Explain the terms analogous and homologous organs with examples.
Homologous organs are the organ whose origin is similar (or are embryologically similar) but perform different functions. Such as the forelimbs of humans and the wings of birds look different externally but their skeletal structure is similar. It means that their origin is similar (as wings in birds are modifications of the forearm) but functions are different - the wings help in flight whereas human forearms help in various activities.
Outline a project which aims to find the dominant coat colour in dogs.
How is the sex of the child determined in human beings?
A man with blood group A marries a woman with blood group O and their daughter has blood group O. Is this information enough to tell you which of the traits – blood group A or O – is dominant? Why or why not?
How do Mendel’s experiments show that traits are inherited independently?
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?
Explain how sexual reproduction gives rise to more viable variations than asexual reproduction. How does this affect the evolution of those organisms that reproduce sexually?
How do Mendel’s experiments show that traits may be dominant or recessive?
Will geographical isolation be a major factor in the speciation of an organism that reproduces asexually? Why or why not?
How does the creation of variations in a species promote survival?
Why are traits acquired during the life-time of an individual not inherited?
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?
What is the importance of DNA copying in reproduction?
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?
What is a balanced chemical equation? Why should chemical equations be balanced?
A coil of insulated copper wire is connected to a galvanometer. What will happen if a bar magnet is (i) pushed into the coil, (ii) withdrawn from inside the coil, (iii) held stationary inside the coil?
How much energy is given to each coulomb of charge passing through a 6 V battery?
Name some devices in which electric motors are used.
One-half of a convex lens is covered with a black paper. Will this lens produce a complete image of the object? Verify your answer experimentally. Explain your observations.
Why do HCl, HNO3, etc., show acidic characters in aqueous solutions while solutions of compounds like alcohol and glucose do not show acidic character?
Which of the following is not an example of a bio-mass energy source?
(a) wood (b) gobar-gas
(c) nuclear energy (d) coal
Why is a normal eye not able to see clearly the objects placed closer than 25 cm?
Why does an aqueous solution of an acid conduct electricity?
Why does dry HCl gas not change the colour of the dry litmus paper?