What are fossils? What do they tell us about the process of evolution?
Fossils are the remains or impression of the ancient organisms preserved naturally. During the formation of sedimentary rocks, dead animals of the sea or the lakes and of the land sink down or are buried in the rocks. The animals, thus preserved in the rocks formed the fossils. Fossils are the main evidence which show the process of evolution from how the origination of life occurs in ancient times or how it has been started to the life found on earth in today’s time.
When a 12 V battery is connected across an unknown resistor, there is a current of 2.5 mA in the circuit. Find the value of the resistance of the resistor.
Outline a project which aims to find the dominant coat colour in dogs.
Draw the structure for the following compounds.
(i) Ethanoic acid (ii) Bromopentane*
(iii) Butanone (iv) Hexanal.
*Are structural isomers possible for bromopentane?
A hot plate of an electric oven connected to a 220 V line has two resistance coils A and B, each of 24 Ω resistance, which may be used separately, in series, or in parallel. What are the currents in the three cases?
How is the sex of the child determined in human beings?
(a) What property do all elements in the same column of the Periodic Table as boron have in common?
(b) What property do all elements in the same column of the Periodic Table as fluorine have in common?
Calculate the number of electrons constituting one coulomb of charge.
What is an homologous series? Explain with an example.
Why is variation beneficial to the species but not necessarily for the individual?
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?
The position of three elements A, B and C in the Periodic Table are shown below –
Group 16 Group 17
- -
- A
- -
B C
(a) State whether A is a metal or non-metal.
(b) State whether C is more reactive or less reactive than A.
(c) Will C be larger or smaller in size than B?
(d) Which type of ion, cation or anion, will be formed by element A?
Draw the structure of a neuron and explain its function.
Why does the sky appear dark instead of blue to an astronaut?
Why do stars twinkle?
Why is variation beneficial to the species but not necessarily for the individual?
Why are decomposition reactions called the opposite of combination reactions? Write equations for these reactions.
Which signals will get disrupted in case of a spinal cord injury?
What are the two properties of carbon which lead to the huge number of carbon compounds we see around us?
What is meant by saying that the potential difference between two points is 1 V?
Explain the meanings of malleable and ductile.