Human Health and Disease — BIOLOGY STD 12 Science — Question

The number of trophic levels in an ecosystem are limited. Comment.

How is sex determined in human beings?

Human female is not fertile after menopause whereas males can produce gametes at any age after puberty. Analyse the statement and schematically represent a comparison between gametogenesis in males and females.

Illustrate the design of a bioreactor. Highlight the difference between a flask in your laboratory and a bioreactor which allows cells to grow in a continuous culture system.

Read the following and answer any four questions from (i) to (v) given below:

Plants having foreign genes in their genome through genetic engineering are called transgenic plants. Genes can be incorporated either through a vector or through direct introduction of DNA. Bt cotton is a genetically modified organism which is pest resistant. It contain gene cry I Ac and cry II Ab of Bacillus thuringiensis. It is used to control lepidopterans, coleopterans and dipterans. Bt cotton can resist cotton bollworm and produce higher yields. Cry gene produces cry protein or Bt toxin. It is an endotoxin which remains as protoxin in plants and converted to active toxin after getting ingested by the insects. Alkaline pH of the insect gut solubilises the protein crystals, the activated toxin creates pores to the mid guts wall of the insects which cause them to death.

1. Bt cotton crops are:

1. Fungal resistant.
2. Insect resistant.
3. Drought resistant.
4. All of these.

2. Cotton bollwonns are killed by the protein encoded by the gene:

1. cry I Ac
2. cry I Ab
3. cry I Ab
4. Both (a) and (c).

3. Which of the following is not an advantage of GM crops?

1. GM plants enhance nutritional value of food.
2. GM plants are more tolerant to abiotic stresses.
3. GM plants have helped to reduce post harvest losses.
4. GM plants can cause gene transfer to non-target plant species.

4. Bacillus thuringiensis is a:

1. Air borne bacteria.
2. Soil borne bacteria.
3. Soil borne fungus.
4. Food borne bacteria.

5. Assertion: Cotton bollworms are killed by ingesting the leaves of the transgenic plant.

Reason: Bt toxin binds with the midgut wall of the insect and make pores in them.

1. Both assertion and reason are true and reason is the correct explanation of assertion.
2. Both assertion and reason are true but reason is not the correct explanation of assertion.
3. Assertion is true but reason is false.
4. Both assertion and reason are false.

Fill in the blanks in the different column of the table given below:

Disease	Casual organisms	Medium of transfer	Symptoms
Amoebiasis	Entamoeba histolytica	a	Diarrhoea
Typhoid	b	Contaminated food	Sustained high fever
c	Plasmodium	Bite of infected female Anopheles mosquito	Chill and high fever
Pneumonia	Steptococcus	d	Fever and cough

Double fertilisation is immediately followed by development of endosperm. Explain the link between the two processes.

Differentiate between dominance and co–dominance.

diagram.###What is transcription? Explain the transcription process in bacteria by making a labelled diagram.###Explain the transcription process in bacteria and make a diagram.

Answer the following questions:
Differentiate between gametogenesis in human males and females on the basis of:

1. Time of initiation of the process.
2. Products formed at the end of the process.