Aqa As Biology Unit 2

Front 1

How is a quaternary structure distinguished?

Back 1

More than one polypeptide chain

Front 2

Why may haemoglobin differ in organisms?

Back 2

Different primary structures

Front 3

Explain what is meant by a phylogenetic relationship.

Back 3

Shows evolutionary relationship

Front 4

Explain why samples of hybrid DNA are made from the same gene.

Back 4

Base sequences are similar, so the bases will bind together

Front 5

A Zonkey is infertile. Suggest why.

Back 5

Odd number of chromosomes, which cannot pair.

Front 6

What information is required to calculate an index of diversity for a particular community?

Back 6

Number of species

Front 7

Explain how clearing a forest decreases the diversity of insects in the area.

Back 7

• Fewer habitats

• Fewer food sources

• Fewer plant species

Front 8

How can genes be passed from one species of bacteria to another?

Back 8

Horizontal gene transmission, through conjugation

Front 9

Suggest how adding antibiotics to the food of cattle increased profit for the farmers.

Back 9

• Kills pathogens

• Diseases are less likely

Front 10

Use your knowledge of selection to explain why adding antibiotics to the food of cattle is banned.

Back 10

• Resistant bacteria are more likely to survive

• Increase in numbers

Front 11

Explain how the structures of the walls of arteries and arterioles are related to their functions.

Back 11

• Elastic tissue stretches under pressure, then recoils, evening out the pressure/flow

• Muscle contracts, reducing the diameter of the lumen, changing the pressure/flow

Front 12

Explain how muscle fibres in arterioles reduce blood flow to capillaries.

Back 12

Muscles contract and the arterioles constrict

Front 13

What is an organ?

Back 13

Bundle of tissues

Front 14

Give an advantage for the blood flow in capillaries being slow.

Back 14

More time for diffusion

Front 15

Explain why a lack of protein in the blood causes a build up of tissue fluid.

Back 15

• Water potential in the capillary is higher

• Water moves out of capillary

• By osmosis

Front 16

Explain what is meant by a genetic bottleneck.

Back 16

A drop in population, so a reduced gene pool.

Front 17

Give two precautions when setting up a potometer.

Back 17

• No air bubbles

• Turn off the tap

Front 18

Suggest one ethical argument for maintaining biodiversity.

Back 18

• Prevent extinction

• Loss of populations

• Loss of habitats

Front 19

Suggest one economic argument for maintaining biodiversity.

Back 19

• Medical uses

• Commercial products

• Tourism

• Agriculture

Front 20

Explain how a mutation in a gene coding for an enzyme could lead to the production of a non-functional enzyme.

Back 20

• Change in amino acid sequence

• Change in hydrogen bonds

• Alters tertiary structure

Front 21

Describe how DNA is replicated.

Back 21

• Hydrogen bonds break

• DNA Helicase

• Nucleotides attach

• Complementary base pairings

• Hydrogen bonds reform

• Semi-conservative replication

Front 22

Why should you repeat your measurements several times?

Back 22

• Allows anomalies to be ruled out

• Makes the average/mean more reliable

Front 23

Explain how the structure of cellulose is related to its role in plant cell walls.

Back 23

• Long chains of glucose

• Joined by hydrogen bonds

• Prove strength/rigidity

Front 24

Explain the importance of elastic fibres in the wall of the aorta.

Back 24

• Stretches when ventricles contract

• Recoils when ventricle relaxes

• Maintains blood pressure

Front 25

What name is used for the non-coding sections of a gene?

Back 25

Introns

Front 26

Why place a potometer under water?

Back 26

To prevent air from entering

Front 27

Explain why comparing the base sequence of a gene provides more information than an amino acid sequence.

Back 27

• Triplet code

• Introns

Front 28

Describe how carbon dioxide in the air outside a leaf reaches mesophyll cells inside the leaf.

Back 28

• Enters via stomata

• Guard cells open stomata

• Diffuses through air spaces

Front 29

Explain why a gene for a polypeptide can contain more than a specific number of bases.

Back 29

Can contain introns

Front 30

Frequent treatment with antibiotics can result in resistant strains of bacteria. Explain how.

Back 30

• Mutation occurs

• Resistant gene/allele

• Vertical gene transmission

Front 31

Describe what causes root pressure.

Back 31

• Ions in xylem

• Lowers water potential (in xylem)

• Water enters by osmosis

Front 32

Explain how oxygen is loaded, transported and unloaded in the blood.

Back 32

• Haemoglobin carries oxygen

• In red blood cells

• Association in the lungs

• At high partial pressure

• Dissociates at tissues

• At low partial pressure

Front 33

Describe andexplain one way the production of gametes by meiosis contributes to this variation.

Back 33

• Crossing over

• Exchange of genetic material

Front 34

Give two ways in which meiosis contributes to genetic variation in the mature sperms.

Back 34

• Crossing over

• Independent segregation

Front 35

What is the biological importance of reducing the chromosome number when the celldivides by meiosis?

Back 35

Fertilisation

Front 36

The sequence of bases on one strand of DNA is important for protein synthesis.What is its role?

Back 36

Determines amino acid sequence

Front 37

Explain why meiosis is important in sexual reproduction, apart from producing gametesthat are genetically different.

Back 37

• Produces haploid cells

• Maintains chromosome numbers

Front 38

In humans, substances move out of the capillaries to form tissue fluid. Describe how this tissue fluid is returned to the circulatory system.

Back 38

• Hydrostatic pressure is lower in the capillary

• Water returns to capillary

• By osmosis