Plants 2 Flashcards
Why are land plants monophyletic?
Because they only moved to land once as it was difficult
Why move onto land?
Land has light
Land has no predators(herbivores)
Readily available CO2
Abundance of uncolonized land
What made the transition to land hard?
-Dehydration
-Needed to develop new dispersal mechanisms (because in water, the water would disperse the offspring by floating)
-UV
Nonvascular Land plants
-Bryophytes: mosses, liverworts
-Algae
Key Innovation : Sunscreen
-Plants made suncreen to protect themselves from the UV(UV can damage DNA)
-Plants made compounds that absorb UV light
What were the first land plants?
Bryophytes(mosses)
Characteristics of Bryophytes
-no true roots(can grow on rocks/shallow soil)
-small and short
-thin leaves
-absorb nutrients and water through their leaves
-grow in moist/damp environments
Key Innovation: Cuticle
A layer of waxes and lipids that covers the surface area of a plants leaves and prevents them from drying out
Key Innovation: structures to protect reproductive cells and structures
- Spores: encased and protected cells used for dispersal
2.Protected reproductive structures to prevent desiccation - Retain the embryos on the plant (undergo a developmental phase on the plant before being released)
Alternation of generations
-All plants that reproduce sexually go through this life cycle
-Alternate between gametophyte stage(haploid) and the sporophyte stage(diploid)
Haploid Stage(n)
gametophyte
Diploid Stage(2n)
sporophyte
Mitosis vs Meiosis
Mitosis: One cell divides to produce to identical daughter cells(diploid)
Meiosis: One cell divides and produce s cells with half the number of chromosomes(haploid cells)
Reproduction in Bryophytes
