CBSE Class X

Question 12:

What are the differences between the transport of materials in xylem and phloem?

Answer

 

Question 11:

Describe double circulation in human beings. Why is it necessary?

Answer

The human heart is divided into four chambers − the right atrium, the right ventricle,

the left atrium, and the left ventricle.

Flow of blood in the heart:

• The heart has superior and inferior vena cava, which carries de-oxygenated blood

    from the upper and lower regions of the body respectively and supplies this de-

    oxygenated blood to the right atrium of the heart.

Flow of blood in the human heart

• The right atrium then contracts and passes the de-oxygenated blood to the right

    ventricle, through an auriculo-ventricular aperture.

• Then the right ventricle contracts and passes the de-oxygenated blood into the two

   pulmonary arteries, which pumps it to the lungs where the blood becomes

   oxygenated. From the lungs, the pulmonary veins transport the oxygenated blood

   to the left atrium of the heart.

• Then the left atrium contracts and through the auriculo-ventricular aperture, the

   oxygenated blood enters the left ventricle.

• The blood passes to aorta from the left ventricle. The aorta gives rise to many

    arteries that distribute the oxygenated blood to all the regions of the body.

Schematic diagram of blood circulation in humans

Therefore, the blood goes twice through the heart. This is known as double circulation.

Importance of double circulation:

The separation of oxygenated and de-oxygenated blood allows a more efficient

supply of oxygen to the body cells. This efficient system of oxygen supply is very

useful in warm-blooded animals such as human beings.

As we know, warm-blooded animals have to 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, they require more O₂ for

more respiration so that they can produce more energy to maintain their body

temperature. Thus, the circulatory system of humans is more efficient because of

the double circulatory heart.

Question 10:

What would be the consequences of a deficiency of haemoglobin in our bodies?

Answer

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.

Question 9:

How are the alveoli designed to maximise the exchange of gases?

Answer

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.

Question 8:

What are the differences between aerobic and anaerobic respiration? Name some

organisms that use the anaerobic mode of respiration.

Answer

 

Anaerobic respiration occurs in the roots of some waterlogged plants, some parasitic

worms,animal muscles, and some micro-organisms such as yeasts.

Question 7:

What are the necessary conditions for autotrophic nutrition and what are its by-

products?

Answer

Autotrophic nutrition takes place through the process of photosynthesis. Carbon

dioxide, water, chlorophyll pigment, and sunlight are the necessary conditions

required for autotrophic nutrition. Carbohydrates (food) and O₂ are the by-products

of photosynthesis.

Question 6:

What is the role of saliva in the digestion of food?

Answer

Saliva is secreted by the salivary glands, located under the tongue. It moistens the

food for easy swallowing. It contains a digestive enzyme called salivary amylase,

which breaks down starch into sugar.

Question 5:

How are fats digested in our bodies? Where does this process take place?

Answer

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.

Question 4:

The breakdown of pyruvate to give carbon dioxide, water and energy takes place in

(a) cytoplasm.

(b) mitochondria.

(c) chloroplast.

(d) nucleus.

Answer

(b) The breakdown of pyruvate to give carbon dioxide, water and energy takes place

      in mitochondria.

Question 3:

The autotrophic mode of nutrition requires

(a) carbon dioxide and water.

(b) chlorophyll.

(c) sunlight.

(d) all of the above.

Answer

(d) The autotrophic mode of nutrition requires carbon dioxide, water, chlorophyll and

      sunlight.

Question 2:

The xylem in plants are responsible for

(a) transport of water.

(b) transport of food.

(c) transport of amino acids.

(d) transport of oxygen.

Answer

(a) In a plant, the xylem is responsible for transport of water.

Question 1:

The kidneys in human beings are a part of the system for

(a) nutrition.

(b) respiration.

(c) excretion.

(d) transportation.

Answer

(c) In human beings, the kidneys are a part of the system for excretion.

Question 3:

How is the amount of urine produced regulated?

Answer

The amount of urine produced depends on the amount of excess water and dissolved

wastes present in the body. Some other factors such as habitat of an organism and

hormone such as Antidiuretic hormone (ADH) also regulates the amount of urine

produced.

Question 2:

What are the methods used by plants to get rid of excretory products?

Answer

Plants can get rid of excess of water by transpiration. Waste materials may be stored

in the cell vacuoles or as gum and resin, especially in old xylem. It is also stored in

the leaves that later fall off.

Question 1:

Describe the structure and functioning of nephrons.

Answer

Nephrons are the basic filtering units of kidneys. Each kidney possesses large number

of nephrons,approximately 1-1.5 million. The main components of the nephron are

glomerulus, Bowman’s capsule, and a long renal tubule.

Structure of a nephron

Functioning of a nephron:

• The blood enters the kidney through the renal artery, which branches into many

   capillaries associated with glomerulus.

• The water and solute are transferred to the nephron at Bowman’s capsule.

• In the proximal tubule, some substances such as amino acids, glucose, and salts

   are selectively reabsorbed and unwanted molecules are added in the urine.

• The filtrate then moves down into the loop of Henle, where more water is absorbed.

• From here, the filtrate moves upwards into the distal tubule and finally to the  

   collecting duct. Collecting duct collects urine from many nephrons.

• The urine formed in each kidney enters a long tube called ureter. From ureter, it

   gets transported to the urinary bladder and then into the urethra.

Question 5:

How is food transported in plants?

Answer

Phloem transports food materials from the leaves to different parts of the plant body.

The transportation of food in phloem is achieved by utilizing energy from ATP. As a

result of this, the osmotic pressure in the tissue increases causing water to move

into it. This pressure moves the material in the phloem to the tissues which have

less pressure. This is helpful in moving materials according to the needs of the

plant. For example, the food material, such as sucrose, is transported into the

phloem tissue using ATP energy.

Question 4:

How are water and minerals transported in plants?

Answer

The components of xylem tissue (tracheids and vessels) of roots, stems, and leaves

are interconnected to form a continuous system of water-conducting channels that

reaches all parts of the plant. Transpiration creates a suction pressure, as a result

of which water is forced into the xylem cells of the roots. Then there is a steady

movement of water from the root xylem to all the plant parts through the

interconnected water-conducting channels.

 

Question 3:

What are the components of the transport system in highly organised plants?

Answer

In highly organised plants, there are two different types of conducting tissues −

xylem and phloem. Xylem conducts water and minerals obtained from the soil (via

roots) to the rest of the plant. Phloem transports food materials from the leaves to

different parts of the plant body.

Question 2:

Why is it necessary to separate oxygenated and deoxygenated blood in mammals and

birds?

Answer

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.

Question 1:

What are the components of the transport system in human beings? What are the

functions of these components?

Answer

The main components of the transport system in human beings are the heart, blood,

and blood vessels·

• Heart pumps oxygenated blood throughout the body. It receives deoxygenated

   blood from the various body parts and sends this impure blood to the lungs for

   oxygenation.

• Being a fluid connective tissue, blood helps in the transport of oxygen, nutrients,

   CO₂, and nitrogenous wastes.

• The blood vessels (arteries, veins,and capillaries) carry blood either away from the

   heart to various organs or from various organs back to the heart.