HOW ARE CHARACTERISTICS TRANSMITTED TO PROGENY : -
The characteristics of traits of parents are transmitted to their progeny through genes present on their chromosomes during the process of sexual reproduction.
HOW BLOOD GROUPS ARE INHERITED : -
A person has one of the four blood groups: A, B, AB or O. This blood group system is controlled by a gene which has three different forms denoted by the symbols IA, IB and IO. The genes IA and IB show no dominance over each other, that is, they are co dominant. However, genes IA and IB both are dominant over the gene IO.
SEX DETERMINATION : -
A person can have a male sex or a female sex. The process by which the sex of a person is determined is called sex determination. There are two types of sex chromosomes: X and Y chromosomes.
ACQUIED IRED TRAITS : -
A trait of an organism which is ‘not inherited’ but develops in response to the environment is called an acquired trait. Example: If a beetle does not get sufficient food for a considerable time. The acquired traits of organism cannot be passed on to their future generations.
INHERITED TRAIT : -
A trait of an organism which is caused by a change in its genes is called an inherited trait.
EVOLUTION : -
Evolution is the sequence of gradual changes which take place in the primitive organisms over millions of years in which new species are produced.
EVIDENCES FOR EVOLUTION : -
1. HOMOLOGOUS ORGANS PROVIDE EVIDENCE FOR EVOLUTION : -
Those organs which have the same basic structure but different functions are called homologous organs. Example: the forelimbs of a man, a lizard (reptile), a frog (amphibian), a bird and a bat (mammal).
2. ANALOGOUS ORGANS PROVIDE EVIDENCE FOR EVOLUTION : -
Those organs which have different basic structure but have similar appearance and perform similar functions are called analogous organs.
3. FOSSILS PROVIDE EVIDENCE FOR EVOLUTION : -
The remains of dead animals or plants that lived in the remote past are known as fossils.
SPECIATION : -
The process by which new species develop from the existing species is known as speciation.
