Respiration

1.  What is respiration?

The process of breakdown of food in the cells to generate energy for various life processes is called respiration.

2.  Why do organisms require the process of respiration?

All living organism require energy to survive, maintain and sustain their life processes.
Respiration is oxidation of food to produce energy in the form of ATP. This energy rich chemical compound serves as an energy currency in all life processes.

3.  Name the chemical compound that acts as the starting material for the breakdown process during respiration.

Glucose

4.  Do all organisms follow same pathway to generate energy through respiration?

No, organisms follow different pathways to generate energy.

5.  Name two main types of pathways followed by living organisms during respiration.

Two main types of pathways followed during respiration are
(i) Aerobic respiration
(ii) Anaerobic respiration

6.  Explain the first step that is common in all cases of respiration. Where does it take place?

In all organisms the first step during the process of respiration is the breakdown of glucose molecules (six carbon) into pyruvate (three carbon)
This step (Glycolysis) takes place in the cytoplasm of the cell.

7.  What is fermentation?  Why is it also referred as anaerobic respiration?

In yeast and many bacteria, the pyruvate molecule formed in the first step of respiration is further converted to ethanol, (2 carbon) and carbon dioxide in absence of oxygen.  Energy is also produced during the reaction.
Since the process takes place in absence of air or oxygen, it is also called as anaerobic respiration.

8.  Explain the process of aerobic respiration.

- Aerobic respiration takes place in most of the cells of multicellular organisms.
- It occurs in the mitochondria of the cell.
- This process requires presence of oxygen.
- It involves the breakdown of pyruvate molecule (three carbon) to three molecules of carbon dioxide (one carbon).
- Water is also produced in the process
- This process releases more energy as it involves complete breakdown of glucose.

9.  Name a part of our body where anaerobic respiration may occur due to lack of oxygen.

Muscle cells

10.  Explain the process of anaerobic respiration taking place in muscle cells.

During anaerobic respiration due to lack of oxygen in muscle cells, pyruvate is converted into lactic acid (3-carbon molecule). Energy released in the process is used by muscle cells.

11.  Differentiate between aerobic and anaerobic respiration taking place in muscle cells.

Differences between aerobic and anaerobic respiration is as follows:

Respiration

12.  Draw a flow chart showing different pathways of breakdown of glucose during respiration.

13.   Name the energy rich molecules synthesised during respiration in living organisms.

ATP or adenosine triphosphate is the energy rich molecule synthesised during respiration.

14.  How is ATP utilized by living beings?

ATP molecule is broken down to produce a fixed amount of energy.  Living organisms use this energy during various life processes.

15.  Describe an activity to demonstrate that air contains carbon dioxide.

Activity to demonstrate that air contains carbon dioxide is as follows:

Procedure

- Take some freshly prepared lime water in a test tube
- Use a syringe or pichkari to pass air in it
- Observe carefully the lime water
Observation - Lime water turns milky
Conclusion Air contains carbon dioxide

16.  Describe an activity to demonstrate that the air we exhale out is rich in carbon dioxide.

Activity to demonstrate that air we exhale out is rich in carbon dioxide is as follows
Procedure:
- Take some freshly prepared lime water in a test tube
- Take a glass tube and blow the air
- Observe the lime water.
Observation:
Lime water turns milky
Conclusion:
Exhaled air contains carbon dioxide.

17.  Describe an activity to demonstrate that fermentation produce carbon dioxide.

Activity to demonstrate that fermentation produces CO₂ is as follows:

Procedure - Take some fruit juice or sugar solution in a test tube
- Add some yeast in this solution
- Fit a one-holed cork with bent glass tube in this test tube.
- Dip the free end of the glass tube into a test tube containing freshly prepared lime water.
- Observe the lime water Observation:
- The mixture of fruit juice and yeast shows formation of froth
- Lime water turns milky Conclusion Fermentation produce CO₂. 

Respiration

                                           Respiration in Plants

1.  What is the common mode of respiration in green plants?

Common mode of respiration in green plants is aerobic respiration.

2.  Name the part of plant that is involved in exchange of gases.

Stomata present on the surface of leaves.

3.  How does exchange of gases occurs in plants?

Exchange of gases in plants takes place by the process of simple diffusion. The large inter-cellular spaces ensure that all cells are in contact with air.

