Evolution

Question 1

Define gene mutation

Answer 1

1. Random change in the base sequence of DNA.
2. Results in the formation of a new allele.

Question 2

TRUE or FALSE:

Mutations arise spontaneously during DNA replication

Answer 2

TRUE

Question 3

Types of mutation

Answer 3

Substitution
Addition
Deletion
Inversion
Duplication
Translocation
Non-disjunction

Question 4

Primary souce of genetic variation

Answer 4

random mutations

Question 5

TRUE or FALSE:

Creating new combinations of alleles does not contribute to genetic variation

Answer 5

FALSE

Question 6

Processes that create new combinations of alleles (and therefore genetic variation)

Answer 6

1. Independent segregation of homologous
   chromosomes/pairs;
2. Crossing over between homologous
   chromosomes/pairs (non-sister chromatids);
3. Random fertilisation of gametes;
4. (Produces) new combinations of alleles;

Question 7

Sources of phenotypic diversity

Answer 7

Mutations that create new alleles

Crossing over

Independent segregation

Random fusion of gametes

Epigenetics

Question 8

Biotic factors that act as
selective pressures

Answer 8

Predation

Disease

Interspecific competition

Question 9

Abiotic factors that act as selection pressures

Answer 9

Temperature

Light intensity

Carbon dioxide concentration

Soil pH

Salinity

Humidity

Windspeed

Question 10

TRUE or FALSE:

Organisms develop advantageous phenotypes because of a change in the environment.

Answer 10

FALSE

Random mutations produce phenotypic variation, then SELECTED FOR/AGAINST

Question 11

Bullet point the key mark points for natural selection (5 marks).

Answer 11

• Random mutations produce phenotypic variation (within a population)
• (Named) selection pressure in the environment (biotic or abiotic)
• Organisms with (named) advantegous phenotypes are more likely to survive AND reproduce
• Pass on advantageous alleles to the next generation
• Frequency of advantageous allele increases over many generations in the gene pool

Question 12

Selection that favours one
extreme phenotype

Answer 12

Directional

Question 13

Directional selection examples

Answer 13

Antibiotic resistance

Giraffe neck length

Peppered moth

Question 14

Type of selection that favours the mean / most common phenotype

a

Answer 14

Stabilising

Question 15

Stabilising selection examples

Answer 15

Newborn / baby birthweight

Number of eggs in a birds nest

Question 16

Type of selection that favours both extreme phenotypes

Answer 16

Disruptive

Question 17

Type of selection that reduces variation and therefore the opportunity for evolutionary change

Answer 17

Stabilising

Question 18

Types of selection that brings about evolutionary change

Answer 18

Directional

Disruptive

Question 19

Clostridium difficile is a bacterial species that causes disease in humans.

Antibiotic-resistant strains of C. difficile have become a common cause of infection acquired when in hospital.

Explain how the use of antibiotics has led to antibiotic-resistant strains of bacteria becoming a common cause of infection acquired when in hospital (3 marks).

Answer 19

1. (Some bacteria have) random mutations produce alleles for resistance;
2. More antibiotics used in hospital (compared with elsewhere) and exposure to antibiotics is the selection pressure
3. Resistant bacteria survive & reproduce;
4. Pass on resistance allele to next generation
5. high frequency of resistance allele over many generations (in bacterial population);

Question 20

Lactose is the main sugar in milk and is hydrolysed by the enzyme lactase. Lactase is essential to newborn mammals as milk is their only source of food. Most mammals stop producing lactase when they start feeding on other food sources. Humans are an exception to this because some continue to produce lactase as adults. The ability to continue producing lactase is known as lactase persistence (LP) and is controlled by a dominant allele.

One hypothesis for LP in humans suggests that the selective pressure was related to some human populations farming cattle as a source of milk.

Describe how farming cattle as a source of milk could have led to an increase in LP (4 marks).

Answer 20

1. LP allele due to random mutation;
2. Milk provides named nutrient /
   e.g. glucose, galactose, protein and its presence act as selection pressure
3. Individuals with LP more likely to survive and reproduce
4. Pass on LP allele to next generation
5. Frequency of LP allele increases
   (in the offspring/next generation);
6. This is an example of directional selection;

Question 21

Type of selection that can lead to speciation

Answer 21

Disruptive

Question 22

All new species evolve from existing species via a process known as ____________.

Answer 22

speciation

Question 23

Species key features

Answer 23

1. Capable of interbreeding to produce fertile offspring.
2. Same genes but different alleles.
3. (May show a) wide range of variation in phenotype.

Question 24

Types of speciation

Answer 24

Allopatric

Sympatric

Question 25

Reproductive ____________ is required for speciation.

Answer 25

isolation

Question 26

In allopatric speciation, what causes reproductive isolation?

Answer 26

A geographical barrier
(e.g. river, mountain, road)

Question 27

Describe and explain how a river separating two populations of lemurs can result in new specieis (5 marks).

Answer 27

1. Allopatric speciation;
2. River leads to reproductive isolation
   OR No gene flow
   OR Gene pools separate;
3. Variation due to random mutations (in different populations);
4. Different selection pressures (either side of the river);
   OR Different environmental/abiotic conditions/factors;
5. (Different/advantageous) allele/s passed on/selected OR change in frequency of alleles;
6. (Eventually different species either side of river) cannot interbreed to produce fertile offspring;

Question 28

n sympatric speciation, what causes reproductive isolation?

Answer 28

Random mutations may cause change in behaviour e.g. feeding or mate preferences / timings

Question 29

TRUE or FALSE:

In sympatric speciation, reproductive isolation still occurs despite the species occupying the same habitat / area.

Answer 29

TRUE

Question 30

Lord Howe Island in the Tasman Sea possesses two species of palm tree which have arisen via sympatric speciation. The two species diverged from each other after the island was formed 6.5 million years ago. The flowering times of the two species are different.

Using this information, suggest how these two species of palm tree arose by sympatric speciation (5 marks).

Answer 30

1. Occurs in the same habitat / environment / population / place;
2. Random mutation/s cause different flowering times;
3. Reproductive isolation
   OR No gene flow
   OR Gene pools remain separate;
4. Different allele/s passed on / selected
   OR Change in frequency of allele/s
5. Eventually different species cannot interbreed to produce fertile offspring;
6. Example of disruptive selection;

Question 31

Genetic drift

Answer 31

Random increase OR decrease in allele frequency due to chance events

Question 32

Explain why small populations are vulnerable to genetic drift.

Answer 32

Random loss of individuals with certain alleles;

Individuals that survive will then reproduce;

Pass on alleles to next generation;

Results in a large change in the frequency of alleles (in a shorter period of time);

Question 33

Contrast genetic drift vs.
natural selection

Answer 33

atural selection involves differential survival and reproduction of organisms in response to selection pressures whereas genetic drift is not influenced by environmental pressures or the relative advantage of alleles.

Genetic drift is a random change in allele frequency whereas natural selection isn’t