Origin of Eukaryotes Flashcards
Oldest fossil record of Eukaryotic cells dates back to:
1.8 BYA
Ways Eukaryotes differ from prokaryotes:
- DNA in linear chromosomes in a membrane-bound organelle
- membrane-bound organelles such as mitochondria and chloroplasts
- generally much larger
- Cytoskeleton (internal network of proteins)
- have dynamic membranes that facilitate movement and feeding
- Sexual reproduction promotes genetic diversity
Meiosis
creates unique gametes (chromosomal recombination)
fertilization
fuses gametes at random creating unique combinations of alleles
endosymbiont theory
mitochondria and plastids (chloroplasts and related organelles) were formerly small prokaryotes living within larger host cells
endosymbiosis
a relationship between two species in which one organism lives inside the cell of another organism
endosymbiont
a cell that lives within a host cell
Process of serial endosymbiosis
- ancestral prokaryote calls developed structures gradually by infoldings of the plasma membrane
- Ancestral prokaryote cells took into endosymbiotic aerobic, heterotrophic prokaryote
- One ancestral heterotrophic eukaryote lineage engulfed a photosynthetic prokaryote
Ancestral prokaryote cells took into endosymbiotic aerobic, heterotrophic prokaryote
likely enguphed an alpha bacteria (uses oxygen and organic material to generate energy) which eventually became mitochondrion
Primary Endosymbiosis
prokaryotic cells are taken up as endosymbionts by prokaryotic or eukaryotic cells
Secondary endosymbiosis
eukaryotic cells are taken up as endosymbionts by other eukaryotic cells
Mitochondria genomes are most similar to the genomes of
alpha proterobacteria
Chloroplast genomes are most similar to the genomes of
cyanobacteria
Mitochondria and Chloroplast proof of being endosymbiots
1. Mitochondria and chloroplasts have small, circular DNA (like prokaryote circular genomes), which they replicate, transcribe, and translate independently of nuclear DNA.
- The organelle’s inner membranes
are homologous to plasma
membranes of prokaryotes - These organelles and
prokaryotes divide by binary
fission. - The organelle ribosomes (sites of
protein synthesis) are more
similar to prokaryotic than
eukaryotic ribosomes. - The organelles resemble
prokaryotes in size and structure.
Multicellularity evolved independently ______
multiple times
Oldest multicellular organism
1.2 BYA small algae
Disparities between molecular phylogenies can be explained by the occurrence of _____
horizontal gene transfer
Protist
taxonomically diverse group of mostly unicellular eukaryotes
Protist is not a monophyletic group because
it excludes plants, animals, and fungi
Most eukaryotes are:
protists and most protists are unicellular
____ are the most diverse Eukariotic group
protists
Photoautotrophs
use chloroplasts to fix inorganic carbon using light energy (e.g. algae and phytoplankton)
Chemoheterotrophs
absorb organic molecules or ingest larger food particles
Mixotrophs
combine photoautotrophic (photosynthesis) and chemoheterotrophic nutrition.
Protist diversity has origins in ______
endosymbiosis
The plastid-bearing lineage of
protists that arose from ____
endosymbiosis evolved into
photosynthetic protists: ______
primary, red and green algae
Plastid genome DNA of red algae and
green algae closely resemble DNA of
______
cyanobacteria
On at least three occasions during
eukaryotic evolution, red and green
algae underwent secondary endosymbiosis, in which they:
were
ingested by a heterotrophic
eukaryote