4.  List the factors on which the direction of diffusion of gases in plants depends.

The factors on which the direction of diffusion of gases in plants depends are:
1. Environmental conditions like presence or absence of light
2. Plant requirements.

5.  Explain how the direction of diffusion of gases in plants varies depending upon the environmental conditions and the requirements of the plants.

Exchange of gases at night:

At night in absence of light, the process of photosynthesis slows down. Thus, the requirement of CO₂ reduces.  The major exchange activity during night is therefore removal of carbon dioxide and intake of oxygen for the process of respiration.Exchange of gases at day:

During daytime requirement of CO₂ increases for the process of photosynthesis. The CO₂ produced during respiration also gets used up for photosynthesis, hence there is no CO₂ release. The major exchange activity during day is therefore removal of oxygen and intake of carbon dioxide for the process of photosynthesis.

                                        Respiration in Animals

1.  How do multicellular organisms ensure the process of exchange of gases during respiration?

Multicellular animals have evolved different organs like gills and lungs for the uptake of oxygen from the environment and for getting rid of the carbon dioxide produced.

2.  How do aquatic animals exchange gases?

Aquatic animals use oxygen dissolved in water for respiration.  In these animals, water is constantly taken in and is exposed to the respiratory surface.  As the water moves over the respiratory surface, oxygen diffuses in and carbon dioxide diffuses out of the blood.  Water is then forced out of the body.

3.  Why is the rate of breathing in terrestrial animals slower than aquatic animals?

Amount of dissolved oxygen in water is fairly low as compared to amount of oxygen in the atmosphere (air).  So in order to increase the absorption of oxygen, aquatic animals have faster rate of breathing as compared to terrestrial animals.

4.  What are the characteristics of respiratory organs in animals that ensures efficient exchange of gases?

Respiratory organs of animals show following characteristics:
(i) The structure of these organs is such so as to provide large surface area for exchange of gases.
(ii) Respiratory organs are richly supplied with blood vessels for efficient gas exchange.
(iii) Respiratory surfaces are very thin and delicate to facilitate easy diffusion of gases.

5.  Why are respiratory organs usually placed inside the body of the terrestrial animals?

Respiratory organs are placed inside the body to prevent injury to thin and delicate respiratory surfaces.  

Respiration

                                      Human Respiratory System

1.  Name the parts of respiratory system in man. Draw a labelled diagram of human respiratory system.  

Parts of respiratory system are: Nostrils, nasal cavity, pharynx, trachea, lungs, bronchus, bronchioles, alveoli and diaphragm.

2.  Where are lungs located?

Lungs are located in the thoracic cavity, which is separated, by abdominal cavity by a muscular partition called diaphragm.

3.  What is the function of nasal cavity?

- In the nasal cavity, the air is warmed, moistened.
- The dust particles are entrapped in the mucous and by the fine hair present on the inner lining of nose. 
- The nasal cavity is separated from oral cavity by a bony palate, so we can breathe in air even when we eat.

4.  Why we cannot breathe while swallowing the food? 

The nasal cavity is separated from oral cavity by a bony palate, so we can breathe in air even while we eat. But at the time of swallowing, the food is in the pharynx region. The pharynx leads into trachea or windpipe through a slit called glottis.  
While swallowing food, glottis is covered by a small cartilaginous flap of skin called epiglottis.  This results in closure of trachea. 
This prevents entry of food in trachea. Closure of trachea stops breathing while swallowing. 

5.  Why the trachea does not collapse when there is not much air present in it?

Trachea does not collapse when there is not much air in it, as it is supported by rings of cartilage.  

6.  Name the region in lungs where actual gas exchange takes place.

 Alveoli.

7.   Explain the mechanism of breathing in human beings.  

Breathing has two events: Taking in of air (inhalation) and taking out of air (exhalation). Inhalation occurs when

- diaphragm and muscles attached to ribs contract
- chest cavity expands
- rib cage move upwards and outwards
- volume inside chest cavity increases
- air pressure decreases inside and air from outside rushes into lungs through nostrils, trachea and bronchi.
- alveolar sacs get filled with oxygen rich air (air moves in)
- exchange of gases takes place through the thin walls of alveoli and blood capillaries.

Exhalation occurs when
- carbon dioxide absorbed by blood from the tissues is carried to the alveoli of lungs for exhalation
- diaphragm and rib muscles relax
- chest cavity comes back to its original size
- rib cage comes back to its original size
- volume inside chest cavity decreases
- air pressure increases inside and air from inside rushes out through alveoli, bronchi, trachea and nostrils.
- Carbon dioxide is subsequently pushed out of lungs.

