sqa extended response answers - duncanrig …...10. example of a stem cell source (ii) research into...

Higher Biology

SQA Extended Response Answers

Units 1, 2 and 3

Unit 1

Key

area

Year Question Allocated

marks

1.2 2014

specimen

Describe DNA under the following headings.

(i) Structure of DNA

(ii) Replication of DNA

9

(i) Structure of DNA

1. double strand of nucleotides/double helix

2. deoxyribose sugar, phosphate and base

3. sugar phosphate backbone

4. complementary bases pair or A-T and C-G

5. H bonds between bases

6. antiparallel structure with deoxyribose and phosphate at 3´ and 5´ends

7. proteins/histones

(ii) Replication of DNA

8. DNA unwinds into 2 strands

9. primer needed to start replication

10. DNA polymerase adds nucleotides to 3´(deoxyribose) end of strand

11. DNA polymerase adds nucleotides in one direction

12. one strand replicated continuously, the other in fragments

13. fragments joined by ligase

Additional Guidance

No more than 4 marks should be awarded

from points 8 – 13.

Check any diagram(s) for relevant

information not present in text and award

accordingly.

Unit 1

Key

area


marks

1.3 2015 Write notes on gene expression in eukaryotes

under the following headings:

(i) production of mRNA; 5

(ii) translation of mRNA. 4

9

(i) Production of mRNA

1. RNA polymerase unzips/ unwinds DNA or separates DNA into two strands

2. Hydrogen bonds between strands/base pairs break

3. RNA polymerase aligns/brings in/joins/attaches RNA nucleotides with their complementary

nucleotides /bases on DNA (template)

OR

A to U and T to A and C to G in diagram

4. a primary transcript is produced

5. exons are coding and introns are non-coding (regions of the primary transcript)

6. introns/non-coding regions are removed OR exons/coding regions are retained

7. exons are spliced/joined together to form mature mRNA)/transcript

(ii) Translation of mRNA

8. tRNA has an anticodon and an amino acid attachment site

9. tRNA binds/joins to/carries/collects specific/correct amino acid

10. tRNA carries (specific) amino acid to ribosomes

11. anticodons are complementary/pair with codons on mRNA

12. there are start and stop codons

13. peptide bonds form between amino acids

OR

a polypeptide forms

Additional Guidance



Unit 1

Key

area


marks

1.4 2012

RH

Write notes on stem cells under the following

headings:

(i) differentiation of stem cells;

(ii) research into stem cells and their therapeutic

value.

10

(i) differentiation of stem cells

1. stems cells are unspecialised/undifferentiated cells (in animals)

2. stem cells (continue to) divide

3. differentiate/develop into specialised cells/different cells for different functions OR

differentiated cells cannot return to an undifferentiated state/change into other cell types

4. there are adult and embryonic stem cells

5. embryonic stem cells differentiate into all cells types

6. tissue/adult stem cells differentiate into cells which need to be replaced

7. adult stem cells give rise to more limited cell type

8. following differentiation a cell only expresses certain genes

9. that produce proteins characteristic of that cell type

10. example of a stem cell source

(ii) research into stem cells and their therapeutic value.

11. stem cell research provides information on cell process

12. example of 11 i.e. cell growth, differentiation, gene regulation

13. therapeutic use includes repair of damaged/diseased organs/tissue/cells/eg OR

eg of the use eg diabetes, Parkinson’s disease, leukemia, skin graft, corneal graft, bone

marrow transplant

14. stem cell research must be/is often regulated

15. example of an ethical issue related to stem cell research embryos could develop into

humans OR method of avoiding the issues OR the use of induced pleuripotent stem

cells/nuclear transfer techniques

Additional Guidance





Unit 1

Key

area


marks

1.4 2014

RH

Give an account of stem cells, their therapeutic

use and the ethical issues surrounding their use.

