Subject: Life Sciences Grade: 12 (Matric) Focus: DNA, Genetics, Evolution, and Human Physiology
Introduction
Life Sciences (Biology) in Grade 12 is about understanding life at a molecular level (DNA) and a macro level (Evolution). It requires memorization of terms and understanding of complex processes.
This guide breaks down the curriculum based on the Examination Guidelines.
Paper 1: Life Processes in Plants and Animals (150 Marks)
This paper focuses on how organisms function and reproduce.
1. Reproduction in Vertebrates (±8 Marks)
- Strategies: Understand the differences between:
- External vs. Internal Fertilization.
- Ovipary (eggs), Vivipary (live birth), and Ovovivipary (eggs hatch inside).
- Amniotic Egg: Know the structure and function of the amnion, chorion, yolk sac, and allantois.
2. Human Reproduction (±41 Marks)
This is a major section.
- Structure: Label the male and female reproductive systems.
- Processes:
- Gametogenesis: Formation of sperm (spermatogenesis) and eggs (oogenesis).
- Menstrual Cycle: Understand the hormonal control (FSH, LH, Oestrogen, Progesterone) and the changes in the ovary and uterus.
- Fertilization & Development: From zygote to blastocyst to implantation.
3. Responding to the Environment (Humans) (±54 Marks)
- Nervous System:
- Neurons: Sensory, Motor, and Interneurons. Know the structure and function of a synapse.
- Reflex Arc: Be able to draw and label the path of a reflex action.
- The Brain: Functions of the Cerebrum, Cerebellum, Medulla Oblongata, Hypothalamus.
- The Eye & Ear: Structure and function. Focus on Accommodation (focusing) and Pupillary Mechanism (light adjustment) in the eye.
- Endocrine System: Know the glands (Pituitary, Thyroid, Adrenal, Pancreas) and the hormones they secrete. Understand Negative Feedback Mechanisms (e.g., TSH and Thyroxin).
4. Responding to the Environment (Plants) (±13 Marks)
- Tropisms: Phototropism (light) and Geotropism (gravity). Understand the role of Auxins.
- Plant Hormones: Functions of Gibberellins and Abscisic Acid.
Paper 2: Life at the Molecular, Cellular and Tissue Level (150 Marks)
This paper deals with genetics and evolution.
1. DNA: The Code of Life (±27 Marks)
- Structure: Nucleotides, double helix, base pairing (A-T, C-G).
- Replication: When and how DNA copies itself.
- Protein Synthesis: Transcription (DNA to mRNA) and Translation (mRNA to Protein). You must know the steps in detail.
2. Meiosis (±21 Marks)
- Process: Phases of Meiosis I and II.
- Importance: How it creates genetic variation (Crossing over, Random arrangement).
- Abnormalities: Non-disjunction leading to Down Syndrome.
3. Genetics and Inheritance (±48 Marks)
- Monohybrid Crosses: Complete dominance, Incomplete dominance, Co-dominance.
- Sex-linked Inheritance: Colour blindness and Haemophilia (carried on the X chromosome).
- Pedigree Diagrams: Be able to trace a trait through a family tree.
- Genetic Engineering: Cloning, Stem Cells, GMOs.
4. Evolution (±54 Marks)
- Evidence: Fossil record, Biogeography, Genetics.
- Theories:
- Lamarckism: Inheritance of acquired characteristics (disproven but important).
- Darwinism: Natural Selection.
- Punctuated Equilibrium: Rapid change vs. gradual change.
- Human Evolution:
- Out of Africa Hypothesis: Evidence (fossils like Australopithecus and Homo habilis, mitochondrial DNA).
- Hominid Characteristics: Bipedalism, brain size, dentition.
My Top Tips for Distinction
1. Master “Protein Synthesis” This is a guaranteed long question (essay or structured). Memorize the sequence: DNA unzips -> mRNA forms (Transcription) -> mRNA moves to ribosome -> tRNA brings amino acids (Translation).
2. Genetics Calculations Practice your Punnett Squares. Don’t lose marks on simple ratios. Remember to state the Phenotype and Genotype clearly.
3. Know Your Diagrams You will be asked to label diagrams (Eye, Ear, Brain, Sperm, etc.). Spend time drawing and labeling them from memory.
Conclusion
Life Sciences requires a lot of reading and understanding. Don’t just memorize; try to visualize the processes. Paper 1 is about systems (how the body works), and Paper 2 is about origins (where we come from).
Good luck with your Matric Finals!