8.  Differentiate between the process of inhalation and exhalation.

Respiration

9.   How does exchange of gases takes place in alveoli?

- In alveoli the concentration of oxygen is higher and that of carbon dioxide is low as compared to concentration of these gases in the blood capillaries. 
- Difference in concentration results in the exchange of gases due to simple diffusion.
- Oxygen diffuses into the blood and carbon dioxide diffuses out.

10.  In large animals, diffusion pressure alone cannot carry oxygen to all body parts.  How is this problem solved in these organisms?

In large animals, diffusion pressure alone cannot carry oxygen to all body parts. To solve this problem animals have respiratory pigment in blood, which carry oxygen to all body parts during circulation.  In human, this respiratory pigment is haemoglobin.

11.   Name the pigment present in the red blood corpuscles which is responsible for transport of oxygen.

Haemoglobin 

12.  How are gases carried through blood?

The process of transport of gases through blood is as follows:

Transport of oxygen- Oxygen gas enters blood in the alveoli region of the lungs.
- Blood contains respiratory pigment haemoglobin which has high affinity for oxygen
- Oxygen binds with haemoglobin and is then is then carried to various body parts through blood circulation.
- In the tissue region oxygen diffuses from blood to the tissue.

Transport of carbon dioxide

- Tissue have more concentration of carbon dioxide which diffuses into the blood. - CO₂ is mainly transported in the dissolved form through blood plasma.
- Once blood reaches alveoli, CO₂ diffuses out into the lungs. 

Transportation in Human Beings

1.  What is transportation?

Transportation is a life process in which a substance absorbed or synthesised in one part is moved or transported to other parts of the body.

2.  What is the need for transportation in living beings?

Transportation in living beings is required for the transport of
(i) nutrients
(ii) metabolic wastes
(iii) respiratory gases
(iv) hormones, enzymes and other metabolites
(v) water, ions and heat
(vi) protection against disease. 

3.   What is the need of special tissues or organs for transport of substances in multicellular organisms?

All living organisms require certain basic material for survival and maintenance like oxygen, water, food etc.  
In unicellular organism, these materials are picked, synthesised and utilised by the same single cell. 
In multicellular organisms, these important materials may be picked or synthesised in one part of body but utilised in some other part or parts.
So there is a requirement of special tissue or organs, which can transport these materials to various body parts of the organism.

4.  What are the basic things required for transportation of material in human body?

Basic things required for transportation of material in human body are:(i) Fluid medium to carry material - Blood
(ii) A pump to push this fluid - Heart
(iii) A network of tubes to carry this fluid to various body parts- Blood vessels
(iv) A system that ensure maintenance and repair of this network of tubes damaged- Platelets.

5.  Name the fluid connective tissue that helps in transportation in human beings.

Blood

6.  How are different material carried through blood? 

Blood consists of fluid medium called plasma in which various corpuscles are present. Plasma transports salts, food, carbon dioxide and nitrogenous wastes in dissolved form. Oxygen is carried by haemoglobin present in the red blood corpuscles.

                                           Human Heart

1.   Draw a labelled diagram of external structure of human heart.

2.  Describe the structure of human heart.    

- Human heart is four chambered.
-Two upper chambers are atria and two lower are ventricles.
- Atria receives blood and ventricles transport blood out of the heart.
- These chambers are separated by partition called septa.
- Between left auricle and right ventricle valves are present to prevent back flow of blood.
- Heart is made of special muscles called cardiac muscle fibres.

3.  Draw a labelled diagram showing internal structure of human heart.

Transportation in Human Beings

1.  What is transportation?

Transportation is a life process in which a substance absorbed or synthesised in one part is moved or transported to other parts of the body.

2.  What is the need for transportation in living beings?

Transportation in living beings is required for the transport of
(i) nutrients
(ii) metabolic wastes
(iii) respiratory gases
(iv) hormones, enzymes and other metabolites
(v) water, ions and heat
(vi) protection against disease. 

3.   What is the need of special tissues or organs for transport of substances in multicellular organisms?

All living organisms require certain basic material for survival and maintenance like oxygen, water, food etc.  
In unicellular organism, these materials are picked, synthesised and utilised by the same single cell. 
In multicellular organisms, these important materials may be picked or synthesised in one part of body but utilised in some other part or parts.
So there is a requirement of special tissue or organs, which can transport these materials to various body parts of the organism.

