Genetic Diversity and Natural Selection

Question 1

What are alleles?

Answer 1

Different versions/forms of the single gene

Question 2

What is genetic diversity?

Answer 2

Number of different alleles of genes in a species or population

Question 3

What factors increase genetic diversity within a population?

Answer 3

• Mutations in the DNA- forming new alleles
• Different alleles being introduced into the population when individuals from another population migrate into them and reproduce - gene flow

Question 4

What is gene flow?

Answer 4

Different alleles being introduced into the population when individuals from another population migrate into them and reproduce

Question 5

What is a population?

Answer 5

A group of organisms of one species living in a particular habitat

Question 6

What is a gene bottle neck?

Answer 6

An event that causes a big reduction in a population e,g when large number of organisms within a population die before reproducing

Question 7

What is the effect of genetic bottleneck?

Answer 7

• Reduces the number of different alleles in the gene pool - reduces genetic diversity

Question 8

How is a larger population produced from genetic bottle neck?

Answer 8

Survivors reproduce to create a larger population is created from few invidiuals

Question 9

What is an example of a genetic bottleneck event?

Answer 9

Northern Elephant Seals

• These seals were hunted by humans in the late 1800s
• Their original population reduced to 50 seals since the produced population of 170 000
• Population has little genetic diversity compared to southern elephant seals who never suffered a reduction in their numbers

Question 10

What does the founder affect describe?

Answer 10

What happens when a few organisms from population start a new colony and there is a small number of different alleles in the inital gene pool

Question 11

What happens to the frequency in the founder effect?

Answer 11

• Frequency of each allele in new colony different to frequency in original population e.g allele rare in original population is more common in new colony - higher incidence of genetic disease

Question 12

What else can the founder effect explain?

Answer 12

• Occur as a result of migration leading to geographical separation
• or
• new colony is separated from original population for another reason , such as religion

Question 13

An example of the founder effect

Answer 13

Amish People

• Amish population of North America were descended from a small number of Swiss who migrated there
• Showed little genetic diversity
• Remained isolated from the surrounding population due to religious beliefs
• New alleles introduced - high incidence of genetic disorders

Question 14

What do randomly-occurring mutations sometimes result in?

Answer 14

New allele being formed

Question 15

Why new allele being formed is harmful?

Answer 15

Mutated allele quickly dies out

Question 16

How are mutations useful? -NATURAL SELECTION

Answer 16

Can produce allele that is beneficial to the organism (an e.g protein produced works better than original) helping the organisms to survive in certain environments

When allele codes for characteristics, increase the chance of organisms surviving its frequency within the population increase

Question 17

Process of natural selection:

Answer 17

• Indiviviudals have an allele that increase their chance of survival and reproduce to pass on their genes (including the beneficial allele) than invidiual with different alleles
• A greater proportion of the next generation to inherit this beneficial allele
• More likely to survive, reproduce and pass on genes
• Frequency of beneficial allele increases from generation to generation
• Over generations, this lead to evolution as the advantageous allele becomes more common in the population

Question 18

Whats differential reproductive success?

Answer 18

Not all individuals are more likely to reproduce

Individuals that have an allele that increase their chances of survival and more likely to survive to reproduce and pass on their genes (including beneficial allele) than individual with different alleles

Question 19

What are the both two key factors in evolution?

Answer 19

• Adaptation
• Selection
• (a gradual chance in species over time) (evolution led to huge diversity of living organisms in Earth)

Question 20

Why are adaptations useful?

Answer 20

Help the organisms to survive in their environment

Question 21

What are the different types of adaptations?

Answer 21

1. Behavioural adaptation
2. Physical adaptations
3. Anatomical adaptations

Question 22

What is a behavioural adaptation ?

Answer 22

Ways an organism acts increase its chance of survival and reproduction

e.g possums sometimes ‘play dead’ if they are being threatened by a predator to escape an attack

Question 23

What is physiological adapatation?

Answer 23

Processes inside an organism’s body that increase its chance of survival

For example brown bears hibernate over winter. They lower teir rate of metabolism (all chemical reaction take place in body)

This helps to conserve energy so they don’t need to look for food in months when its scarce.

Question 24

What are anatomical adaptations?

