Explain the process of nutrition in Amoeba.
1. Ingestion: Amoeba engulfs food particles such as algae and small organisms by extending finger-like projections called pseudopodia. These pseudopodia surround the food and form a food vacuole.
2. Digestion: Inside the food vacuole, digestive enzymes are secreted that break down complex food substances into simpler, absorbable forms.
3. Absorption: The digested food is absorbed directly into the cytoplasm, where it is utilized for growth, repair, and producing energy.
4. Assimilation: Absorbed nutrients become part of the cell’s structure or are used to produce energy for vital activities.
5. Egestion: The undigested food material is expelled from the body by the vacuole moving near the cell surface and rupturing.
Describe the alimentary canal of man.
The human alimentary canal is a long, muscular tube extending from the mouth to the anus. Its major parts include:
1. Mouth cavity: Food is chewed and mixed with saliva, which contains amylase for starch digestion.
2. Oesophagus: A muscular tube through which food passes to the stomach by peristalsis.
3. Stomach: A sac-like organ that secretes hydrochloric acid, pepsin, and mucus. Here, proteins are partially digested.
4. Small intestine: Main site for digestion and absorption of nutrients. Enzymes from pancreas and bile from liver aid digestion. Villi increase the surface area for absorption.
5. Large intestine: Absorbs water and salts. Undigested food is compacted into faeces.
Explain the process of breathing in man.
1. Passage of air: Air enters through nostrils, passes into nasal cavity, then through pharynx, larynx, trachea, bronchi, bronchioles, and finally reaches the alveoli in the lungs.
2. Gaseous exchange: In alveoli, oxygen diffuses into blood and carbon dioxide diffuses out into the alveolar air due to concentration gradients.
3. Role of diaphragm: During inhalation, the diaphragm contracts and flattens, increasing thoracic volume and drawing air into the lungs. During exhalation, it relaxes and becomes dome-shaped, pushing air out.
4. Function of rib muscles and alveoli: Intercostal muscles lift the ribs during inhalation and lower them during exhalation, helping in ventilation. Alveoli provide a large surface area for gaseous exchange.
Explain the importance of soil for plant growth.
1. Anchoring the plant: Soil provides physical support to plants by anchoring their roots firmly.
2. Source of water and minerals: Soil supplies essential water and minerals required for various metabolic processes.
3. Availability of oxygen for root respiration: Air spaces in soil provide oxygen for respiration of root cells.
4. Symbiotic association with microbes: Soil hosts microbes that help in nitrogen fixation and decomposition, enriching soil fertility for plant growth.
Draw the diagram of alimentary canal of man and label the following parts: Mouth, Oesophagus, Stomach, Intestine.
The alimentary canal of man consists of:
1. Mouth: Opening through which food enters the body.
2. Oesophagus: A muscular tube that carries food to the stomach by peristalsis.
3. Stomach: A sac-like organ where proteins are digested.
4. Intestine (Small and Large): Small intestine digests and absorbs nutrients; large intestine absorbs water.
(Diagram should depict the labelled structures as described.)
How do carbohydrates, proteins and fats get digested in human beings?
Carbohydrate digestion: Begins in the mouth where salivary amylase breaks starch into maltose. In the small intestine, pancreatic amylase converts starch into simple sugars, and intestinal enzymes convert them into glucose.
Protein digestion: In the stomach, pepsin breaks proteins into peptides. In the small intestine, trypsin and peptidases convert them into amino acids.
Fat digestion: Bile emulsifies fats into small droplets. Lipase from pancreas and intestinal glands breaks fats into fatty acids and glycerol.
Explain the mechanism of photosynthesis.
1. Absorption of light energy by chlorophyll: Chlorophyll absorbs sunlight and becomes activated.
2. Conversion of light energy to chemical energy: Activated chlorophyll converts light energy into chemical energy in the form of ATP and NADPH.
3. Splitting of water: Light energy splits water into \( H_2 \), \( O_2 \), and electrons. Oxygen is released, while hydrogen is used in the next stage.
4. Reduction of carbon dioxide: CO2 is reduced to carbohydrates using hydrogen and chemical energy.
Explain the three pathways of breakdown in living organisms.
1. Aerobic respiration: Pyruvate produced during glycolysis enters mitochondria and breaks down into \( CO_2 \), \( H_2O \), and releases large amounts of energy.
2. Anaerobic respiration (yeast): Pyruvate is converted into ethanol, \( CO_2 \), and small amounts of energy.
3. Anaerobic respiration (muscles): During vigorous activity, pyruvate converts into lactic acid and energy in absence of oxygen, causing muscle cramps.
Describe the flow of blood through the heart of human beings.
1. Right side of the heart: Deoxygenated blood from the body enters the right atrium via vena cava. It moves to the right ventricle, which pumps it to the lungs through the pulmonary artery.
2. Gas exchange in lungs: In the lungs, blood releases CO2 and absorbs oxygen.
3. Left side of the heart: Oxygenated blood returns via pulmonary veins to the left atrium. It flows to the left ventricle, which pumps it to the entire body through the aorta.
This double circulation ensures separation of oxygenated and deoxygenated blood.
Describe the process of urine formation in kidneys.
1. Filtration: Blood enters the glomerulus where water, urea, salts, and small molecules are filtered into Bowman’s capsule forming filtrate.
2. Reabsorption: Useful substances such as glucose, amino acids, and water are reabsorbed back into blood from the renal tubule.
3. Secretion: Additional wastes like ions and toxins are secreted into the tubule from blood.
The remaining fluid becomes urine, which passes into the ureter and is stored in the urinary bladder before excretion.