(a) What is meant by a species ? Give two examples of plant species and two of animals.

(a) A species is a population of organisms consisting of similar individuals which can breed  together and produce fertile offspring’s. Plant species – Wheat, Paddy, Sunflower etc. Animal  species – Cat, Dog, Tiger, etc.  

(b) The important factors which could lead to the rise (or formation) of a new species are the  following:  

1. Geographical isolation of a population caused by various types of barriers (such as  mountain ranges, rivers and sea). The geographical isolation leads to reproductive  isolation due to which there is no flow of genes between separated groups of  population.  

2. Genetic drift caused by drastic changes in the frequencies of particular genes by chance  alone.  

3. Variations caused in individuals due to natural selection.