Aqa B2 Topics For Argumentative Essays

Biology, Chemistry and Physics topics for AQA Additional Science:


Cells and simple cell transport
Tissues, organs and organ systems
Organs in animals, Organs in plants
Organisms and their environment
Distribution of organisms
Proteins - their functions and uses
Proteins and enzymes
Aerobic and anaerobic respiration
Cell division and inheritance
DNA and cell division, Genetic variation and genetic disorders
Old and new species


Structure and bonding
Ionic bonding, Covalent bonding, Structure properties and uses
Atomic structure, analysis and quantitative chemistry
Atomic structure, Analysing substances, Quantitative chemistry
Rates of reaction
Rates of reaction
Exothermic and endothermic reactions
Exothermic and endothermic reactions
Acid, bases and salts
Acids, bases and salts


Forces and their effects
Resultant forces, Forces and motion, Forces and braking, Forces and terminal velocity, Forces and elasticity
Kinetic energy
Forces and energy, Momentum
Static electricity, Current and voltage in electrical circuits, Resistance, Household electricity, Charge, current and power
Atoms and radiation
Atomic structure, Nuclear radiation, Nuclear fission and fusion
Life cycles of stars
Life cycles of stars

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Characteristics are passed on from one generation to the next in both plants and animals. Simple genetic diagrams can be used to show this. There are ethical considerations in treating genetic disorders.

Candidates should use their skills, knowledge and understanding to:

  • explain why Mendel proposed the idea of separately inherited factors and why the importance of this discovery was not recognised until after his death

Additional guidance:

Candidates should be familiar with principles used by Mendel in investigating monohybrid inheritance in peas. They should understand that Mendel's work preceded the work by other scientists which linked Mendel's 'inherited factors' with chromosomes.

  • interpret genetic diagrams, including family trees
  • higher tier only: construct genetic diagrams of monohybrid crosses and predict the outcomes of monohybrid crosses and be able to use the terms homozygous, heterozygous, phenotype and genotype

Addtional guidance:

Foundation Tier candidates should be able to interpret genetic diagrams of monohybrid inheritance and sex inheritance but will not be expected to construct genetic diagrams or use the terms homozygous, heterozygous, phenotype or genotype.

  • predict and/or explain the outcome of crosses between individuals for each possible combination of dominant and recessive alleles of the same gene
  • Make informed judgements about the social and ethical issues concerning the use of stem cells from embryos in medical research and treatments
  • Make informed judgements about the economic, social and ethical issues concerning embryo screening.

Additional guidance:

Data may be given for unfamiliar contexts.

B2.7.1 Cell Division

a) In body cells the chromosomes are normally found in pairs. Body cells divide by mitosis.

Additional guidance:

Knowledge and understanding of the stages in mitosis and meiosis is not required.

b) The chromosomes contain the genetic information.

c) When a body cell divides by mitosis:

  • copies of the genetic material are made
  • then the cell divides once to form two genetically identical body cells

Additional guidance:

Throughout section 2.7 candidates should develop an understanding of the relationship from the molecular level upwards between genes, chromosomes, nuclei and cells and to relate these to tissues, organs and systems (2.2 and 2.3).

d) Mitosis occurs during growth or to produce replacement cells.

e) Body cells have two sets of chromosomes; sex cells (gametes) have only one set.

f) Cells in reproductive organs – testes and ovaries in humans – divide to form gametes.

Additional guidance:

For Foundation Tier, knowledge of meiosis is restricted to where the process occurs and that gametes are produced by meiosis.

g) The type of cell division in which a cell divides to form gametes is called meiosis.

h) Higher Tier only: When a cell divides to form gametes:

  • copies of the genetic information are made
  • then the cell divides twice to form four gametes, each with a single set of chromosomes.

i) When gametes join at fertilisation, a single body cell with new pairs of chromosomes is formed. A new individual then develops by this cell repeatedly dividing by mitosis.

Additional guidance:

Candidates should understand that genetic diagrams are biological models which can be used to predict the outcomes of crosses.

j) Most types of animal cells differentiate at an early stage whereas many plant cells retain the ability to differentiate throughout life. In mature animals, cell division is mainly restricted to repair and replacement.

k) Cells from human embryos and adult bone marrow, called stem cells, can be made to differentiate into many different types of cells, eg nerve cells.

Additional guidance:

Knowledge and understanding of stem cell techniques is not required.

l) Human stem cells have the ability to develop into any kind of human cell.

m) Treatment with stem cells may be able to help conditions such as paralysis

n) The cells of the offspring produced by asexual reproduction are produced by mitosis from the parental cells. They contain the same alleles as the parents

B2.7.2 Genetic Variation

a) Sexual reproduction gives rise to variation because, when gametes fuse, one of each pair of alleles comes from each parent.

b) In human body cells, one of the 23 pairs of chromosomes carries the genes that determine sex. In females the sex chromosomes are the same (XX); in males the sex chromosomes are different (XY).

c) Some characteristics are controlled by a single gene. Each gene may have different forms called alleles.

d) An allele that controls the development of a characteristic when it is present on only one of the chromosomes is a dominant allele.

e) An allele that controls the development of characteristics only if the dominant allele is not present is a recessive allele.

f) Chromosomes are made up of large molecules of DNA (deoxyribo nucleic acid) which has a double helix structure.

Additional guidance:

Candidates are not expected to know the names of the four bases or how complementary pairs of bases enable DNA replication to take place.

g) A gene is a small section of DNA

h) Higher Tier only: Each gene codes for a particular combination of amino acids which make a specific protein.

i) Each person (apart from identical twins) has unique DNA. This can be used to identify individuals in a process known as DNA fingerprinting.

Additional guidance:

Knowledge and understanding of genetic fingerprinting techniques is not required.

B2.7.3 Genetic Disorders

a) Some disorders are inherited.

b) Polydactyly – having extra fingers or toes – is caused by a dominant allele of a gene and can therefore be passed on by only one parent who has the disorder.

Additional guidance:

Attention is drawn to the potential sensitivity needed in teaching about inherited disorders.

c) Cystic fibrosis (a disorder of cell membranes) must be inherited from both parents. The parents may be carriers of the disorder without actually having the disorder themselves. It is caused by a recessive allele of a gene and can therefore be passed on by parents, neither of whom has the disorder.

d) Embryos can be screened for the alleles that cause these and other genetic disorders.

Additional guidance:

Knowledge and understanding of embryo screening techniques is not required.

Suggested ideas for practical work to develop skills and understanding include the following:

  • observation or preparation and observation of root tip squashes to illustrate chromosomes and mitosis
  • using genetic beads to model mitosis and meiosis and genetic crosses
  • making models of DNA
  • extracting DNA from kiwi fruit.

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