Answer 24

• Structural features of an organism’s body that increase its chance of survival
  e. g whales have a thick layer of blubber (fat) which helps them to keep warm in the cold sea

Question 25

Tawny owls show variation in colour. They are light grey owls and darker brown owls. Before the 1970s there are more grey owls than brown owls in Finland. Since then, climate change has been causing a decrease in the amount of snowfall in Finland. During this period, the darker brown owls have become more common

a) Suggest why the brown owls are better adapted to living in an area with less snowfall than grey owls

Answer 25

e.g brown owls might be camouflaged better/blend in with landscape than grey pw;s

as there is no snow cover

this makes them less likely to be eaten by predator

Question 26

Tawny owls show variation in colour. They are light grey owls and darker brown owls. Before the 1970s there are more grey owls than brown owls in Finland. Since then, climate change has been causing a decrease in the amount of snowfall in Finland. During this period, the darker brown owls have become more common

b) Explain how brown owls have become more common

Answer 26

Brown owls are more likely to survive and reproduce when these is less snow cover

pass on their allele for darker/brown colouring to their offspring

Over time, the allele for brown colouring will become more common in the population

Question 27

There are many different species of rat snake, all found in different habitats and with slightly different colorings. The black rat snake lives in wooded habitats and has a dark, brown-black coloring

Describe how natural selection could explain the evolution of a rat snake with black-coloring in a wooded habitat

Answer 27

As a result of a mutation, some individuals in the population have a darker coloring that helps to blend into the environment

This is beneficial as it helps to avoid predators and sneak up on prey-

More likely to survive and reproduce to pass on allele for darker coloring

Frequency of allele for darker coloring will increase

many more generations, most of the organisms in population will carry the allele for darker coloring

Question 28

DDT is a chemical insecticide that was first used to kill malaria-carrying mosquitos around the time of WWII

In 1950s, DDT-resistance mosquitos began to appear in areas of widespread DDT use

Describe how DDT-resistance became widespread in some mosquito population

Answer 28

Some individuals in the population have a mutated allele that gives resistance to DDT

The population is exposed to DDT, killing the mosquitoes without the resistance allele

Individuals with resistance allele survive, reproduce and pass allele

Frequency of the resistance allele increase in population

many generations, most organisms in the population carry DDT-resistance allele

Question 29

What is a gene pool?

Answer 29

Containing a wide variety of alleles

Question 30

Explain how a difference in its DNA might lead to an organism having different appearances and hence the species showing greater genetic diversity

Answer 30

Different DNA

Different codes for amino acids - different protein shape - different protein function (e.g non-functional enzyme)

chance in feature determined by protein - altered appearence

greater genetic diversity

Question 31

What is the difference between genetic diversity within a species and genetic diversity between species?

Answer 31

Within a species – there is diversity between the alleles

Between species – there is diversity between genes

Question 32

Explain genetic diversity in the context of blood type in humans.

Answer 32

– all humans have the gene for blood type

-Different alleles determine the blood type

Question 33

Identify two mechanisms that increase genetic diversity

Answer 33

– mutations

• alleles introduced by new individuals to the population (immigration)

Question 34

Explain how a mutation can be positive?

Answer 34

– change in the base sequence

• codes for a different order of amino acids.
• this new protein has advantageous properties in survival and/or reproduction

Question 35

Give one example of a natural event that reduces genetic diversity and one event linked to human interaction.

Answer 35

Natural: volcano, earthquake, flood, fire, meteorite, extreme weather etc.

Human interaction: deforestation, construction, global warming etc.

Question 36

How do genetic bottlenecks occur and reduce genetic diversity?

Answer 36

– an event causes of large reduction in the size of a population

-there are fewer alleles so less diversity -the new population is created from fewer alleles

Question 37

How does the founder effect differ from a simple genetic bottleneck?

Answer 37

– a few organisms from a population leave and form a new population

Question 38

Why is a reduction in population size genetically disadvantageous?

Answer 38

– fewer alleles in the population

• more chance of inbreeding/one disease could destroy the whole population

Question 39

What is meant by the term ‘survival of the fittest’?

Answer 39

Organisms that are better adapted have a higher chance of survival Therefore have more chance of reproducing and passing on their genes

Question 40

What is the definition of a behavioural adaptation?

Answer 40

– the way in which an organism acts in order to increase its chances of finding food to survive and ultimately reproduce.

Question 41

) What is the difference between anatomical and physiological adaptations?

Answer 41

• Anatomical is adaptations in the structure of the body
• Physiological are adapted processes within the body

Question 42

What is evolution?

Answer 42

Change in allele frequency over time