Animals Sexual reproduction

1 animals

1.1 insects
1.2 birds
1.3 mammals
1.4 fish
1.5 reptiles
1.6 amphibians
1.7 mollusks

animals

insects


australian emperor laying egg, guarded male

insect species make more two-thirds of extant animal species. insect species reproduce sexually, though species facultatively parthenogenetic. many insects species have sexual dimorphism, while in others sexes identical. typically have 2 sexes males producing spermatozoa , females ova. ova develop eggs have covering called chorion, forms before internal fertilization. insects have diverse mating , reproductive strategies resulting in male depositing spermatophore within female, stores until ready egg fertilization. after fertilization, , formation of zygote, , varying degrees of development, in many species eggs deposited outside female; while in others, develop further within female , born live.

birds

mammals

there 3 extant kinds of mammals: monotremes, placentals , marsupials, internal fertilization. in placental mammals, offspring born juveniles: complete animals sex organs present although not reproductively functional. after several months or years, depending on species, sex organs develop further maturity , animal becomes sexually mature. female mammals fertile during periods during estrous cycle, @ point ready mate. individual male , female mammals meet , carry out copulation. mammals, males , females exchange sexual partners throughout adult lives.

fish

the vast majority of fish species lay eggs fertilized male, species lay eggs on substrate rock or on plants, while others scatter eggs , eggs fertilized drift or sink in water column.

some fish species use internal fertilization , disperse developing eggs or give birth live offspring. fish have live-bearing offspring include guppy , mollies or poecilia. fishes give birth live young can ovoviviparous, eggs fertilized within female , eggs hatch within female body, or in seahorses, male carries developing young within pouch, , gives birth live young. fishes can viviparous, female supplies nourishment internally growing offspring. fish hermaphrodites, single fish both male , female , can produce eggs , sperm. in hermaphroditic fish, male , female @ same time while in other fish serially hermaphroditic; starting 1 sex , changing other. in @ least 1 hermaphroditic species, self-fertilization occurs when eggs , sperm released together. internal self-fertilization may occur in other species. 1 fish species not reproduce sexual reproduction uses sex produce offspring; poecilia formosa unisex species uses form of parthenogenesis called gynogenesis, unfertilized eggs develop embryos produce female offspring. poecilia formosa mate males of other fish species use internal fertilization, sperm not fertilize eggs stimulates growth of eggs develops embryos.

reptiles

common house geckos (hemidactylus frenatus) mating



amphibians

mollusks