8

Give an account of stem cells

1. Stem cells are unspecialised/ undifferentiated cells (in animals)

2. capable of cell division/ mitosis OR can divide

3. can become more stem cells

4. (products of cell division) can differentiate/ specialise

5. embryonic stem cells can differentiate into/give rise to/become/ specialise into all cell

types OR are totipotent/are pluripotent

6. adult/tissue stem cells can differentiate into/give rise to/become/ specialise into more

limited cell types OR are multipotent

7. adult/tissue stem cells replenish cells needing to be replaced OR cells which are worn

out/damaged/diseased/dead cells/tissue

7a. if 5,6 or 7 not awarded 1 mark can be awarded for naming adult/tissue and embryonic

stem cells

8. Differentiated/specialised cells produce protein/express genes characteristic of that cell

type OR example

Therapeutic use

9. can be used to repair/replace damaged/diseased/dead organs/tissue

10. Example eg bone marrow/corneal transplant

Ethical issues surrounding their use

11. ethical issue – requirement to alleviate suffering

another ethical issue – requirement to conserve life/living embryos

another ethical issue – requirement to obey laws/regulations

12. Another one

Additional Guidance





Unit 1

Key

area


marks

1.6 2015 Write notes on mutation under the following

headings:

(i) single gene mutations;

(ii) chromosome mutations and polyploidy.

9

(i) Single gene mutations

1. (single gene) mutations are random changes in DNA sequences/genes/ alleles/the genome

2. single gene mutation name AND description

substitution – base/base pair/ nucleotide is replaced/substituted by another

insertion – base/base pair/ nucleotide is added/inserted

deletion – base/base pair/ nucleotide is removed/deleted

3. another single gene mutation name AND description

4. If 2 or 3 not awarded – all 3 mutation names

5. Insertion/deletion results in a frameshift mutation/expansion of a nucleic acid sequence

6. (single nucleotide) substitutions include missense, nonsense and splice site mutations

7. splice site mutations can alter the mature mRNA OR result in exon removal OR result in

introns remaining present

(ii) Chromosome mutations and polyploidy

8. chromosome mutation can involve changes to chromosome number/structure

9. chromosome mutation name AND description;

Translocation: genes/sections of chromosome from one chromosome become attached to

another chromosome

Deletion: genes/sections of chromosome deleted from chromosome

Inversion: genes/sections of chromosome/rotate through 180º/flipped

Duplication: genes/sections of chromosome/pieces of chromosome are

duplicated/repeated

10. another chromosome mutation name AND description

11. If b or c not awarded - all 4 names but no descriptions

12. polyploidy results from errors during the separation of chromosomes /nondisjunction /

spindle failure during cell division /meiosis/mitosis/gamete formation (NOT – more than 1

set of chromosomes)

13. polyploidy is the possession of complete extra sets/double/triple the number of

chromosomes OR a whole genome duplication OR 2n becomes 3n

14. polyploidy is important in evolution of food crops OR duplication provides material upon

which natural selection can work/is important in evolution

15. polyploid crops/plants/named example show desirable features/ higher yields/other

appropriate examples of desirable features

Additional Guidance

Part (i)

When describing mutations acceptable

terms are one/two/three/a few

base(s)/base pair(s)/nucleotide(s) – not

a sequence of bases




from points 8 - 15.

Unit 1

Key

area


marks

1.7 2014

specimen

Describe the evolution of new species under the

following headings.

(i) Isolation and mutation

(ii) Selection

9

(i) Isolation and mutation

1. isolation barriers prevent gene flow between populations/ populations interbreeding

2. geographical isolation leads to allopatric speciation

3. behavioural isolation leads to sympatric speciation

4. ecological isolation leads to sympatric speciation

5. different mutations occur on each side of isolation barrier

6. some mutations may be favourable

(ii) Selection

7. natural selection is non-random increase in frequency of genetic sequences that increase

survival

8. sexual selection is non-random increase in frequency of genetic sequences that increase

reproductive success

9. Any 2 from disruptional / directional / stabilising selection

10. third type of selection from 9

11. after many generations/long period of time

12. new species form

13. if populations can no longer interbreed to produce fertile young then different species.

Additional Guidance

1 mark should be allocated for each

correct description.




from points 7– 13.

Check any diagram(s) for relevant

information not present in text and award

accordingly.

Unit 1

Key

area


marks

1.7 2012

RH

Write notes on evolution under the following

headings:

(i) natural selection;

(ii) genetic drift.

