T/F: multicellularity has independently occurred between organisms with no common ancestor
- true
What’s the most diverse group of eukaryotes?
- opisthokonts
What’s included under opisthokonts?
- animals
- choanoflagellates
- fungi
What has the most diversity under animals?
- insects
What does opisthokonts mean?
- single, posterior (opisthios) flagellum (knots
What’s a clue that you’re looking at a opisthokont?
- highly folded mitochondria
- flat cristae
What’s a likely explanation of how animals originated?
- likely from a colony of choanolagellate (which is an opisthokont)
1) colonial flagellated protist with unspecialized cells
2) certain cells became specialized for feeding and other functions
3) a developmental reorganization produced a 2-layered animal with a sac-within-a-sac body plan (digestive cavity)
What are 7 characteristics of opisthokont animals?
- multicellular eukaryote
- chemoheterotrophic
- no cell walls (cell membranes contact adjacent cell membranes)
- motile (at some stage, can be a short period)
- oxidative phosphorylation to supply ATP (mitochondira)
- sense and respond to the environment
- usually diploid stage is dominant, haploid is short lived
What does chemoheterotrophic mean?
- it gets its energy from eating high energy molecules
- doesn’t get energy directly from sun
- gets carbon from preexisting carbon molecules (don’t make them)
T/F: pretty much every living thing can sense and respond to the environment, but animals are very adept because they are highly mobile
- true
What 3 diagnostic characteristics only found in animals?
- develops from a blastula
- certain extracellular matrix molecules (ex the proteoglycan collagen) aka things that glue animals together
- certain cell-cell membrane junctions
What junctions are specific to animals?
- tight/septate junctions
- desmosomes
- gap junctions
What are tight/ septate junctions?
- no leaky
stops stuff from leaking between cells - tight = vertebrate
- septate = invertebrate
What are desmosomes?
- leaky links between cells
- wants fluid to move between cells
What are gap junctions?
- cell membrane connect through a pore
- electrical connection
- allows ions to pass through to communicate different things to each other
What’s included under archaeplastids?
- glaucocystophytes
- red algae
- green algae aka land plants
What are 5 characteristics of archaeplastida plants?
- multicellular eukaryotes
- photoautotrophic (mostly)
- cell walls
- sessile
- alternation of generations life cycle
What are the 2 generations in the life cycle of plants?
- haploid (gamteophyte)
- diploid (sporophyte)
- both of these are prominent and multicellular
T/F: the only photosynthetic organisms are some plants
- false
- lots throughout eukaryotes
What does multicellularity and photosynthesis have in common?
- they both independently/ randomly appeared in the phylogenetic tree with no common ancestor
When did the first land plants appear? Were they the only plants?
- 460 million years ago
- there were other plants
When did the first animals appear?
- 600 million years ago
What are the differences in cell structure between opisthokonts and archaeplastida?
- cell wall
- large vacuole
- chloroplast
How does the cell wall support the plant?
- helps cell grow large while still being supported
- important for water transport, large difference in osmatic pressure between the inside and outside of the cell - uses those differences to move fluids around the plant
