Explanation: Kidneys filter the blood to remove nitrogenous waste products like urea and uric acid in the form of urine. Hence, they are the main organs of the excretory system.
[Image of human excretory system showing kidneys]
Q2
The xylem in plants is responsible for:
(a) Transport of water
(b) Transport of food
(c) Transport of amino acids
(d) Transport of oxygen
Answer: (a) Transport of water
Explanation: Xylem tissue transports water and dissolved minerals from the roots to the leaves (upward movement). Phloem transports food.
Q3
The autotrophic mode of nutrition requires:
(a) Carbon dioxide and water
(b) Chlorophyll
(c) Sunlight
(d) All of the above
Answer: (d) All of the above
Explanation: Autotrophs (plants) perform photosynthesis to make their own food. This process requires $\text{CO}_2$, water, sunlight, and chlorophyll.
Explanation: The breakdown of pyruvate using oxygen is called Aerobic Respiration. This process occurs inside the mitochondria and releases a large amount of energy (ATP). (Note: Breakdown of Glucose to Pyruvate happens in Cytoplasm).
Q5
How are fats digested in our bodies? Where does this process take place?
Location: Small Intestine.
Process:
1. Emulsification by Bile: Fats are present as large globules. Bile juice (from Liver) breaks them down into smaller globules (emulsified fats) to increase efficiency.
2. Digestion by Lipase: The enzyme Lipase (from Pancreatic juice) breaks down emulsified fats.
3. Final Product: The walls of the small intestine secrete intestinal juice which converts fats into Fatty Acids and Glycerol.
Q6
What is the role of saliva in the digestion of food?
Saliva contains a digestive enzyme called Salivary Amylase.
Function: It breaks down starch (complex carbohydrate) present in food into sugar (maltose).
Additionally, saliva moistens the food, making it easier to swallow.
Q7
What are the necessary conditions for autotrophic nutrition and what are its by-products?
Conditions:
1. Presence of Carbon dioxide ($\text{CO}_2$).
2. Presence of Water ($\text{H}_2\text{O}$).
3. Presence of Chlorophyll (to absorb light).
4. Presence of Sunlight (Energy source).
By-products:
1. Oxygen ($\text{O}_2$) – released into the air.
2. Water ($\text{H}_2\text{O}$ vapor).
[Image of photosynthesis process diagram]
Q8
What are the differences between aerobic and anaerobic respiration? Name some organisms that use the anaerobic mode of respiration.
Aerobic Respiration
Anaerobic Respiration
Takes place in presence of Oxygen.
Takes place in absence of Oxygen.
Complete breakdown of glucose.
Incomplete breakdown of glucose.
End products: $\text{CO}_2$ + Water.
End products: Ethanol/Lactic Acid + $\text{CO}_2$.
Releases huge energy (38 ATP).
Releases less energy (2 ATP).
Organisms: Yeast, some bacteria, and human muscle cells (during heavy exercise).
Q9
How are the alveoli designed to maximise the exchange of gases?
1. Large Surface Area: The lungs contain millions of alveoli. If spread out, they would cover about 80 square meters, providing a massive area for gas exchange.
2. Thin Walls: The walls of alveoli are very thin (one cell thick) to allow easy diffusion of gases.
3. Rich Blood Supply: They are surrounded by a dense network of blood capillaries to efficiently transport oxygen and carbon dioxide.
[Image of alveoli structure diagram]
Q10
What would be the consequences of a deficiency of haemoglobin in our bodies?
Haemoglobin is the respiratory pigment that carries oxygen from the lungs to different body cells.
Consequences:
1. The oxygen-carrying capacity of blood will decrease.
2. Cells will not get sufficient oxygen for respiration.
3. This leads to less energy production, causing weakness, fatigue, and breathlessness (Anaemia).
Q11
Describe double circulation of blood in human beings. Why is it necessary?
Description: Blood flows through the heart twice in one complete cycle:
1. Pulmonary Circulation: Deoxygenated blood moves from Heart (Right Ventricle) $\rightarrow$ Lungs $\rightarrow$ Heart (Left Atrium) as Oxygenated blood.
2. Systemic Circulation: Oxygenated blood moves from Heart (Left Ventricle) $\rightarrow$ Body Organs $\rightarrow$ Heart (Right Atrium) as Deoxygenated blood.
Necessity: It prevents the mixing of oxygenated and deoxygenated blood. This ensures a highly efficient supply of oxygen to the body, which is essential for warm-blooded animals like humans to maintain body temperature.
Q12
What are the differences between the transport of materials in xylem and phloem?
Transport in Xylem
Transport in Phloem
Transports water and minerals.
Transports food (sugar/amino acids).
Movement is generally upward only.
Movement is bidirectional (up and down).
Driven by physical forces (Transpiration pull).
Active process requiring energy (ATP).
Q13
Compare the functioning of alveoli in the lungs and nephrons in the kidneys with respect to their structure and functioning.
Alveoli (Lungs)
Nephrons (Kidneys)
Structure: Balloon-like air sacs.
Structure: Cup-shaped (Bowman’s capsule) and tubular.
Function: Exchange of gases ($\text{O}_2 / \text{CO}_2$).
Function: Filtration of blood to remove nitrogenous waste.