8

(i) Natural Selection

1. organisms show (genomic) variation (upon which natural selection acts)

2. natural selection is non-random increase in frequency of genetic sequences that increase

survival

3. (survivors) pass on their favourable/beneficial gene sequence/alleles/ characteristics to

offspring/next generation

4. deleterious/damaging sequences/alleles/genes/characteristics are reduced in frequency /

removed from the population

5 and 6. Any two from disruptional / directional / stabilising selection and appropriate

descriptions

7. sexual selection is non-random increase in frequency of genetic sequences that increase

reproductive success

8. over many generations/a long time

(ii) Genetic Drift

9. genetic drift is random increases and decreases in frequency of sequences/alleles/genes

10. particularly in small populations

11. results of neutral mutations

12. (or as results of the) founder effect/principle

13. founders of new populations have gene sequences which are not representative of the

whole population/are in abnormal percentages of the whole population

Additional Guidance





Unit 1

Key

area


marks

1.8 2014

RH

Give an account of genomics and its importance

in phylogenetics and personalised medicine.

8

Genomics

1. Genomics is the study of/ sequencing of genomes / DNA / bases / nucleotides

2. has been undertaken within in disease causing organisms/ pest species/ models for

research OR example

Phylogenetics

3. phylogenetics is use of DNA / gene sequence data

4. to study evolutionary relatedness/ relationships of organisms

5. sequence divergence gives estimates of time since lineages/ phylogenetic groups

diverged

6. e.g. divergence of the three domains of life / names

7. used with fossil evidence to determine the main sequence of events in evolution/

construction phylogenetic trees

8. example; emergence of cells/ last universal ancestor/ photosynthesis etc

OR divergence from common ancestor

9. shows genetic/genome/sequence conservation across different lineages/groups

Personalised medicine

10. personal genomics is analysis of an individual human genome

11. could lead to/have a role in personalised medicine OR medicine suitable for the

individual can be worked out OR example

12. though knowledge of genetic component of susceptibility/likelihood of treatment

success OR example

Additional Guidance

No more than 1 mark should be awarded





from points 10 –12.

Unit 2

Key

area


marks

2.1a 2016 Describe and compare anabolic and catabolic

reactions.

4

1. Anabolism is a synthesis/build up reaction

OR

Anabolism is build-up of molecules/ substances

OR

Anabolism is where simple molecules are built up into more complex/large molecules

2. Anabolism requires the input/ take up… of energy/ATP

3. Catabolism is breakdown/ degradation ….. of….. molecules/substances

OR

Catabolism is a….. break down/degradation……. reaction

OR

Catabolism is where complex/large molecules are changed into more simple molecules

4. Energy/ATP is released/given off in catabolism (NOT – catabolism does not require

energy)

5. Both can have reversible and irreversible steps

6. Both can have alternative routes

Additional Guidance

NB: For full marks to be awarded candidates

must have provided at least 1 correct point for

anabolism AND at least 1 point for catabolism.

No more than 4 marks should be

awarded.

Unit 2

Key

area


marks

2.1b 2013

RH

Give an account of enzyme action and enzyme

inhibition.

8

Enzyme action

1. activity depends on flexible / dynamic shape of enzyme molecules

2. (there is an) affinity of the substrate for active site

3. induced fit

4. active site orientates reactants

5. activation energy (of transition state) lowered

6. products have low affinity for active site

7. substrate and product concentration affects direction and rate of reactions OR describe

the effects of increasing substrate concentration as increasing/speeding up/driving forward

the rate of the reaction

8. enzymes act in groups / multi-enzyme complex

Enzyme inhibition

9. (in) competitive inhibition

10. there is a resemblance between the substrate and the inhibitor OR inhibition is reduced

by increase in substrate concentration

11. (in) non-competitive inhibition

12. the active site shape is changed OR the affinity of substrate for enzyme is lowered

13. (there can be) product inhibition / feedback inhibition / eg / description

Additional Guidance





Unit 2

Key

area


marks

2.1b 2015 Describe competitive and non-competitive

inhibition of enzyme action.

4

1. A competitive inhibitor binds to/blocks the active site

2. Competitive inhibition is reversed/reduced by increasing substrate concentration

3. Non-competitive inhibition is where a molecule binds to the enzyme not on the active site

4. Non-competitive inhibitor changes (the shape of) the active site

5. Non-competitive inhibition is irreversible/not affected by substrate concentration.

Additional Guidance


awarded.

Unit 2

Key

area


marks

2.2 2013

RH

Give an account of glycolysis and the citric acid

cycle in cells.

