Lesson 80-81 - Evolutionary relationships and investigating populations

Question 1

Define ‘non-coding base sequences’ and describe where the non-coding multiple repeats are positioned in the genome.

Answer 1

1. DNA that does not code for protein/polypeptides/sequences of amino acids/tRNA/rRNA
2. Positioned between genes

Question 2

Why do characteristics vary continuously and hard to distinguish and categorise?

Answer 2

Many observable characteristics are controlled by several genes (polygenic).
Phenotypes are often affected by the environment.

Question 3

How can technology determine the sequence of bases in the nucleotides of samples from the DNA of an organism?

Answer 3

• Each base is tagged with a fluorescent dye and can be analysed by a computer.
• The number of differences in the base sequence of different organisms within/between species can be compared (bioinformatics) to show genetic diversity and evolutionary relationships.

Question 4

Other than comparing differences in the base sequence of DNA/mRNA, give 2 other ways in which genetic diversity between species is measured.

Answer 4

1. Comparing observable features/characteristics
2. Comparing amino acid sequences/primary structures (of a/named/the same protein)
3. Comparing amount of antibody bound to antigen/protein (in different species)

Question 5

Explain how differences in the primary structure of haemoglobin molecules can provide evidence of phylogenetic (evolutionary) relationships between species.

Answer 5

1. Mutations change base/nucleotide sequence
2. Causing change in amino acid sequence
3. Mutations build up over time
4. More mutations/difference in amino acid sequence in closely related species
5. Distantly related species have earlier common ancestor

Question 6

What are quadrats?

Answer 6

Square frames of a known size (eg. 1m²) that are divided into smaller segments that can be used to investigate populations of non-motile species.

Question 7

What are 3 factors to consider when using quadrats?

Answer 7

• The size of quadrat to use
• The number of quadrat samples to record
• The position of each quadrat within the study area

Question 8

What are 2 different sampling techniques?

Answer 8

• Random sampling
• Systematic sampling along a belt transect

Question 9

Why is random sampling used?

Answer 9

To prevent sampling bias by eliminating human involvement in choosing the samples

Question 10

Describe 1 method of random sampling

Answer 10

1. Divide the study area into a grid eg. by stretching two tape measures out at right angles to each other
2. Use randomly generated numbers (eg. using a dice or computer) to obtain a series of coordinates
3. Take samples at each set of coordinates

Question 11

What do you do after you have sampled a number of coordinates, when investigating populations.

Answer 11

1. Place a quadrat at this coordinate
2. Count the number of organisms in this quadrat
3. Calculate the mean number of organisms per m2, of all of the quadrats in the generated coordinates.

Question 12

Give 2 methods for measuring abundance of a specific organism in an area

Answer 12

1. Counting the number of a particular organism in the quadrat.
2. Estimating the percentage of the quadrat that is covered by the organism. Count the number of squares that are more than half covered with the organism and divide that by the total number of squares in the quadrat, then times your answer by 100.

Question 13

What are belt transects used for?

Answer 13

To study the effect of a factor on the distribution of an species across an area, in a straight line.

Question 14

Describe the method used for systematic sampling along a belt transect

Answer 14

1. A tape measure is laid out across the area that is being studied.
2. Quadrats are laid out at regular intervals along the tape measure (e.g. every 2 metres) and the abundance of organisms is counted/calculated at each point.

Question 15

When investigating diversity in biology, how can you avoid bias?

Answer 15

Collect data from random samples

Question 16

When investigating diversity in biology, how can you ensure data is representative?

Answer 16

Use a large sample size

Question 17

When investigating diversity in biology, what 2 things must you calculate?

Answer 17

The mean value of the collected data and the standard deviation of that mean

Question 18

What is standard deviation and how is it represented?

Answer 18

• Standard deviation measures the spread of the data around the mean.
• It can be plotted in graphs as standard deviation bars.
• If these bars overlap, there is no significant difference between the means.
• If these bars don’t overlap there is significant difference between the means.

Question 19

A scientist received a large number of seeds from trees in the city centre and a large number from the country side. Describe how he should collect/process data from these seeds to investigate whether there’s a difference in seed size between these 2 populations of trees.

Answer 19

1. Use a random sample of seeds from each population.
2. Use large enough sample to be representative of whole population
3. Indication of what size was measured e.g. mass
4. Calculate a mean and standard deviation
5. Use t-test
6. Analyse whether there’s a significant difference between the mean of the 2 populations

Question 20

What are 3 ways of clarifying evolutionary relationships?

Answer 20

• Genome sequencing
• Comparing amino acid sequences
• Immunological comparisons

Question 21

How can genome sequencing be used to clarify evolutionary relationships?

Answer 21

• The base sequence of an organism’s DNA can be determined.
• The DNA base sequence of 1 organism can be compared to the DNA base sequence of another organism
• Closely related species will have a higher % similarity in their DNA base sequence

Question 22

How can amino acid sequence be used to clarify evolutionary relationships?

Answer 22

• Proteins are made of amino acids
• The sequence of amino acids in a protein is coded for by the base sequence in DNA
• Related organisms have similar DNA sequences and so similar amino acid sequences in their proteins

Question 23

How can immunological comparisons be used to clarify evolutionary relationships?

Answer 23

• Proteins related to those of another species, will also be recognised (bound) by that antibody
• The more antibodies the protein binds, the more precipitate will form