Explore topic-wise InterviewSolutions in Current Affairs.

(i) The nucleus of any atom composed of protons and neutrons is positively charged and the electrons revolve around it are negatively charged.

(ii) There is an attraction between the nucleus and electron which act as a centrifugal force for the electrons to keep revolving.

(iii) The electrons should fall into the nucleus due the attraction. But this will not happen because of the Bohr’s theory. 

(iv) According to the theory the electrons revolve around the nucleus in specified orbits, he called them as the discrete orbits. 

(v) He also stated that the electrons while moving in these orbits do not radiate energy. 

(vi) Due to which the electrons will keep on revolving in the discrete orbits because there is no loss of energy from the electrons until any external force is applied.

(i) Discrete orbit was the term given by Neils Bohr to specify the imaginary path of the electrons moving around the nucleus without losing energy.

(ii) For the atom to be stable it is important that it has the minimum energy and be electrically neutral.

(iii) For this the electron have to be constantly revolving around the nucleus without radiating or gaining any energy. 

(iv) Neils Bohr gave the postulate that electron will only revolve in the paths or orbits in which it will not radiate any energy and hence the atom will be stable.

(v) So, the special orbits that are present inside the atom in which the electron revolves is given the term of ‘discrete orbit’.

(i) Helium and Neon are both gases and belong to the group of elements called the noble gases. 

(ii) Both the elements Helium and Neon have completely filled outermost shells and are fully stable in this state. 

(iii) The atomic number of Helium is 2 which means it has only 2 electrons which are present in the K shell and Neon has atomic number 10 and has 10 electrons, its electronic configuration is K = 2, L = 8 electrons.

(iv) As we can see the outermost shells for both the atoms are completely filled so they are not required to share their electrons or share the electrons of other atoms to complete their outermost shell and become stable. 

(v) As their last energy shells are full they are inert and does not take part in reactions.

(i) If in an atom the first four shells are completely filled then the total number of the electrons in the atom would be 26. 

(ii) This is because the first four shells of the atom are K, L, M and N. using the formula 2(n²) we can ind out the maximum electron in each shell which comes out to be 

K = 2 electrons 

L = 8 electrons 

M and N = 18 electrons as 

(iii) The maximum number of the electrons in outermost orbit cannot be more than 8.

(iv) So the total number of electrons for first four completely filled shells is 26.

Isobars: Atoms of different elements with different atomic numbers, which have the same mass number are known as isobars.

Eg: Atomic number of calcium is 20, and argon, has atomic number 18. The number of electrons in these atoms is different, but the mass number of both these elements is 40. That is the total number of nucleons is the same in the atoms of this pair of elements.

Isotopes are the elements which have the same atomic number or protons but different mass numbers. In ethyl ethanoate the two oxygen atoms have same electrons that means have same number of protons but different neutrons which lead to different mass numbers for both of them

The valency of chlorine is 1 because valency of an element is either equal to the number of valence electrons in its atom or equal to the number of electrons required to complete 8 electrons in the valence shell. Since chlorine is a non-metal so valency of nonmetal = 8 – the number of valence electrons in its atom which is 8-7 = 1.

Isobars are the atoms of different elements having different atomic numbers but a same mass number. One pair of isobars is ⁴⁰Ar₁₈ and ⁴⁰Ca₂₀. 

Isobars do not have the same number of protons or electrons so the chemical properties are not similar.

Mass Number of X species = 6u + 6u = 12u

Mass Number of Y species = 6u + 8u = 14u

Both species has equal number of protons but they differ in neutrons.

1. If a convex lens is held over a paper in sunlight such that there is a tiny spot of light on the paper for a while the paper bums.

2. This is due to the heat energy of the sun concentrated at a point due to the convex lens.

Let a constant force, F act on an object. Let the object be displaced through a distance S in the direction of the force. Let W be work done. We define work to be equal to the product of the force and displacement.

Work done = force × displacement 

W = F × S.

When we push a huge rock, there is no transfer of muscular energy to the stationary rock. Also, there is no loss of energy because muscular energy is transferred into heat energy, which causes our body to become hot.

The impact force experienced by the fly will be more, because the mass of fly is negligible when compared to the mass of the bus.

The speed of the ball while it moves up decreases gradually, due to negative gravitational force acting on it.

Work done W = F × s 

Here s = 0 

⇒ W = F × 0 = 0 

∴ The work done is zero.

We know that P.E. = mgh 

a) The work done by you does not depend on the path taken by the suitcase, because the height from the ground to the top of the table is fixed in this case, (h constant) 

b) The work done by you does not depend the time taken, in doing so, because the work done is same. If you take less time your power will be more otherwise the power is less.

c) The work done by you depends on the weight of the suitcase. As the weight of the suitcase increases, the work done will also increase (See the formula P.E. = mgh). 

d) The work done by you depends on your weight, we know that a person with more weight can Mft the suitcase easily.