8

Glycolysis

1. glycolysis is the breakdown of glucose to pyruvate

2. 2 ATP used to phosphorylate intermediates (in glycolysis)

3. this is an energy investment phase

4. 4 ATP produced / generated / made in a pay off stage

4a Net gain of ATP OR 2 ATP used and 4 gained

(Award 4a only if points 3 and 4 not awarded)

(ii) Citric Acid Cycle

5. if oxygen is available pyruvate progresses to the citric acid cycle

6. pyruvate is converted / broken down to an acetyl group

7. acetyl group combines with coenzyme A

8. acetyl (coenzyme A) combines with oxaloacetate to form citrate

9. citric acid cycle is enzyme controlled / uses dehydrogenases.

10. ATP generated/synthesised/produced/released (at substrate level) in the citric acid

cycle

11. carbon dioxide released (from the citric acid cycle)

12. oxaloacetate is regenerated

13. NAD/NADH/NADH2/FAD/FADH/FADH2 transports hydrogen ions and high energy

electrons (to electron transport chain / next stage)

Additional Guidance





Unit 2

Key

area


marks

2.2 2015 RH

Give an account of the structure of the inner

membranes of mitochondria and the function of

the electron transport chain in cellular

respiration.

8

Structure of the inner membranes of mitchondria

1. inner membrane has cristae/large surface area

2. membranes have protein and phospholipid

3. proteins act as/are pores/pumps/electron carriers

4. some proteins are enzymes

Function of the electron transport chain

5. dehydrogenase enzymes release hydrogen ions AND high energy electrons

6. NAD(H)/FAD(H2)/coenzymes carry hydrogen AND (high energy) electrons to (the electron

transport) chain

7. high energy electrons cascade/are pushed through/pass down the chain/

producing/creating releasing/energy

8. energy used to pump H ions through/across the inner membrane

9. H ions move/return/pass/go through ATP synthase OR return flow of H ions rotates ATP

synthase

10. ATP produced by ATP synthase

11. oxygen is final electron acceptor

12. oxygen combines with H ions AND electrons to form water

Additional Guidance





Unit 2

Key

area


marks

2.3 2015 Describe the arrangement of heart chambers in

birds and amphibians and relate this to their

metabolic rates.

4

1. Amphibian heart has 2 atria and 1 ventricle

2. Bird heart has 2 atria and 2 ventricles

3. Birds have a higher metabolic rate (or converse)

4. No mixing of oxygenated and deoxygenated blood in bird heart (or converse)

5. More efficient oxygen delivery to bird cells/ muscles/tissues (or converse)

Additional Guidance

NB: For full marks to be awarded

candidates must give at least 1 correct

point for bird and at least 1 for amphibian.


awarded.

Unit 2

Key

area


marks

2.4 2016 Describe and compare metabolism in conformers

and regulators.

4

1. Conformers’ metabolism/ metabolic rate/internal environment is… dependent

on/affected by….. surroundings/external environment/ external factors/external variables

2. Conformers use behaviour to maintain optimum metabolic rate

3. Regulators can maintain/control/ regulate… their … metabolism/metabolic rate/internal

environment/… regardless of external conditions

4. Regulators requires energy for homeostasis/negative feedback

5. Conformers have narrower (ecological) niches (or converse)

6. Conformers have lower metabolic costs/rates of metabolism (or converse)

Additional Guidance

NB: For full marks to be awarded

candidates must give at least 1 correct

point for conformers AND regulators.


awarded.

Unit 2

Key

area


marks

2.5 2014

specimen

Describe how animals survive adverse

conditions.

4

1. metabolic rate reduced

2. dormancy can be predictive or consequential

3. hibernation in winter usually mammals

4. aestivation allows survival in periods of drought or high temperature

5. daily torpor is reduced activity in animals with high metabolic rates

6. example of hibernation or aestivation or daily torpor

Additional Guidance

NB: 1 mark should be allocated for each

correct description up to a maximum of 4.

Unit 2

Key

area


marks

2.6 2015

RH

Give an account of the general pattern of growth

of microorganisms and the conditions needed for

their culture.