4.  What are the basic things required for transportation of material in human body?

Basic things required for transportation of material in human body are:(i) Fluid medium to carry material - Blood
(ii) A pump to push this fluid - Heart
(iii) A network of tubes to carry this fluid to various body parts- Blood vessels
(iv) A system that ensure maintenance and repair of this network of tubes damaged- Platelets.

5.  Name the fluid connective tissue that helps in transportation in human beings.

Blood

6.  How are different material carried through blood? 

Blood consists of fluid medium called plasma in which various corpuscles are present. Plasma transports salts, food, carbon dioxide and nitrogenous wastes in dissolved form. Oxygen is carried by haemoglobin present in the red blood corpuscles.

                                           Human Heart

1.   Draw a labelled diagram of external structure of human heart.

2.  Describe the structure of human heart.    

- Human heart is four chambered.
-Two upper chambers are atria and two lower are ventricles.
- Atria receives blood and ventricles transport blood out of the heart.
- These chambers are separated by partition called septa.
- Between left auricle and right ventricle valves are present to prevent back flow of blood.
- Heart is made of special muscles called cardiac muscle fibres.

3.  Draw a labelled diagram showing internal structure of human heart.

Transportation in Human Beings

4.  Why does human heart has different chambers that are not connected to each other?

- Different chambers in human heart are not connected to each other in order to prevent mixing of oxygenated and deoxygenated blood. - Complete separation of chambers ensures that deoxygenated blood goes to various parts of body. This increases the efficiency of supply of oxygen to the body to meet the high-energy requirements. 

5.  Describe the flow of blood through human heart.

- Blood is received from various body parts into the right atrium by superior and inferior vena cava, when the chambers is relax.
- From right auricle blood flows to right ventricle.
- From right ventricle blood is transported to lungs for purification by pulmonary artery.
- After purification, blood comes back to heart in the left auricle / atrium through pulmonary vein.
- From left atrium blood moves to left ventricle.
- From left ventricle blood is pumped out to all the body parts through aorta.

6.  Give a flow chart of blood circulation through human heart.

7.  Name the following blood vessels which  
i. Brings deoxygenated blood into the right atrium from upper body parts -
ii. Brings deoxygenated blood into the right atrium from lower body parts -iii. Takes deoxygenated blood from right ventricle to lungs.
iv. Brings oxygenated blood from lungs to left atrium -.
v. Largest artery that takes oxygenated blood from left ventricle to all body parts -
vi. Supply blood to heart muscles. 

i. Superior vena cava.
ii. Inferior vena cava.
iii. Pulmonary artery.
iv. Pulmonary vein.
v. Aorta.
vi. Coronary arteries.

8.  Name the chambers of heart that carries
i. Oxygenated blood.
ii. Deoxygenated blood. 

i. Oxygenated blood - left atrium and left ventricle.
ii. Deoxygenated blood - right atrium and right ventricle 

9.  Tabulate the changes taking place in heart when-
i. Both atria and ventricles are relaxed
ii. Atria contracts
iii. Ventricles contracts.

10.  Compare the number of chambers in the heart of following animals
(i) Fish
(ii) Amphibians
(iii) Reptiles
(iv) Birds

11.  What is the importance of separation of oxygenated and deoxygenated blood in the heart of living organisms?

Separation of oxygenated and deoxygenated blood allows a highly efficient supply of oxygen to the body.  This is specially useful in animals that have high energy needs like birds and mammals, which constantly use energy to maintain their body temperature.

12.  Give two examples of animals which can tolerate some mixing of oxygenated and deoxygenated blood in their hearts.  How do these animals manage their energy requirements?

Amphibians and most reptiles have three-chambered heart.  They can tolerate some mixing of oxygenated and deoxygenated blood.These animals can afford such mixing because their body temperature depends on the temperature in the environment and they do not use energy to constantly maintain it. Their energy needs are therefore less. 

Transportation in Human Beings

                                            Blood Vessels

1.  How is blood carried to all parts of the body?

Blood is the fluid connective tissue, which is carried to all body parts through tubes called blood vessels

2.  What are the different types of blood vessels?

There are three main types of blood vessels:

(i)  Arteries - Blood vessels that carry blood away from heart 
(ii)  Veins - Blood vessels that carry blood from body parts to heart.
(iii)  Capillaries - Blood vessels that joins arteries and veins.

