Unit 3.2.9 - Evidence Behind Classification

Question 1

Name two ways you can make genetic comparisons between species?

Answer 1

1. ) Comparing DNA base sequences

2. ) Looking at the protein encoded by the DNA

Question 2

Will distantly related organisms have similar DNA and proteins?

Answer 2

No

Question 3

Name two methods for looking at similarities in DNA

Answer 3

1. ) Comparing DNA sequences

2. ) By DNA hybridisation

Question 4

How can comparing DNA base sequences show how closely related sequences are?

Answer 4

You can look at the order of bases and more closely related species have a higher percentage of similarity in their DNA base sequence

Question 5

What classification system has changed because of comparing DNA base sequences

Answer 5

Flowering plants

Question 6

Give the 4 steps during DNA hybridisation to see how similar DNA is.

Answer 6

1. ) DNA is collected from two species and separated into single strands and mixed together
2. ) Where the DNA base sequence is the same of both strands hydrogen bonds will form between the specific base pairings
3. ) The DNA is then heated to separate the strands again
4. ) The more similar the DNA the more of the same base sequence the more hydrogen bonds will form as so a higher temperature will be required to break the two strands apart.

Question 7

What are the two ways proteins can be compared to show how similar organisms are.

Answer 7

Comparing amino acid sequences and by immunological comparisons

Question 8

How can comparing amino acid sequences show how similar organisms are?

Answer 8

Closely related organisms will have a similar DNA sequence and so it will code for similar amino acid sequence

Question 9

How can immunological comparisons be used to show similar organisms are?

Answer 9

Antibodies are used to determine how similar two proteins are, antibodies will only bind to a specific protein and so only similar proteins will bind with the same antibody

Question 10

When doing an immunological comparison what will you notice in the solution if antibodies bind to the proteins?

Answer 10

A precipitate will form

Question 11

Is it better to compare DNA base sequence or amino acid sequence and why?

Answer 11

DNA because DNA is degenerative and more than one triplet can code for the same amino acid

Question 12

What is courtship behaviour?

Answer 12

Behaviour used to attract a mate of the right species

Question 13

Give two advantages to a species that courtship behaviour is species specific

Answer 13

Prevents interbreeding and makes reproduction more successful (as mating with the wrong species won’t produce fertile offspring)

Question 14

How can courtship behaviour be used to classify organisms?

Answer 14

Courtship behaviour is species specific and so more closely related species will have similarities in their courtship behaviour