Reproduction in Animalia

Fig. 7.1

Types of reproduction Asexual – Binary fission 1 ->2 – Multiple fission or schizogony 1 -> many – Budding – a new organism buds off an existing organism. – Fragmentation – organism breaks into fragments that each for new organisms. – Parthenogenesis – ameiotic or meiotic.

Sexual reproduction Offspring produced from union of gametes from two genetically distinct parents. Dioecious – separate sexes Monoecious – an individual have both male and female reproductive structures – called hermaphrodites

viviparous - give birth to live young oviparous - lay eggs ovoviviparity - eggs are retained inside the female such that she gives birth to live young.

Sponges Asexual – buds Sexual – Produce heterogametes – sperm and eggs from choanocytes or archaeocytes. Some are viviparous – fertilization is internal, zygote is retained and receives nourishment from parent. Others are oviparous – sperm and egg released into water, zygote develops externally. Results in free swimming flagellated larvae.

Fig Craspedacusta spp. Freshwater hydrozoan

Crustacea - Daphnia Sexual and asexual reproduction

Fig Life cycle of human liver fluke Clonorchis sinensis

Fig Mollusca

Fig Annelida

Fig Hemimetabolous metamorphosis

Fig Holometabolous metamorphosis

Fish External fertilization Oviparous May be ovoviviparous, e.g. some sharks Sexes can change, large females become males Some forms of pollution causes sterility in fish

Amphibians Tied to water through reproduction External fertilization Frogs – tadpole stage

Turtles - oviparous - internal fertilization - female burry eggs - nest temperature determines sex

Birds Fertilization internal Incubation external Young precocial or altricial Sex determination by chromosomes (Female heterogametic)

Monotremes Duck-billed Platypus oviparous

Marsupials Viviparous Pouched Choriovitelline placenta Embryo encapsulated in shelled membrane - hatch and then erodes a depression in the placenta

Placental mammals

Fig. 8.25