Why do our ears pop up when we go to higher altitudes or travel in air plane?

Ans : Due to the weight of the molecules in the upper layers of the atmosphere and the force of gravity exerted by the earth, the air molecules are pushed down near the surface and the density goes on decreasing as we go higher where air molecules are far away from each other.

What happens when asteroids collide with planets?

Ans: When asteroids collide with planets a large amount of energy is released in the form of heat, light and sound. This is because of the immense impact which is a result of the large amount of kinetic energy possessed by the asteroids and the planets by virtue of their huge masses and great velocities .

How is a rainbow formed?

Ans: A rainbow appears after heavy rainfall when the sun is in the horizon . It is caused due to the dispersion of sunlight.

When the sunlight passes through the atmosphere each raindrop acts as a tiny glass prism and thus splits the sunlight into a spectrum .

Thus a beautiful rainbow is formed in the sky.

Why does steam cause more severe burns than boiling water?

Ans: Steam causes more severe burns than boiling water because the specific latent heat of steam is 2260 J/g which means every gram of steam that condenses on the skin gives off 2260 J of extra heat.

Why does a fish regardless of its size feel the same pressure at the same depth in water?

Ans: This is because of the pressure exerted by liquid does not depend on the surface area of the object immersed in water but only depends on the depth which acts from all directions .

Why do astronauts wear specially designed pressure suits?

Ans : The astronauts wear specially designed pressure suits as otherwise their bodies will burst because of high pressure of dissolved Oxygen in their blood.

What is the difference between sexual and asexual reproduction?

Ans: Sexual reproduction takes place by the fusion of two sex cells ( gamates ) that is male and female.

Asexual reproduction is a type of reproduction wherein a new individual is produced from a single parent.

Who was the first biologist to coin the term cell?

Ans: Robert Hooke developed a microscope and   observed different objects using two lenses in the year 1665.

He too a thin slice of dead cork and observed a cluster of box-like cubicles piled up together and these he named as cells.

Which are the various shapes of cells?

Ans: Cells have various shapes: oval, spherical, rectangular, elongated, irregular , etc

The red blood cells are spherical or disc- shaped. Their shape enables them to hold more oxygen and flow through fine blood capillaries.

Chlamydomonas is an unicellular green algae which has an oval shape.

Spirogyra is a multicellular green algae that has a cylindrical shape.

The cardiac muscles are cylindrical in shape for easy contraction and relaxation of muscles.

Amoeba is a singlecell organism that has no definite shape It has irregular shape.

The cells of leaf have cubical or rectangular shape.

What is cytology?

The branch of biology which deals with the study of cells is called cytology .

What is rumination?

Animals such as cows and buffaloes swallow grass and store it in a part of the stomach called rumen.

The bacteria present in rumen helps in digestion of grass as it contains cellulose.

The food that is partially digested is called cud.

The cud returns to the mouth in small lumps and the animal chews it. This process is called rumination.

Hybrid seeds

Ans : Flowering plants of some species like Asteraceae and grasses , produce seeds without fertilization called Apomixis. It is a form of asexual form of reproduction 

If hybrids are made into apomicts,  there is no segregation of characters in the hybrid progeny. Hence farmers then can use hybrid seeds to raise crops year after year. 

How is the vapour pressure of a solvent affected when a non - volatile solute is dissolved in it ?

Answer : When a non - volatile solute is added to a solvent, its vapour pressure decreases because some of the surface sites are occupied by solute molecules. Thus, less space is available for the solvent molecule to vaporise. 

What is Apomixis ? What is its advantages ?

Flowering plants of some species like Asteraceae and grasses , produce seeds without fertilization called Apomixis. It is a form of asexual form of reproduction 

If hybrids are made into apomicts,  there is no segregation of characters in the hybrid progeny. Hence farmers then can use hybrid seeds to raise crops year after year. 

Why is the male reproductive system called the urinogenital system?

The male reproductive system consists of a pair  of testes , ducts , a penis and other accessory glands namely the seminal vesicle , prostate glands and the bulbourethral glands. In males ,since the urinary and the reproductive system are  found together in a single unified system , the male reproductive system is called " Urinogenital system "

Why are endocrine glands called ductless glands

The endocrine glands do not have ducts to secrete their  hormones so they are called ductless glands. They release  hormones directly into the blood stream. These hormones reach the concerned body part through the blood and act on it. 

What is meant by photonasty?

Ans : The non - directional movement of a plant part usually the petals of a flower in response to light is called photonasty. 

Examples : A dandelion flower opens up  in the morning in bright light but closes in the evening when the light fades and it gets dark. Whereas a moonflower behaves exactly  opposite. The petals of moonflower close during the day when there is bright light but open up at night when it  is dark and there is no light. 

Male and female rats whose tails are cut cannot produce tail-less rats .Why?

Cutting of the tail  is a change in non - productive tissues. Such changes cannot  be passed on to the DNA of the reproductive cells

Why is organic manure considered better than fertilisers?

Ans : There are various reasons which makes organic manure a better substitute than fertilisers 

(1) It enhances the water holding capacity of soil 

(2) It makes the soil porous due to which exchange of gases becomes  easy. 

(3) It increases the number of friendly microbes. 

(4) It improves the texture of the soil. 

Why are Adrenal glands often called ' glands of emergency'

Adernaline hormone is secreted by the adrenal glands. It is secreted in large amounts when a person is frightened hence it prepares our body for action. It speeds up heart beat and breathing, raises blood pressure and allows more glucose to go into into the blood to give us a lot of energy quickly to fight from the frightening situation. For this reason Adrenal glands are often called ' glands of emergency .'