History of life on earth

Question 1

what are fossils?

Answer 1

preserved remains of past life on earth

Question 2

who studies fossils?

Answer 2

Paleontologists

Question 3

fossils can be dated using?

Answer 3

elemental isotopes in accompanying rocks

Question 4

what is Half-life?

Answer 4

length of time required for a radioscope to decay to exactly one-half of its initial quantity

Question 5

bias in the fossil record

Answer 5

anatomy, size, number, environment, time, geological processes and paleontology

Question 6

four eons

Answer 6

Phanerozoic, Proterozoic, Archaean and Hadean

Question 7

what are stromatolites?

Answer 7

Layered rock formed when organisms (cyanobacteria) bind particles of sediment together, forming thin sheets

Question 8

what is symbiosis?

Answer 8

two species live in direct contact

Question 9

what is Endosymbiosis?

Answer 9

one organism (an endosymbiont) lives inside another (the host)

Question 10

evolution of multicellular eukaryotes?

Answer 10

probably evolved by differentiation of cells of same species that congregated into colonies

Question 11

multicellular eukaryotes evolved in?

Answer 11

Proterozoic Eon

Question 12

first animals were ___?___ and most animals exhibit ___?___ that facilitates locomotion

Answer 12

invertebrates, bilateral symmetry

Question 13

Phanerozoic eon is subdivided into three eras, what are they?

Answer 13

Cenozoic era, Mesozoic era and Paleozoic era

Question 14

the periods in Paleozoic era

Answer 14

• Permian period
• Carboniferous period
• Devonian period
• Silurian period
• Ordovician period
• Cambrian period

Question 15

Cambrian “explosion”

Answer 15

abrupt increase in diversity of animal species

Question 16

Burgess Shale

Answer 16

site where many fossils from the Cambrian period were found

Question 17

periods of Mesozoic era (age of the dinosaurs)

Answer 17

Triassic, Jurassic and Cretaceous

Question 18

what happened during cretaceous period?

Answer 18

• Another mass extinction at the end of the period
• Dinosaurs and many other species died out
• Large meteorite/asteroid or volcanic eruptions blamed

Question 19

periods of Cenozoic era (the Age of Mammals)

Answer 19

Tertiary and Quaternary periods

Question 20

Gram-positive bacterial cell walls consist of a single, relatively thick ___?___

Answer 20

peptidoglycan layer

Question 21

Gram-negative bacterial cell walls consist of a relatively thin peptidoglycan sheath surrounded by an outer

Answer 21

lipopolysaccharide (LPS) membrane

Question 22

gram-positive bacteria

Answer 22

single, relatively thick peptidoglycan layer

Question 23

Gram-negative bacteria

Answer 23

Relatively thin peptidoglycan sheath surrounded by outer membrane

Question 24

Gram stain technique

Answer 24

¡ Stain with crystal violet
¡ Rinse with ethanol
¡ Counterstain with safranin

Question 25

significance of gram-negative vs. gram positive bacteria

Answer 25

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

Question 26

Flagella

Answer 26

rigid helical proteins that rotate like propellers

Question 27

Pili

Answer 27

Rigid shafts of protein extending from cell walls, Help them adhere to other cells

Question 28

what are antibiotics?

Answer 28

Natural or synthetic substance that kills or inhibits growth of bacteria and other
microorganisms

Question 29

what is biofilm?

Answer 29

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

Question 30

cyanobacteria

Answer 30

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

Question 31

proteobacteria subgroups

Answer 31

• α – proteobacteria
  (Ancestors of mitochondria, Rhizobium, Agrobacterium)
• β – proteobacteria (Nitrosomonas)
• γ – proteobacteria
  (Neisseria, Vibrio, Salmonella, Escherichia coli)
• ε – proteobacteria (Helicobacter)

Question 32

Archaea are also known as?

Answer 32

Extremophiles

Question 33

properties of extremophiles

Answer 33

¡ 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

Question 34

properties of methanogens (a type of archaea)

Answer 34

¡ 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