What evidence do we have for the origin | Class 10 Science Chapter Heredity and Evolution, Heredity and Evolution NCERT Solutions

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.

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?

What is an homologous series? Explain with an example.

Why is variation beneficial to the species but not necessarily for the individual?

Consider a circular loop of wire lying in the plane of the table. Let the current pass through the loop clockwise. Apply the right-hand rule to find out the direction of the magnetic field inside and outside the loop.

How are the alveoli designed to maximise the exchange of gases?

Give any two ways in which biodegradable substances would affect the environment.

The xylem in plants are responsible for

         (a) transport of water.                   (c) transport of amino acids.
         (b) transport of food.                     (d) transport of oxygen.

What is the role of saliva in the digestion of food?

Explain the role of mouth in digestion of food.

What are the problems caused by the non-biodegradable wastes that we generate?

How can we explain the reddish appearance of sun at sunrise or sunset? Why does it not appear red at noon?

What would be the consequences of a deficiency of haemoglobin in our bodies?

Colonies of yeast fail to multiply in water, but multiply in sugar solution. Give one reason for this.