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. 13.12

Craspedacusta spp.Freshwater hydrozoan

Crustacea - Daphnia

Sexual and asexual reproduction

Fig. 14.14Life cycle of human liver flukeClonorchis sinensis

Fig. 16.19Mollusca

Fig. 17.21

Annelida

Fig. 21.25

Hemimetabolous metamorphosis

Fig. 21.22

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