3.  Differentiate between arteries, veins and capillaries.

4.  Why are the wall of arteries thicker than veins?

Arteries have thicker walls than veins because blood pumped from the heart flows through these arteries with high pressure. 

5.  Why do veins have valves in them?

Veins have valves in them to prevent backflow of blood.

6.  Actual exchange of material between blood and surrounding takes place in which of blood vessels.

Blood capillaries

7.  Why are the walls of capillaries only one cell thick?

The walls of capillaries are one celled thick to facilitate easy diffusion of gases and other materials across it.

                       Maomtemamce and repair of blood  

1.  Under what conditions can one suffer from blood loss?

One may suffer from blood loss during injury or during a surgery.

2.  What would happen if the bleeding is not minimised or stopped?

If the bleeding is not minimised there will be a drop in blood pressure.  This would reduce the efficiency of the pumping system and may cause death of the individual.

3.  Name the cells that help in plugging the leaks in the blood vessels. Where are they located?

Platelet cells helps in plugging the leaks in the blood vessels.  These are present in the blood plasma.

4.  How do platelet cells helps in minimising blood loss during injury?

Platelets circulate around the body in the blood vessels. Whenever there is an injury, platelets plug the leaks in the blood vessels by forming blood clots at the point of injury.                   

                                                Lymph

1.  Name one fluid other than blood that is also involved in the process of transportation

Lymph

2.  Why is lymph also referred to as tissue fluid?

As lymph is present between the intercellular spaces in the tissue, hence it is also called tissue fluid.

3.  How is lymph formed?

Some amount of plasma, proteins and blood cells (mainly WBC) escape from capillaries and spread into the intercellular spaces in the tissues.  This fluid forms the lymph.

4.  What are the components of lymphatic system?

Components of lymphatic system are- lymph, lymphatic capillaries, lymph vessels, lymph nodes and lymph glands.

5.  Differentiate betweens lymph and blood . 

6.  What are the functions of lymph?

1. Lymph contains lymphocytes, which fight against infection and help in body's defense mechanism.
2. Lymph also carries digested fat.
3. Lymph returns proteins and fluid from circulation to tissues.

Transportation in Plants

 1.  List the materials that require transportation in plants.

Water, minerals, sugars and other metabolites synthesised in leaf, hormones synthesised at shoot and root tips, stored food from part of storage to other plant part, etc.

2.  Name the two conducting tissues of plants.

Xylem and phloem.

3.  Why do plants require a proper system of transportation?

In trees and big plants, diffusion process is not sufficient to provide raw material to the leaves from the roots and energy reserves to the roots from the leaves. Therefore, a proper system of transportation is essential in plants.

4.  Why plants can afford to have a slow transport system as compared to animals? 

Plants do not move and have a large proportion of dead cells in many tissues. Therefore, their energy needs are less and therefore they can afford to have a slow transport system as compared to animals.

5.  What is root pressure?

The pressure that is created due to difference in concentration of salts which forces water absorbed from the soil, to move through the roots and up the stem of the plant is known as root pressure.

6.  Why root pressure alone cannot be responsible for transport of water in plants?

Root pressure alone cannot be responsible for transport of water in plants because this pressure created due to concentration gradient and osmosis is not enough to move water over great heights of commonly found tall plants.

7.  Explain the mechanism of upward movement of water and minerals in plants.

The events during movement of water and minerals in plants are as follows:
 - The tissue responsible for it is xylem
 - Water enters roots through special structures called root hair. These are the epidermal outgrowths of roots.
- Root hair of plants are in direct contact with the film of water in between the soil particles.
- Water and minerals dissolved in it enters through root hair due to osmosis and move through root cortex, endodermis, root xylem, stem xylem, xylem of petiole and finally to leaves. This creates concentration difference and hence water is forced to move in.
- The pressure that forces water in is called root pressure.
- Since root pressure is not sufficient to pull water, suction force created by transpiration pulls water till the leaves.

8.  Explain the mechanism of movement of water from soil into the root.

The cells of the root in contact with soil take up ions along with the water by simple diffusion. This creates a difference in the concentration of these ions between soil and the roots, which draws water into the roots from the soil. This leads to steady movement of water into root xylem, forming a column of water that is steadily pushed upwards.

