Topic 11 Flashcards
Origin of Eukaryotes
First fossilized eukaryotic cells appeared 1.8 bya and were triggered by the Great Oxidation Event
4 Key Features of Eukaryotic cells
- Nucleus with linear chromosomes in a membrane-bound nucleus
- Membrane-bound organells
- Eukaryote cells are larger than prokaryote cells
- Contain a cytoskeleton and cellular dynamics
Meiosis
Sexual reproduction mechanism of Eukaryotes involving chromosome recombination and independent assortment of alleles, generating unique gametes
Endosymbiosis
A symbiosis between two species in which one organism lives inside another organism’s cells or tissues
Endosymbiont
Any organism residing within the body of cells of another organism, typically in a mutualistic relationship
Endosymbiont Theory
Proposes that mitochondria and plastids in eukaryotic cells were once small prokaryotes residing within larger host cells.
Theory is supported by physical, biochemical, and genetic similarities between chloroplasts and cyanobacteria, and between mitochondria and aproteobacteria
Serial Endosymbiosis
Hypothesis mitochondria evolved before plastids in a series of primary endosymbiotic events
Evolution of Multicellularity
evolved independently in multiple lineages of algae, plants, fungi, and animals
Advantages of multicellularity
- Cell specialization where cells perform different tasks
- Increased size and complexity
- Extended life span through cell growth and renewal processes
- Predation avoidance
3 Domains of Life
Bacteria, Archaea, and Eukarya
There is evidence of significant genetic exchange between domains
Origin of Eukaryotes and Example
Horizontal gene transfer has been key to the evolution of both prokaryotes and eukaryotes.
Ex) photosynthesis originated from primary endosymbiosis
Protist
An informal term for a diverse group of mostly unicellular eukaryotes that is not a monophyletic group that does not share a common ancestor and excludes plants, animals, and fungi
Protist Diversity
Can be more complex than multicellular organisms and can get nutrition by being a photoautotroph, a chemoheterotroph, or a mixotroph.
Primary Endosymbiosis Consequence
Led to formation of eukaryotic mitochondria and an ancestral aerobic a-proteobacterium
Eukaryotic plastids formed through Primary endosymbiosis of a photosynthetic cyanobacteriam
How did photosynthetic protists evolve?
Through secondary endosymbiosis.
Red and green algae were ingested by a heterotrophic eukaryote multiple times in evolutionary history, leading to photosynthetic protists
Four Major Supergroups of Eukaryotes
- Excavata
- SAR (Stramenopiles, Alveolates, Rhizarians)
- Archaeplastida (includes plants, green and red algae)
- Unikonta (includes animals, fungi, and some protists
Includes numerous clades of protists, and basal polytomies of unresolved groups
