Why are angiosperm anthers called dithecous? Describe the structure of its microsporangium
If implementation of better techniques and new strategies are required to provide more efficient care and assistance to people, then why is there a statutory ban on amniocentesis? Write the use of this technique and give reason to justify.
Why is pedigree analysis done in the study of human genetics? State the conclusions that can be drawn from it.
Identify ‘a’, ‘b’, ‘c’, ‘d’, ‘e’ and ‘f’ in the table given below :
No. |
Syndrome |
Cause |
Characteristic of affected individuals |
Sex Male/Female/ both |
1 |
Down’s |
Trisomy of 21 chromosome |
‘a’ (i) (ii) |
‘b’ |
2 |
‘c’ |
XXY |
Overall masculine development |
‘d’ |
3 |
Turner |
45 with XO |
‘e’ (i) (ii) |
‘f’ |
Community Service department of your school plan a visit to a slum area near the school with an objective to educate the slum dwellers with respect to health and hygiene.
(a)Why is there a need to organize such visits?
(b)Write the steps you will highlight, as a member of this department, in your interaction with them to enable them to lead a healthy life.The following graph shows the species – area relationship. Answer the following questions as directed
(a) Name the naturalist who studied the kind of relationship shown in the graph. Write the observations made by him.
(b) Write the situations as discovered by the ecologists when the value of ‘Z’ (slope of the line) lies between (i) 0.1 and 0.2 (ii) 0.6 and 1.2 What does ‘Z’ stand for ?
(c) When would the slope of the line ‘b’ become steeper ?
Name and describe the technique that helps in separating the DNA fragments formed by the use of restriction endonuclease.
State the function of a reservoir in a nutrient cycle. Explain the simplified model of carbon cycle in nature.
Since the origin of life on the earth, there were five episodes of mass extinction of species.
(i)How is the 'Sixth Extinction', presently in progress, different from the previous episodes?
(ii)Who is mainly responsible for the 'Sixth Extinction''?
(iii)List any four points that can help to overcome this disaster.
(a) Where does fertilization occur in human ? Explain the events that occur during this process.
(b) A couple where both husband and wife are producing functional gametes, but the wife is still unable to conceive, is seeking medical aid. Describe any one method that you can suggest to this couple to become happy parents.(a) Fertilization occur in the fallopian tube of females in human.
The events that occur during this process are :
i. The sperms come in contact with zona pellucida of the ovum.
ii. The sperm induces change in the membrane.
iii. Blocks entry of other sperms / ensures only one sperm fertilizes the ovum / prevents polyspermy.
iv. The secretion of acrosome helps the sperm to enter the cytoplasm of the ovum by degrading the wall of the ova.
v. Entry of sperm induces completion of second meiotic division forming ovum and 2nd polar body
vi. The haploid nucleus of Sperm and that of ovum fuses.
vii. Fertilisation completes on the formation of diploid Zygote.
b. Method suggested for the couple :
In vitro fertilisation followed by embryo transfer (ET)
In this method, popularly known as test tube baby programme, ova from the wife/donor (female) and sperms from the husband/donor (male) are collected and are induced to form zygote under simulated conditions in the laboratory