SEX QUESTION ANSWERED

 

   

Sexuality of animals

 

Q. 13. Comment on the sexuality of animals?

Ans. Animals in general are more evolved form of life than plants. Human being is the most developed animal with the most evolved brain. Reproduction is mainly sexual behavior though primitive form of animals also reproduce by binary fission and asexual methods. Certain primitive animals are hermaphrodites, though all developed animals are unisexual. New species are created by mutation and sometimes by cross-breeding and hybridization. Parthenogenesis is a special type of reproduction in which an egg develops into an individual without fertilization as in water flea, rotifier, aphid, thrip and honeybee. Parthenogenesis has \ been artificially induced in egg of frog, certain fishes, silk worm, moth and rabbit by subjecting eggs to various physical stimulants like sudden exposure to heat and cold, pricking of eggs with needle and by use of Certain chemical agents. Protandry is the condition in which the gonads of the same animal alternately produce spermatozoa and ova as in oyster and hagfish. Some form of animals have the capacity to produce offsprings of a particular superior gender under conditions of stress and certain environmental temperature. Such an urge is there for maintaining the balance of the population as well as the number of the two genders of that species in nature. Some species of turtles, crocodiles and alligators produce all females if hatched below 30°C and all males if hatched above 33°C. A mixture of both the genders is produced between 30°C and 33°C. Therefore if the female of that species has an urge of producing females it hatches the eggs in shallow water for lower temperature and if the impulse for producing males is there, it hatches the eggs in warm sandy distant shore for higher environmental temperature. Some species of fish produce all female offsprings if fed on oestrogens prior to hatching and all male offsprings if fed on androgens prior to hatching. All this indicates that there is just a minor difference in the two genders even at the level of chromosomes and sex ethics hormones. Canniblastic behaviour of extreme sadism is seen in female praying mantis, some spiders and certain scorpions that kill the male just after the sexual act.

> The unicellular protozoan mostly reproduce by binary fission, multiple fission and cyst formation though a few have sexual reproduction. Porifers and coelenterates have both asexual and sexual reproduction and the members may be unisexual or bisexual. The other higher animals reproduce sexually Platyhelminths, most annelids, a few arthropods and some molluscs are bisexuality while other animals are unisexual. External fertilization is seen in a few arthropods, some molluscs, prochordates, cyclostomes, most pisces and most amphibians. Other animals exhibit internal fertilization inside the body of female. Mammals have breasts, placenta and give birth to young ones. Prototheria is a class of mammals which lays eggs though feed the young ones with milk like duck billed platypus and spiny anteater. Metatheria is a class of mammals which deliver immature young ones which develop in abdominal skin pouch of the mother and suckle milk like kangaroo and opossum. Eutheria are developed mammals and include human being sex . On the other hand non-mammals like scoliodon (Pisces) and salamander (amphibian) are viviparous with the females giving birth to young ones.