NCERT Class X Science Class: Chapter –6. Life Processer – Part-12

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Question 68:

What will happen if platelets were absent in the blood?

Answer:

In the absence of platelets, the process of clotting will be affected.

If there are no platelets in the blood, our skin would not be able to stop the bleeding if we are wounded or cut; because platelets are there to induce the clotting action which stops bleeding and loss of blood. thus, there would be overflow of blood and we would lose life

Question 69:

Plants have low energy needs as compared to animals. Explain.

Answer:

Plants do not need to move from one place to another. Movements in a plant are usually at the cellular level and hence a far less amount of energy is required by plants. Animals, on the other hand, need to move from one place to another; in search of food. So, the energy need of animals is pretty higher than of plants.

Question 70:

Why and how does water enter continuously into the root xylem?

Answer:

Cells of root are in close contact with soil and so actively take up ions. The ion-concentration, increases inside the root and hence osmotic pressure increases the movement of water from the soil into the root which occurs continuously.

Image water enter continuously into the root xylem

Image Water Enter Continuously into the Root Xylem

Image water enter continuously into the root xylem

Question 71:

Why is transpiration important for plants?

Answer:

Transpiration is important because

(a) It helps in absorption and upward movement of water and minerals from roots to leaves

(b) It prevents the plant parts from heating up.

Image transpiration important for plants

Image Transpiration Important for Plants

Image transpiration important for plants

Question 72:

How do leaves of plants help in excretion?

Answer:

Leaves of plants helps in excretion in many ways. Excess of water in plants is discarded by transpiration and guttation that takes place through leaves. Carbon dioxide and oxygen that can be considered as waste products of respiration and photosynthesis respectively are excreted through stomata present on leaves.

Besides these leaves helps in excretion through a process called abscission. Abscission is falling off old and yellow leaves. By the help of this process plants get rid off toxins etc.

Image the excretion in plants

Image the Excretion in Plants

Image the excretion in plants

Long Answer Questions

Question 73:

Explain the process of nutrition in Amoeba.

Answer:

The mode of nutrition in Amoeba is holozoic.

Image the nutrition in Amoeba

Image the Nutrition in Amoeba

Image the nutrition in Amoeba

The various steps involved in the process of nutrition are:

Ingestion: Amoeba ingests food with the help of its finger-like extensions, called pseudopodia. When a food particle approaches Amoeba, it forms pseudopodia around it and forms a food vacuole inside the Amoeba.

Digestion: Various enzymes from the cytoplasm enter into the food vacuole and break them down into simple soluble molecules.

Absorption: The simple soluble food is absorbed by cytoplasm of Amoeba from food vacuoles through the process of diffusion.

Assimilation: Amoeba cell obtains energy from the absorbed food through respiration. This energy is utilized by Amoeba for its growth and repair of the body.

Egestion: When a considerable amount of undigested food gets collected inside Amoeba, its cell membrane ruptures and throws out the undigested food.

Question 74:

Describe the alimentary canal of man.

Answer:

Human digestive system involves various parts which performs different functions where in digestive juices with enzymes takes part alimentary canal is a long tube extending from mouth to anus process of taking food in the body is called ingestion mastication of food takes place in mouth which leads to the formation of bolus during mastication ptyalin present in saliva breaks down carbohydrate into maltose and dextrin after mastication bolus passes through esophagus by peristalsis and reaches stomach contains gastric glands which secretes gastric juice and due to which protein gets partially digested by pepsin present in gastric juice as a result of churning chyme is formed which reaches duodenum through pyloric sphincter bile secreted by liver and pancreatic juice secreted by pancreas gets released into duodenum emulsification of the fats is done by bile lipase is pancreatic juice converts emulsified fats into fatty acids and glycerol’s while trypsin helps in partial digestion of proteins peptidases is an intestinal juice converts peptides of proteins into amino acids absorption of digested food takes place through villi present in walls of small intestine undigested food moves into large intestine where water is absorbed faces are stored in rectum temporarily and are expelled out through anus which is also called egestion or defecation.

Image alimentary canal of man

Image Alimentary Canal of Man

Image alimentary canal of man

Question 75:

Explain the process of breathing in man.

Answer:

Human respiratory system: The human respiratory system begins from nose cavities called nostrils. The air from cavity enters into the pharynx and then into the trachea (or wind pipe). The trachea runs down the neck and divides into two tubes called bronchi. Each bronchi is connected to a lung. In the lungs each bronchi divides into a large number of thin tubes called bronchioles. The bronchioles have a tiny air sac at their ends called alveoli. It is in the alveoli where exchange of gases takes place.

Mechanism of breathing:

When we breathe in air, the diaphragm contracts which results in the increase in volume of chest cavity. Due to this expansion of chest cavity, the air pressure in the lungs decreases. Thus, air from outside rushes into the lungs through nostrils, trachea and bronchi. Therefore, air sacs of lungs get filled with air when we breathe in. The exchange of gases between alveoli and blood takes place by the process of diffusion.

Image respiratory system

Image Respiratory System

Image respiratory system

Now, the air present in air sacs of the lungs is rich in C02. When we breathe out air, the diaphragm relaxes which results in the decrease in volume of chest cavity. This contraction pushes the air from the lungs into the trachea, nostrils and then out of the body into air. Breathing in air is called inhalation and breathing out air is called exhalation.

Mechanism of gaseous exchange during respiration: The oxygen is carried by blood to all the parts of the body. As the blood passes through the tissues of the body, the oxygen from the blood diffuses into the cell, whereas the which is produced during respiration diffuses into the blood and is carried to the lungs.