Genetic diversity and natural selection

What is genetic diversity and what can it lead to?

The number of different alleles of a gene in a population. It can lead to natural selection

Define variation

Differences that exist between individuals in a population

What 2 factors can cause variation and give examples

Enviromental:

• climate change

• Availability of food/waterI

• Intensity of light

Genetic:

• Mutations

• Meiosis

• Fertilisation of gametes

Whath is mutation?

random changes in DNA or change in structure of DNA

How can mutaions cause variation?

Changes in DNA can result in new alleles of a gene

What two ways can meiosis cause variation?

• Independent segregation of homologous chromosomes creating variation in gametes

• Crossing over creates different alelle combinations

What is the correlation between genetic diversity and adaptation and why?

• The greater the genetic diversity the more likely the species will be able to adapt to the enviromental change

  • This is because there is a wider range of alleles therefore ider range of characteristics.

What does decreasing genetic diversity also decrease?

Decrease number of different alleles

Give 3 ways to reduce genetic diversity

• Bottleneck effect

• Founder effect

• Selective breeding

What is meant by bottleneck effect and how can it reduce genetic diversity?

• An event that causes a large reduction in a population

• This reduces the number of different alleles in the gene pool and so reduces genetic variation

What is meant by the founders effect and why may it occur?

• Small number of organisms moves leave main population, populate a new area, and found a new population and there are only a small number of different aleles in the inital gene pool

• This may occur due to migration

Describe how selective breeding works and how can it reduce genetic diversity

• Selecting individuals with desired characteristcis and alleles to breed them and stop those without desired charactertsics from breding

  • Over generations population will have desired characteristics only but will have lower genetic diversity

What is the defintion of evolution?

Change in allele frequence over many generations in a population

What is natural selection?

Increases number of advantageous alleles within a population

What is a benefit of natural selection?

Results in species becoming better adapted to their enviroments

Describe the process of natural selection?

• Random mutations can produce new alleles of a gene

• These new alleles can increase survival and reproductive chance

• This reproduction passes on the advantageous alleles to the next generations

• As a result over many generations new allele increases in frequency in population.

What is meant by slection pressures and give examples?

• organisms that are unable to survive or reproduce due to various reaspns

  • e.g. predators, disease, or competition for resources (food,water, and light)

What are the 2 different types o selection?

• Directional selection

• Stabilising selection

What is directional selection and when does it occur?

• Its natural selection that produces a gradual change in allele frequencies over several generations

• Occurs when there’s a change in enviroment/selection pressure

What is an example of directional selection?

• Antibiotic resistant bacteria stains are becoming more common due to overuse of antibiotis

• Antibiotic is a selection pressure, mutations occur.

What is stabilising selection?

Natural selection that keeps allele frequences relatively constant over generations.

What is an example of stabilising selection?

Human birth weights

• Baby’s birth weights vary, normal birth weights are beneficial

• Having too small or large birth weight can make it hard to survive.

• Natural selection keeps birth weights in the middle range.

What are adaptations?

Traits that have been selected for to increase chance of survival and reproduction.

What are the 3 types of adaptations?

• Anatomical

• Behavioural

• Physiological

Describe what is meant by anatomical adaptations

Physicals features that have evolved to increase chance of survival.

Give an example of an anotmical adaptation and how it can increase survival chances

• Giraffes evolved to have long necks to allow them to access food in top levels of trees

  • Increases survival bc no other species can reach food at this height so no competition

Describe what is meant by physiological adaptations

Processes within the body that have evolved to increase chance of survival

Give an example of a physiological adaptation and how it can increase chance of survival.

• Mammals have evolved to shiver in cold environments which helps generate body heat

  • Increases chance of survival bc maintains optimal body temp to survive

Describe what is meant by behavioural adaptations

Actions that are learnt or inherited which have evolved to increase chance of survival

Gve an example of a behavioural adaptation and how it can increase chance of survival

• Spiders have evolved to create complex webs which allows them to catch flies, insect for food

  • Increases survival bc they can catch their food easier.