Science (English Medium) Class 12 - CBSE Question Bank Solutions for Biology

Write a short note on pyramid of numbers and pyramid of biomass.

Non-biodegradable pollutants are created by ______.

Which of the following material takes the longest time for biodegradation?

What is the raw material for polyblend?

Blends of polyblend and bitumen, when used, help to increase road life by a factor of three. What is the reason?

What is the best solution for the treatment of electronic wastes?

Write a short note on electronic waste. List the various sources of e-wastes and the problems associated with its disposal.

What are the basic characteristics of a modern landfill site? List any three and also mention the reasons for their use.

In the figure given below, parts A and B show the level of hormones which influence the menstrual cycle. Study the figure and answer the questions that follow:

1. Name the organs which secrete the hormones represented in parts A and B.
2. State the impact of the hormones in part B on the uterus of the human female during 6 to 15 days of the menstrual cycle.

(a) Given below is a pyramid of biomass in an ecosystem where each bar represents the standing crop available in the trophic level. With the help of an example explain the conditions where this kind of pyramid is possible in nature.

(b) Will the pyramid of energy be also of the same shape in this situation? Give a reason for your response.

(a) Draw a pyramid of numbers where a large number of insects are feeding on the leaves of a tree. What is the shape of this pyramid?

(b) Will the pyramid of energy be also of the same shape in this situation? Give a reason for your response.

‘An HIV patient normally doesn't die of ‘AIDS’, but death is caused due to many other infections.’ Do you agree with the statement? Give explanatory reasons in support of your answer.

Farmers are often suggested to use the following organism in their crop land so as to improve the soil fertility. Explain.

Rhizobium

Farmers are often suggested to use the following organism in their crop land so as to improve the soil fertility. Explain.

Anabaena 

Explain the principle on which the AIDS diagnostic test works.

Name the type of genetic material present in AIDS causing pathogen.

The graph given below shows the number of primordial follicles per ovary in women at different ages. Study the graph and answer the questions that follow.

1. What is the average age of the women at the onset of menopause?
2. At what age are maximum primordial follicles present in the ovary, according to the given graph?

1. Give an example of a genus of fungi that forms mycorhizal association with plants. 
2. How does the plant derive benefits from this association?

The biomass of a standing crop of phytoplankton is 4 kg/m², which supports a large standing crop of zooplankton having a biomass of 11 kg/m². This is consumed by small fishes having a biomass of 25 kg/m², which are then consumed by large fishes with a biomass of 37 kg/m².

Draw an ecological pyramid indicating the biomass at each stage and also name the trophic levels. Mention whether it is an upright or inverted pyramid.

With the help of a flow chart, illustrate how an infected animal cell can survive while viruses are being replicated or released.