptations to land
- Alternation of Generations
- Apical meristem (root and shoot)
- Waxy cuticle
- Cell walls with lignin
Alt. Of Gens: Haplodiplontic life cycle
both haploid and diploid multicellular stages
Gametophyte
multicellular haploid form
* Produced gametes via mitosis
Sporangium
produces spores in seedless plants
Sporangium 2 types:
Homosporous – produces one type of spores
Heterosporous – produces 2 types of spores
Sporophyte
Multicellular diploid form
* Produce “spores” via meiosis
Gametangia
Produces gametes in seedless plants
Apical Meristems
- Site of rapid cell division
- Root tip and shoot tip
- Undifferentiated cells – continued proliferation
- Allows for root and shoot elongation
Apical Meristems: Lateral meristem
gives trees girth
Vascular tissue
structure and nutrient movement
Xylem
water and ions from root to shoot
Phloem
Food derived via photosynthesis throughout plant
Lignin
adds to strength of tissues
Waxy cuticle
Prevents H2O loss, stifles CO2 uptake
Stomata
pores for gas exchange
Additional Adaptations of Land Plants
- UV protective flavonoids
- Chemical deterents
–> smells etc
Paleozoic Era
has six periods
* Cambrian, Ordovician, Silurian, Devonian, Carboniferous, Permian
Ordovician
colonization of land by plants (> 500 MYA)
End of Devonian
Ferns, Horsetails (seedless) and seed plants populated
* Gave rise to trees and forests
* Vegetation-enriched air with O2
* Provided food for land animals
Major divisions land plants
- Non-vascular: moss, horn-worts/liver-worts
- Seedless Vascular: Horsetails
- Seed Plants: Gymnosperms (ex. conifers) & Angiosperms (Monocots and Dicots)
Groups of Green Algae
Charophytes and Chlorophytes
Charophytes and Chlorophytes
- Same chlorophyll a & b, and carotenoids as land plants – Archaeplastida
- Store carbohydrates as starch (like land plants)
Chlorophytes
sea lettuce and volvox
Charophytes ex.
Chara
Structure of Green Algae
single cellular, colonial (even in long chains), multicellular
Green algae cannot survive without…
thin film of H2O
Green Algae reproduces…
*Asexual – Fragmentation (ex.clippings) or dispersal of spores
*Sexual – fusion of gametes
How Algae differ from plants: Molecular analysis
Land plants and Charophytes = sister groups (share common ancestor, diverged)
Similarities of Land Plants and Charophytes
- Cells divide along cell plates
- Plasmodesmata – intercellular channels
- Apical growth
Streptophyta
New monophyletic group including land plants and Charophytes
Closest living relative of land plants
Charales
Charophytes 3 groups
1) Charales
(420MYA– freshwater habitats
Ex. Chara or Skunkweed–stem has no supportive tissue= not a plant Haplontic lifecycle)
*more important than the others
2) Zygnematales
(More like embryophytes
Reproduce sexually and asexually, haplontic lifecycle)
3) Coleochaetales
Bryophytes
- Closest extant relatives of early terrestrial plants (450 MYA)
- 25,000 species
- Thrive in Tundra, moist habitats
- Lack xylem and lignin (so no fossils)
- conducting cells move water and nutrients cell to cell
Liverworts (Hepaticophyta)
- Most closely related to ancestor of vascular plants – it is terrestrial but still moist (hepatico = liver, phyta = plant, )
- 7,000 species
- Lobe (like lobe of liver) like flat thallus (some are leaf-like)
- Organelles allow movement of gas (not stomata)
- Sporophyte (on top of gametophyte) contained in archegonium
- Asexual and sexual reproduce