Lecture Notes: National 5 Biology - Unit 2: Multicellular Organisms - Key Area 3: Reproduction

Overview

• Focus on sexual reproduction
• Requires two parents producing gametes (sex cells)
• Sexual reproduction occurs in both plants and animals

Gametes

• Male Gametes:
  • Animals: Sperm
  • Plants: Pollen
• Female Gametes:
  • Animals: Egg
  • Plants: Ovule

Chromosomes in Gametes

• Gametes carry half the chromosomes for the new organism
  • 50% chromosomes from mother, 50% from father
• Humans:
  • Body cells: 46 chromosomes
  • Gametes: 23 chromosomes
  • Zygote (fertilized egg): 46 chromosomes (diploid)
• Terms:
  • Diploid: Full set of chromosomes (46 in humans)
  • Haploid: Half set of chromosomes (23 in human gametes)

Examples of Chromosome Numbers

• Giraffe:
  • Body cells: 62 chromosomes
  • Gametes: 31 chromosomes (haploid)
• Hedgehog:
  • Body cells: 88 chromosomes
  • Gametes: 44 chromosomes (haploid)
• Woolly Mammoth:
  • Gametes: 29 chromosomes
  • Body cells: 58 chromosomes (diploid)
• Tiger:
  • Gametes: 19 chromosomes
  • Body cells: 38 chromosomes (diploid)
• Plant:
  • Gametes: 630 chromosomes
  • Other plant cells: 1260 chromosomes (diploid)

Production of Gametes

• Plants:
  • Male gamete (pollen) produced in anthers
  • Female gamete (ovule) produced in ovaries
• Animals:
  • Male gamete (sperm) produced in testes
  • Female gamete (egg) produced in ovaries

Fertilization

• Definition: Fusion of the nucleus of a haploid sperm and the nucleus of a haploid egg to form a diploid zygote
• Site of fertilization: Oviduct (Philippian tubes)
• Post-fertilization:
  • Fertilized egg = zygote (diploid)
  • Implants in uterus wall to grow into embryo, fetus, then baby

Additional Information

• Quizzes and resources available for further study
• More videos and skills questions coming soon
• Students encouraged to engage with content through comments or messages

End of Notes