8

Pattern of growth of microorganisms

1. lag phase (of slow growth) when enzyme induction occurs

2. log phase of exponential growth/ maximum/fastest rate of growth OR phases of

exponential growth

3. stationary phase when secondary metabolites produced/culture becomes depleted

4. death phase when toxic wastes accumulate/nutrients/resources in short supply/lack of

substrates

4b All stages named

Conditions needed for cultivation

5. growth is influenced by growth medium AND environmental conditions

6. they require an energy source AND raw material/simple chemical compounds for

synthesis

7. energy comes from substrate/example or light

8. some microorganisms can produce all the complex substances required for growth AND

others need some complex substances included in their growth medium

9. some fermentations require precursors/inducers/inhibitors

10. culture conditions require sterility/asepsis/aseptic techniques

11. control of /the optimum/the right temperature AND oxygen level

12. control of pH by buffers OR acids and alkalis

Additional Guidance





Unit 2

Key

area


marks

2.7 2014

specimen

Describe recombinant DNA technology. 4

1. plant/animal gene transferred into microorganism that makes plant/animal protein

2. restriction endonuclease to cut gene out/cut plasmid

3. genes introduced to increase yield or prevent microbe surviving in external environment

4. ligase seals gene into plasmid

5. recombinant yeast cells to overcome polypeptides being incorrectly folded or lacking

post translational modifications

6. regulatory sequences in plasmids/artificial chromosomes to control gene expression

Additional Guidance


awarded.

Unit 3

Key

area


marks

3.1a 2014

RH

Write notes on human food supply under the

following headings:

(i) food security and population;

(ii) factors affecting food production.

10

(i) Food security and population

1. (food security is ability of human population to access) sufficient/enough/correct/right

supply/quantity/amount of food

2. sufficient/enough/correct/right quality of food OR example

2a. If nether 1 nor 2 scored mention of quantity and quality of food

3. increasing population increases the demand/need for food OR food security more

difficult to achieve

4. production/supply is sustainable OR example

5. does not degrade/destroy natural resources/environment/land on which agriculture

depends OR example

(ii) Factors affecting food production

6. (food production) depends on photosynthesis

7. food production limited by area of crop/land

8. factors which limit/affect photosynthesis include light/temperature/carbon dioxide

availability (any 1)

9. second factor

10. high-yielding/ polyploid cultivars OR GM/selectively bred organisms increase food

production OR example described

11. pests eat/damage crops/livestock OR weeds compete with crops OR disease/parasites

kill/damage crops/livestock

12. vetinary care/pesticides/fungicides/herbicides/insecticides OR biological control/cultural

methods control pests/weeds/diseases

13. increased irrigation/water availability/multiple cropping/agricultural machinery/fertilizers

increases food production

14. livestock produce less food per unit area than crops due to energy loss at each trophic

level

15. livestock can be grazed/raised/kept on habitats/land not suitable for crops

Additional Guidance





Unit 3

Key

area


marks

3.1b 2013

RH

Write notes on photosynthesis under the

following headings:

(i) energy capture and photosynthetic pigments;

ii) use of captured energy and the light

dependent stage

10

(i) Energy capture and photosynthetic pigments

1. light absorbed (for photosynthesis)

2. some light is transmitted / reflected

3. chlorophyll (a) absorbs mainly in the blue and red regions /colours / wavelengths of the

spectrum

4. chlorophyll b / carotenoids / accessory pigments extend the wavelengths of light

absorbed / broaden/widen the absorption spectrum / absorb light wavelengths/colours not

absorbed by chlorophyll

5. chlorophyll b / carotenoids / carotene and xanthophyll / accessory pigments pass

energy/electrons onto chlorophyll (a) (NOT light energy)

5a. names of pigments if 3, 4 or 5 not awarded

6. Absorbed/captured) energy excites electrons in pigments / pigment molecules /

chlorophyll (Not : Chloroplasts)

(For points 1,3 and 4 : Penalise -1 once for the use of light captured/trapped as an

alternative to light absorbed Point 1 can be scored in addition if points already 3 and 4

scored)

(ii) Use of captured energy and the light dependent stage

7. (high energy) electrons pass through electron transport chains /electron transport

system / cytochrome chain / cytochrome system (to release energy)

8. ATP generated by ATP synthase

9. energy is used for photolysis

10. energy is used to split water to produce / release hydrogen and oxygen

11. hydrogen transferred to/reduces/joins to (coenzyme) NADP OR NADPH /NADPH2 is

produced

12. oxygen evolved/released OR oxygen produced as a waste product/ by-product

13. ATP is transferred to / used in / needed for / needed in the carbon fixation stage/Calvin

cycle (Not : light independent stage / dark stage / stroma)

14. NADPH2 transferred to / used in / needed for / needed in carbon fixation stage / Calvin

cycle

Additional Guidance





Unit 3

Key

area


marks

3.1b 2012

RH

Give an account of the capture of light energy

and its conversion into chemical energy in the

light dependent stage of photosynthesis.

