NCERT Solutions for Class 10 Science CBSE Book

Class 10 science Introduction •

All the plants and animals [Including human beings] are alive or living. The characteristics of living things are as follows: (1) Living things can move by themselves.

(2) Living things can grow.

(3) Living things need food, air and water.

(4) Living things can respond to changes around them. They are sensitive.

(5) Living things respire, excrete and reproduce.

•

The basic functions performed by living organisms to maintain their life on this earth are called life processes. The basic life processes common to all the living organisms are : Nutrition, Respiration, Transport, Excretion, Control and Coordination, Growth, Movement and Reproduction.

Nutrition “Nutrition” is a process of intake as well as utilization of nutrients by an organism. It also includes breakdown of nutrients into smaller molecules and their absorption. Food provides us energy. It contains different type of nutrients in varying amounts according to the need of our body.

Nutrition in Plants

Autotrophs •

The organisms which make their own food from CO2 and H2O in the presence of sunlight and chlorophyll are called autotrophs. e.g.: green plants and bacteria. All green plants are autotrophic and use light as a source of energy for the synthesis of materials.

Heterotrophs •

The organisms which cannot make their own food and depend directly or indirectly on autotrophs. E.g.; animals, fungi and most prokaryotic organisms.

Different types of heterotrophic nutrition is ¨ Saprophytic ¨ Parasitic ¨ Holozoic On the basis of mode of feeding, Hetrotrophs are categorized as:

¨ Saprophytic

• • •

Organisms which get their food supply from dead or decaying organic matter are known as saprophytes.

Common examples of saprophytes are bacteria, fungi like yeast and mushrooms, moulds etc.

Saprophytes produce digestive enzymes which break down food into soluble form and it is then absorbed.

¨ Parasitic • The parasite is an organism which lives outside or inside the body of another organism called the host.

• Parasite derives its nutrition from the host and in turn cause harm to the host.

• Examples of parasites are disease causing Protozoans like Plasmodium, Trypanosoma, worms like round worms, flat worms and many fungi.

• Among the plants Cuscuta is a very common example of parasitism. ¨ Holozoic • Complex organic matter is taken in by the body (ingestion), which is then digested and absorbed.

• On the basis of food habits, holozoic animals are classified into three types: • Herbivores – Cow, Sheep, Deer, Elephant • Carnivores – Tiger, Leopard, Sharks, Snake • Omnivores – Amoeba, Frog, Cockroach, Man Autotrophic Nutrition • Plants are photoautotrophic in nature. They prepare their own food hence they are called as producers.

• They contain a green pigment called chlorophyll which can entrap solar energy which is then converted into chemical energy in the form of food and the process is called as “Photosynthesis” Photosynthesis (i) Definition: The synthesis of organic compounds like glucose from simple inorganic molecules like CO2 and H2O by the cells of green plants having chlorophyll in the presence of sunlight is called as photosynthesis. (ii) Equation of photosynthesis: Sunlight 6CO2 + 12H2O ¾¾¾¾¾¾ ® C6H12O6 + 6O2 + 6H2O Chlorophyll

(iii) Steps of photosynthesis: Photosynthesis is a two step process : (A) Light reaction

(B) Dark Reaction