6 3 the development of understanding of genetics and evolution

Darwin developed his theory by:

False. Natural selection can only occur when variation is present. This is why populations with no, or limited, genetic variation are unable to adapt to changes in their environment.

Darwin's theory of natural selection states that:

Darwin's theories were accepted gradually during his lifetime due to:

Lamarck's theory of evolution is incorrect because it suggests that characteristics gained during an organism's lifetime can be passed on to offspring; we now know that such acquired characteristics cannot be inherited in this way.

False. Alfred Russel Wallace proposed his theory of natural selection independently of Darwin.

Wallace is best known for his work on:

Speciation is the process by which new species arise from existing species.

The events of speciation shown in the diagram include:

The units referred to by Mendel are alleles which are passed from parents to offspring.

False. Mendel worked during the mid 19th century and the behaviour of chromosomes during cell division was not observed until the late 19th century.

Scientists concluded that genes are located on chromosomes due to the observation that chromosomes behaved in a similar way to the 'units' described by Mendel.

Gene theory covers the concept that traits are passed from parents to offspring through gene transmission

Evidence that has aided the acceptance of Darwin's theory of evolution by natural selection include:

Fossils are the remains of organisms from millions of years ago found in rocks.

False. Trace fossils are not preserved parts of organisms, but are indications of their presence, e.g. burrows or footprints.

Fossils can form when:

False. Early life forms had soft bodies which did not fossilise, meaning that the fossil record does not show how life began.

The fossil record shows how species have changed over time.

The evolutionary tree shows that:

Extinction has occurred when there are no living members of a species remaining.

Factors that contribute to extinction include:

Antibiotic resistance is the ability of bacteria to withstand the effects of an antibiotic; bacteria with resistance to a particular antibiotic are more likely to survive when they are exposed to the drug.

Antibiotic resistance can evolve quickly because of the rapid reproduction rate of bacteria.

True. Random mutations in bacterial DNA can lead to antibiotic resistance, enabling some bacteria to survive antibiotic treatment.

Antibiotic resistant strains of bacteria can arise by the following process:

Antibiotic use can increase the probability that a resistant population of bacteria will arise because the antibiotics kill any non-resistant individuals, meaning that any randomly occurring alleles for resistance become highly advantageous. The resistance alleles are therefore more likely to be passed on.

Infections caused by antibiotic resistant strains of bacteria can be hard to control because:

True. MRSA stands for methicillin resistant Staphylococcus aureus.

The development of antibiotic resistance can be reduced by measures such as: