STUDY GUIDE TITLE

At a glance: what Paper 2 is

Life Sciences Paper 2 is a 150 mark, 2.5 hour paper written in three sections: Section A (Question 1, 50 marks: multiple choice, biological terminology, matching items and short structured items), Section B (Questions 2 and 3, 40 marks each) and Section C (Question 4, one 20 mark essay).

Topic	What it covers
Meiosis	Phases, crossing over, chromosome number, abnormal meiosis and non-disjunction, comparison with mitosis.
DNA: the code of life	DNA and RNA structure, replication, transcription, translation, DNA profiling, genetic engineering, stem cells.
Genetics and inheritance	Monohybrid and dihybrid crosses, complete and incomplete dominance, co-dominance, blood groups, sex linkage, pedigree diagrams, mutations, variation.
Evolution	Evidence, Lamarck, Darwin and natural selection, speciation, reproductive isolation, biogeography, punctuated equilibrium, artificial selection.
Human evolution	Ape and human anatomy, bipedalism, hominid fossils, out of Africa, mitochondrial DNA, cultural evidence, phylogenetic trees.

The 2025 Diagnostic Report states that "the section on evolution comprises 36% (54 marks) in Paper 2". Evolution plus human evolution is more than a third of the paper, and it is where candidates performed worst.

What the 2025 examiners actually said about Paper 2

Average performance per sub-question, Paper 2 (2025)

Sub-question	Topic	Average
1.1	Multiple choice	64%
1.2	Biological terms	64%
1.3	Matching	71%
1.4	Meiosis and mitosis	58%
1.5	Translation	57%
2.1	Meiosis	44%
2.2	DNA profiling	46%
2.3	Pedigree diagram	54%
2.4	Blood groups	52%
2.5	Incomplete dominance	52%
3.1	Human evolution: anatomical features of humans and apes	50%
3.2	Human evolution: hominid fossils	44%
3.3	Biogeography and speciation	34%
3.4	Investigation on natural selection	40%

The report names five topics that "appeared not to have been taught well": meiosis, DNA profiling, human evolution, speciation and biogeography, and scientific investigations. Q3.3 on biogeography and speciation was the worst answered question in the whole paper at 34%.

One line from the 2025 report is worth sitting with: "Many of the errors and misconceptions ... have been highlighted in previous diagnostic reports. This indicates that this document is not being used as a remedial tool." Everything in the confusable pairs table below is a mark that the examiners have already told you how to get.

The exact terminology errors recorded in 2025

• Mitochondria instead of mitochondrial DNA
• "Stem" or "stem cell research" instead of stem cell
• "Helix" or "double stranded" instead of double helix
• "Discontinuous" or "continuous" alone instead of discontinuous variation or continuous variation
• Locust instead of locus
• "Miss Ples" instead of Mrs Ples, and "Taung" instead of Taung child
• Skull instead of cranium
• "Variation" instead of genetic variation when describing crossing over
• "Artificial breeding" or "genetic engineering" instead of artificial selection
• Blood group B written as iBi, iBi0 or iBiB instead of I^BI^B or I^Bi

Confusable pairs: the marks you lose to the wrong word

Every pair below comes from an error the 2025 or 2024 Diagnostic Report actually recorded. The quiz tab tests every one of them.

You wrote	The memo wanted	The difference
Chromatid	Chromosome	A chromosome is made of two chromatids joined by a centromere. After anaphase the chromatids become chromosomes.
Single-stranded chromosome	Single chromosome	Recorded in 2025 as a direct cause of lost marks in Q2.1.5. A chromosome is single or double stranded, a "single chromosome" is a count.
Mitosis	Meiosis II	They look similar, but meiosis II starts with a haploid cell and follows meiosis I. Mitosis starts with a diploid cell and produces two identical diploid cells.
Transcription	Translation	Transcription is DNA to mRNA, in the nucleus. Translation is mRNA to protein, at the ribosome.
Variation	Genetic variation	The result of crossing over is specifically genetic variation. "Variation" on its own is too general and scores nothing.
Continuous	Continuous variation	"Continuous" alone is not a biological term. Include the word variation.
Locust	Locus	The locus is the position of a gene on a chromosome. A locust is an insect.
Mitochondria	Mitochondrial DNA	The organelle is not the evidence. The DNA inside it is.
Stem, or stem cell research	Stem cell	Give the full term. No marks for incomplete answers.
Helix, or double stranded	Double helix	The shape of a DNA molecule is a double helix.
Co-dominance	Incomplete dominance	Incomplete dominance gives an INTERMEDIATE phenotype (red and white give pink). Co-dominance expresses BOTH alleles equally and separately (black and white feathers give speckled).
Genetic engineering	Artificial selection	Artificial selection is humans choosing which organisms breed. Genetic engineering moves genes between organisms in a laboratory.
DNA fingerprinting	DNA profiling	The 2025 report instructs teachers to stop using "fingerprinting". The Examination Guidelines say profiling.
DNA profiling	DNA profile	Profiling is the process. The profile is the bar code pattern produced. The Code of Life practical memo marks this distinction explicitly.
DNA, or DNA sample	DNA bands, or DNA profile	When comparing profiles, you must refer to the bands.
Non-disjunction of autosomes	Non-disjunction of gonosomes	Down syndrome is chromosome pair 21, an autosome. Turner and Klinefelter are sex chromosomes. Read which one the question is about.
Homozygous, heterozygous	The phenotype only	Never use genotype words when the question asks for a phenotype in a genetic cross.
iBi, iBi0, iBiB	IBIB or IBi	Blood group notation. Superscript capital letters on I, lower case i for the recessive allele.
Receives blood group A from one parent	Inherits the IA allele from one parent	You inherit alleles, not blood groups.
2:2, 4:4, 1:1:1:1	The smallest ratio	Only the simplified ratio is marked correct.
Cream-coloured horse	Cream-coloured coat	The phenotype is the characteristic, not the whole animal.
Analogous structures	Homologous structures	Homologous have the same basic plan and different functions, showing common ancestry. Analogous have different basic plans and the same function, showing no common ancestry.
Hypothesis	Theory	A hypothesis is a testable statement based on limited data, which can be accepted or rejected. A theory is supported by a large body of evidence and persists.
A group of species that can interbreed	A group of organisms that can interbreed and produce fertile offspring	Recorded in 2025: candidates confused the biological species definition with the definition of a population.
Viable offspring	Fertile offspring	Viable means it survives. Fertile means it can reproduce. The definition needs fertile.
Gradualism	Punctuated equilibrium	Gradualism is slow continuous change. Punctuated equilibrium is long periods of little change punctuated by short periods of rapid change.
Skull	Cranium	Cranial capacity is the volume of the cranium, which houses the brain. Say cranium and link it to brain volume.
Foramen magnum in a forward position	In a MORE forward position	It is a comparison. Drop the "more" and you drop the mark.
Short and narrow pelvis	Short and WIDE pelvis	The human pelvis is short and wide. The ape pelvis is long and narrow.
Miss Ples, Taung	Mrs Ples, Taung child	Use the exact fossil names.
Intelligence	Increased brain volume gives greater intelligence	State the link, not just the endpoint.
The effect of food availability	The availability of food	The independent variable is the factor changed. "The effect" belongs to the dependent variable.
The characteristic was passed on	The ALLELE for the characteristic was passed on	Natural selection passes on alleles, not acquired characteristics.
Flies with resistance increased	The next generation had a HIGHER PROPORTION of resistant flies	Natural selection changes proportions in a population.
Reliability	Validity	Validity is fairness, everything constant except the independent variable. Reliability is repeats and sample size. Never mention both.

Meiosis

Meiosis is the reduction division that produces four haploid daughter cells from one diploid cell, in the ovaries and testes. It halves the chromosome number and introduces genetic variation.

The phases

Phase	What happens
Interphase	DNA replicates, each chromosome now has two chromatids
Prophase I	Chromosomes shorten and thicken, homologous chromosomes pair up (synapsis), crossing over occurs at the chiasmata, nuclear membrane disappears, spindle forms
Metaphase I	Homologous pairs line up at the equator, random arrangement
Anaphase I	Homologous chromosomes separate and move to opposite poles
Telophase I	Two haploid nuclei form, cytokinesis follows
Prophase II	Spindle re-forms in each haploid cell
Metaphase II	Chromosomes line up singly at the equator
Anaphase II	Chromatids separate and move to opposite poles
Telophase II	Four haploid nuclei form, cytokinesis gives four haploid cells

Meiosis II versus mitosis

	Meiosis II	Mitosis
Starting cell	Haploid	Diploid
Preceded by	Meiosis I	Interphase only
Number of divisions in the whole process	Two	One
Daughter cells	Four haploid, genetically different	Two diploid, genetically identical
Crossing over	Occurred in prophase I	Never
Where	Gonads only	Growth and repair, all over the body

The report is specific: "In many cases, teaching in Grade 12 only focuses on meiosis I and meiosis II, which results in gaps in learners' understanding of mitosis." Revise the phases of mitosis from Grade 10.

Sources of genetic variation in meiosis

• Crossing over in prophase I: homologous chromosomes exchange genetic material at the chiasmata, which results in new combinations of alleles and therefore increases genetic variation.
• Random arrangement of homologous pairs at the equator in metaphase I.
• Random fertilisation, any sperm may fuse with any ovum.

Non-disjunction

Non-disjunction is the failure of homologous chromosomes (meiosis I) or chromatids (meiosis II) to separate. One gamete gets an extra chromosome and one gets none.

Chromosomes involved	Zygote	Condition
Autosome pair 21	Three copies of chromosome 21	Down syndrome (trisomy 21)
Gonosomes, XX + O	XO	Turner syndrome
Gonosomes, XX + Y	XXY	Klinefelter syndrome
Gonosomes, XX + X	XXX	Triple X

DNA: the code of life

Structure

	DNA	RNA
Strands	Double helix, two strands	Single strand
Sugar	Deoxyribose	Ribose
Bases	Adenine, thymine, guanine, cytosine	Adenine, uracil, guanine, cytosine
Where	Nucleus and mitochondria	Nucleus and cytoplasm

A nucleotide is one phosphate, one deoxyribose sugar and one nitrogenous base. The bases pair by hydrogen bonds: A with T, C with G. Amino acids in a protein are joined by peptide bonds.

Replication, transcription, translation

Process	Where	What happens
DNA replication	Nucleus, during interphase	The double helix unwinds, hydrogen bonds break, each strand acts as a template and free nucleotides pair with the exposed bases, giving two identical DNA molecules
Transcription	Nucleus	One strand of DNA is used as a template to build mRNA. The mRNA leaves through the nuclear pores into the cytoplasm
Translation	Ribosome in the cytoplasm	tRNA anticodons pair with mRNA codons, each tRNA brings a specific amino acid, the amino acids are joined by peptide bonds to form a protein

Working backwards. Candidates lost marks in 2025 because they could not work from a codon back to a DNA triplet. Practise the chain in both directions: DNA triplet, mRNA codon, tRNA anticodon. If a DNA triplet is TAC, the mRNA codon is AUG and the tRNA anticodon is UAC.

DNA profiling

A DNA profile is the bar code pattern of bands produced from a DNA sample. DNA profiling is the process of producing and comparing it. The 2025 report gives this table for how it is used:

Use of DNA profile	What to look for
Forensics: identifying a criminal, family member or deceased person	All the DNA bands of the suspect or family member must be identical to the DNA profile of the sample from the crime scene or missing person
Paternity testing	Each band of the child must match either that of the mother or of the potential father. If the child has a band that does not match either parent, that excludes that male as the father

Genetic modification and stem cells

Genetic modification is finding a desirable gene, isolating it, and moving it into the cells of another organism. Stem cells are undifferentiated cells that can develop into any type of cell. Sources include embryonic stem cells from embryos, foetal stem cells from the umbilical cord or amniotic fluid, and adult stem cells from bone marrow.

Genetics and inheritance

The vocabulary that must be exact

Term	Meaning
Gene	A section of DNA that codes for a specific characteristic
Allele	Two or more alternative forms of a gene at the same locus
Locus	The position of a gene on a chromosome
Genotype	The genetic make-up, the alleles present
Phenotype	The physical and functional expression of a gene
Homozygous	Two identical alleles for a characteristic
Heterozygous	Two non-identical alleles for a characteristic
Autosomes	Chromosomes not responsible for sex determination
Gonosomes	The sex chromosomes
Genome	All the genes that make up an organism
Karyotype	A representation of the number, shape and arrangement of all the chromosomes in the nucleus of a somatic cell

Types of dominance

Type	What the heterozygote looks like	Example
Complete dominance	Identical to the homozygous dominant, the recessive allele is masked	Tall and short pea plants
Incomplete dominance	An intermediate phenotype, neither allele is completely dominant	Red and white snapdragons give pink. A chestnut and a cream horse give a golden coat
Co-dominance	Both alleles are expressed equally and separately	Black and white feathers give an erminette (speckled) chicken. Blood group AB

Blood groups

This is the table the report tells teachers to give learners.

Phenotype (blood group)	Genotype
A	Homozygous IAIA, or heterozygous IAi
B	Homozygous IBIB, or heterozygous IBi
AB	Heterozygous IAIB
O	Homozygous ii

Blood group AB is inherited when the child inherits the I^A allele from one parent and the I^B allele from the other. Say allele, never blood group.

Sex-linked inheritance

Haemophilia and colour blindness are carried on the X chromosome. Males have only one X chromosome. If that chromosome carries the recessive allele the male is affected, because there is no other allele to mask it. Females have two X chromosomes and need two recessive alleles to be affected, since a dominant allele on the other X will mask the effect.

The report warns that "there is a misconception that disorders are only caused by recessive alleles". CADASIL, tested in 2025, is an autosomal DOMINANT disorder. Read the stem.

Setting out a genetic cross

The marks are for the layout as much as the answer. Write:

1. P1 phenotype
2. P1 genotype
3. Meiosis, then the gametes
4. Fertilisation
5. F1 genotype
6. F1 phenotype

Use the letters given in the question. Give the smallest ratio. Never write homozygous or heterozygous where a phenotype is asked for.

Evolution

Lamarck versus Darwin

Lamarck	Darwin, natural selection
A structure that is used more becomes better developed, one that is used less becomes reduced	There is variation in a population, some individuals have an allele that others do not
These acquired characteristics are passed on to the offspring	A selection pressure acts on the population
Over generations the whole population changes	Individuals with the favourable allele survive and reproduce, those without it die
	They pass the ALLELE on to their offspring
	The next generation has a HIGHER PROPORTION of individuals with that characteristic

Marks were lost in 2025 for saying "the characteristic was passed on" instead of "the allele was passed on", and for saying the resistant flies "increased" instead of "the next generation had a higher proportion of resistant flies". Learn the five step Darwin answer and apply it to whatever organism the question gives you.

Evidence for evolution

Evidence	What it shows
Fossil record	Mineralised remains of organisms that lived in the past, showing change over time
Homologous structures	Same basic plan, different functions, indicating a common ancestor and divergent evolution
Analogous structures	Different basic plan, same function, indicating no common ancestor and convergent evolution
Vestigial structures	Reduced structures with no known function, which other organisms have in a functional form, indicating common ancestry
Biogeography	The present day distribution of organisms across the continents, explained by continental drift
Genetic evidence	Similarity of DNA and of mitochondrial DNA between species

Speciation, the answer that scores

This is the structure the memos reward, using the baobab example:

1. The original population was separated into two populations, by a geographical barrier such as the ocean formed by continental drift.
2. There was no gene flow between the two populations.
3. Each population was exposed to different environmental conditions, that is, different selection pressures.
4. Natural selection occurred independently in each population.
5. The individuals of the two populations became very different from each other, genotypically and phenotypically.
6. Even if the two populations were to mix again, they would not be able to interbreed.
7. They are now two different species.

The 2025 report notes that in the biogeography question, "many responses failed to mention that continental drift separates original populations". Biogeography and speciation must be explained together.

Reproductive isolation mechanisms

• Breeding at different times of the year
• Species-specific courtship behaviour
• Adaptation to different pollinators
• Prevention of fertilisation
• Infertile offspring

Punctuated equilibrium

Evolution takes place over long periods of time where very little or no change occurs, known as equilibrium. This alternates with, or is punctuated by, short periods of time where rapid change occurs, through natural selection. Transitional fossils are not associated with punctuated equilibrium.

Theory versus hypothesis

Hypothesis	Theory
Possible prediction or explanation of a phenomenon after observation	Scientific explanation of events supported by results
Based on limited data	Supported by a lot of evidence
Can either be accepted or rejected	Reliable, and the basic ideas persist in science

Human evolution

What humans share with African apes

All are in the family Hominidae. Shared characteristics include: large brain, eyes in front of the skull, binocular or stereoscopic vision, eyes with cones giving colour vision, freely rotating arms, long upper arms, rotation around the elbow and wrist joints, five digits per limb (pentadactyl), bare fingertips with flat nails instead of claws, opposable thumbs giving a precision grip, upright posture, sexual dimorphism, and two mammary glands.

Anatomical differences: ape and human

Feature	African ape	Human
Foramen magnum	Towards the back of the skull	In a MORE forward position
Vertebral column	C-shaped or bow shaped	S-shaped
Pelvis	Long and narrow	Short and wide, bowl shaped
Jaw	Prognathous, protruding	Less prognathous, or non-prognathous
Palate	Long and rectangular, U-shaped	Short and semi-circular, more rounded
Canines	Long, large and pointed	Short and small
Diastema	Spaces between the teeth present	No spaces between the teeth
Brow ridges	Prominent	Reduced
Cranial capacity	Small	Large
Temporal muscle	Larger, greater bite power for hard raw food	Smaller, softer and cooked food

Bipedalism

Anatomical evidence for bipedalism: the foramen magnum is in a more forward position, the spine is S-shaped, and the pelvis is short and wide.

Advantages of bipedalism, each stated as feature plus benefit:

• Frees the arms, so they can carry offspring, tools or food, and manipulate things
• Allows the ability to see further, to spot danger or food
• Reduces the surface area exposed to the sun, so less heat is absorbed, which improves thermoregulation
• Exposes the genitals, to attract the opposite sex
• More efficient locomotion, which allows travelling longer distances

The 2025 report records that candidates could state the feature but not its significance: "the S-shaped spine allows an upright posture" scored nothing, where "better distribution of body weight, to absorb shock, allow flexibility" scored. Always give the feature AND the reason.

South African hominid fossils

Fossil	Species	Found by / where
Taung child	Australopithecus africanus	Raymond Dart, Taung
Mrs Ples	Australopithecus africanus	Robert Broom, Sterkfontein
Little Foot	Australopithecus	Ron Clarke, Stephen Motsumi and Nkwane Molefe, Sterkfontein
Karabo	Australopithecus sediba	Lee Berger, 2012, Malapa
Homo naledi	Homo naledi	Lee Berger, 2015, Rising Star cave

All of these come from the Cradle of Humankind, which is so named because the site has produced a large number of hominin fossils in the human lineage.

Out of Africa

The hypothesis states that modern humans originated in Africa and then migrated to other continents. Two lines of evidence support it: fossil evidence, and mitochondrial DNA.

The fossil argument. Fossils of Ardipithecus, Australopithecus and Homo habilis are found in Africa only. The oldest fossils of Homo erectus and Homo sapiens are found in Africa, and the youngest are found on other continents, which indicates migration out of Africa.

The mitochondrial DNA argument. Every cell has mitochondria with DNA. Mitochondrial DNA is inherited only through the maternal line. Analysis of the mutations on mitochondrial DNA traces the line of descent to an ancestral female who lived in Africa, and shows that all humans descended from her, called mitochondrial Eve.

Cultural evidence

Cultural evidence for human evolution is the development and use of tools, the use of fire, and the use of art. Homo habilis, the "handy man", was the first Homo species to use tools.

Brain size

Cranial capacity increased through the hominid line. An increase in brain volume allows for greater intelligence, and for storing and processing large amounts of information quickly. Cranial capacity is used to estimate brain volume because the cranium houses the brain.

Scientific investigations in Paper 2

The natural selection investigation in 2025 averaged 40%. The rules are the same as in Paper 1 and are worth revising here.

• Independent variable: what the investigator changes. "The availability of food", not "the effect of food availability".
• Dependent variable: what is measured, in full. Not "time taken for flies to die" but "time taken for 80% of the flies to die from starvation".
• Validity: everything constant except the independent variable. Start with "same".
• Reliability: repeats, large sample, long duration. Quote the actual numbers from the extract.
• Describing results: describe what the data shows, with the correct range and units. A conclusion is a different thing and comes from the aim.
• Applying Darwin: never give a generic natural selection answer. Name the organism, the specific variation, the specific selection pressure.

Exam-style questions with memos

Show memo: Explain how mitochondrial DNA is used to show that modern humans originated in Africa. (4)

Every cell has mitochondria with DNA. Mitochondrial DNA is inherited only through the maternal line. The analysis of mutations on the mitochondrial DNA shows that the oldest female ancestor was located in Africa, and that all humans descended from her, mitochondrial Eve.

Show memo: Explain how different species of baobab could have evolved on different continents. (6)

The common ancestor population of the baobab was separated into two populations by the ocean. There was no gene flow between the two baobab populations. Each population was exposed to different environmental conditions, that is other selection pressures. Natural selection occurred independently in each of the two populations, such that the individuals of the two populations became very different from each other, genotypically and phenotypically. Even if the two populations were to mix again they would not be able to interbreed.

Show memo: Explain how a population of fruit flies became more resistant to starvation over generations. (7)

There was variation amongst the population. Some had the allele for starvation resistance and some did not. When exposed to the selection pressure of limited food, those without the allele died. Those with the allele survived and reproduced, passing the allele for starvation resistance to their offspring. The next generation had a higher proportion of flies with starvation resistance.

Show memo: Explain why a male is far more likely to be haemophiliac than a female. (3)

Males have only one X chromosome. If this chromosome carries the recessive allele the male will have haemophilia, as there is no other allele that could mask the effect of the recessive allele.

Show memo: Define punctuated equilibrium. (4)

Evolution takes long periods of time where very little, gradual or no change occurs, known as equilibrium. This alternates with, or is punctuated by, short periods of time where rapid change occurs, through natural selection.

Further reading and where to go next

• 2025 NSC Diagnostic Report, Chapter 8, sections 8.5 to 8.7 are Paper 2. Read the "Common errors and misconceptions" under each question.
• 2024 NSC Diagnostic Report, Chapter 8. The 2025 report refers back to it for the meiosis teaching tips, the blood group table and the evolution guidance.
• 2021 NSC Diagnostic Report. The 2025 report points to it twice: for the steps on interpreting a pedigree diagram, and for a similar biogeography and speciation question set in November 2021 Q3.2.
• CAPS Examination Guidelines. Use its process descriptions rather than longer textbook versions, and use its terminology (DNA profiling, not fingerprinting).

One-page summary

• Evolution and human evolution together are 54 marks, 36% of the paper, and the weakest section in 2025.
• Biogeography and speciation was the worst answered question at 34%. Learn the seven step speciation answer and always mention continental drift separating the original population.
• Natural selection: variation, selection pressure, survivors reproduce, the ALLELE is passed on, the next generation has a HIGHER PROPORTION.
• Incomplete dominance gives an intermediate phenotype. Co-dominance expresses both alleles equally.
• Blood group notation is I^A, I^B and i. You inherit alleles, not blood groups.
• Only the smallest ratio is marked. Never use homozygous or heterozygous for a phenotype.
• Crossing over increases GENETIC variation. "Variation" alone scores nothing.
• DNA profile is the bar code. DNA profiling is the process. Compare BANDS, not "DNA".
• Human pelvis: short and WIDE. Foramen magnum: MORE forward. Cranium, not skull.
• Mrs Ples, Taung child. Get the fossil names exactly right.
• Feature plus significance. Never state a bipedal feature without saying what it achieves.
• Independent variable is the factor changed, not "the effect of" anything.