POST- FERTILIZATION EVENTS

Zygote formation

In some organisms like fungi and algae, the zygote develops a thick wall around it which is resistant to damage and undergoes a period before germination.
Further development of zygote depends on the type of life cycle of organisms and the environment in which they are surviving.
In all sexually reproducing organisms, a diploid zygote is formed as a result of fertilization and later the zygote develops into a new organism.

Embryogenesis

The process of development of embryo from the zygote is called embryogenesis.
Embryogenesis includes cell division and cell differentiation in the zygote.
Cell division increases the number of cells and cell differentiation helps to form tissues and organs to form a fully developed organism.

Fig. embryogenesis

Depending on the development of zygote inside or outside the body of the female parent, animals are classified into oviparous and viviparous animals.
Oviparous animals are those which lay eggs and the eggs develop into new organisms. Example- amphibians, fishes, birds, reptiles etc.
Viviparous animals are those which give birth to their young ones. Example- mammals.
In some oviparous animals like reptiles and birds the fertilized eggs remain covered by hard calcareous shell and such eggs are called cleidoic
In flowering plants, the zygote is formed inside the ovule and the sepals, petals, stamens of the flower usually fall off.
The zygote develops into embryo
Ovules develop into seeds
The ovary develops into the fruit.
The ovary wall develops into a protective layer called pericarp.