protists Flashcards
Eukaryotic organims
Euukaryotic cells differ from prokaryotes
- presence of a cytoskeleton
- compartmentalization. (nucleus and organelles)
Apearance of eukaryotes in microfossils ocurred about 1.5 BYA
figure 29.2
- The nucleus and endoplasmic reticulum arose from infolding of prokaryotic cell membrane
Endosymbiosis
Many organelles evolved via endosymbiosis between ancestral eurkayote and a bacterial cell
Endosymbiosis
Mitochondria
Aerobic bacteria enngulfed by larger bacteria
Endosymbiosis
Chloroplasts
- Larger bacteria smaller photosynthetic bacteria
- chloroplast come from single line of cyanobacteria
- hosts are not monophyletic
Endosymbiosis
Brown alagae engulfed red algae that already had chloroplasts
- Secondary endosymbiosis
Evidence fro endosymbiosis
Endosymbiosis supported by
- DNA inside mitochondria and chloroplasts
- DNA similar to bacteria DNA in size and character
- Ribosomes inside mitochondria similar to bacterial ribosome
- Chloroplast and mitochondria replicated by binary fission-not mitosis
- mitosis envolved in Eukaryotes
Mitosis evolved in Eukaryotes
- Prokaryotes carry genes on single DNA molecule
- Eukaryotes have multiple chromosomes
- Mitosis and cytokinesus developed to separates chromosomes and other cell contents during cell divison
Overview of protist
- Most diverse of the four eukaryotic kingdoms
- United on the basis that they are not fungi, plants, or animals
- Vary considerably in very other aspect
unicellular, colonial, and multicellular groups
Most are microscopics buy some are huge
all symmetries
all types of nutritions
Protists are present in all eukaryotic supergroups
- Protist are not monophyletic
- paraphyletic
- Protists are present in all six eukaryotic supergroups
- Excavata
- chromalveolata
- Archaeplastida
- Amoeboza
- Ophisthokonta
Cell surface in protists
- Protists have varied array of cell surfaces
- Plasma membrane
- Extracelllar matrix (ECM) in some
- Diatoms- silica shells
- Cysts
- Dormant cell with resistant outer covering
- used for disease transmission
Locomotion in Protists
Flagella
- One or more
Locomotion in Protists
Cilia
- Shorter and more numerous than flagella
Locomotion in Protists
Pseudopodia (“fakse feet”)
- Chief means of locmotion for amoebas
- Used by other protists as well
Nutrition in protists
Autothrophs
- Some photosynthetic
- some chempautotrophic
Nutrition in protists
Heterotrophs
- Phagotrophs- ingest particulate food matter
- Mixothrophs are both phototrophic and heterotrophic
Reproduction in protists
Asexual reproduction
- Typically mode of reproduction
- Some species have unusual mitosis
- mitosis- equal size daugther cells
- Budding- one daughter cell smaller
- Schizogony- cell division preceded by several nuclear divisions; produces several individuals
Reproduction in protists
Sexual reproduction
- Some regularly reproduce sexually, some under stress
- Meiosis is a major eukaryote innovation
- Union pf haploid gametes which are reproduced by meiosis
- Advantage in allowing frequent genetic recombination
Protist are bridge to multicellular
- From single cells to colonies to true multicellularity
- Arisen multiple times
- Fosters specialization
- Few innovation have had as great an influence on the history of life
Excavata
- This group consists of diplomonads, parabasalids, and euglenozoans
- They share similarities in cytoskeletal features and DNA sequences
Diplomonads
- Unicellular
- Move with multiple flagella
- 2 nuclei
- Giardia- parasite
- Lack functional mitochondria
Parabasalids
- Some live in termites guts
- Have symbiotic relationship with cellulose-degrading bacteria
- Trichomonas vaginalis-STD
- Undulating membarne for locomotion
- Use flagella
- Have semifunctional mitochondria
Euglenozoa
- Bodies change shape when swimming-alternate between being stretched out and rounded up
- Can change shape becuase they lack cell walls
- Amongs the earliest eukaryotes to poseses mitochondria
- Include free-living euglenids and parasitic kinetoplastids
Euglenids
- 1/3 of euglenids have chloroplast and are heterotrophic
- Reproduction is asexual; occurs viaa mitosis
- Euglena have 2 anterior (and unequal) flagella
- Attatched at reservoir
- Contractile vacuoles- collect excess water
- Stigma- movement towards light
- Numerous small chloroplasts
- Likely evolved from symbiotic relationship thrpugh ingestion of green algae
Parasitic Kinetoplastids #1
- 2nd major group in Euglenozoa
- Unique, single mitochondrion
- DNA maxicircles and minicircles- responsible for rapid glycolysis and unusual RNA editing
- Trypanosome cause Human diseases
- Africxan sleeping sickness- tsetse fly
- Leishmaniasis-sand fly
- Chagas disease- skin contact with urine or blood of infected wild animal
Parasitic Kinetoplastids #2
- Difficult to control because organism repeatedly change their proective coat
- Elaborate genetic mechanism for changing antigen on coat
- Difficult to make a vaccine; other methods used to control flies
- Sequencing of genomes revealed core of cmmon genes in all 3
- ## hope for single drug target
Chromalveolates
- Supergroup consisting of 2 branches: the stramenopiles
- They may have arisen by one or more secondary
