CBSE 12 Biology Question Paper-2021 Tem-2

Humans have innate immunity for protection against pathogens that may enter the gut along with food. What are the two barriers that protect the body from such pathogens?

A patient admitted in ICU was diagnosed to have suffered from myocardial infarction. The condition of coronary artery is depicted in the image below. Name two bioactive agents and their mode of action that can improve this condition.

Identify the compound chemical structure shown below. State any three of its physical properties.

Water samples were collected at points A, B, and C in a segment of a river near a sugar factory and tested for BOD level. The BOD levels of samples A, B, and C were 400 mg/L, 480 mg/L, and 8 mg/L respectively. What is this indicative of? Explain why the BOD level gets reduced considerably at the collection point C.

An ecologist studies an area with population A, thriving on unlimited resources and showing exponential growth, introduced population B and C to the same area. What will be the effect on the growth pattern of populations A, B, and C when living together in the same habitat?

With the decline in the population of fig species it was noticed that the population of wasp species also started to decline. What is the relationship between the two and what could be the possible reason for the decline of wasps?

How do normal cells get transformed into cancerous neoplastic cells? Elaborate giving three examples of inducing agents.

Recognition of an antigenic protein of a pathogen or exposure to a pathogen occurs during many types of immune responses, including active immunity and induced active immunity. Specify the types of responses elicited when human beings get encountered by a pathogen.

In a pathological lab, a series of steps were undertaken for finding the gene of interest. Describe the steps, or make a flow chart showing the process of amplification of this gene of interest.

The Evil Quartet describes the rates of species extinction due to human activities. Explain how the population of organisms is affected by fragmentation of habitats.

The image shown below is of a sacred grove found in India. Explain how has human involvement helped in the preservation of these biodiversity-rich regions.

The image below depicts the result of gel electrophoresis. If the ladder represents sequence length up to 3000 base pairs (bp), which of the bands (I - IV) correspond to 2500 bp and 100 bp respectively?

Some restriction enzymes break a phosphodiester bond on both the DNA strands, such that only one end of each molecule is cut and these ends have regions of single-stranded DNA. BamH1 is one such restriction enzyme. What is the objective of this action?

GM crops, especially Bt crops, are known to have higher resistance to pest attacks. To substantiate this, an experimental study was conducted in four different farmlands growing Bt and non-Bt-Cotton crops. Which of the above four farmlands has successfully applied the concepts of Biotechnology to show better management practices and use of agrochemicals?

Cotton Bollworms were introduced in another experimental study on the above farmlands wherein no pesticide was used. Explain what effect would a Bt and Non-Bt crop have on the pest.

What is the role of the BOD (Biological Oxygen Demand) in assessing the quality of water?

What is the effect of temperature on the rate of enzymatic reactions in living organisms?

A disease caused by the spread of pathogenic microbes from infected areas to non-infected areas is an example of?

The use of chemical agents to reduce or eliminate pathogens is known as?

In an ecosystem, which of the following relationships would be categorized as mutualism?

Which of the following is a characteristic feature of an ecosystem's trophic structure?

What is the primary factor responsible for the formation of soil?

What is an example of a primary consumer in an ecosystem?

Which of the following is a biotic factor in an ecosystem?

Which of the following is a major impact of deforestation on the environment?

The increase in the global temperature due to human activities is known as?

What does the term 'sustainable development' refer to?

What is the effect of excessive use of chemical fertilizers on soil?

Which of the following best describes the term 'biodiversity hotspot'?

Which of the following is an example of an invasive species?