Growth and Development in Animals
Most animal cells except the nerve cells retain their power of division.
Thus, there is continued breakdown and replacement of cells.
Animals cells undergo rapid cell division and cell differentiation, unlike plant cells, they undergo very little cell enlargement.
Types of growth in Animals
(a) Continuous growth
Growth occurs throughout lifetime.
(b) Discontinuous growth
Growth occurs at intervals e.g., arthropods.
Arthropods like insects show rapid growth immediately after moulting with long periods when no growth occurs due to presence of a hard exoskeleton.
Some insects reproduce sexually while other asexually.
Sexual reproduction involves fertilisation of the ova by the spermatozoa.
Asexual reproduction where the eggs are usually produced without being fertilized and are able to hatch into adult insects. This form of asexual reproduction is called Parthenogenesis.
Parthenogenesis is reproduction where female gametes (ova) develop into a new individual without fertilization.
