How is free oxygen present into the earth's atmosphere, whereas there was no free oxygen at the time of origin of life?

A piece of DNA molecule that can serve as a carrier for the gene to be cloned is called as a

A. Virus

B. Vector

C. DNA junk

D. Gene factor

According to who amongthe following, "although the intermediate basis of the variations which make evolution possible is genetic segregation and recombination, its ultimate source is mutation"?

A. Correns

B. de Vries

C. V. Tschermak

D. Stebbins

A haploid organism contains only one set of chromosomes, and is said to be

A. Homozygous

B. Heterozygous

C. Hemizygous

D. Holozygous

Which of the following is the correct pair?

A. Darwin - Use and disuse of organs

B. de Vries - Mutation theory

C. Lamarck - Origin of life

D. Haldane - Law of heredity