Microbes in Human Welfare — BIOLOGY STD 12 Science — Question

Read the following and answer any four questions from (i) to (v) given below:
Each testicular globule of testis contains one to three highly coiled seminiferous tubules. Wall of each seminiferous tubule is formed of single layered germinal epithelium. Majority of cells in this epithelium are cuboidal, called male germ cells. Study the transverse section of part of seminiferous tubule and answer the following questions.

1. What is the characteristic of K?

1. K is spermatogonium which grows into primary spermatocyte.
2. K is Sertoli cell which provides nutrition to spermatids.
3. K is secondary spermatocyte which undergo meiosis II to form spermatid.
4. K is spermatid being converted into sperm.

2. Which of the following cell undergo reduction division to form secondary spermatocyte?

1. J
2. M
3. L
4. K

3. How many among the following have 46 chromosomes?

1. 2
2. 4
3. 5
4. 3

4. Select an option that correctly identifies different labels.

1. L- Primary spermatocyte, N - Spermatozoa, M - Secondary spermatocyte.
2. J - Spermatogonium, K - Sertoli cell, O - Spermatozoa.
3. L- Primary spermatocyte, M - Secondary spermatocyte, N - Spermatozoa.
4. J - Spermatogonium, K - Primary spermatocyte, N - Spermatid.

5. Which hormone initiates spermatogenesis at puberty?

1. FSH
2. ICSH
3. ABP
4. GnRH

Read the following and answer any four questions from (i) to (v) given below:
In angiosperms, the pollen grains are being transferred from the anther to the stigma and is termed pollination. This phenomenon was first discovered by Camerarius (1694) in the end of seventeenth century. Pollen grains are immobile. They cannot reach the stigma by themselves. An external agent is required for this. The pollination is mainly of two types-self pollination and cross pollination. The diagram given below shows two plants of the same species showing different types of pollination.

1. What is transferred between the plants in the process indicated by arrow P?

1. Ova.
2. Pollen.
3. Nutrients.
4. Seeds.

2. Which of the following statements is correct regarding processes P, Q and R?

1. Processes P, Q and R introduce genetic variability in the offspring of sexually reproducing plants X and Y.
2. Wind serves as agent for process Q if plants X and Y belong to Genus Salvia.
3. Flowers of plants X and Y need to produce odour and nectar for completion of processes P and Q if they are entomophilous.
4. If plants X and Y belong to Genus Cannabis, then their flowers need to produce sticky and heavy pollens in very small amount for accomplishment of process Q.

3. Identify the processes P, Q and R.

S. No	P	Q	R
(a)	Geitonogamy	Xenogamy	Autogamy
(b)	Allogamy	Chasmogamy	Cleistogamy
(c)	Autogamy	Geitonogamy	Xenogamy
(d)	Geitonogamy	Allogamy	Autogamy

4. In Catliarantl1us, the growth of style brings the stigma in contact of ripe anthers present on the mouth of corolla tube. This is an example of:

1. Homogamy.
2. Cleistogamy.
3. Geitonogamy.
4. Xenogamy.

5. Which of the given processes represents a type of pollination that would result in greater adaptability of the particular species to potential environmental changes?

1. P.
2. Q.
3. R.
4. All of these.

Read the following and answer any four questions from (i) to (v) given below:
In a study to test a new vaccine against a viral disease, mouse model testing is done. In this process, mice are vaccinated and their blood samples were tested. Mice developed mild disease symptom. After few days those mice were again infected with the virus. This time they do not show any disease symptoms. Their blood samples were tested. Two graphs show antibody concentration for the first and second infection in mice blood.

Based on the above information, answer the following questions.

1. P and Qin the given graphs indicate.

1. IgM and IgG respectively.
2. IgG and IgM respectively
3. IgG and IgM respectively
4. IgM and IgA respectively.

2. Which form of pathogen is used in vaccination?

1. Activated and strong pathogenic antigen.
2. Inactivated and weakened pathogenic antigen.
3. Hyperactive and strong pathogen.
4. Preformed antibodies.

3. Which of the following is incorrect for P?

1. It is the most abundant class of lg.
2. It is found in blood, lymph, and intestine.
3. It is unable to cross the placental barrier.
4. It is a monomer.

4. How does vaccination work?

1. The immune system produces antibodies which stay in the blood.
2. Memory lymphocytes remain in the body to fight off any future infection with the same pathogen.
3. The dead pathogen stays in the body and constantly stimulates the immune system.
4. All of these.

