Module 5 Summarised Notes

Resource Description

IQ1: How does reproduction ensure the continuity of a species?

1.1 explain the mechanisms of reproduction that ensure the continuity of a species, by analysing
sexual and asexual methods of reproduction in a variety of organisms, including but not limited to:

− animals: sexual reproduction, advantages of external and internal fertilisation

• Sexual reproduction involves the union of a male gamete (sperm) and female gamete (ovum)
  to form a unique individual.
• The two main purposes of sexual reproduction are to form a population with genetic variation
  in offspring and to facilitate adaptation/promote continuity of species.
• Gametes (haploid, n) are the sex cells in the body e.g. sperm or egg cells.
• Somatic cells (diploid, 2n) are basically every single other non-sex cell in the body e.g. muscle
  cells or nerve cells.
  o When two gametes are unified and create a zygote (fertilisation), the two haploid
  cells combine and it becomes the body’s first somatic cell, now diploid.

INTERNAL AND EXTERNAL FERTILISATION

• As animals moved from protective aquatic environments to exposed terrestrial ones, there
  was a need to shift from external to internal to prevent dehydration + predation of gametes.

CLASSIFICATIONS FOR INTERNAL FERTILISATION

• Placental – fetus is nourished in utero and born fully developed e.g. humans
•  Marsupials – young are born at a very early stage and continue developing outside the uterus
  (usually protected by a mother’s pouch) e.g. kangaroos
•  Monotremes –  lay fertilised eggs covered in tough membranes, protecting them until young
  hatch e.g. platypus

and more…