What is the importance of DNA copying in reproduction?
Reproduction is a process by which every living organism makes a copy like itself as seen in parents to their children. This is only done because of replication of DNA (deoxyribonucleic acid) by transferring the genetic information from the parents to their offsprings or simply we can say that passing their physical or mental character genetically to main the chromosome number of species.
Why is variation beneficial to the species but not necessarily for the individual?
Draw a labelled diagram of the longitudinal section of a flower.
What are the functions performed by the testis in human beings?
Why does menstruation occur?
How will an organism be benefited if it reproduces through spores?
Asexual reproduction takes place through budding in
(a) amoeba.
(b) yeast.
(c) plasmodium.
(d) leishmania.
Can you think of reasons why more complex organisms cannot give rise to new individuals through regeneration?
How does the embryo get nourishment inside the mother’s body?
How does reproduction help in providing stability to populations of species?
What are the advantages of sexual reproduction over asexual reproduction?
Did Döbereiner’s triads also exist in the columns of Newlands’ Octaves? Compare and find out.
What is a good source of energy?
Why is diffusion insufficient to meet the oxygen requirements of multi-cellular organisms like humans?
What are trophic levels? Give an example of a food chain and state the different trophic levels in it.
What changes can you make in your habits to become more environment-friendly?
What is the difference between a reflex action and walking?
If a trait A exists in 10% of a population of an asexually reproducing species and a trait B exists in 60% of the same population, which trait is likely to have arisen earlier?
Why should a magnesium ribbon be cleared before burning in air?
Define the principal focus of a concave mirror.
You have been provided with three test tubes. One of them contains distilled water and the other two contain an acidic solution and a basic solution, respectively. If you are given only red litmus paper, how will you identify the contents of each test tube?
(a) Lithium, sodium, potassium are all metals that react with water to liberate hydrogen gas. Is there any similarity in the atoms of these elements?
(b) Helium is an unreactive gas and neon is a gas of extremely low reactivity. What, if anything, do their atoms have in common?
Draw the structure of a neuron and explain its function.
You are given kerosene, turpentine and water. In which of these does the light travel fastest? Use the information given in Table 10.3.
Material medium |
Refractive index |
Material medium |
Refractive index |
Air | 1.0003 | Canada Balsam |
1.53 |
Ice | 1.31 | ||
Water | 1.33 | Rock salt | 1.54 |
Alcohol | 1.36 | ||
Kerosene | 1.44 | Carbon disulphide |
1.63 |
Fused quartz |
1.46 | ||
Turpentine oil |
1.47 | Ruby | 1.71 |
Benzene | 1.50 | Sapphire | 1.77 |
Crown glass |
1.52 | Diamond | 2.42 |
You must have seen tarnished copper vessels being cleaned with lemon or tamarind juice. Explain why these sour substances are effective in cleaning the vessels.
List two methods of producing magnetic fields.
In the Modern Periodic Table, which are the metals among the first ten elements?
What are the components of the transport system in human beings? What are the functions of these components?
Which metals do not corrode easily?
A shiny brown coloured element ‘X’ on heating in air becomes black in colour. Name the element ‘X’ and the black coloured compound formed.
Imagine that you are sitting in a chamber with your back to one wall. An electron beam, moving horizontally from back wall towards the front wall, is deflected by a strong magnetic field to your right side. What is the direction of magnetic field?