What is the main cause for the extinction of some species in tropical forest?

• Deforestation

• Afforestation

• Pollution

• Soil erosion

The presence of diversity at the junction of territories of two different habitats is known as

• bottleneck effect

• edge effect

• junction effect

• Pasteur effect

In Cycas, pollination takes place in

• 3- celled stage

• 4- celled stage

• 2- celled stage

• 1- celled stage

74.

A eukaryotic gene contains two kinds of base sequences. Which of these plays an important role in protein synthesis?

• Introns

• Exons

• Both (a) and (b)

• None of these

L- shaped chromosomes are also called

• acrocentric

• telocentric

• sub- metacentric

• None of these

A bacterium divides after every 35 min, if a culture containing 10⁵ cells per mL is grown, then cell concentration per mL after 175 mins will be

• 175$\times$10⁵

• 125$\times$10⁵

• 48$\times$10⁵

• 32$\times$10⁵

Biological concept of species is mainly based on

• reproductive isolation

• morphological features only

• methods of reproduction only

• morphology and methods of reproduction

In the treatment of waste water discharge, which treatment stage involves biological treatment?

• Primary treatment

• Secondary treatment

• Tertiary treatment

• Reverse osmosis stage

Nucellus forms which of the following part of fruit?

• Seed coat

• Perisperm

• Seed

• Raphe

If root of a flowering plant has 24 chromosomes, then its gamete has how many chromosomes?

• 24

• 12

• 4

• 8