The speed of the ball at its maximum height is zero.

• When a boy pushes a wall, the displacement in the wall is zero.
• When a boy stands for some time at one place, then there is no displacement in the boy.
• Wind causes the swing in trees, but the tree does not have any displacement.

In general view, work is said to be done while reading, writing, eating or even standing for some time. We cannot observe any displacement in these cases. But in scientific view, work is said to be done when there is a displacement in the direction of force applied.

The energy inside our body causes increase in the P.E. of the bicycle and our self. 

As we are pushing the bicycle upon incline, the work done by the gravitational force is negative. Hence the energy loses.

The capacity of doing work by an object on another object depends on position and state of the object which is doing work.

We know work done W = F × s 

Here F = 0

⇒ W = 0 × s = 0 

∴ The work done is zero.

Though the person standing is not doing any work externally, a lot of work is being done inside the body. 

The muscles of the body become stretched when he stands for long time and heart has to pump more blood to muscles. This leads to loss of energy inside the body and hence he gets tired.

The toy car is at rest before winding the key but the same toy gets energy to move when the key attached to it is wound up.

Energy is the capability to do work.

During its downward motion, the ball starts from zero velocity * and its velocity gradually increases due to the positive gravitational force acting on it.

No, we cannot do any work without transfer of energy.

Energy can exists in several forms like mechanical energy, light energy, thermal energy, sound energy, electrical energy, magnetic energy, etc. These energies, though they are artificial, they ultimately depend on the Sun.

Green plants produce food from sunlight, by means of photosynthesis.

The other natural sources of energy are wind energy, tidal energy, gravitational energy, etc. The artificial sources of energy are electrical energy, heat energy, muscular energy, etc.

The Davisson and Germer experiment directly indicated the wave nature of material particles and quantitatively verified the de Broglie hypothesis for the existence of matter waves.

[Note : The aim of the experiment was not to verify wave like properties of electrons. The realisation came only later, an example of serendipity.]

[Note : Like X-rays, electrons exhibit wave nature under suitable conditions. When the wavelength of matter waves associated with moving electrons is comparable to the interatomic spacing in a crystal, electrons show diffraction effects. In 1927, Sir George

Thomson (1892 – 1975), British physicist, with his student Alex Reid, observed electron diffraction with a metal foil. It is found that neutrons, atoms, molecules, C E - particles, etc. show wave nature under suitable conditions.]

If work has a negative value, the body on which the work has been done losses energy.

The material contained in the bodies of plants and animals is Called ‘Biomass’.

The answer is (c) inhibit growth

• Auxins increase the length of cells. 
• Cytokinins promote cell division. Gibberlins promote growth of stem

Within a plant, the apoplast is the free diffusional space outside the plasma membrane. It is interrupted by the casparian strip in roots, air spaces between plant cells and the cuticula of the plant. Structurally the apoplast is formed by the continuum of cell walls of adjacent cells as well as the extracellular spaces, forming a tissue level compartment comparable to the symplast. The apoplastic route facilitates the transport of water and solutes across a tissue or organ. This process is known as apoplastic transport.

The symplast of a plant is the inner side of the plasma membrane in which water can freely diffuse. The plasmodesmata allow the direct flow of small molecules such as sugar, amino acids and ions between cells. Larger molecules, including transcription factors and plant viruses ! can also be transported through with the help of actin structures.

(a)

(b) Exudation of water from smaller plants; under low evaporation conditions; is called guttation. Evaporative loss of water from plants is called transpiration. In guttation, water comes out in liquid form; while in transportation, water comes out in gaseous form.

A. wild buffalo 

Wild buffalo has become extinct about 50 years back from Satpura park.

The answer is (d) phototropism

• Growth of plant roots towards or away from moisture is called hydrotropism.
• Plant growth in response to gravitational force is called as geotropism.
• Growth of plant in response to chemical stimulus is called chemotropism.

1. Gir national park – (d) Gujarat 

2. Sundarabans National Park – (c) West Bengal 

3. Indira Gandhi National Park – (e) Tamil Nadu 

4. Corbett National Park – (b) Uttarangal 

5. Kanha National Park – (a) Madhya Pradesh

Apoplast:

The term apoplast was coined in 1930 by Munch in order to separate the living symplast from the dead apoplast.
The apoplast is the space outside the plasma membrane within which material can disperse freely. It is broken up by the Casparian strip in roots, by air spaces between plant cells and by the plant cuticle.
The apoplast route facilitates the transportation of water and solutes across a tissue or organ. This process is called apoplastic transport.

Symplast:

The symplast is the inner side of the plasma membrane in which the water and low-molecular- weight solutes can freely diffuse. Symplast cells have more than one nucleus. The water enters the cytoplasm of the cell all the way through the plasma membrane; hence, the symplastic pathway should cross cell membranes. Since the symplastic pathway crosses the cell membrane, it is also called transmembrane pathway. The movement of water in the symplastic pathway is assisted by cytoplasmic streaming.

