Heredity and Evolution
Important Definitions and Terms
Q1: Define Genetics
Answer: Genetics is the branch of Biology which deals with the study of heredity and variation.
Q2: Define Heredity
Answer: Heredity refers to process by which certain features (inheritable) are transmitted from parent to offspring.
Q3: Define Variation
Answer: Offspring of same parents do not exactly resemble each other as well to their parents. It is called variation.
Q4: What are analogous organs?
Answer: The organs that have same functions but different structures and origin are called analogous organs. e.g. the wings of a bat and the wings of an insect are analogous.
Q5: What are homologous organs?
Answer: The organs that have the same structure, origin and components but may be performing different functions are called homologous organs. Eg: hands of a human and the forelimbs of a horse.
Q6: What are vestigial organs?
Answer: The organs which appears function less in an organism but is functional in other organisms are called vestigial organs. e.g. Appendix in man is function-less but in herbivore (eg buffalo) it is functional.
Q7: Define gene.
Answer: Gene is a unit of inheritance. Genes are the segments of DNA and are located on chromosomes.
Q8: Define fossils.
Answer: Remains of plants and animals of distant past.
Q9: Define genotype.
Answer: It is the genetic constitution of an organism, i.e. the combination of genes.
Q10: Define phenotype.
Answer: It constitutes the observable features of an organism, which are a combination of its genes and environmental factors.
Q11: Define evolution.
Answer: Evolution is the formation of wide varieties of organisms which have been evolved from pre-existing organisms through their gradual changes since the beginning of life. Isolation, Natural Selection and Speciation are the major reasons for evolution.
Q12: Define monohybrid inheritance.
Answer: It refers to the inheritance of single gene with two alleles/traits (e.g. T and t giving three possible genotypes i.e. TT, Tt and tt)
Q13: Define Speciation
Answer: It is the process of geographical isolation of two populations of a species and action of natural selection on them over generations may lead to formation of a new species.
Q14: Define Genetic Drift
Answer: The elimination of the genes of certain traits when a section of a population of a species migrate or dies of natural calamity. This process is called genetic drift.
Q15: What are autosomes?
Answer: Any chromosome in an organism which is not a sex chromosome. It regulates the general features like facial features, height, eye colour etc. e.g. In humans there are 23 pairs of chromosomes. Out of which 22 pairs are autosomes.
Q16: What are sex chromosomes?
Answer: The pair of chromosomes which determine the sex of progeny before birth are called sex chromosomes. It can be of two types XY and X0. e.g. in mammals and humans, the 23rd pair is the sex chromosome. If it is of XY it develops into a male. If it is XX, it develops into female. In grasshoppers it is X0 type i.e. XX indicates female while X alone indicates male.
Q17: Define Natural Selection.
Answer: Natural selection is the process in which those organisms whose genes give them a selective advantage (positive selection pressure) are more likely to survive, reproduce and pass their genes on to the next generation.
Q18: Define Artificial Selection.
Answer: It is the method when breeding is controlled for specific characteristics. This results in the formation of new breeds, but not new species