Biology Unit 3 - Topic 14 - Oviparous and Viviparous

  

Oviparous and Viviparous

Based on how a new organism is born, animals can be divided into two kinds: Oviparous and Viviparous

Oviparous

They are animals which are incubated and emerge from an egg.

Viviparous

Animals that are born from the womb of the mother. Mammals are the most important viviparous group. There are only two types of mammals that lay eggs.  The platypus and the echidna, an both live in Australia.

 

The Egg

 

 

The young of snakes, hens, other birds, and insects first grow in an egg.  After the zygote has been formed as a result of the union of the male and female gametes, a protective shell is formed around it. This is what we call the egg. The nutrition organism is complete, the creature breaks the egg, emerges from it, and lives as an independent individual.

 

Some oviparous animals, mainly insects and amphibians, undergo important changes in their development from eggs to adults.  These transformations in form and way of life are the stages of a process known as a metamorphosis.

 

Many insects develop inside an egg. They emerge in a developed state, or in a form that will change as it grows.  The sexes are separate and reproduction is usually sexual.  Most insects, like butterflies, silk moths, or flies, have a complete metamorphosis with four stages:  egg, larva, pupa, and adult.  Others, like dragonflies or grasshoppers, do not go through the pupa stage; the larva is similar to a small adult but has different colors and no wings.

 

Oviparous

In some insects there is o metamorphosis. The insect emerges from the egg as a miniature adult.

 

Amphibians, like frogs and toads, also go through different stages. The eggs are usually laid in the water.  Tadpoles, the amphibian larvae, do not have arms or legs.  They swim with a tail and breathe through gills.  They gradually develop their bodies before coming out of the water.

 

See how a tadpole grows into a frog.