BIOL1131 Lecture Notes - Lecture 3: Sensory Nerve, Symmetry In Biology, Adrenal Gland
7 Jun 2018
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Course
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Animal Development and Reproduction
• Sexual reproduction
o Males and female gametes are produced by male and female
gonads (testes and ovaries) released through gonoducts (vas
deferens and oviduct)
• Meiosis
o Reduces the number of chromosomes by half (2n to n, diploid to
haploid)
o Mixes up the combination alleles by recombination
o Where as mitosis produces exact replicas of the parent cell with
identical chromosomes and gene sequences (diploid)
• Gametogenesis (spermatogenesis and oogenesis)
o The production of gametes by primordial germ cells
o Occurs in the primary sex organs (gonads)
• Spermatogenesis
o Primary spermatocyte (product of mitotic divisions)
o First meiotic division – primary spermatocyte gives rise to
secondary spermatocytes
o Second meiotic division – secondary spermatocytes gives rise to
spermatids
o Spermatid matures into a spermatocyte
▪ Loss of most of cytoplasm
▪ Development of long flagellum (tail)
▪ Formation of secretory acrosome at anterior of head
section
• Oogenesis
o Primary oocyte (product of mitotic divisions)
o First meiotic division – primary oocyte gives rise to secondary
oocyte and first polar body
o Second meiotic division – secondary oocyte gives rise to ovum
(egg) AND second polar body
o First polar body usually gives rise to two or more polar bodies
o Ovum matures
▪ Huge increase in size
▪ Increase in organelles
▪ Increase in nutritive materials
▪ Development of protective extracellular membranes, e.g.
vitelline membrane
• A sperm MUST
o Find an egg
o Find the right egg
o Prevent other sperm from fertilizing the right egg
o For internal fertilization there are several options
▪ Intromittent organ (penis, claspers)
▪ Spermatophore (sperm packet)
▪ Injected through body wall
• Fertilisation – fusion of egg and sperm
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