PREPARATORY EXAMINATION

GRADE 12

LIFE SCIENCES P2

SEPTEMBER 2020

MARKS: 150

MARKING GUIDELINES

This marking guideline consists of 14 pages.

Life Sciences P21FS/September 2020Grade 12 Prep. Exam.Marking Guidelines

Life Sciences P24FS/September 2020Grade 12 Prep. Exam.Marking Guideline

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PRINCIPLES RELATED TO MARKING LIFE SCIENCES

1. If more information than marks allocated is given

Stop marking when maximum marks is reached and put a wavy line and 'max' in the right-hand margin.

2. If, for example, three reasons are required and five are given

Mark the first three irrespective of whether all or some are correct/incorrect.

3. If whole process is given when only a part of it is required

Read all and credit the relevant part.

4. If comparisons are asked for, but descriptions are given

Accept if the differences/similarities are clear.

5. If tabulation is required, but paragraphs are given

Candidates will lose marks for not tabulating.

6. If diagrams are given with annotations when descriptions are required

Candidates will lose marks.

7. If flow charts are given instead of descriptions

Candidates will lose marks.

8. If sequence is muddled and links do not make sense

Where sequence and links are correct, credit. Where sequence and links are incorrect, do not credit. If sequence and links become correct again, resume credit.

9. Non-recognised abbreviations

Accept if first defined in answer. If not defined, do not credit the unrecognised abbreviation, but credit the rest of the answer if correct.

10. Wrong numbering

If answer fits into the correct sequence of questions, but the wrong number is given, it is acceptable.

11. If language used changes the intended meaning

Do not accept.

12. Spelling errors

If recognisable, accept the answer, provided it does not mean something else in Life Sciences or if it is out of context.

13. If common names are given in terminology

Accept, provided it was accepted at the national memo discussion meeting.

14. If only the letter is asked for, but only the name is given (and vice versa)

Do not credit.

15. If units are not given in measurements

Candidates will lose marks. Memorandum will allocate marks for units separately.

16. Be sensitive to the sense of an answer, which may be stated in a different way.

17. Caption

All illustrations (diagrams, graphs, tables, etc.) must have a caption.

18. Code-switching of official languages (terms and concepts)

A single word or two that appear(s) in any official language other than the learner's assessment language used to the greatest extent in his/her answers should be credited, if it is correct. A marker that is proficient in the relevant official language should be consulted. This is applicable to all official languages.

19. Changes to the memorandum

No changes must be made to the memoranda. The provincial internal moderator must be consulted.

SECTION A

QUESTION 1

1.1

1.1.1

1.1.2

1.1.3

1.1.4

1.1.5

1.1.6

1.1.7

1.1.8

1.1.9

1.1.10

D

B

A

C

B

B

B

D

B

A (10 x 2)

(20)

1.2

1.2.1

Evolution

1.2.2

Homologous chromosomes

1.2.3

Australopithecus

1.2.4

Interphase

1.2.5

Transitional fossils

1.2.6

Cytokinesis

1.2.7

Variation

1.2.8

Binocular vision/stereoscopic vision

1.2.9

Hominidae

1.2.10

Discontinuous variation (10 x 1)

(10)

1.3

1.3.1

1.3.2

1.3.3

Both A and B

Both A and B

None (3 x 2)

(6)

1.4

1.4.1

1.4.2

1.4.3

1.4.4

Suspect 1

All the bars of the DNA-profile of the skin tissue correspond with ALL the bars of the DNA- profile of suspect 1

· By repeating the test with the DNA sample several times

to make sure they get the same results

· To do the test at different laboratories

to make sure they get the same results (1 x 2)

(Mark first ONE only)

Yes /Saliva could be used

Saliva will have some DNA containing cells from the lining of the mouth.

(1)

(2)

(2)

(2)

(7)

1.5.

1.5.1

1.5.2

1.5.3

Nucleus

(a) Amino acid

(b) Peptide

(a) UAU

(b) ACA

(1)

(1)

(1)

(2)

(2)

(7)

Total Section A:

50

SECTION B

QUESTION 2

2.1

2.1.1

2.1.2

2.1.3

2.1.4

Haemophilia

a)Male with haemophilia/affected male

b)XHXh

Individual 3 is a male and his genotype is XhY

The Y chromosome is inherited from the father

The Y chromosome does not carry an allele

The Xh chromosome is inherited from the mother

which is heterozygous/XHXh

P1 Phenotype Unaffected female x Unaffected male

Genotype XHXh x XHY

Meiosis

G/gametes XH, Xh x XH,Y

Fertilization

F1 Genotype XHXH XHY XHXh XhY

0% * Compulsory mark

P1 and F1

Meiosis and fertilization

(6)

*Compulsory 1 + Any 5

[40]

OR

P1 Phenotype Unaffected female x Unaffected male

Genotype XHXh x XHY

Gametes

XH

Xh

XH

XHXH

XHXh

Y

XHY

XhY

1 mark for correct gametes

1 mark for correct genotypes

Meiosis

Fertilisation

F1

Genotype XHXH XHY XHXh XhY

0% *Compulsory mark

P1 and

F1

Meiosis and fertilization*Compulsory 1 + Any 5

(1)

(1)

(2)

(4)

(6)

(14)

2.2

2.2.1

2.2.2

2.2.3

m-RNA

(a) 270

(b) 90

Translation*

· Each t-RNA carries a specific amino acid

· When the anticodon on the t-RNA

· matches the codon on the m-RNA

· then t-RNA brings the required amino acid

· to the ribosome

· Amino acids become attached by peptide bonds – to form the required protein *Compulsory 1 + Any 5

(1)

(1)

(1)

(6)

(9)

2.3

2.3.1

2.3.2

2.3.3

2.3.4

2.3.5

Female

The two gonosomes/pair 23 are similar/pair 23 is XX/same size

45

Down syndrome/Trisomy 21

· During Anaphase I/II

· homologous chromosomes

· at chromosome pair 21

· fail to separate/non-disjunction takes place

· An abnormal gamete forms with 24 chromosomes/extra chromosomes at pair 21

· If the abnormal gamete fuses with a normal gamete

/with 23 chromosomes

· the new cell has a chromosome number of 47 and Down syndrome comes about Any 6

(1)

(1)

(1)

(1)

(6)

(10)

2.4

2.4.1

2.4.2

Genetic manipulation/Genetic engineering/Genetic modification

(a)

· Bananas are easily accessible You don’t have to go to a clinic or a hospital for an injection/you can buy it at a shop

· Eating a banana with vaccines of hepatitis B are more comfortable and easy than an injection that needs to be sterilized and given by an experienced person/nurse/doctor

· Bananas do not need to be carefully stored

and are administered easily where as a vaccine must be refrigerated and administrated (Any 2 x 2)

(Mark first TWO only)

(b)

· Expensive/research money could be used for other needs/the initial cost will be high in the beginning

· Interfering with nature/Ethical issues

· Potential health impacts on humans

· Unsure of long-term effects on the enviroment (Any 2)

(Mark first TWO only)

(1)

(4)

(2)

(7)

[40]

QUESTION 3

3.1

3.2

3.1.1

3.1.2

3.1.3

3.1.4

3.1.5

3.1.6

3.2.1

3.2.2

Tim White

A smaller cranium /brain

and modern humans have a larger cranium/brain

Face sloping/Forehead slope more backwards and in modern humans it is less backwards

Brow ridges pronounced and modern humans less pronounced

Larger canines and

modern humans have smaller canines

Diastema (spaces between the teeth) exist and

modern humans has no diastema

Big jaw and are prognathous and

modern humans have small jaw and is non prognathous

Poorly developed chin and

modern human has a well developed chin

(Mark first THREE only) (Any 3 x 2)

They could look for tools (pots, knives, weapons etc.) that are cultural evidenceof human evolution

Increased awareness of the environment in

sensing danger/food

Freeing of the hands to

use implements/carry objects/weapons/ offspring

Exposure of a large surface area for

thermoregulation/lose body heat to surroundings in hot conditions/reduce overheating

Display of sex organs /breasts

as part of courtship behaviour

(Mark first TWO only) (Any 2 x 2)

H. erectus/H.habilis/Australopithecus

Brain volume of different homo species

SPECIES

BRAIN VOLUMES

H. habilis

600 cm3

H. erectus

860 cm3

H. sapiens

1300 cm3

Table

(1)

Heading of the table

(1)

Colum’s and rows captures

(1)

Correct information

(2)

FFBB

ffbb

a) ffBB

b) ffBB OR ffBb

c) Few bunches and big fruits

Many bunches and big fruits

Few bunches and small fruits

Many bunches and small fruits

(1)

(6)

(2)

(4)

(1)

(5)

(19)

(2)

(1)

(1)

(4)

(8)

3.3

· Because of the random arrangement of chromosomes at the equator during metaphase /any one of two alleles of a characteristic can sort with any two of another characteristic

(Ft) and (Bb)

