Topic 8 Flashcards
What is the oxygen revolution?
oxygen began accumulating ~2.7 BYA
photosynthetic cyanobacteria: use sun’s energy to split water into hydrogen and oxygen
O2 was toxic to most early life
other prokaryotes adapted to oxygen-rich atmosphere and began respiring aerobically
What is the domain of eukarya?
DNA in linear chromosomes in membrane bound nucleus
membrane-bound organelles such as mitochondria and chloroplasts
often much larger than prokaryotes
diverse morphology
What is the theory of endosymbiosis?
- Infoldings of cell membrane (endoplasmic reticulum, nuclear envelope)
- Ancestral host cell took on an endosymbiotic aerobic heterotrophic prokaryote (uses oxygen and organic matter for energy, eventually become mitochondrion)
- Other lineages engulfed photosynthetic prokaryotes (most likely cyanobacteria, use light and CO2 to make organic compounds)
What is the evidence for endosymbiosis found in the mitochondria and chloroplasts?
self-replicating (binary fission)
resemble bacteria in size and nature
DNA: circular (as in prokaryotes)
2 cell membrane layers: inner one homologous to plasma membrane of prokaryotes
What is primary endosymbiosis?
2 membranes
What is secondary endosymbiosis?
3 membranes
What is a protist?
the informal name of group of mostly unicellular eukaryotes, but there are some colonial and multicellular species
What is the kingdom Protista?
animals, fungi, plants each closely related to a different protist group
group is paraphyletic
What is the support for supergroup?
all eukaryotes seem to possess mitochondria or related organelles from alpha-proteobacteria
Chromalveolata, excavata, and plantae have plastids from cyanobacteria
What are the advantages of multicellularity?
strength in numbers
specialization
protection
size
structural diversity
mobility
different types of cells
survival
What are the disadvantages of multicellularity?
slow reproduction = evolve slowly
high metabolic cost
easier to see
cancer
What are the two hypotheses of multicellualrity?
- Large Size is Advantageous (diffusion is effective only over short distances)
- “Left Wall of Minimum Complexity” (no other option)
How did multicellularity evolve?
- Symbiosis (two cells of different DNA)
- Internal Division of Multinucleate Organisms (cells have different DNA)
- Coloniality (best of the three)
What are autotrophic protists (algae)?
photoautotroph: make own food with chloroplast
aquatic
single cells or multicellular
asexual and sexual reproduction
alternation of generations
function in global ecosystem (production of energy, uptake of CO2 and release of O2)
cause environmental problems
How are red and green algae closely related to land plants?
over a billion years ago, a heterotrophic protist acquired a cyanobacterial endosymbiont
photosynthetic descendants of this ancient protist evolved into red algae and green algae
land plants are descended from algae
What is plantae?
the supergroup that includes red algae, green algae, and land plants
chloroplasts have two membranes
What is red algae?
reddish in color due to accessory pigment called phycoerythrin, which masks the green of chlorophyll
usually multicellular, largest are seaweeds
What are single-celled algae?
major component of marine and freshwater plankton
What are chlorophytes (green algae)?
green pigments in chloroplasts
live in fresh water
range in size from single cells to mutlicellular
What are charophytes (green algae)?
multicellular + morphologically complex
closely-related to land plants
charophytes and land plants share a common ancestor
sister taxon to land plants
What is the supergroup Unikonta?
this group is somewhat controversial and has recently been divided into two supergroups Amoebozoans and Opisthokonts
What are the five supergroups?
Excavata
Chromalveolata
Rhizaria
Archaeplastida
Unikonta
How do protists asexually reproduce?
is based on mitosis and cell division in eukaryotic organisms as well as fission in bacteria and archaea
results in daughter cells genetically identical to the parent
How do protists sexually reproduce?
is based on meiosis and fusion of gametes
results in cells that are genetically different from their parents and from each other
most undergo asexual reproduction routinely but sexual reproduction intermittently
What’s the benefit of sex?
meiosis is adaptive because genetically variable offspring may be able to thrive if the environment changes
the genotypes of many protists and pathogens evolve very quickly