5. Assertion: Mice do not show any disease symptoms during second exposure to the pathogenic virus.

Reason: The antibody production is accelerated and more intense during secondary immune response.

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.

Define ecological pyramids and describe with examples, pyramids of number and biomass.

Read the following and answer any four questions from (i) to (v) given below:
Age sex structure of a population can be depicted in the form of a pyramid by plotting the percentage of population of each sex in each age class. Two age sex pyramids are as follows.

1. Which of the following is correct regarding pyramid B?

1. It represents stable population.
2. It represents expanding population.
3. It represents declining population.
4. Both (a) and (b).

2. Total number of individuals of a species per unit area per unit time is called.

1. Population size.
2. Population density.
3. Demography.
4. Population dynamics.

3. Which of the following is correct regarding age sex pyramid A and B?

1. A represents the age sex pyramid of developed country.
2. B represents the age sex pyramid of developing country.
3. A represents rapidly growing population.
4. Both (a) and (b).

4. A population with a large proportion of older individuals than younger ones will likely to:

1. Grow larger first and then decline.
2. Continue to grow indefinitely.
3. Decline.
4. None of these.

5. Assertion: Bell shaped age pyramid represents a stable population.

Reason: ln a stable population, proportion of individuals in reproductive age group is higher than the individuals in pre reproductive age group.

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.

Read the following text carefully and answer the questions that follow:
When a microorganism invades a host, a definite sequence of events usually occur leading to infection and disease, causing suffering to the host. This process is called pathogenesis. Once a microorganism overcomes the defense system of the host, development of the disease follows a certain sequence of events as shown in the graph. Study the graph given below for the sequence of events leading to appearance of a disease and answer the questions that follow:

i. In which period, according to the graph there are maximum chances of a person transmitting a disease/infection and why? (1)
ii. Study the graph and write what is an incubation period. Name a sexually transmitted disease that can be easily transmitted during this period. Name the specific type of lymphocytes that are attacked by the pathogen of this disease. (1)
iii. Draw a schematic labelled diagram of an antibody. (2)
OR
In which period, the number of immune cells forming antibodies will be the highest in a person suffering from pneumonia?
Name the immune cells that produce antibodies. (2)

Read the following and answer any four questions from (i) to (v) given below:
Human male reproductive system comprises of a pair of testes, primary sex organs associated with formation of gametes and production of sex hormone. Study the given figure of human male reproductive system and answer the following questions.

1. Which of the following is correct for labelled part P?

1. P is rete testis which transports sperms to outside.
2. P is epididymis which secretes fluid that nourish the sperms.
3. P is epididymis that carry sperms and secretion of seminal vesicles.
4. P is rete testis, which lies along inner side of each testis and stores the sperms.

2. Identify the correctly matched pair.

1. Q - Vasa efferentia.
2. R - Ejaculatory duct.
3. S - Seminal vesicle.
4. T - Cowper's gland.

3. Which statement is incorrect for Q?

1. It carries spermatozoa from epididymis to ejaculatory duct.
2. Q are only 2 in number.
3. It arises from rete testis.
4. It constitutes male sex accessory duct.

4. Which structure passes through the prostate gland and carries sperms and secretion of seminal vesicle?

1. P.
2. T.
3. S.
4. R.

5. Assertion: Mucus present in secretion of bulbourethral gland decreases the number of sperms damaged during ejaculation.

Reason: Mucus lubricates the end of penis and lining of the urethra.

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.

Read the following and answer any four questions from (i) to (v) given below:
A 23 year old Sahil has been diagnosed with an infection of reproductive tract caused by bacteria. He complains about burning sensation during urination, pus-containing discharge and pain around genitalia. This infection has incubation period of 2-5 days but can be cured.

1. From which disease is Sahil suffering?

1. Chlamydiasis.
2. Herpes.
3. Gonorrhoea.
4. Syphilis.

2. Which among the following reproductive tract infections is transmitted by bacteria?

1. Trichomoniasis.
2. Chancroid.
3. Genital warts.
4. Both (a) and (b).

3. Which mode of treatment would be useful for Sahil?

1. Cryosurgery.
2. Use of Podophyllum preparation.
3. Use of antibiotic ampicillin.
4. It cannot be treated.

4. What technique was used to diagnose Sahil's disease?

1. Gram staining of discharge and culture.
2. ELISA Test.
3. Antibody detection.
4. Antigen test.

5. Find the odd one out.

1. Treponema pallidum.
2. Neisseria gonorrhoeae.
3. Haernophilus ducreyi.
4. Trichomonas vaginalis.