Lecture 5 Flashcards
Distinguishing features of a prokaryote
No nuclear membrane
No membrane-enclosed organelles
No separate cellular compartments for genetic material, proteins and metabolites
Age of prokaryotes
Appear ~3.6 Ga
Dimension of prokaryotes
< 10 um
Distinguishing features of a eukaryote
True nucleus with nuclear membrane
Membrane-enclosed organelles
Genetic material (chromosomes) enclosed in nucleus
Age of eukaryotes
Oldest fossils 1.6-2 Ga
Shared features of protists
Most species are single-celled; eukaryotic cell organization
Sexual or asexual reproduction
Many bear plastids and/or well-developed flagella
Generalities of protists
Small
Many secrete protective shell/test
Various types of nutrition
Highly sensitive to environmental stimuli
Large range of reproductive strategies
Single-celled but some form colonies
Pelagic
Live in the water column
Benthic
Live in or on the sediment floor
Plankton
Drifters: Organisms that move with the currents (as opposed to the free-swimming Nekton)
Give examples of the size range of protists
Variable size
Bacteria-giant jellyfish
Phytoplankton
Those that photosynthesize
Zooplankton
Those that eat other organisms
Name the 5 types of photosynthetic protists
Acritarchs
Coccolithopores
Diatoms
Dinoflagellates
Silicoflagellates
Morphology of acritarchs
Cyst or phycoma
With or without ornamentation (e.g., spines)
Acritarch composition
Composed of refractory original material
Ecology of acritarchs
Likely the remains of different kinds of organisms, marine or terrestrial aquatic environments
Likely algal affinities
Acritarch stratigraphy
Precambrian-present
Acritarch acme
Paleozoic
Acritarch importance in rock record
Useful biostratigraphic tracers
Coccolithophores protist morphology
Spherical coccolithophore
Cell protected by CaCO3 plates (coccoliths)
Coccolithophores fossil morphology
Coccoliths - small rounded plates
Coccolithophores ecology
Photoautotrophs
Planktic
Marine
Coccolithophore stratigraphy
Jurassic-present
Coccolithophore acme
Late Cretaceous
Possible roles of the coccoliths
Decrease predation
Decrease penetration by bacteria
Increase buoyancy
2 types of diatoms
Pennate
Centric
Diatom morphology
Cell protected by a transparent SiO2 frustule
Colony or solitary
Diatoms ecology
Planktonic, benthic (moist or submerged surfaces) and sympagic (sea-ice)
Photoautotrophs
All aquatic environments (lakes, rivers, oceans, etc.)
Complex life cycle, has sexual and asexual phases
Diatoms stratigraphy
Mesozoic-present
Diatoms acme
During Cenozoic
Frustule structure
Porous SiO2 matrix
Composed of 2 valves and multiple ring-shaped girdle bands
Centric diatoms
Radial symmetry
Solitary cells or colonies
Large diversity in size
Pennate diatoms
Bilateral symmetry
Solitary cells or colonies
Large diversity of size
What does dinoflagellate signify?
Whirling whip
Characteristic movement: 2 perpendicular flagella
Zooxanthellae example
Dinoflagellates are taken as residents in soft tissues of coral
Pro of zooxanthellae
Allows the organism to grow very quickly
Morphology of dinoflagellate protist
Theca composed of cellulosic plates
Dinoflagellate morphology of fossil
Cyst composed of refractory organic material, a few taxa are composed of CaCO3
Dinoflagellate ecology
Mostly epipelagic, a few are benthic
Phototrophs, mixotrophs or heterotrophs
Aquatic: lacustrine (some species) to oceanic (many species)
Dinoflagellate stratigraphy
Triassic-present
Dinoflagellate acme
During Cretaceous
Dinoflagellate cysts
Envelope that protects the cell
Is fossilizable
