Human Health and Disease — BIOLOGY STD 12 Science — Question

1. Draw a simplified model of phosphorus cycling in a terrestrial ecosystem.
2. Write the importance of such cycles in ecosystems.

Name and describe the steps involved in the technique widely used in forensics that serves as the basis of paternity testing in case of disputes.

1. Comment on the pattern in which all communities undergo a change in composition and structure with changing environmental conditions.
2. Explain 'climax community' and 'sere'.
3. Differentiate between primary and secondary Succession, with examples.

1. Trace the succession of plants on a dry bare rock.
2. How does phosphorus cycle differ from carbon cycle?

"Analysis of age-pyramids for human population can provide important inputs for long-term planning strategies." Explain.

Answer the following questions:
Explain the changes the primary oocyte undergoes while in different follicular stages before ovulation.

The following table shows certain diseases, their causative organisms and symptoms. Fill the gaps.

	Name of the Disease	Causative organism	Symptoms
i.	Ascariasis	Ascaris	________
ii.	________	Trichophyton	Appearance of dry, scaly lesions on various parts of the body.
iii.	Typhoid	________	High fever, weakness, headache, stomach pain, constipation.
iv.	Pneumonia	Streptococcus pneumoniae	________
v.	________	Rhino viruses	Nasal congestion and discharge, sorethroat, cough, headache.
vi.	Filariasis	________	Inflammation in lower limbs.

Explain the ovarian and uterine events that occur during a menstrual cycle in a human female, under the influence of Pituitary and Ovarian hormones respectively.

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.

Explain how xerarch succession progresses from serie to mesic condition and forms a stable climax community. You may use a flow chart.