B6: EVIDENCE FOR EVOLUTION (FOSSILS + ANTIBIOTIC-RESISTANT BACTERIA)

Question 1

What is some evidence for evolution?

Answer 1

-fossil record
-antibiotic-resistant bacteria
-inheritance

Question 2

What are fossils?

Answer 2

remains of organisms from millions of years ago

Question 3

How do fossils provide evidence for evolution?

Answer 3

comparing fossils with today’s species informs us of evolution over time

Question 4

What are the 3 ways in which fossils are formed?

Answer 4

-preservation due to lack of decay
-replacement by minerals
-preserved traces of organisms (eg: footprints, burrows, rootlet traces)

Question 5

Preservation due to lack of decay

Answer 5

-conditions (eg: cold temps of ice, no O2/moisure in tar pits) prevent decomposition

Question 6

Replacement by minerals

Answer 6

-parts of organism replaced by minerals
-soft tissues decayed whilst teeth, shells and bones take longer to decay

Question 7

Preserved traces of organisms (eg: footprints, burrows, rootlet traces)

Answer 7

-hardening of clay with impressions
-buried in clay which hardens, organism decays leaving behind the preserved cast of the organism

Question 8

Why don’t we have fossils for every organism that has ever existed?

Answer 8

-soft-bodied organisms decayed without forming fossils
-geological activity destroyed fossils/traces of early life

Question 9

How do antibiotics work?

Answer 9

antibiotics work by stopping cell wall synthesis/protein synthesis in order to kill bacteria

Question 10

What is the name of the bacteria resistant to penicillin?

Answer 10

MRSA

Question 11

MRSA

Answer 11

-resistant to most known antibiotics
-often affects patients in hospitals
-can be fatal if it enters bloodstream

Question 12

Describe how antibiotic resistant strains develop (6 marks)

Answer 12

-mutation – random changes to Bacterium DNA resulting in a new useful characteristic/ allele for antibiotic resistance
-variation – Variation in population of bacteria = strains that are antibiotic-resistant & strains that are not resistant
-best suited to environment – antibiotic-resistant bacteria are best suited to an environment with antibiotics, as antibiotics are unable to kill these bacteria. Non-resistant bacteria are killed by antibiotic ​
-survival & reproduction – Antibiotic- resistant bacteria survive and reproduce rapidly (binary fission)
-inheritance – useful characteristic/ allele (antibiotic resistance) passed on
-population of resistant strain increases

Question 13

Why do resistant strains of bacteria spread?

Answer 13

-lack of immunity
-lack of effective treatment
-less competition (non-resistant bacteria die so there is less competition for resources so resistant bacteria survive and thrive)

Question 14

Ways to reduce rate of development of antibiotic-resistant bacteria

Answer 14

-avoid prescribing antibiotics for non-serious bacterial infections/viral infections
-patients should complete their course of antibiotics
-agricultural use of antibiotics should be restricted