Lecture 8 Flashcards
symbiotic relationships
occur when members of two species live in close, often obligatory, contact with each other - mutualism, competition, commensalism, amensalism, predation, parasitism
host
larger organism in symbiotic relationship
symbiont
smaller organism in symbiotic relationship
endosymbiotic
inside host organism
oldest fossil eukaryote
1.8 BYA
4 eukaryotic cell characteristics
- DNA in linear chromosomes in membrane-bound nucleus
- other membrane-bound organelles such as mitochondria and plastids (chloroplasts)
- often larger than prokaryotes
- cytoskeleton allows them to change shape
ancestral pre-eukaryotic cell
possibly a member of Archaea
origin of eukaryotic cell
ancestral host cell developed some structures (endoplasmic reticulum, nuclear envelope) gradually by infoldings of cell membrane, then the ancestral host cell took on an endosymbiotic aerobic heterotrophic prokaryote
proteobacterium
endosymbiotic aerobic heterotrophic prokaryote, used oxygen and organic matter to make energy, eventually became mitochondrion
origin of photosynthetic protists and plants
eukaryotes engulfed photosynthetic prokaryotes (cyanobacteria), became plastids
serial endosymbiosis
first mitochondria and then plastids were endosymbiotically acquired by the ancestors of photosynthetic eukaryotes
3 evidences for endosymbiosis in evolution of eukaryotes
- mitochondria and chloroplasts have own DNA, replicated independently
- this DNA is circular like prokaryotic DNA
- plastids have 2 or more cell membrane layers
primary endosymbiosis
free-living prokaryote being taken on by another cell - eg. red and green algae
secondary endosymbiosis
taking on a photosynthetic (plastid-containing) eukaryotic cell by a heterotrophic eukaryotic cell, engulfed red or green algae
horizontal gene transfer through endosymbiosis
make tree of life very complicated
first wave of diversification
metabolic diversification of prokaryotes
second wave of diversification
catalyzed by greater structural diversity of eukaryotic cell
third wave of diversification
origin of multicellular bodies
new ways of reproduction in eukaryotes
mitosis, meiosis, and syngamy
mitosis
one diploid cell divides once to form two diploid (2n) cells
meiosis
one diploid cell divides twice to form four haploid (1n) cells (reduction division)
syngamy
occurs when two 1n gametes fuse, form 2n zygote (fertilized egg)
embryo
multicellular, formed when zygote grows by mitotic cell division
larval stage
morphologically different stage before reproductively mature adult
sexual reproduction
two parents produce offspring with novel combinations of genes from both parents, requires meiosis and subsequent fusion of haploid nuclei from different parents
protists
the common name for a non-monophyletic group of mostly unicellular eukaryotes that are not plants, fungi or animals
protist characteristics
phototrophic/heterotrophic/mixotrophic, diverse reproductive modes, single-celled
mixotrophic
both photoautotrophic and heterotrophic
5 groups of protists (basal polytomy)
- diplomonads
- apicocomplexans
- ciliates
- amoebozoans
diplomonads
“primitive” protists, appear to lack mitochondria, but mitosomes and mitochondrial genes are present, suggests that they ancestrally had regular mitochondria but lost them during evolution, found in anaerobic habitats, multiple flagella, two separate nuclei
Giardia duodenalis
type of diplomonad, infects human intestines causing diarrhea, from contaminated drinking water, beaver fever, has mitosomes
apicocomplexans
parasites of animals, complex of organelles for penetrating host tissues at apex of cell, organelles have 4 membranes and cyanobacterial DNA; evidence of
secondary endosymbiosis, often require 2 or more
host species to complete life cycle
Plasmodium spp.
apicocomplexan parasites that cause malaria, need mosquitoes and vertebrates, resistant mosquitoes and plasmodium have caused malarial resurgence
ciliates
large and morphologically diverse group named for the presence of many cilia used for locomotion and/or food capture, free-living species feed on bacteria
and smaller protists by phagocytosis, some very active move on fused leg-like cilia, reproduce asexually by
binary fission, sometimes engage in sexual reproduction (conjugation)
ciliate example
Paramecium
amoebozoans
flexible body shape that move by extending blunt
lobes called pseudopodia and feed by phagocytosis, may be related to unikonta
3 groups of amoebozoans
- amoebae
- plasmodial slime molds
- cellular slime molds
plasmodial slime molds
start out with a single nucleus but then undergo repeated mitosis without cell division, become a single giant supercell with free-flowing cytoplasm and nuclei that hunts bacteria on the forest floor
amoebae
amorphous solitary protists, mainly predators of bacteria and smaller protists
cellular slime molds
start out as separate
single-celled individuals, if food becomes scarce, cells get together but maintain separate cell membranes, communal ‘slug’ migrates to a high spot, some cells form stalk, other cells climb up stalk and develop hard coat to withstand drying, disperse in the wind and land
somewhere wet, helpful cells that formed the stalk die
algae
general term for photoautotrophic eukaryotes that are not members of the Kingdom Plantae, not monophyletic, single-celled (diatoms), or multicellular (brown algae, alternation of generations)
diatoms
major components of marine and freshwater plankton
brown algae
kelp and other seaweeds
green algae
have green pigments in chloroplasts, chlorophytes and charophytes (multicellular and morphologically complex, thought to be sister to Plantae)
Chara
common charophyte lakeweed in Alberta
