SSC CGL GK Questions 2026

In that year the International Astronomical Union adopted a formal definition of a planet: a body that orbits the Sun, is massive enough for its own gravity to pull it into a nearly round shape, and has cleared the neighbourhood around its orbit.

The Moon is on average about 384,400 kilometres from the Earth. Light covers about three lakh kilometres in a second, so it crosses that distance in a little over a second.

The asteroid belt is a broad band of rocky bodies, from dust-sized grains to bodies hundreds of kilometres across, going round the Sun between the orbit of Mars and that of Jupiter.

Saturn is a huge ball of hydrogen and helium spread over an enormous volume, and its average density is less than that of water.

The axis of the Earth is tilted about 23.5 degrees from the vertical and keeps pointing in the same direction throughout the year.

Almost every planet, the Earth included, rotates from west to east, which is why the Sun appears to rise in the east.

Jupiter is the fifth planet from the Sun and the largest of all by both diameter and mass; it is a gas giant of hydrogen and helium.

The Sun is about 149.6 million kilometres from the Earth, a distance called one astronomical unit, and light travels about three lakh kilometres in a second.

Venus is wrapped in a very thick atmosphere of carbon dioxide, which lets sunlight in but does not let the heat escape.

DDT and mercury compounds are not broken down in the body and are not excreted, so they build up in the tissues of every organism that takes them in and are passed on to whatever eats it.

Gross primary productivity is the total amount of energy that producers fix by photosynthesis. Plants use a part of it for their own respiration, and what remains stored in plant bodies is the net primary productivity.

In a pond the producers are phytoplankton, tiny floating plants whose total weight at any one moment is small. They multiply very rapidly, however, so over time they can feed a far greater mass of zooplankton and fish.

Bears, crows, pigs and human beings eat both plant and animal food, which allows them to occupy more than one trophic level at the same time and makes them a good example of why food webs, rather than single food chains, describe nature better.

Detritus is dead organic matter such as fallen leaves, dead bodies and animal waste. Organisms like earthworms, termites, bacteria and fungi feed on it, and they in turn are eaten by small birds and other animals.

Energy enters an ecosystem as sunlight, is fixed by green plants, and then moves from producers to herbivores, to carnivores and finally to decomposers.

They feed on dead bodies, fallen leaves and waste matter, break the complex organic substances into simple ones and release nutrients back into the soil, water and air, where plants can take them up again.

Energy is lost as heat at every transfer from one trophic level to the next, so a higher level can never hold more energy than the level below it.

It says that only about ten per cent of the energy present at one trophic level is passed on to the next, since the rest is used in respiration and other life processes and is lost to the surroundings as heat.

Green plants make their own food from carbon dioxide and water by photosynthesis, using the energy of sunlight, so they are also called autotrophs.

The British botanist Arthur George Tansley used the word ecosystem in 1935 for a unit in which living organisms and their non-living surroundings are treated together as one system exchanging energy and matter.