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when did eukaryotes first appear?
about 2 billion years ago
what are 4 defining features of eukaryotes?
- true nucleus
- membrane-covered organelles
- flagella and cilia have 9+2 pattern of microtubules
- most are aerobic
What are 2 ways that organelles may have formed in eukaryotes?
- infolding of the plasma membrane
- endosymbiosis (engulfing other cells)
what are some examples of organelles that formed through infolding of the plasma membrane? (4)
- endoplasmic reticulum
- Golgi complex
- nuclear envelope
what are 2 examples of organelles that formed through endosymbiosis?
mitochondria and chloroplasts
what 4 organisms do eukaryotes include?
Protists are traditionally divided into 3 informal nutritional groups, what are they?
- if heterotrophic, called protozoans
- if photosynthetic, called algae
- some look like fungus, but are protists
what are the 2 major organisms in Group 1 of the 5 major groups? Briefly describe each.
- Euglenids: photosynthetic or mixotrophic
- Trypanosomes: several cause human diseases (African sleeping sickness)
what common ancestor may be a descended from all the organisms in Group 2 of the 5 major groups? (
- a common ancestor that engulfed a photosynthetic cell about 1 billion years ago
- (not all are photosynthetic now)
what are the 5 organisms in Group 2 of the 5 major groups?
- animal parasites with complex life histories
In group 2 of the 5 major groups, what are 6 characteristics of dinoflagellates ? HINT: (how they move, armour, food chain, poison, fix, population increase)
- spin through water
- internal cellulose armour
- fix carbon b/c photosynthetic (mostly)
- bottom of marine food chains
- population increase can cause red tide
- some produce toxins
what is an example of animal parasites with complex life histories from Group 2 of the 5 major groups of eukaryotes?
plasmodium- the cause of malaria
what are 4 characteristics of ciliates from group 2 of the 5 major groups of eukaryotes? HINT: habitat, covered in?, type of organism, nucleus
- mostly free-living in freshwater
- have lots of cilia
- most complex single-celled organisms
- 2 kinds of nucleus in a cell
what are 5 characteristics of diatomes from group 2 of the 5 major groups of eukaryotes? HINT: carry out, walls, store food, food chain
- singled-celled; most planktonic
- carry out 20-25% of photosynthesis on earth
- bottom of aquatic food chain
- internal porous glass walls
- store food as oil
what are 3 characteristics about phaeophyta (brown algae)from group 2 of the 5 major groups of eukaryotes?
- marine, multicellular
- photosynthetic (colour due to carotenoids)
- diverse in temperature oceans
what are the names for leaf, stem, and root for an algae/seaweed?
where have the phaeophyta (brown algae) adapted to?
adapted to life near the edge of the ocean
one of the challenges of phaeophyta (brown algae) is to have a big surface area to capture light, how to the overcome this challenge? (2)
- keep blades close to surface of water
- many have gas-filled stipes and/or floats that hold the blade
one of the challenges of phaeophyta (brown algae) is to avoid being washed away, how to they overcome this challenge?
many have holdfasts
why can't phaeophyta (brown algae) just float at the surface and capture light?
they need to be attached close to shore because there are inorganic minerals present close to shore
one of the challenges of phaeophyta (brown algae) is to avoid being thrashed, how do they overcome this?
- they have a strong, flexible, slippery body
- strength: comes from cellulose in cell wall
- slippery body: comes from gel-forming polysaccharides
what are the 2 organisms in group 3 of the 5 major groups of eukaryotes and what are there 2 distinctive features?
- both single-celled and no fixed shape
Describe 2 characteristics of foraminifera from group 3 of the 5 major groups of eukaryotes?
- ray-like pseudopods extended though the holes in the internal CaCO3 shell
- most sit at bottom of water, some are planktonic
Describe a characteristic of radiolaria from group 3 of the 5 major groups of eukaryotes?
thread-like pseudopods that extend through microscopic silica "skeleton"
what are the 3 organisms in group 4 of the 5 major groups of eukaryotes? What do they all have in common?
- rhodophyta (red algae)
- chlorophyta (green algae)
- all are photosynthetic and are descendants from ancient protists that engulfed a cyanobacteria
how do rhodophyta from group 4 of the 5 major groups of eukaryotes have a red colour? (2)
- a red photo pigment masks the green of the chlorophyll
- red pigment absorbs blue and green light
what do chlorophyta from group 4 of the 5 major groups of eukaryotes have that make it green?
have green chloroplasts with chlorophyll
what is the order in which the seaweeds are living in the water, what are 3 reasons this happens?
- green in shallow water, brown a little deeper, red deepest
- this is because of the penetration of light into water and how the pigments absorb the light and the nutrients washed off from land
what are the 5 organisms in group 5 of the 5 major groups of eukaryotes?
- slime molds
where do amoebas, from group 5 of the 5 major groups of eukaryotes, live and how to they eat?
- move and eat via lobe-shaped pseudopods
- engulf prey via phagocytosis
- live in marine, fresh water, and sometimes wet soil
what is unique about slime molds, from group 4 of the 5 major groups of eukaryotes?
they have a multi-nucleated plasmodia
describe how the choanoflagellates, from group 5 of the 5 major groups of eukaryotes, look like. (3) and how they stay together.
- have collar of microvillia, flagellum, and nucleus
- form colonies and make gelatinous secretions that hold them together
which ancestors do choanoflagellates from group 5 of the 5 major groups of eukaryotes, represent?
ancestor of sponges