Gametes & Fertilisation (Cambridge O Level Biology)

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Gametes & Fertilisation

  • Fertilisation is the fusion of the nuclei from a male gamete (sperm cell) and a female gamete (egg cell)
  • It occurs in the oviducts
  • This results in the formation of a zygote which will undergo cell division and grow to form an embryo
  • Gametes have adaptations to increase the chances of fertilisation and successful development of an embryo

Adaptations of Gametes

Gamete Adaptive feature Reason
Sperm Has a flagellum (tail) Enables it to swim to the egg
Contains enzymes in the head region (acrosome) To digest through the jelly coat and cell membrane of an egg cell when it meets one
Contains many mitochondria Provide energy from respiration so that the flagellum can move back and forth for locomotion
Egg Cytoplasm containing a store of energy Provides energy for the dividing zygote after fertilisation
Jelly-like coating that changes after fertilisation Forms an impenetrable barrier after fertilisation to prevent other sperm nuclei entering the egg cell

Comparison of Male & Female Gametes Table

  Sperm Egg
Size Very small (45µm) Large (0.2mm)
Structure Head region and flagellum, many structural adaptations Round cell with few structural adaptations, covered in a jelly coating
Motility Capable of locomotion Not capable of locomotion
Numbers Produced every day in huge numbers (around 100 million per day) Thousands of immature eggs in each ovary, but only one released each month

Comparing sperm and egg cells Comparing sperm and egg cells

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Marlene

Author: Marlene

Expertise: Biology

Marlene graduated from Stellenbosch University, South Africa, in 2002 with a degree in Biodiversity and Ecology. After completing a PGCE (Postgraduate certificate in education) in 2003 she taught high school Biology for over 10 years at various schools across South Africa before returning to Stellenbosch University in 2014 to obtain an Honours degree in Biological Sciences. With over 16 years of teaching experience, of which the past 3 years were spent teaching IGCSE and A level Biology, Marlene is passionate about Biology and making it more approachable to her students.