History of life on earth Flashcards
what are fossils?
preserved remains of past life on earth
who studies fossils?
Paleontologists
fossils can be dated using?
elemental isotopes in accompanying rocks
what is Half-life?
length of time required for a radioscope to decay to exactly one-half of its initial quantity
bias in the fossil record
anatomy, size, number, environment, time, geological processes and paleontology
four eons
Phanerozoic, Proterozoic, Archaean and Hadean
what are stromatolites?
Layered rock formed when organisms (cyanobacteria) bind particles of sediment together, forming thin sheets
what is symbiosis?
two species live in direct contact
what is Endosymbiosis?
one organism (an endosymbiont) lives inside another (the host)
evolution of multicellular eukaryotes?
probably evolved by differentiation of cells of same species that congregated into colonies
multicellular eukaryotes evolved in?
Proterozoic Eon
first animals were ___?___ and most animals exhibit ___?___ that facilitates locomotion
invertebrates, bilateral symmetry
Phanerozoic eon is subdivided into three eras, what are they?
Cenozoic era, Mesozoic era and Paleozoic era
the periods in Paleozoic era
- Permian period
- Carboniferous period
- Devonian period
- Silurian period
- Ordovician period
- Cambrian period
Cambrian “explosion”
abrupt increase in diversity of animal species
Burgess Shale
site where many fossils from the Cambrian period were found
periods of Mesozoic era (age of the dinosaurs)
Triassic, Jurassic and Cretaceous
what happened during cretaceous period?
- Another mass extinction at the end of the period
- Dinosaurs and many other species died out
- Large meteorite/asteroid or volcanic eruptions blamed
periods of Cenozoic era (the Age of Mammals)
Tertiary and Quaternary periods
Gram-positive bacterial cell walls consist of a single, relatively thick ___?___
peptidoglycan layer
Gram-negative bacterial cell walls consist of a relatively thin peptidoglycan sheath surrounded by an outer
lipopolysaccharide (LPS) membrane
gram-positive bacteria
single, relatively thick peptidoglycan layer
Gram-negative bacteria
Relatively thin peptidoglycan sheath surrounded by outer membrane
Gram stain technique
¡ Stain with crystal violet
¡ Rinse with ethanol
¡ Counterstain with safranin
significance of gram-negative vs. gram positive bacteria
Gram-positive bacteria (killed by penicillin)
- Appear purple because crystal violet retained
Gram-negative bacteria (outer membrane protects from penicillin)
- Appear pink because crystal violet lost
Flagella
rigid helical proteins that rotate like propellers
Pili
Rigid shafts of protein extending from cell walls, Help them adhere to other cells
what are antibiotics?
Natural or synthetic substance that kills or inhibits growth of bacteria and other
microorganisms
what is biofilm?
Complex aggregation of microorganisms attached to surface and surrounded by film of polymers. Harmful when attached to surgical equipment and supplies but beneficial when used in sewage treatment plants or in cleanup of toxic
organic molecules in groundwater
cyanobacteria
Photosynthetic bacteria abundant in fresh water,
oceans and wetlands and on surfaces of arid soils
¡ Named for blue-green or cyan colour
¡ The only prokaryotes that generate oxygen as a product of photosynthesis
proteobacteria subgroups
- α – proteobacteria
(Ancestors of mitochondria, Rhizobium, Agrobacterium) - β – proteobacteria (Nitrosomonas)
- γ – proteobacteria
(Neisseria, Vibrio, Salmonella, Escherichia coli) - ε – proteobacteria (Helicobacter)
Archaea are also known as?
Extremophiles
properties of extremophiles
¡ Can occupy habitats with extreme conditions
¡ High salt content – halophiles
¡ Acidity
¡ High methane levels
¡ High temperatures – hyperthermophiles
¡ Example: Methanopyrus
¡ Grows in deep-sea thermal vents at 98° Celsius
¡ Cannot grow at temps under 84° Celsius
properties of methanogens (a type of archaea)
¡ Methane generators
¡ Live in low-oxygen environments
¡ Obligate anaerobes
¡ Found in:
¡ Anoxic sediments of swamps, lakes, marshes, sewage works
¡ Rumen of cattle and sheep
¡ Large intestine of dogs and humans
¡ Hindguts of insects
