Biology Delhi Set 1 2019-2020 Science (English Medium) Class 12 Question Paper Solution

Which one of the following part of the plant when put into the soil is likely to produce new offspring?

Part of an internode

A stem cutting with a node

Part of a primary root

A flower

In a bacterium when RNA-polymerase binds to the promoter on a transcription unit during transcription, it ______.

terminates the process

helps remove introns

initiates the process

inactivates the exons

The hypothesis that “Life originated from preexisting non-living organic molecules” was proposed by ______.

Oparin and Haldane

Louis Pasteur

S.L. Miller

Hugo de Vries

Mating of a superior male of a breed of a cattle to a superior female of another breed is called ______.

in breeding

out crossing

out breeding

cross breeding

Large-holes in ‘Swiss-Cheese’ are due to ______.

Propionibacterium sharmanii

Saccharomyces cerevisae

Penicillium chrysogenum

Acetobacter aceti

Increased concentration of DDT in fish-eating birds is due to ______.

eutrophication

bio-magnification

cultural eutrophication

accelerated eutrophication

The species-area relationship is represented on a log scale as ______.

inverted

rectangular hyperbola

hyperbola

linear

Suggest two advantages to a farmer for using apomictic seeds of hybrid varieties.

What is degeneracy of genetic code?

Give reasons:

Genetic code is ‘universal’.

Differentiate between opioids and cannabionoids on the basis of their

1. specific receptor site in human body.
2. mode of action in human body.

Name the two techniques employed to meet the increasing demand of fish in the world.

Name two freshwater fish.

Describe the contributions of Alexander Flenting, Ernest Chain and Howard Florey in the field of microbiology.

All cloning vectors do have a ‘selectable marker’. Describe its role in recombinant DNA-technology.

Mention how have plants developed mechanical and chemical defence against herbivores to protect themselves with the help of one example of each.

Name and explain the processes earthworm and bacteria carry on detritus.

Explain three different modes of pollination that can occur in a chasmogamous flower.

Explain the formation of placenta after the implantation in a human female.

State Mendel’s law of dominance. How did he deduce the law? Explain with the help of a suitable example.

What are ‘SNPs’?

Where are SNPs located in a human cell?

State any two ways the discovery of SNPs can be of importance to humans.

State what does the study of Fossils indicate.

Rearrange the following group of plants according to their evolution from Palaeozoicto Cenozoic periods:

Rhynia, Arborescent Lycopods, Conifers, Dicotyledon.

Explain the mode of action of Cu++ releasing IUDs as a good contraceptive. How is hormone releasing IUD different from it?

Why is ‘Saheli’ a preferred contraceptive by women (any two reasons)?

Explain why bee-hives are setup on the farms for some of our crop-species. Name any two such crop species.

List any three important steps to be kept in mind for successful bee keeping.

Why GMOs are so called?

List the different ways in which GMO plants have benefitted and have become useful to humans.

Differentiate between “Pioneer-species”; “Climax-community” and “Seres”.

Explain any three ways other than zoological parks, botanical gardens and wildlife safaries, by which threatened species of plants and animals are being conserved ‘ex situ’.

Explain ‘Integrated organic’ farming as successfully practiced by Ramesh C. Dagar, a farmer in Sonepat (Haryana).

Study the diagram showing the entry of HIV into the human body and the processes that are followed:

1. Name the human cell ‘A’ HIV enters into.
2. Mention the genetic material ‘B’ HIV releases into the cell.
3. Identify enzyme ‘C’.

Following a road accident four injured persons were brought to a nearby clinic. The doctor immediately injected them with tetanus antitoxin.

1. What is tetanus antitoxin?
2. Why were the injured immediately injected with this antitoxin?
3. Name the kind of immunity this injection provided.

“The population of a metro city experiences fluctuations in its population density over a period of time.”

1. When does the population in a metro city tend to increase?
2. When does the population in metro city tend to decline?
3. If ‘N’ is the population density at the time ‘t’, write the population density at the time ‘t + 1’.

Describe the process of megasporogenesis in an angiosperm.

Draw a diagram of the mature embryo sac of an angiospermic ovule and label any four parts in it.

Where and how in the testes process of spermatogenesis occur in humans?

Draw a diagram of a human sperm. Label any four parts and write their functions.

Why did T.H. Morgon select Drosophila melanogaster for his experiments?

How did T.H. Morgan disprove Mendelian dihybrid F₂ phenotypic ratio of 9 : 3 : 3 : 1? Explain giving reasons.

List any four major goals of Human Genome project.

Write any four ways the knowledge from HGP is of significance for humans.

Expand BAC.

Mention the importance of BAC.

Name the insect that attacks cotton crops and causes lot of damage to the crop. How has Bt cotton plants overcome this problem and saved the crop? Explain.

Write the role of gene Cry IAb.

Explain the different steps carried out in Polymerase Chain Reaction, and the specific roles of the enzymes used.

Mention the application of PCR in the field of biotechnology.

Mention the application of PCR in the field of diagnostics.