· the alleles of different genes move independently of each other into the gametes

· They can therefore appear in the gametes in different combinations /Hence FfBb provides the following combinations FB, Fb, fB, fb

(3)

3.4

3.4.1

3.4.2

3.4.3

The average height of the plants decreases as the altitude increases

OR

The average height of the plants increasesas the altitude decreases

- All seeds from different altitudes were planted under the

same environmental conditions

- Same number of seeds for each height was used

- Seeds from the same species (Achillea millefolium) are

used

- Different altitudes must be kept constant Any 2

(Mark 1st TWO only)

- There is variation in the height of the plant species

(Achilea millefolium)

- Some plants are short at high altitudes and

some are tall at low altitudes

- The tall plants survive at low altitudes because there are

less strong winds and harsh environmental conditions

- Short plants survive at high altitudes because they are not

damaged by strong winds and harsh environmental

conditions

- The allele for short plants were passed to the next

generation at high altitudes and

- The allele for tall plants were passed to the next

generation at low altitudes.

- Higher altitudes have a bigger ratio of short plants and

- Lower altitudes have a bigger ratio of taller plants Any 6

(2)

(2)

(6)

(10)

TOTAL SECTION B:

[40]

80

SECTION C

QUESTION 4

· The population of a single species warblers*compulsory

· becomes separated by a geographical barrier (dessert) *compulsory

· The population splits into two

· There is now no gene flow between the two populations

· Since each population may be exposed to different environmental conditions/the selection pressure may be different

· Natural selection occurs independently in each of the two populations

· such that the individuals of the two populations become very different

· from each other genotypically and phenotypically,

· Even if the two populations were to mix again

· they will not be able to interbreed

· The two populations are now different species

Reproductive isolation mechanisms that help to keep species separate

· They use species-specific courtship behaviour

· Males sing songs to attract females

· and females do not even respond to other males' songs/recognize it

Other ways they can keep species apart

· Breeding at different times of the year

· Infertile offspring

· Prevention of fertilization

Any 3

Content:

Synthesis:

(2*+9)

(3)

(3)

(17)

(3)

(20)

ASSESSING THE PRESENTATION OF THE ESSAY

Criterion

Relevance (R)

Logical sequence (L)

Comprehensive (C)

Generally

All information provided is relevant to the topic.

Ideas are arranged in a logical sequence for each process.

All aspects required by the essay have been sufficiently addressed.

In this essay

Only information relevant to speciation, reproductive isolation mechanisms and species specific courtship behaviour

(No irrelevant information)

Speciation, species specific courtship and reproductive isolation mechanisms described in a logical order

Compulsory marks 2/2

Speciation 6/9

Species specific courtship 2/3

Reproductive isolation mechanisms 1/3

Mark

1

1

1

TOTAL SECTION C:

GRAND TOTAL:

20

150

OR

SEE NEXT PAGE FOR ALTERNATIVE ESSAY

ALTERNATIVE ESSAY FOR SCHOOLS CHOOSING OPTION 1 OF THE ADENDUM

SECTION C

QUESTION 4

Differences

· During replication, both DNA strands form a template

· on which DNA is formed

· During transcription, only one strand of DNA will form a template

· on which RNA is formed

· During replication A = T bind

· During transcription A = U bind

· During replication, two identical strings are formed

· that remains in the nucleus

· During replication mRNA is formed and

· leaves the nucleus (Any 8)

Similarities

· In both processes DNA serves as template

· Both processes take place in the cell nucleus

· In both processes G = S bind (3)

Importance of replication

· Doubling of genetic material

· forms identical daughter cells

· The DNA is identical

· in the new cells

· formed by mitosis (Any 4)

Importance of transcription

· The code provided by mRNAis used

· for the formation of a protein/ protein synthesis (2)

Content:

Synthesis:

(8)

(3)

(4)

(2)

(17)

(3)

(20)

ASSESSING THE PRESENTATION OF THE ESSAY

Criterion

Relevance (R)

Logical sequence (L)

Comprehensive (C)

Generally

All information provided is relevant to the topic.

Ideas are arranged in a logical sequence for each process.

All aspects required by the essay have been sufficiently addressed.

In this essay

Only information relevant to differences between replication and translation, similarities and importance of the 2 processes

(No irrelevant information)

Differences between replication and translation, similarities and importance of the 2 processes given in a logical order

NB!

Learners lose this mark if differences are given in a table

Differences 5/8

Similarities 2/3

Importance 4/6

Mark

1

1

1

TOTAL SECTION C:

GRAND TOTAL:

20

150

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