Test: Life On The Earth - UPSC MCQ

Tropical grasslands, or savannas, lie north and south of tropical rain forests that are on the equator. Some areas beyond savannas are hot deserts. Other savannas may be lined with mountains, dense forests, and seas. South America is a home to several large savannas.

In parasitic nutrition organism derives its food from the body of another living organism called host without killing it. Parasitic mode of nutrition is observed in several fungi, bacteria, few plants like Cuscuta and some animals like Plasmodium and round worms. Plasmodium causes malarial disease.

All ecosystems consist of abiotic and biotic factors. Abiotic factors include rainfall, temperature, sunlight, atmospheric humidity, soil conditions, inorganic substances. Biotic factors include the producers, consumers and decomposers.

The process of releasing energy from food is called respiration. The energy is stored in the form of ATP (Adenosine tri phosphate) in the body cells which is used for various purposes like contraction of muscles, conduction of nerve impulses, synthesis of proteins and many other activities related to the functioning of cells. Therefore, ATP is known as the energy currency of cells.

Temperate steppes are areas with a semiarid continental climatic regime in which, despite maximum summer rainfall, evaporation usually exceeds precipitation. It is in parts of Eurasia and North America.

Aquatic ecosystems can be classed as marine and freshwater ecosystems. Marine ecosystem includes the oceans, coastal estuaries and coral reefs. Freshwater ecosystem includes lakes, ponds, streams, marshes and bogs.

The distinguishing features of terrestrial biomes are determined mainly by climate. Terrestrial biomes include tundras, temperate forests and grasslands, chaparral, temperate and tropical deserts, and tropical forests and grasslands.

Desert is very fragile in many ways, because of the scarcity of water and plants. Most plants that live in the desert take a long time to grow. Once plants are destroyed, it will take many years for them to grow back. Since, soil in the desert is held down by plant roots, once plants are destroyed the soil is, too. The soil will quickly erode away in the strong winds. Soils often have abundant nutrients because they need only water to become very productive and have little or no organic matter.

Aquatic ecosystems can be classed as marine and freshwater ecosystems. Marine ecosystem includes the oceans, coastal estuaries and coral reefs. Freshwater ecosystem includes lakes, ponds, streams, marshes and bogs.

Mineral salts come directly from the earth’s crust by weathering where the soluble salts enter the water cycle, eventually reaching the sea.