8

Capture of light energy

1. photosynthetic pigments/chlorophyll absorb/capture light/have specific absorption

spectra

2. absorbed/captured/trapped energy/light excites electrons in pigment

molecules/chlorophyll

3. chlorophyll a and b and carotenoids mentioned

4. chlorophyll b/carotenoids/accessory pigments extend the range of wavelengths

absorbed/absorb light wavelengths not absorbed by chlorophyll

5. pass energy to chlorophyll

Conversion of light energy

6. high energy electrons transferred along electron transport chain

7. electron transfer chains release energy to regenerate/produce ATP

8. ATP synthase OR ADP + Pi → ATP/ATP made

9. photolysis (occurs) 1

10. water split into oxygen and hydrogen

11. hydrogen transferred to NADP OR NADP reduced

12. ATP used in carbon fixation/passed to Calvin cycle

Additional Guidance





Unit 3

Key

area


marks

3.3 2016 Write notes on crop protection under the

following headings:

(i) weeds, pests and diseases; 4

(ii) methods of control. 4

8

(i) Weeds, pests and diseases;

Weeds:

1. Weeds compete with/inhibit (crop) plants

AND

reduce productivity/growth/yield

2. Annual weeds have... rapid growth/short life cycles/ complete life cycle within a year/

produce many seeds/ produce seeds with long term viability

OR

Perennial weeds have storage organs/vegetative reproduction

Pests

3. Pests eat/damage… crops/plants/plant parts

AND

reduce productivity/growth/yield

4. Any 2 from nematodes/insects/molluscs (NOT – examples eg aphid)

Diseases :

5. Diseases are caused by bacteria/fungi/viruses

6. Diseases are often spread by invertebrates/pests

NB: For full marks to be awarded, candidates must give at least 1 correct point

for weeds AND at least 1 correct point for pests AND at least 1 correct point for

diseases

(ii) Methods of control

7. Weeds/pests/diseases can be controlled by cultural means

AND

example (ploughing/ weeding/ roguing/ crop rotation/ time of sowing)

8. Selective weed killer/selective herbicide… only kills/affects… certain plant species/broad

leaved weed (NOT – descriptions of herbicides mimicking plant hormones etc.)

9. Systemic weed killer… spreads through(vascular system) / enters plant

AND

kills (whole) plant/stops regrowth/ regeneration

OR

Systemic pesticide/insecticide… spreads through/enters plant/ in the phloem

AND

kills pest feeding on plant

10. Applications of fungicide based on disease forecasts are more effective than treating

diseased crop

11. Compensatory mark to be awarded if none of points b /c /d awarded but fungicide,

pesticide / insecticide and herbicide are all named

12. Biological control is use of predator/parasite of pest

13. example of a problem with chemical/biological control

ANY one from :

toxicity to non pest/target species

persistence in the environment

accumulation/magnification in food chains/food webs

production of resistant populations

predator/parasite/control organism/disease organism becomes… invasive/

outcompetes/ preys on/ parasitizes other species h. Integrated pest management

combines biological and chemical control OR chemical and cultural control OR

biological and cultural control OR biological, cultural and chemical control

Additional Guidance





Unit 3

Key

area


marks

3.5 2012

RH

Give an account of parasitism and mutualism as

types of symbiosis.

8

Parasitism

1. symbiosis relationship/association between two different species

2. coevolution/coevolved

3. parasites gain energy/resources/nutrients

4. host is harmed by/made weaker by these losses OR one benefits and the other is

harmed

5. parasites can have limited metabolism

6. often cannot survive outside host/reproduction requires host OR obligate

7. transmission/transfer method to new host or vector eg direct contact/resistant stage

8. secondary hosts as vector

9. e.g. of parasite and host

Mutualism

10. mutualism involves benefit for both species

11. interdependent relationship OR one cannot live without the other

12. example of mutualism

13. benefits to one described

14. benefits to other described

Additional Guidance





Unit 3

Key

area


marks

3.6 2016 Write notes on social behaviour in animals under

the following headings:

(i) social hierarchy and cooperative hunting;

(ii) social insects.