9.   When does root pressure becomes a major driving force for movement of water in plants and why?

At night, root pressure becomes a major driving force for movement of water in plants. This is because the stomata are closed during nighttime and transpiration is not possible.

10.  What is transpiration? What is its importance?

The loss of water in the form of water vapours from the leaves into the atmosphere is called transpiration. Evaporation of water molecules from cells of a leaf due to transpiration creates suction, which is responsible for pulling water from xylem cells. Hence, movement of water and minerals from roots to leaves in the form of a continuous column is due to transpirational pull. This water is utilised by plant during photosynthesis.

Transportation in Plants

 1.  List the materials that require transportation in plants.

Water, minerals, sugars and other metabolites synthesised in leaf, hormones synthesised at shoot and root tips, stored food from part of storage to other plant part, etc.

2.  Name the two conducting tissues of plants.

Xylem and phloem.

3.  Why do plants require a proper system of transportation?

In trees and big plants, diffusion process is not sufficient to provide raw material to the leaves from the roots and energy reserves to the roots from the leaves. Therefore, a proper system of transportation is essential in plants.

4.  Why plants can afford to have a slow transport system as compared to animals? 

Plants do not move and have a large proportion of dead cells in many tissues. Therefore, their energy needs are less and therefore they can afford to have a slow transport system as compared to animals.

5.  What is root pressure?

The pressure that is created due to difference in concentration of salts which forces water absorbed from the soil, to move through the roots and up the stem of the plant is known as root pressure.

6.  Why root pressure alone cannot be responsible for transport of water in plants?

Root pressure alone cannot be responsible for transport of water in plants because this pressure created due to concentration gradient and osmosis is not enough to move water over great heights of commonly found tall plants.

7.  Explain the mechanism of upward movement of water and minerals in plants.

The events during movement of water and minerals in plants are as follows:
 - The tissue responsible for it is xylem
 - Water enters roots through special structures called root hair. These are the epidermal outgrowths of roots.
- Root hair of plants are in direct contact with the film of water in between the soil particles.
- Water and minerals dissolved in it enters through root hair due to osmosis and move through root cortex, endodermis, root xylem, stem xylem, xylem of petiole and finally to leaves. This creates concentration difference and hence water is forced to move in.
- The pressure that forces water in is called root pressure.
- Since root pressure is not sufficient to pull water, suction force created by transpiration pulls water till the leaves.

8.  Explain the mechanism of movement of water from soil into the root.

The cells of the root in contact with soil take up ions along with the water by simple diffusion. This creates a difference in the concentration of these ions between soil and the roots, which draws water into the roots from the soil. This leads to steady movement of water into root xylem, forming a column of water that is steadily pushed upwards.

9.   When does root pressure becomes a major driving force for movement of water in plants and why?

At night, root pressure becomes a major driving force for movement of water in plants. This is because the stomata are closed during nighttime and transpiration is not possible.

10.  What is transpiration? What is its importance?

The loss of water in the form of water vapours from the leaves into the atmosphere is called transpiration. Evaporation of water molecules from cells of a leaf due to transpiration creates suction, which is responsible for pulling water from xylem cells. Hence, movement of water and minerals from roots to leaves in the form of a continuous column is due to transpirational pull. This water is utilised by plant during photosynthesis.

Excretion in Human Beings

 1.  How do plants get rid of gaseous wastes generated during photosynthesis or respiration?

Plants remove oxygen produced during photosynthesis and carbon dioxide produced during respiration by the process of simple diffusion through stomata and their general body surface 

2.   How do animals get rid of the gaseous wastes generated during respiration?  

Animals remove CO₂ the gaseous waste generated during respiration by the process of simple diffusion through their respiratory organs like lungs and gills.

3.  What are the various types of wastes generated in the body of living organisms?

Various types of wastes generated in the body of living organisms are as follows: 

(i) Digestive wastes generated in the digestive tract during the process of nutrition.
(ii) Photosynthetic wastes in plants 
(iii) Respiratory wastes in the form of CO₂ gas 
(iv) Nitrogenous wastes produced at the end of metabolic processes. 

4.  What is excretion?

Excretion is the biological process involved in the removal of nitrogenous wastes produced during metabolic processes in the body.

5.  How do unicellular organisms remove their metabolic wastes?  

Unicellular organisms remove their metabolic wastes by simple diffusion from the body surface into the surrounding environment.

