Unit 3- Natural Selection and speciation

Question 1

What are the 3 types of evidence supporting Darwin’s theory of evolution?

Answer 1

1- the DNA molecule is the same in all organisms, inherited from a common ancestor
2- DNA and proteins contain a record of genetic changes that have occurred over time, we can find how closely 2 species are related by comparing DNA or amino acids
3- by assessing the speed of mutations in DNA we can gather species have evolved over a vast time frame

Question 2

Summaries natural selection:

Answer 2

1- there is genetic variation in characteristics within a population
2- individuals with characteristics that make them less well adapted to their environment will die young from predation, disease or competition, not passing on their alleles
3- individuals with characteristics that make them well adapted to their environment will live longer and reproduce, passing on their alleles to their offspring
4- the allele frequency will change in each generation

Question 3

What is adaption?

Answer 3

When organisms undergo changes that make them suit a new environment

Question 4

What does niche mean?

Answer 4

The role of the organism in a particular community

Question 5

Explain the term niche using the sea anemone as an example

Answer 5

• a niche is the role the sea anemone plays in the community
• it occupies 2 trophies levels, as a predator by controlling population of prey and as prey by providing food for predators

Question 6

Adaption takes place to whole populations of organisms over a long time period, what types of adaption are there?

Answer 6

• anatomical
• physiological
• behavioural

Question 7

Give an example of each type of adaption

Answer 7

Anatomical- spines on a cactus
Physiological- a change in internal functioning, eg Sherpas have more haemoglobin thin their blood
Behavioural- mating in birds which includes dancing and singing to find a partner

Question 8

What is a good example of natural selection due to mutation?

Answer 8

Antibiotic resistant bacteria, who’s DNA has mutated to produce an enzyme that can break down penicillin

Question 9

Describe how humans have adapted through natural selection to have lactose tolerance

Answer 9

• around 10000 years ago there was genetic variation in the human population
• as farming became more popular humans who through a chance mutation could drink milk without feeling ill were healthier and more likely to live longer to reproduce
• humans without the lactose tolerance allele would fall ill and were less likely to live as long
• the allele for lactose tolerance was passed on to offspring at a higher frequency

Question 10

What is molecular phylogeny?

Answer 10

The analysis of genetic material of organisms o establish their evolutionary relationship

Question 11

What technique is used in molecular phylogeny to detect how closely related 2 species are?

Answer 11

• DNA and RNA sequencing using gel electrophoresis

Question 12

What is DNA and RNA sequencing?

Answer 12

DNA is cut into fragments by restriction endonucleases in a test tube
The DNA fragments are loaded into wells in agarose gel
A buffer solution is added of the gel
2 electrodes are put at either side of the gel plate, so negatively charged DNA moves to positive electrode, and the fragments separate out