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Reproduction General Zoology LS February 2011

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1 Reproduction General Zoology LS2014 11 February 2011
Following Hickman et al Integrated Principles of Zoology, 15th ed., McGraw-Hill, NY. Ch. 7 pp , , Donald Winslow

2 Types of reproduction asexual sexual binary fission budding
ameiotic parthenogenesis sexual dioecy (separate sexes)‏ monoecy (hermaphroditism)‏ meiotic parthenogenesis, haplodiploidy conjugation

3 Generalized sexual lifecycle
female male meiosis Ovum (gametes, 1N)‏ sperm fertilization zygote (2N)‏ development embryo

4 Figure 07.1 From Hickman et al (13th ed.)‏

5 The cost of sexual reproduction
Half of all alleles are thrown away during meiosis! Males can’t produce eggs, so why have sons?

6 From Hickman et al. 2006 (13th ed.)‏

7 The function of sexual recombination
Increased variability—new combinations of alleles. Sexual populations better able to adapt to changing environment. (Group selection)‏

8 Somatic cells and germ line cells
Germ line cells give rise to the gametes. Gametogenesis (spermatogenesis & oogenesis)‏ Oogenesis results in 3 polar bodies for each ovum. Somatic cells give rise to all the tissues of the body.

9 Mechanisms of sex determination
Y chromosomes In humans, presence of Y induces male development. Ratio of X chromosomes to autosomes In Drosophila flies, ratio of X chromosomes to autosomes determines whether male or female. Temperature In reptiles, temperature of nest often determines sex ratio of hatchlings.

10 Levels of maternal physiological investment
Ovipary Development takes place after female deposits egg. Ovovivipary Development takes place within mother’s body, but without nutritional investment from mother. Vivipary Development takes place within mother’s body, with nutritional investment from mother. Example: placental mammals

11 Karen Bays in gestation

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