TOPIC 4: Biodiversity and Natural Resources

Question 1

Describe how aseptic techniques are used when handling bacterial cultures. (3)

Answer 1

• work near bunsen burner
• sterilise work surfaces
• sterilise equipment w/ heat

Question 2

Explain the role of a placebo (2)

Answer 2

• provides a control group for comparison
• therefore ensuring that the drug is causing the effect

Question 3

Explain the role of a double blind trial. (2)

Answer 3

• bcs neither doctors nor patients know who has received the actual drug

^ therefore, removing bias from trial

Question 4

Explain why the agar plate was incubated at 25oC. (2)

Answer 4

• to allow bacteria to multiply
• without encouraging pathogenic organisms

Question 5

Explain why bacteria are able to multiply in the bloodstream when they enter the body. (3)

Answer 5

• warm conditions
• suitable for bacterial enzymes
• glucose used for energy

Question 6

Describe the structure of starch. (3)

Answer 6

• polysaccharide made from alpha glucose
• monomers in chains joined by 1,4 glycosidic bonds
• branches joined to chains via 1,6 glycosidic links

Question 7

Describe how nitrate ions are transported from the root to the leaves. (2)

Answer 7

• through the xylem
• in water

Question 8

Name the monomer that makes up cellulose

Answer 8

beta-glucose

Question 9

Compare and contrast the structure of chitin and a cellulose molecule. (3)

Answer 9

similarities:
- both have glycosidic bonds
- every other monomer is inverted

differences:
- chitin contains nitrogen but cellulose doesn’t

Question 10

Compare and contrast the structure of cellulose and amylopectin. (3)

Answer 10

similarities:
- both = polymers of glucose
- both contain 1,4 glycosidic bonds

differences:
- cellulose made of beta-glucose
amylopectin = alpha-glucose

Question 11

Name the bond between adjacent cellulose molecules in a cellulose microfibril. (1)

Answer 11

hydrogen bond

Question 12

Explain why a seedling needs a supply of magnesium ions. (2)

Answer 12

• needed to make chlorophyll
• which is required for photosynthesis

Question 13

Name the plant tissue that has lignin in its cell walls

Answer 13

xylem

Question 14

Explain the role of the middle lamella when a plant cell completes mitosis. (2)

Answer 14

• produced b/w adjacent new cells
• bcs middle lamella holds cell walls together

Question 15

Explain the structure of the plasmodesma. (2)

Answer 15

• cytoplasmic connection
• which allows communication b/w cells

Question 16

give 2 reasons why a sieve tube element doesn’t need a rER and ribosomes. (2)

Answer 16

• no transcription
• no proteins will be synthesised to be processed in ER

Question 17

Define: tensile strength

Answer 17

the force the fibre can withstand before breaking

Question 18

Explain how the structure and properties of starch are related to its function as a storage molecule. (3)

Answer 18

• contains glucose needed for respiration
• amylose is coiled, making starch compact
• amylopectin is branched -> rapidly hydrolysed

Question 19

Describe the positions in the stem of those tissues that contain lignin. (2)

Answer 19

• sclerenchyma on outer side of vascular bundle
• xylem on inner side of vascular bundle

Question 20

Describe arrangement of glucose monomers in a cellulose molecule. (2)

Answer 20

• monomers connected by 1,4 glycosidic bonds
• alternate monomers are inverted

Question 21

Explain the relationship b/w the composition of starch and the rate of hydrolysis by enzymes. (4)

Answer 21

• the less amylose present, the greater the proportion of amylopectin
• amylose is unbranched
• amylopectin: 1,4 & 1,6 glycosidic bonds
• branches increase rate of hydrolysis

Question 22

State why the Scottish wildcat is described as endemic. (1)

Answer 22

it’s only found in Scotland

Question 23

The Scottish wildcat can successfully interbreed w/ domestic cats.
Explain the effect this could have on their genetic diversity. (2)

Answer 23

-increases genetic diversity

• bcs new alleles introduced

Question 24

Define: allele

Answer 24

• alternative form of a gene

Question 25

Define: endemic

Answer 25

found only in one geographical location

Question 26

Explain how the primary structure of trypsin molecules can be used to produce a phylogenetic tree. (3)

Answer 26

• determine sequence of A.As
• determine number of differences in sequences of A.As b/w species
• the greater the number of differences, the less closely related the species

Question 27

Explain why they are now classified as different species. (2)

Answer 27

• bcs populations have become reproductively isolated
• can no longer interbreed to produce fertile offspring

Question 28

Describe how the Hardy-Weinberg equation can be used to provide evidence for changes in the elephant population in Mozambique. (2)

Answer 28

• calculate allele frequency
• regular sampling over a period of time

Question 29

Describe how mutations can cause a population to become separate species. (4)

Answer 29

• mutations produce new alleles
• selection pressure causes alleles to be advantageous
• individuals w/ advantageous alleles more likely to survive & reproduce
• after time, population not able to reproduce with other species to produce fertile offspring

Question 30

Define: species richness

Answer 30

measures number of species in a habitat

Question 31

Define: heterozygosity index

Answer 31

a measure of genetic diversity within a species

Question 32

Define: species

Answer 32

A group of organisms that can interbreed to produce fertile offspring

Question 33

Explain how a Hardy-Weinberg can be used to show natural selection. (2)

Answer 33

• H.W equation shows allele frequency in a population
• if natural selection is occurring, there’d be a change in allele frequency over time