Overview
This study guide is designed to help Grade 12 students prepare for Life Sciences exams, summarizing core concepts, definitions, processes, and skills aligned with the CAPS curriculum, along with exam tips and exemplar questions.
DNA: Structure, Function, and Protein Synthesis
- DNA and RNA are nucleic acids made of nucleotide monomers.
- DNA is double-stranded, contains thymine, and has deoxyribose sugar; RNA is single-stranded, contains uracil, and has ribose sugar.
- DNA replication produces identical DNA molecules for cell division, ensuring genetic continuity.
- Protein synthesis involves transcription (DNA to mRNA in nucleus) and translation (mRNA to protein in cytoplasm).
Meiosis and Genetic Variation
- Meiosis is the division of a diploid cell into four genetically unique haploid gametes.
- It involves two successive divisions: Meiosis I (homologous chromosomes separate) and Meiosis II (sister chromatids separate).
- Crossing over and independent assortment create genetic variation.
- Errors such as non-disjunction can lead to disorders like Down syndrome.
Reproduction in Humans and Vertebrates
- Male reproductive system produces and transports sperm; testosterone triggers secondary male traits.
- Female reproductive system produces ova and supports embryo development; hormones regulate the menstrual cycle.
- Fertilization forms a zygote, which implants in the uterus and develops into a fetus.
Genetics and Inheritance
- Genes are DNA sections coding for traits; alleles are gene variants.
- Dominant alleles mask recessive ones; co-dominance and incomplete dominance also occur.
- Sex-linked traits are carried on sex chromosomes; pedigree diagrams trace inheritance.
- Mutations introduce genetic diversity and can cause disorders.
Human Nervous and Endocrine Systems
- The nervous system (brain, spinal cord, neurons) coordinates body responses to stimuli and reflex actions.
- The endocrine system uses hormones to regulate processes like growth, metabolism, and homeostasis (e.g., glucose, water, salt balance).
- Negative feedback maintains internal balance (homeostasis).
Responding to Environment: Humans and Plants
- The brain controls voluntary/involuntary functions; neurons transmit signals; reflex arcs enable quick responses.
- The eye and ear provide vision and hearing/balance; defects can be corrected with glasses or aids.
- Plants use hormones (auxins) for growth towards stimuli (phototropism, geotropism) and defense.
Evolution and Human Impact
- Evolution is supported by fossil, genetic, and cultural evidence; variation arises from mutations, meiosis, and sexual reproduction.
- Darwin (natural selection) and Lamarck (inheritance of acquired traits) explained evolution differently.
- Human evolution traced through fossil record and genetic evidence ("Out of Africa" hypothesis).
- Human activity impacts environment via climate change, pollution, biodiversity loss, and resource use.
Practical Skills for Exams
- Line, bar, and pie graphs display data; diagrams must be neat and labelled.
- Essay questions require clear structure, logical flow, and definition of key terms.
- Practise using blank diagrams and exemplar exam papers.
Key Terms & Definitions
- Nucleotide — Building block of nucleic acids (DNA/RNA).
- Meiosis — Cell division creating four unique gametes.
- Allele — Variant form of a gene.
- Phenotype — Observable characteristics of an organism.
- Homeostasis — Maintenance of stable internal conditions.
- Negative feedback — Process restoring balance in the body.
- Auxin — Plant hormone controlling growth.
- Natural selection — Process where traits that aid survival increase in frequency.
Action Items / Next Steps
- Practise drawing and labelling biological diagrams provided in the guide.
- Complete exemplar exam papers under timed conditions.
- Review areas marked as not covered in the guide using your textbook/class notes.
- Use mobile notes, mnemonics, and mind maps to reinforce key concepts.
- Check off topics mastered using the learner’s checklist.