Evidence used in classification 4.3.3

Question 1

What is traditional classification based on?

Answer 1

Observed characteristics (say what you see!)
- Organisms adapt to their environment so often look similar if they live in a similar habitat

Question 2

What is convergent evolution?

Answer 2

When two unrelated species could adapt in similar ways and therefore look similar

Question 3

How can biological molecules be used in classification?

Answer 3

• Certain biological molecules are found in all living organisms, although they may not be identical in all species.
• The differences between these molecules in different species reflect the evolutionary relationships

Question 4

How can DNA sequences reflect classification?

Answer 4

• Changes in DNA are caused by mutations
• The more differences there are the less closely related two species are, as they will have evolved separately for a longer period of time.

Question 5

How will the DNA sequence of closely related organisms be reflected in classification?

Answer 5

Closely related = similar DNA sequences

Question 6

Describe the steps involved in DNA hybridisation

Answer 6

• DNA from 2 species is extracted, purified & cut into small pieces
• DNA is heated to about 90°C to break the H bonds
• On cooling, a strand from species A and a strand from B will combine. The more similar the species, the more H bonds will form

Question 7

How does hybridisation work?

Answer 7

• To separate the strands again they are heated
• The higher the temperature needed to break the strands apart = more H bonds
• Therefore the more closely related the species are.

Question 8

What can hybridisation be used for?

Answer 8

• Used recently to aid the classification of flowering plants

Question 9

What did Carla Woese do?

Answer 9

He introduced domain as a new taxonomic rank
And molecular biology is now given a greater weight than other features

Question 10

What are the 3 domains of life?

Answer 10

• Bacteria
• Archaea
• Eukarya

Question 11

What do the organisms in each group contain?

Answer 11

RNA sequences that are unique to their domain

Question 12

Name 5 features of the domain Bacteria

Answer 12

• Prokaryotic
• DNA is circular
• No membrane bound organelles
• Has no cytoskeleton
• Has a cell wall made of peptidoglycan

Question 13

Name 5 features of the domain Archaea

Answer 13

• Prokaryotic
• Circular DNA
• No membrane bound organelles
• Some introns
• No cytoskeleton

Question 14

Name 5 features of the domain Eukarya

Answer 14

• Eukaryotic
• Linear DNA
• Has introns
• Has membrane bound organelles
• Does have a cytoskeleton