A human RBC is placed in 1.5% salt solution. It will

• swell up

• shrink

• remain unaffected

• burst

Which floral family has (9) + 1 arrangement or anthers in the androecium ?

• Malvaceae

• Rutaceae

• Fabaceae

• Caesalpinaceae

During the cell cycle, DNA content is doubled in the

• G₁ phase

• S phase

• G₂ phase

• end of M phase

Barr body is found in the cytoplasm during

• interphase in cell of female mammal

• interphase in cell of male mammal

• prophase in cell of female mammal

• prophase in cell of male mammal

Which of these are most widely used in genetic engineering?

• Plastid

• Plasmid

• Mitochondrion

• Ribosome

The respiratory centre in the brain is stimulated by

• CO₂ concentration in venous blood

• O₂ concentration in artery blood

• CO₂ concentration in artery blood

• O₂ concentration in venous blood

If a stimulus, several times greater than the threshold stimulus is provided to a muscle fibre, it will

• contract with a larger force

• contract with a smaller force

• contract with the same force

• undergo tetany.

Wooden doors swell up and get stuck during the rainy season. This is due to the phenomenon of

• imbibition

• endosmosis

• capillarity

• deplasmolysis

Which of these are considered most essential in the origin of life?

• Enzymes

• Nucleic acids

• Carbohydrates

• Proteins

Porous wood has abundance of 

• vessels

• fibres only

• tracheids

• sieve tubes