The answer is (b) cerebellum

• Cerebrum is responsible for sensory processing. Medulla controls involuntary functions.
•  Pons regulates respiration and controls involuntary actions sensations such as touch and pain.

1. World Wildlife Fund 

2. endemic 

3. International Union for conservation of Nature 

4. Nilgiris 

5. March 3

The answer is (b) medulla

• The medulla oblongata or simply medulla is a long stem-like structure which makes up part of the brainstem.
• It is anterior and partially inferior to the cerebellum. 
• It is a cone-shaped neuronal mass responsible for autonomic (involuntary) functions ranging from vomiting to sneezing.

Wildlife Protection Act was implemented in 1972.

(b) on site conservation

Conservation is the protection, preservation, management of wildlife and natural resource such as forest and water. 

Types:

In-situ conservation: It is conservation of living resources within the natural ecosystem in which they occur.

1. National Parks:

• It is an area which is strictly reserved for the betterment of the wildlife.
• Here, activities like forestry, grazing or cultivation are not permitted. 
• Eg – Guindy National Park in Chennai district.

2. Wildlife sanctuaries: 

• A sanctuary is a protected area reserved for the conservation of animals only.
• Human activities like harvesting of timber, collection of forest products and private ownership rights are allowed here. 
• Controlled interference like tourist activity is also allowed.

3. Biosphere reserves:

• It is a protected area where human population also forms the part of the system. 
• The area of these places will be around 5000 square kilometers. 
• They conserve the eco system, species and genetic resources. 
• Eg – These areas are set up mainly for economic development.

Ex-situ Conservation: 

It is the conservation of wildlife outside their habitat. Establishing zoos and botanical gardens, conservation of genes, seedling and tissue. 

1. Botanical gardens:

• It is a place where flowers, fruits and vegetables are grown.
• These places provide a healthy and calm environment.

2. Zoological parks: 

• Zoological parks are the areas where wild animals are conserved.
• In India there are about 800 zoological parks. 

3. Tissue Culture:

It is a technique of growing plant cells, tissues, organs, seeds or other plant parts in a sterile environment on a nutrient medium.

4. Seed bank: 

The seed bank preserves dried seeds by storing them in a very low temperature. 

5. Cryo Bank: 

It is a technique by which a seed or embryo is preserved at a very low temperature.

(d) None of these

Destruction of forests in order to make the land available for different uses is known as deforestation.

Causes of Deforestation: 

• Fires and floods are the natural causes for deforestation.
• Human activities are responsible for deforestation include agricultural expansion, cattle breeding, illegal logging, mining, oil extraction, dam construction and infrastructure development.

1. Agricultural Expansion:

• With increasing population, there is an overgrowing demand for food production. 
• Hence, large amount of trees are chopped down for crops and for cattle grazing.

2. Urbanization:

• Increase in population needs the expansion of cities. 
• More land is needed to establish housing and settlement. 
• Requirements like construction of roads, development of houses, mineral exploitation and expansion of industries also arise due to urbanisation. 
• Forests are destroyed to meet all these needs.

3. Mining:

• Mining of coal, diamond and gold require a large amount of forest land. 
• Large number of trees are cut down to clear the forest area. The waste that comes out from mining pollutes the environment and affects the nearby plants.

4. Construction of dams:

To provide water supply to the increasing population, large size dams are constructed. Hence, a great extend of forest area is being cleared.

5. Timber Production:

• Wood-based industries like paper, matchsticks, furniture need a substantial amount of wood supply. 
• Wood is the most commonly used fuel, thus, a large number of trees are being cut down for fuel supplies. 
• Illegal wood cutting is the main reason for the destruction of some valuable plants.

6. Forest fire: 

• Forest fire be caused by humans, accidents or natural factors. 
• Forest fires wipe out thousands of acres of forest land each year all over the world. This has tremendous effects on biodiversity and the economy as well.

7. Cyclones: 

Cyclones destroy the trees on a massive scale.

Effects of Deforestation: 

1. Extinction of species: 

Deforestation has resulted in the loss of many wonderful species of plants and animals and many are on the verge of extinction.

2. Soil Erosion: 

• When the trees are cut down, soils are exposed to the Sun’s heat. 
• Extreme temperature of the summer dries up the moisture and makes the nutrients to evaporate, ft also affects the bacteria that helps in the breakdown of organic matter. 

3. Water cycle: 

When trees are cut down, the amount of water vapour released decreases for transpiration and hence there is a decrease in the rainfall.

4. Floods: 

When the trees are cut down, the flow of water is disrupted and it leads to flooding.

1. It helps to evaluate the population of a particular species. 

2. The data given in this book can be used to evaluate the species at the global level. 

3. The risk of a species becoming globally extinct can be estimated with the help of this book. 

4. It provides guidelines for implementing protective measures for endangered species.