Name the following:
(a) The process in plants that links light energy with chemical energy
(b) Organisms that can prepare their own food
(c) The cell organelle where photosynthesis occurs
(d) Cells that surround a stomatal pore
(e) Organisms that cannot prepare their own food
(f) An enzyme secreted from gastric glands in the stomach that acts on proteins
(a) Photosynthesis
(b) Autotrophs
(c) Chloroplast
(d) Guard Cells
(e) Heterotrophs
(f) Pepsin
“All plants give out oxygen during day and carbon dioxide during night”. Do you agree with this statement? Give reason.
During daytime, the rate of photosynthesis is more than the rate of respiration, so oxygen is released. At night, photosynthesis stops and only respiration occurs, causing release of carbon dioxide.
How do the guard cells regulate opening and closing of stomatal pores?
Guard cells absorb water and become turgid, causing stomatal pores to open. When they lose water and become flaccid, the stomatal pores close.
Two green plants are kept separately in oxygen-free containers, one in the dark and the other in continuous light. Which one will live longer? Give reasons.
The plant kept in continuous light will live longer because it can photosynthesise and produce oxygen required for respiration.
If a plant is releasing carbon dioxide and taking in oxygen during the day, does it mean that there is no photosynthesis occurring? Justify your answer.
This indicates that the rate of respiration is higher than the rate of photosynthesis. Carbon dioxide produced in respiration is used in photosynthesis, so no CO₂ is released normally. If CO₂ is released, photosynthesis is very slow or not occurring.
Why do fishes die when taken out of water?
Fishes respire through gills, which can absorb oxygen only when it is dissolved in water. Out of water, they cannot absorb oxygen and die.
Differentiate between an autotroph and a heterotroph.
| Autotroph | Heterotroph |
|---|---|
| 1. Organisms that prepare their own food. | 1. Organisms dependent on others for food. |
| 2. They have chlorophyll. | 2. They lack chlorophyll. |
Autotrophs prepare their own food and possess chlorophyll, while heterotrophs depend on other organisms for food and lack chlorophyll.
Is 'nutrition' a necessity for an organism? Discuss.
Nutrition is necessary because it provides energy for metabolic processes, supports growth and repair of cells, and helps develop resistance against diseases.
What would happen if green plants disappear from earth?
All herbivores would die due to starvation, followed by carnivores. Life would collapse because green plants are the main source of energy for all organisms.
Leaves of a healthy potted plant were coated with vaseline. Will this plant remain healthy for long? Give reasons for your answer.
No, the plant will not remain healthy because:
(a) It will not get oxygen for respiration.
(b) It will not get carbon dioxide for photosynthesis.
(c) Transpiration will stop, hindering upward movement of water and minerals.
How does aerobic respiration differ from anaerobic respiration?
| Aerobic respiration | Anaerobic respiration |
|---|---|
| 1. Oxygen is utilised. | 1. Oxygen is not required. |
| 2. Occurs in cytoplasm and mitochondria. | 2. Occurs only in cytoplasm. |
| 3. End products: carbon dioxide and water. | 3. End products: lactic acid or ethanol and carbon dioxide. |
| 4. More energy released. | 4. Less energy released. |
Aerobic respiration uses oxygen, occurs in cytoplasm and mitochondria, produces CO₂ and water, and releases more energy. Anaerobic respiration occurs without oxygen, happens only in cytoplasm, produces lactic acid or ethanol, and releases less energy.
Match the words of Column (A) with those of Column (B).
| Column (A) | Column (B) |
|---|---|
| (a) Phloem | (i) Excretion |
| (b) Nephron | (ii) Translocation of food |
| (c) Veins | (iii) Clotting of blood |
| (d) Platelets | (iv) Deoxygenated blood |
(a) (ii)
(b) (i)
(c) (iv)
(d) (iii)
Differentiate between an artery and a vein.
| Artery | Vein |
|---|---|
| 1. Thick, elastic muscular walls | 1. Thin, non-elastic walls |
| 2. Narrow lumen | 2. Wide lumen |
| 3. Carry blood from heart to body parts | 3. Carry blood from body parts to heart |
| 4. Carry oxygenated blood (except pulmonary artery) | 4. Carry deoxygenated blood (except pulmonary vein) |
Arteries have thick elastic walls, a narrow lumen, carry blood from the heart, and usually carry oxygenated blood. Veins have thin non-elastic walls, a wide lumen, carry blood to the heart, and usually carry deoxygenated blood.
What are the adaptations of leaf for photosynthesis?
Leaves have a large surface area, are arranged to avoid overlapping, contain many veins for quick transport, possess numerous stomata, and have more chloroplasts on the upper surface.
Why is small intestine in herbivores longer than in carnivores?
