Haemorrhage frequently happens in viral dengue fever. Compare this condition with haemophilia.
Answer
In Dengue fever, the platelet count drops sharply. This leads to coagulation of blood slowly, which can lead to haemorrhage. On other hand, haemophilia is a genetic disorder in which the body's blood clotting process is impaired due to the absence of clotting factors.
Differentiate in the rate of photosynthesis for the increase in temperature.
- 20°C to 30°C
- 40°C to 50°C
Answer
(a) The rate of photosynthesis gets doubled since it increases with increase in temperature up to the optimum temperature of 35°C.
(b) Photosynthesis stops at 40°C.
Name the nitrogenous base with which Guanine pairs up in the helical structure of DNA and through how many hydrogen bonds?
Answer
Cytosine pairs with Guanine through 3 Hydrogen-bonds.
When an irritant enters the nose, a sneezing reflex happens. Identify the stimulus and the response.
Answer
The stimulus is irritant and the response is sneezing.
An atomic explosion in 1945 in Japan led to a large number of persisting deformities in the bodies of plants and animals. What might have happened?
Answer
Atomic explosion leads to radiation exposure. This radiation exposure leads to change in DNA i.e. mutation. Such mutations are responsible for a large number of persisting deformities in the bodies of plants and animals.
Why is a bicuspid valve in the human heart named so?
Answer
The bicuspid valve in the human heart is named so because it has two flaps.
Under which condition does a leaf take carbon dioxide from the atmosphere?
Answer
A leaf takes carbon dioxide from the atmosphere when the concentration of CO2 outside the leaf is higher than inside the leaf.
A pregnant lady is suffering from viral fever. Will the foetus be infected?
Answer
No, the foetus will not be infected because the placenta does not allow the passage of germs from the mother to the foetus. There is no mixing of blood between mother and foetus.
Why the blood flows through the glomerulus under great pressure?
Answer
The afferent arteriole entering the glomerulus is thicker but the efferent arteriole is thinner. This increases the pressure of blood in glomerulus.
Differentiate between genotype and phenotype.
Answer
| Genotype | Phenotype |
|---|---|
| Set of genes present in any organism is known as its genotype. | Characters expressed or physical appearance of characters is called phenotype. |
| Can be determined by genotyping method. | Can be determined by observation. |
| It is formed by expressed and unexpressed genes. | It consists of only expressed genes. |
The number of asthma patients increases during winters in metropolitan cities like Delhi. Why is it so? How can it be reduced?
Answer
During winters in metropolitan cities like Delhi, the fog and smoke together form smog. Inhalation of smog causes rise in patients of asthma.
It can be reduced by:
- Installation of tall chimneys in factories with filters.
- Electrostatic precipitators.
In our country, the infant mortality rate is high, but the population is still increasing in India. Explain.
Answer
In our country, the infant mortality rate is high specially in rural areas or weaker section but the population keeps on rising because people of weaker section think it safer to produce more children so that at least some may survive.
Justify the statement – “Vermiform appendix is a vestigial organ in humans.”
Answer
The vermiform appendix projects from the blind end of the caecum in humans. It is called a vestigial organ because it no longer has a vital function for us. It might have been useful to our ancestors for digesting tough plant materials, but now it serves little purpose.
What is Adrenal Virilism?
Answer
Adrenal virilism is a condition that results from excessive production of androgens (male hormones) by the adrenal glands. It leads to the development of male physical characteristics in females like the development of a beard, moustache and deep voice. It is caused by overgrowth of the adrenal cortex in a mature woman.
Explain the function of corpus luteum when:
(a) ovum is fertilised.
(b) ovum is not fertilised.
Answer
(a) Corpus luteum releases progesterone and keeps the uterus in a state suitable for implantation.
(b) The Corpus luteum stops producing progesterone.
Shruti’s mother gave birth to two male babies. Both the babies had a strong resemblance to each other. The doctor said that they have been formed from a single ovum.
(a) What kind of twins are they?
(b) Why are they of the same gender?
Answer
(a) They are identical twins.
(b) Identical twins (monozygotic twins), are always of the same gender because they originate from a single fertilized egg (zygote). Their gender is decided at the time of fertilization.
State the effect of Adrenaline on:
(a) Pupils of eyes
(b) Heartbeat
Answer
(a) Adrenaline cause dilation of pupil of eyes.
(b) Adrenaline increase heartbeat in order to increase blood circulation.
When is albumin passed out in urine? Name this condition.
Answer
Albumin may be passed out in urine under following conditions:
- due to high blood pressure
- due to increased permeability of the bowman’s capsule membrane on account of bacterial infection
This condition is known as Albuminuria.
Mention the significance of the Testes being located inside the scrotum.
Answer
Testes are responsible for the production of male gametes i.e., sperms. The normal body temperature does not allow the maturation of the sperms. Being suspended outside the body cavity, the temperature in the scrotal sac is 2 to 3°C lower than that of the body which is the suitable temperature for the maturation of the sperms.
Give two examples of natural resources which cannot keep pace with the rising population.
Answer
Two examples of natural resources which cannot keep pace with the rising population:
- Food
- Water
Keshav enters a dark room from a brightly lit area. He experiences difficulty in viewing objects, but gradually his vision improves.
Explain the role of the photoreceptors in this case.
Answer
Rhodopsin is the pigment which is responsible for vision in dim lights. It gets bleached in bright light. It takes a few seconds for it to regenerate in dim light. Then, the vision improves. Iodopsin responsible for vision in bright light does not function in dim light.
On a winter night, a group of workers slept in a closed room, having a burning furnace to keep themselves warm. Most of them died in their sleep. What is the reason for their fatality?
Answer
Due to deficiency of oxygen in the room, the burning furnace will emit carbon monoxide. This carbon monoxide when inhaled, combines with oxygen to form a stable compound, Carboxyhaemoglobin, which cuts off the supply of oxygen to tissues, leading to death due to asphyxiation.