Reproduction and Inheritance

IGCSE Edexcel Biology
3.1–3.39 Reproduction, Inheritance, Variation and Evolution
Key Concepts: Sexual reproduction involves fertilisation and produces variation; asexual reproduction makes genetically identical offspring. Inheritance is controlled by genes on chromosomes. Variation arises from genes, environment, and random fertilisation.

Section A: Reproduction Basics

1. Compare sexual and asexual reproduction (two differences). [4]
2. Define fertilisation. [2]

Section B: Reproduction in Flowering Plants

3. Describe two features of insect-pollinated flowers and two features of wind-pollinated flowers. [4]
4. Describe how fertilisation happens in flowering plants (pollen tube, zygote, seed/fruit). [4]
5. State the conditions needed for seed germination. [3]
6. Explain how a germinating seed uses its food reserves. [2]
7. Give one natural and one artificial method of asexual reproduction in plants. [2]

Section C: Human Reproduction

8. Name four structures of the male reproductive system and four structures of the female reproductive system. [8]
9. Describe the roles of oestrogen and progesterone in the menstrual cycle. [4]
10. State the role of the placenta and how the embryo is protected by amniotic fluid. [4]
11. Describe the roles of testosterone and oestrogen in secondary sexual characteristics. [4]

Section D: Inheritance Concepts

12. Define genome and gene. [2]
13. Define: dominant, recessive, homozygous, heterozygous, genotype, phenotype. [6]

Section E: Genetic Diagrams

14. Tall (T) is dominant to dwarf (t). Cross Tt × tt and give the expected genotype and phenotype ratios. [4]
15. Use a genetic diagram to show how sex is determined in humans (XX and XY). [3]
16. What is a pedigree diagram used for? [2]

Section F: Cell Division, Variation and Evolution

17. Compare mitosis and meiosis (two differences). [4]
18. Explain why random fertilisation increases variation. [2]
19. Define mutation and state one possible effect. [2]
20. Explain Darwin's theory of evolution by natural selection. [4]
21. Explain how antibiotic resistance can increase in bacterial populations. [4]
Total marks: 64

Mark Scheme

1. Sexual: two parents, involves gametes/fertilisation, produces variation; Asexual: one parent, no gamete fusion, clones (any two differences) [4]
2. Fusion of male and female gamete nuclei to form a zygote [2]
3. Insect: large petals, scent/nectar, sticky pollen, anthers inside; Wind: small petals, no scent/nectar, light pollen, anthers exposed (any four) [4]
4. Pollen lands on stigma, grows pollen tube to ovule, male nucleus fuses with egg to form zygote; ovule becomes seed and ovary becomes fruit [4]
5. Water, oxygen, suitable temperature [3]
6. Food reserves are respired to release energy for growth until leaves photosynthesise [2]
7. Natural: runners/tubers/bulbs; Artificial: cuttings/rafting (any one each) [2]
8. Male: testes, sperm duct, prostate, penis (any four); Female: ovaries, oviducts, uterus, cervix, vagina (any four) [8]
9. Oestrogen rebuilds/maintains uterus lining and stimulates ovulation; progesterone maintains uterus lining; levels fall to trigger menstruation (any four) [4]
10. Placenta transfers oxygen/nutrients and removes wastes; amniotic fluid cushions/protects and allows movement [4]
11. Testosterone: facial hair, deeper voice, muscle growth; Oestrogen: breast development, wider hips (any four) [4]
12. Genome = entire DNA; gene = section of DNA coding for a protein [2]
13. Correct definitions for all six terms [6]
14. Genotype ratio 1 Tt : 1 tt; phenotype ratio 1 tall : 1 dwarf [4]
15. XX female, XY male; 50:50 chance shown using Punnett square [3]
16. Shows inheritance of a characteristic through a family across generations [2]
17. Mitosis: two identical diploid cells; Meiosis: four non-identical haploid cells; occurs in growth vs gamete formation (any two differences) [4]
18. Gametes are genetically different; random fusion creates new combinations of alleles [2]
19. Mutation is a rare random change in genetic material; may be harmful/neutral/beneficial (any one effect) [2]
20. Variation, competition, survival of the fittest, inheritance of advantageous traits (any four points) [4]
21. Random mutation produces resistant bacteria; antibiotics kill non-resistant; resistant survive and reproduce; frequency of resistance increases [4]