What are the features of eukaryotes?
Presence of cytoskeleton and compartmentalization (nucleus and organelles)
What are the origins of eukaryotic organelles?
Infoldings of membranes and endosymbiosis.
What originated from infoldings of membranes?
the nucleus and endoplasmic reticulum originated from infoldings of prokaryotic cell membranes.
How did some organelles originate from endosymbiosis?
Some organelles (mitochondria and chloroplasts) originated when prokaryotic cells engulfed other prokaryotic cells.
what are mitochondria?
- Mitochondria originated from (ancestor) aerobic bacteria that were engulfed by larger bacteria
- Mitochondrial DNA can be used to trace maternal lineage because eggs have mitochondria while sperm usually don’t.
- It needs oxygen to function (aerobic respiration)
What are chloroplasts?
- Chloroplasts originated from larger bacteria that were engulfed by smaller photosynthetic bacteria (endosymbiosis occurred multiple times)
- Chloroplasts come from a single line of cyanobacteria.
- Their hosts were not monophyletic.
What is secondary endosymbiosis?
Secondary endosymbiosis is when a eukaryotic cell engulfs a cell that has already undergone primary endosymbiosis.
What is an example of secondary endosymbiosis?
Brown algae obtained their chloroplasts by engulfing red algae, which already had chloroplasts.
What is symbiosis?
Symbiosis is a close relationship between organisms of different species.
What is an endosymbiont?
Endosymbionts are organisms that form a symbiotic relationship with another cell or organism.
What is endosymbiosis supported by?
Endosymbiosis is supported by
- DNA inside mitochondria and chloroplasts
- DNA that is similar to bacteria DNA in size and character.
- Ribosomes inside mitochondria similar to bacterial ribosomes
- Chloroplasts and mitochondria replicate by binary fission - not mitosis.
How are protists highly variable?
- Unicellular, colonial, and multicellular groups.
- Most are microscopic but some are huge.
- All symmetries
- All types of nutrition
How is a protist’s cell surface?
- plasma membrane
- some have cell walls. Eg. Algae.
- Extracellular material (ECM) in some non-living material on the outer surface
- Cysts - dormant cells with resistant outer covering. Used for disease transmission.
How do protists demonstrate locomotion?
- Flagella - one or more. Move side to side like a tail. Different proteins than those found in prokaryote flagella.
- Cilia - shorter and more numerous than flagella.
- Pseudopodia (‘false feet’)
What are the types of pseudopodia?
- Lobopods: large, blunt. Found in Amoebas.
- Filopods: thin, branching.
- Axopods: thin, long. Found in Foraminifera.
What is a protist`s nutrition?
- Phototrophs
- Heterotrophs
- Phagotrophs - ingest particulate food matter. (E.g. Amoebas using pseudopods)
- Osmotrophs - soluble food matter. (Eg. trypanosomes)
- Mixotrophs are both phototrophic and heterotrophic. Eg. Euglena switches from photosynthetic to heterotroph in low light.
- Some groups contain organisms with more than one type of metabolism. Eg. Dinoflagellates, Euglenozoans.
How is asexual reproduction in protists?
- Typical mode of reproduction
- Some species have an unusual mitosis
*budding: the daughter cell is smaller than the parent cell
*schizogony: several nuclear divisions occur before cell division
How is sexual reproduction in protists?
- May be obligate, or only under stress
- Meiosis is a major eukaryote innovation. Cells with paired chromosomes had to evolve before meiosis. Meiosis produces gametes.
- Union of haploid gametes which are reproduced by meiosis.
- Advantage in allowing frequent genetic recombination. Allows the organism to survive better under changing conditions.
Diplomonads: major characteristics and organisms
- 2 haploid nuclei
- Multiple flagella
- Non-functional mitochondria
Organism: giardia- intestinal parasite.
Parabasalids: major characteristics and organisms
- Flagella
- Use an undulating membrane for movement
- Semi-functional mitochondria
Organism: Termite gut symbionts
Trichomonas vaginalis
Have bacteria endosy