8

(i) Social hierarchy

1. Social hierarchy is a rank order/pecking order in a group of animals OR dominant/ alpha

AND subordinates/lower rank

2. aggression/fighting/conflict/violence reduced

3. ritualistic display/appeasement/ threat/submissive… behaviour

OR

alliances formed to increase social status

OR

descriptive examples

4. ensures… best/successful… genes/characteristics are passed on

OR

guarantees experienced leadership

Cooperative hunting

5. cooperative hunting is where animals hunt in a group/together

AND one from increases hunting success

OR

allows larger prey to brought down

OR

more successful than hunting individually

6. (subordinate) animals all get more food/energy… than hunting alone

7. less energy used/lost per individual

(ii) Social insects.

8. Any 2 examples – bees, wasps, ants, termites

9. Only some members of colony (hive reproduce / are fertile)

OR

Queen AND males/ drones mate/ reproduce

OR

only queen lays eggs

OR

some/most members of colony are sterile/infertile/do not reproduce

OR

some/most of colony are workers who are sterile

10. examples of worker roles ANY one from :

raise relatives

defend the hive

collect pollen/nectar/food

waggle dance to show direction of food etc.

11. social insects show……. kin selection/altruism between related individuals

12. increases/helps survival of shared genes

OR

so shared genes are passed on to next generation

13. Some are keystone species which are crucial for (stability of) the ecosystem/ food

web/pollination/soil fertility

OR

The removal of keystone species can… disrupt/collapse… the ecosystem/food web

Additional Guidance







Unit 3

Key

area


marks

3.6 2013

RH

Write notes on social behaviour under the

following headings:

(i) altruism and kin selection;

(ii) primate behaviour.

10

(i) Altruism and kin selection

1. in context of altruism use of donor and recipient

2. altruistic behaviour harms and benefits / increased survival or descriptions of examples

3. reciprocal altruism involves reversal of roles at a later stage / favour returned or a

description of reversed roles

4. reciprocal altruism often occurs in social animals/social insects OR mention of the

prisoner’s dilemma

5. altruism is (more) common between kin / related individuals / kin selection is altruism

between kin

6. donor can benefit indirectly (through shared genes)

7. increased chance of shared / their genes surviving / being passed on (in recipient’s

offspring)

(ii) Primate behaviour

8. primates have a long period of parental care / spend a long time with their parent(s)/

look after young for a long time

9. this gives opportunity to learn complex social skills

10. (social) primates use ritualistic display / appeasement (behaviour) to reduce

conflict/aggression / ease tension

11. any one example of appeasement / alliance forming / ritualistic behaviour e.g.

grooming / facial expression / body posture / sexual presentation

12. second example of appeasement / alliance forming / ritualistic behaviour

13. individuals form alliances which increase social status OR Social hierarchy exists

14. complexity of social structure is related to ecological niche / resource distribution /

taxonomic group

Additional Guidance





Unit 3

Key

area


marks

3.7 &

3.8

2014

RH

Write notes on biodiversity under the following

headings:

(i) measuring biodiversity;

(ii) threats to biodiversity.

10

(i) Measuring biodiversity

1. genetic diversity, species diversity, ecosystem diversity (any 2)

2. a third component

3. genetic diversity is the number and frequency of alleles/sequences in a population

4. species diversity is the species richness/number of (different) species and relative

abundance/proportion of each species

5. species richness is the number of (different) species

6. relative abundance is the proportion of each species

7. ecosystem diversity is the number of different/distinct ecosystems

(ii) Threats to biodiversity

8. overexploitation

9. example – overhunting/overfishing/deforestation

10. bottleneck effect is loss of genetic variation in small populations/few surviving

individuals OR removal of keystone species decreases biodiversity

11. habitat fragments/islands/reduced habitat areas have a low species richness/low

number of species/species diversity

12. in habitat fragments/islands edge/fringe species outcompete interior/other species

13. invasive species (are naturalised species) which eliminate/ outcompete/prey on

native/keystone species (and reduce biodiversity)

14. invasive species may be free of predators/pathogens/disease (which naturally limit

their populations)

15. human activities/humans/deforestation/burning fossil fuels cause climate change/global

warming OR anthropogenic climate change

Additional Guidance





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