NCERT Solutions for Class 10 Science Chapter 6 Life Processes

The fingers-like structure present on the inner surface of the small intestine are called Villi. About five millions of villi are present in the intestines, thus they increase the absorptive surface of the intestine considerably and facilitate quick absorption of the digested food. Each villi contains a network of blood capillaries with a central lacteal vessel (lymph vessel).

Carbohydrates are utilized for providing energy to the plants and are stored in the form of starch, which serves as the internal energy reserve to be used as and when required by the plant. In animals, carbohydrates are reserved in the form of glycogen, as internal energy reserve. The carbohydrates like starch (in plants) and glycogen (in animals) serve as the internal energy reserve because they are polymer of glucose and their hydrolysis provide glucose molecules to provide energy at the time of need.

Nutrients are substances which an organism obtains from its surroundings and uses it either as an energy source or source of material required for growth and maintenance of the body.

i). The outermost layer of cell i.e., usually the epidermis is not continuous at some place e.g., on the surface of leaves or green herbaceous stems. The epidermis of the young shoot and leaves contains numerous minute pores called stomata. Each stomata opening is surrounded by two semilunar cells known as the guard cells. The term ‘stomata’ (plural – stomata) is applied to the stomatal opening plus the guard cells. The guard cells are living and contains chloroplast. Their inner walls (wall towards opening) are thicker and outer walls thinner.
ii). Function of guard cells: the guard cells regulate the opening and closing of the stomatal pore. The guard cells swell when water flows into them causing the stomatal pore to open. Because inflow of water in guard cells causes the stretching and bulging of outer thin walls in converse shape. This drags thick walls apart leading to opening of the pore. When there is outflow of water from guard cells, the outer thin walls come to their original position resulting in closure of stomatal pore.

Major functions of stomata are:
1. Stomata are essential for exchange of gases between the plants and the atmosphere-Oxygen and carbon dioxide.
2. Normally, plants eliminate excessive water in the form of vapour through stomatal openings. The process is called transpiration.
3. When there is shortage of water, stomatal openings get closed. Thus, reduce water lose. Stomatal opening also close down during night. Thus, stomata regulate water lose from plants i.e., they regulate transpiration.

In desert, temperature is very high so stomata are closed to reduce the loss of water due to transpiration. Therefore, desert plants are adapted to take up carbon dioxide at night when stomata are open. This CO2, taken up in night, prepare an intermediate compound. This intermediate compound is acted upon by the energy absorbed by the chlorophyll during the day to prepare food

Parasitic mode of nutrition: Some organisms derive their nutrition from other plants or animals (hosts). This is known as parasitic mode of nutrition and such organisms are called parasites. Some parasites are ectoparasite. They lived outside of the body of the host and derive their nutrition, the host such as cuscuta, leech, blood sucking mosquitoes etc. are ectoparasite. Some parasites live in the body of the host called endoparasites. For example: tapeworm, some fungi, etc.

Paramoecium is unicellular animal which has a definite shape (slipper – like).
Paramoecium takes in food at a specific point (through oral groove to mouth to gullet). Food such as bacteria or very small organisms are moved to the specific spot (ingestion point) by the movement of cilia which are present all over the single-celled body.
From the gullet a food vacuole is formed which starts circulating in the endoplasm. During circulation food is digested by enzymes. The digested food diffuses into the cytoplasm and undigested food is thrown out through the pore.

Emulsification means a fine dispersion of one liquid in another. In reference to digestion of food, breakdown of large fat globules in the small intestine by the bile juice from liver into fine smaller fat globules so to increase the efficiency of enzyme action, is called emulsification.

Fats are present in the form of large globules in the small intestine. The small intestine gets the secretions in the form of bile juice and pancreatic juice respectively from the liver and the pancreas. The bile salts (from the liver) break down the large fat globules into smaller globules so that the pancreatic enzymes can easily act on them. This is referred to as emulsification of fats. It takes place in the small intestine.

Saliva is secreted by the salivary glands, located under the tongue. It makes the food soft for easy swallowing. It contains a digestive enzyme called salivary amylase, which breaks down starch into sugar.

The alveoli are the small balloon-like structures present in the lungs. The walls of the alveoli consist of extensive network of blood vessels. Each lung contains 300−350 million alveoli, making it a total of approximately 700 million in both the lungs. The alveolar surface when spread out covers about 80 m² area. This large surface area makes the gaseous exchange more efficient.

Haemoglobin is the respiratory pigment that transports oxygen to the body cells for cellular respiration. Therefore, deficiency of haemoglobin in blood can affect the oxygen supplying capacity of blood. This can lead to deficiency of oxygen in the body cells. It can also lead to a disease called anaemia.

In multi-cellular organisms, all the cells may not be in direct contact with the surrounding environment. Thus, simple diffusion will not meet the requirements of all the cells.

Any visible movement such as walking, breathing, or growing is generally used to decide whether something is alive or not. However, a living organism can also have movements, which are not visible to the naked eye. Therefore, the presence of molecular movement inside the organisms used to decide whether something is alive or not.

An organism uses outside raw materials mostly in the form of food (Since life on earth depends on carbon based molecules, most of these food sources are also carbon-based) and oxygen. The raw materials required by an organism can be quite varied depending on the complexity of the organism and its environment.

Role of the acid (HCl) in our stomach: Kills germs present in the food and makes the food acidic, so that pepsin can digest protein.

The small intestine has millions of tiny finger-like projections called villi. These villi increase the surface area for food absorption. Within these villi, many blood vessels are present that absorb the digested food and carry it to the blood stream. From the blood stream, the absorbed food is delivered to each and every cell of the body.

The exchange of gases takes place between the blood capillaries that surround the alveoli and the gases present in the alveoli. Thus, alveoli are the site for exchange of gases. The lungs get filled up with air during the process of inhalation as ribs are lifted up and diaphragm is flattened. The air that is rushed inside the lungs fills the numerous alveoli present in the lungs. Each lung contains 300-350 million alveoli. These numerous alveoli increase the surface area for gaseous exchange making the process of respiration more efficient.

Warm-blooded animals such as birds and mammals maintain a constant body temperature by cooling themselves when they are in a hotter environment and by warming their bodies when they are in a cooler environment. Hence, these animals require more oxygen (O2) for more cellular respiration so that they can produce more energy to maintain their body temperature. Thus, it is necessary for them to separate oxygenated and de-oxygenated blood, so that their circulatory system is more efficient and can maintain their constant body temperature.

Plants use completely different strategies for excretion than those of animals. They can get rid of excess water by transpiration. For other wastes, plants use the fact that many of their tissues consist of dead cells, and that they can even lose some parts such as leaves. Many plant waste products are stored in cellular vacuoles. Waste products may be stored in leaves that fall off. Other waste products are stored as resins and gums, especially in old xylem. Plants also excrete some waste substances into the soil around them.