6.  Name the parts of excretory system in human beings.

Human excretory system includes
(1) Pair of kidneys
(2) Pair of ureters
(3) Urinary bladder
(4) Urethra

7.   Draw a labelled diagram of human excretory system.

8.  Where are kidneys located in human body? 

Kidneys are located in the abdominal region, one on either side of the backbone.

9.  What is the role of each part of human excretory system? 

The role of each part of human excretory system is as follows:
(i) Kidneys: They are the main organs of excretion. The nitrogenous metabolic wastes urea is removed from the blood in the form of fluid called urine.
(ii) Ureters: These are the tubes connecting kidneys to urinary bladder. They carry urine from kidney to urinary bladder.
(iii) Urinary bladder: It is the expandable muscular bag which stores urine. When it gets filled with sufficient quantity of urine, the pressure of expanded bladder leads to urge to pass urine out of the body.
(iv) Urethra: It is the tube through which urine is thrown out of the body. 

10.  Name the basic filtration units present in kidneys.

Nephron .

11.  Explain the structure of nephron.  

- Nephron is the basic filtration unit in the kidney
- There are large number of nephrons present in each kidney.
- Each nephron consists of a cup shaped structure called Bowmans capsule at one end.
- The renal artery entering the kidney branches of and these branches enters the Bowmans capsule
- Inside the Bowmans capsule the renal arteriole further branches to form a tuft of capillary cluster called the Glomerulus.
- The Bowmans capsule leads to a long tubular part of nephron.This part is surrounded by a network of capillaries
- At the end of the tubular part is a collecting duct.
- Collecting ducts from all nephrons finally join and connects with the ureter.

12.   Draw a labelled diagram of nephron.

Excretion in Human Beings

13.  How is urine produced in the kidneys? 

- Renal artery carrying waste material enters the kidney.
- The branches of renal artery take the waste material inside the Bowmans capsule.
- Due to high pressure and diffusion waste material along with lot of water and useful products like glucose amino acids and salt gets filtered from blood to the tubular region of nephron.
- As the filterate moves in the tubular region, water and useful substances are selectively reabsorbed back into the capillaries surrounding the tubular region. These capillaries rejoin to form renal vein. Renal vein carries blood without wastes out of the kidneys.
- The filterate which is urine, is passed to collecting ducts. Collecting ducts passes urine into the ureter which in turn takes it out from kidney into the urinary bladder. 

14.  With the help of flow chart trace the events from the moment blood enters kidneys till the formation of urine.

15.  What is artificial kidney?

Some times kidney infection, injury to kidneys or restricted blood flow to kidneys result in kidney damage and its malfunctioning.
In order to clean the metabolic wastes and maintain normal levels of water and minerals ions in body fluids, blood is passed and cleaned by external machine called artificial kidney.
Clean blood is again transferred back into the patient's body.

16.  Name the procedure used in the working of an artificial kidney.

Dialysis.

17.  What is dialysis?

Dialysis is the technique of removing excretory wastes and other toxic waste artificially from the blood by passing it through long cellulose tubes coiled in a tank with dialysing solution.  
As the blood passes through this artificial kidney the excretory and toxic wastes diffuses out and clean blood is pumped back in to the patient.

18.  Draw labelled schematic diagrams of procedure used in artificial kidney.

18.  Draw labelled schematic diagrams of procedure used in artificial kidney.

Excretion in Plants

 1.  List some wastes produced in the plant body 

(i) O₂ produced during photosynthesis
(2) CO₂ produced during respiration
(3) Excess water absorbed
(4) Gums, resins and other chemical substances

2.  How do plants get rid of their excretory wastes?

Plants remove their excretory wastes in following ways.
(i)  Photosynthetic waste, oxygen gas is removed through stomata and body surface.
(ii) Respiratory waste carbon dioxide is also remove by simple diffusion through stomata and general body surface
(iii) Excess water is removed by the process of transpiration mainly through stomata
(iv) Plants store metabolic wastes in their dead cells like xylem.
(v) In living tissues, wastes material is sometimes stored in vacuoles.
(vi) Waste material may also be stored in plant parts like leaves, which are periodically shed-off.
(vii) Waste products may be stored in the form of gums and resins in old woody (Xylem) regions 
(viii) Plants also give out some volatile waste materials from roots into the surrounding soil.