Evolution of Eukaryotes/Plants
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What is a Eukaryote?
A eukaryote is membrane bound, has compartmentalisation, organelles, and a membrane bound nucleus.
What was the key to eukaryotic innovation?
The nuclear envelope
What is the Endosymbiosis Theory?
The Endosymbiosis Theory was explored by Lynn Margulis 30+ years ago. The idea she promoted was that the mitochondria was a bacterium that had been incorporated into an ancient eukaryotic history/lineage (Mutualism).
Support for Endosymbiosis
- Mitochondria :
- are similar in size to bacteria
- reproduce by fission
- circular genome
- have own ribosomes
- translate proteins
- have a double membrane system
Does endosymbiosis explain eukaryotes having chloroplasts too?
- Yes. Why?
- 1. Not all eukaryotes have them
- 2. In some groups of photosynthetic protists, there was a secondary endosymbiosis
Where did secondary endosymbiosis first occur?
Secondary endosymbiosis first occured in green algae.
Land plants are important because...
- main primary producers
- affect atmospheric gases
- stabilize soil conditions
- moderate local climate
Tradition plant classification
nonvascular, seedless vascular and seed plants
Examples of non vascular plants are:
liverworts, hornworts and mosses
Characteristics of non vascular plants are:
- All non-vascular plants have a cuticle
- Liverworts have simple pores and protected embryos
- Hornworts and Mosses also have stomata
Examples of seedless vascular plants are:
lycophytes, ferns and horsetails
Characteristics of seedless vascular plants are:
- All: Trachieds and roots
- Lycophytes: addition of vascular tissue
- Horsetails and Ferns: true leaves
Examples of seed plants are:
angiosperms and gymnosperms (conifers, cycads, gnetophytesm ginko)
Characteristics of seed plants are:
Benefits of seeds and pollen are:
- Can tolerate drying
- Seeds are packaged with nutrients
- Not dependent on parent during fertilzation
- Heterospory: male and female parts/sporophye
Barriers for plants making the move to land were:
- water loss
- gas exchange
- water and nutrients equisition and movement
Solution for water loss:
Cuticle: a waxy protective layer
Solution for gas exchange:
- First there were pores: openings in the cuticle
- Then there were stomata: pores with control (guard cells)
Solution to reproduction barrier:
"Protected embryos": seeds
What is the process of Alternation of Generations:
- Start: Gametophyte(multicellular haploid organism) n
- Sporophyte(multicellular diploid organism) 2n
- End: Mitosis (n)
Solution for water and nutrient equisition and movement:
- Vascular tissue: xylem and phloem
Gymnosperms vs. Angiosperms
- Angiosperms have:
- triploid endosperm (double fertilization:2 male gametes/3 sets of chromosomes)
- flowers: DIVERSIFICATION
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