Digestion of cellulose takes longer. Herbivores need a longer small intestine for complete digestion of cellulose, whereas carnivores do not digest cellulose and thus have a shorter intestine.
What will happen if mucus is not secreted by the gastric glands?
Mucus protects the inner lining of the stomach from hydrochloric acid and enzymes. Without mucus, the stomach lining would erode, leading to acidity and ulcers.
What is the significance of emulsification of fats?
Emulsification breaks large fat globules into smaller ones, increasing efficiency of fat-digesting enzymes.
What causes movement of food inside the alimentary canal?
Rhythmic contraction and relaxation of muscles of the alimentary canal cause peristalsis, which pushes food forward.
Why does absorption of digested food occur mainly in the small intestine?
Because digestion is completed in the small intestine, its inner lining has villi that increase surface area, and it is richly supplied with blood vessels that transport absorbed food.
Match Group (A) with Group (B).
| Group (A) | Group (B) |
|---|---|
| (a) Autotrophic nutrition | (i) Leech |
| (b) Heterotrophic nutrition | (ii) Paramecium |
| (c) Parasitic nutrition | (iii) Deer |
| (d) Digestion in food vacuoles | (iv) Green plant |
(a) (iv)
(b) (iii)
(c) (i)
(d) (ii)
Why is the rate of breathing in aquatic organisms much faster than in terrestrial organisms?
Aquatic organisms obtain oxygen from dissolved oxygen in water, which is much less than oxygen in air. Hence they breathe faster to meet oxygen needs.
Why is blood circulation in human heart called double circulation?
Because blood passes twice through the heart in one complete cycle: once through the right side carrying deoxygenated blood, and once through the left side carrying oxygenated blood.
What is the advantage of having a four-chambered heart?
It completely separates oxygenated and deoxygenated blood, preventing mixing and ensuring efficient oxygen supply. This is essential for animals with high energy needs.
Mention the major events during photosynthesis.
(a) Absorption of light energy by chlorophyll
(b) Conversion of light energy to chemical energy
(c) Splitting of water molecules into \( H_2, O_2 \) and electrons
(d) Reduction of \( CO_2 \) to carbohydrates
In each of the following situations, state what happens to the rate of photosynthesis:
(a) Cloudy days
(b) No rainfall in the area
(c) Good manuring in the area
(d) Stomata get blocked due to dust
(a) Decreases
(b) Decreases
(c) Increases
(d) Decreases
Name the energy currency in living organisms. When and where is it produced?
Adenosine triphosphate (ATP) is the energy currency. It is produced during respiration in living organisms and during photosynthesis in plants.
What is common for Cuscuta, ticks and leeches?
All are parasites; they derive nutrition from plants or animals without killing them.
Explain the role of mouth in digestion of food.
(a) Food is crushed into small pieces by the teeth.
(b) It mixes with saliva and the enzyme amylase breaks down starch into sugars.
(c) Tongue helps in thorough mixing of food with saliva.
What are the functions of gastric glands present in the wall of the stomach?
(a) Production of pepsin enzyme that digests proteins.
(b) Secretion of mucus for protection of the inner lining of the stomach.
(c) Secretion of hydrochloric acid.
Match the terms in Column (A) with those in Column (B).
| Column (A) | Group (B) |
|---|---|
| (a) Trypsin | (i) Pancreas |
| (b) Amylase | (ii) Liver |
| (c) Bile | (iii) Gastric glands |
| (d) Pepsin | (iv) Saliva |
(a) — (i)
(b) — (iv)
(c) — (ii)
(d) — (iii)
Name the correct substrates for the following enzymes:
(a) Trypsin
(b) Amylase
(c) Pepsin
(d) Lipase
(a) Protein
(b) Starch
(c) Protein
(d) Fats
Why do veins have thin walls as compared to arteries?
Arteries carry blood under high pressure from the heart, so their walls are thick and elastic. Veins carry blood at lower pressure and therefore have thin walls with valves to ensure one-way flow.
What will happen if platelets were absent in the blood?
Blood clotting would be affected, leading to excessive bleeding even from minor injuries.
Plants have low energy needs as compared to animals. Explain.
Plants do not move. They also have many dead cells like sclerenchyma, so they require less energy compared to animals.
Why and how does water enter continuously into the root xylem?
Root cells are in contact with soil and actively take up ions, increasing ion concentration inside the root. This increases osmotic pressure, causing continuous movement of water from soil into the roots.
Why is transpiration important for plants?
(a) It helps in absorption and upward movement of water and minerals from roots to leaves.
(b) It prevents plants from overheating.
How do leaves of plants help in excretion?
Some waste materials are stored in vacuoles of mesophyll and epidermal cells. When old leaves fall, the wastes are removed along with them.