Eduqas A Level Biology Component 2: Continuity of Life Exam Questions

About Eduqas A Level Biology Component 2: Continuity of Life

Component 2 of Eduqas A Level Biology, Continuity of Life, is about how organisms are classified, how cells divide, how humans and flowering plants reproduce, and how genes are inherited and change over time. It finishes with applications of reproduction and genetics such as PCR, genetic engineering and genome sequencing. It draws heavily on AS knowledge of nucleic acids and cell division, so revise those alongside it. Examiners regularly set genetic crosses with chi-squared tests, Hardy-Weinberg calculations, questions on hormones in the menstrual cycle and double fertilisation, and evaluation of the ethics and benefits of gene technology.

What you need to know

• 2.1 Organisms are placed in three domains and a hierarchy from kingdom to species, named using the binomial system. Biodiversity is measured with Simpson's index and assessed using DNA sequences and protein comparisons as well as physical features.
• 2.2 Mitosis produces genetically identical diploid cells for growth and repair; meiosis produces four haploid, genetically different cells through crossing over and independent assortment. Know the stages and how to calculate mitotic index.
• 2.3 Spermatogenesis and oogenesis in the testes and ovaries, the roles of FSH, LH, oestrogen and progesterone in the menstrual cycle, fertilisation, implantation and the functions of the placenta, including hCG.
• 2.4 Flower structure in insect and wind pollinated plants, pollination and the mechanisms that promote cross-pollination, double fertilisation forming a diploid zygote and triploid endosperm, seed structure and germination with gibberellin stimulating amylase.
• 2.5 Monohybrid and dihybrid crosses, codominance, multiple alleles, sex linkage and autosomal linkage. Use the chi-squared test to compare observed and expected ratios.
• 2.6 Variation from mutation, meiosis and random fertilisation; natural selection; the Hardy-Weinberg principle (p + q = 1, p^2 + 2pq + q^2 = 1); allopatric and sympatric speciation through reproductive isolation.
• 2.7 PCR, gel electrophoresis, genetic fingerprinting, recombinant DNA using restriction enzymes and ligase, GM crops, gene therapy, genome sequencing and the use of stem cells, with their ethical issues.

Common mistakes in Component 2: Continuity of Life

• Saying meiosis halves the chromosome number in meiosis II. The reduction from diploid to haploid happens in meiosis I when homologous chromosomes separate.
• Calculating Hardy-Weinberg using 2pq for the recessive phenotype. The homozygous recessive frequency is q^2, so q is the square root of the recessive phenotype frequency.
• Concluding that a chi-squared value proves a hypothesis. If the value is below the critical value at p = 0.05 there is no significant difference, so any difference is due to chance.
• Describing the endosperm as diploid. One male nucleus fuses with the two polar nuclei to give a triploid endosperm nucleus.
• Confusing linkage with sex linkage. Autosomal linkage means two genes are on the same autosome and tend to be inherited together unless crossing over separates them.

Try three Component 2: Continuity of Life exam-style questions