Introduction to Life Processes
Life processes are the essential maintenance functions that sustain living organisms, even when they are not actively performing tasks. These processes prevent damage and breakdown, requiring energy from external sources like food.
- Characteristics of Life: Movement (growth-related or molecular) is a common indicator of life. Molecular movements are crucial as living organisms are organized structures that need constant repair due to environmental effects.
- Why Molecular Movements? Living structures break down over time, and molecular movements are necessary to maintain and repair these structures, ensuring the organism remains alive.
Questions:
- Why is diffusion insufficient to meet the oxygen requirements of multicellular organisms like humans?
- What criteria do we use to decide whether something is alive?
- What are outside raw materials used for by an organism?
- What processes would you consider essential for maintaining life?
5.1 Nutrition
Nutrition is the process of transferring energy from external food sources to the body, providing energy and materials for growth, development, and maintenance.
5.1.1 Autotrophic Nutrition
- Definition: Autotrophs (e.g., green plants, some bacteria) use simple inorganic materials (CO₂, H₂O) and sunlight to synthesize energy-rich organic compounds via photosynthesis.
- Photosynthesis Equation:
6CO₂ + 12H₂O → C₆H₁₂O₆ + 6O₂ + 6H₂O(in the presence of sunlight and chlorophyll). - Process:
- Absorption of light energy by chlorophyll.
- Conversion of light energy to chemical energy, splitting water into hydrogen and oxygen.
- Reduction of CO₂ to carbohydrates.
- Role of Chlorophyll: Chloroplasts contain chlorophyll, essential for capturing light energy. Demonstrated by Activity 5.1 (variegated leaf starch test).
- Role of Stomata: Tiny pores on leaves facilitate CO₂ intake and O₂ release. Guard cells control their opening/closing (Activity 5.2).
- Other Raw Materials: Plants absorb water, nitrogen (as nitrates/nitrites), phosphorus, iron, and magnesium from the soil for protein synthesis and growth.
Figure:Autotrophic nutrition
Activity 5.1: Chlorophyll Necessity
Test a variegated leaf for starch after de-starching and exposing to sunlight. Green areas show starch presence, confirming chlorophyll's role in photosynthesis.
Activity 5.2: CO₂ Necessity
Compare starch presence in leaves from plants with/without CO₂ (using potassium hydroxide). Only the plant with CO₂ shows starch, proving CO₂ is essential.
5.1.2 Heterotrophic Nutrition
- Definition: Heterotrophs (e.g., animals, fungi) rely on complex organic substances, broken down into simpler forms using enzymes.
- Types:
- External breakdown (e.g., fungi like bread molds).
- Internal breakdown (e.g., animals).
- Parasitic nutrition (e.g., cuscuta, ticks).
5.1.3 Nutrition in Organisms
- Unicellular Organisms: Food intake occurs via the entire surface (e.g., Amoeba uses pseudopodia to form food vacuoles; Paramoecium uses cilia).
- Multicellular Organisms: Specialized digestive systems process food based on its complexity and source.
5.1.4 Nutrition in Human Beings
- Alimentary Canal: A long tube from mouth to anus with specialized regions.
- Digestion Process:
- Mouth: Teeth crush food; saliva (containing salivary amylase) breaks down starch into simple sugars (Activity 5.3).
- Oesophagus: Peristaltic movements push food to the stomach.
- Stomach: Gastric glands secrete HCl (creates acidic medium), pepsin (digests proteins), and mucus (protects stomach lining).
- Small Intestine: Receives bile (emulsifies fats) and pancreatic juice (trypsin for proteins, lipase for fats). Intestinal juice converts proteins to amino acids, carbohydrates to glucose, and fats to fatty acids/glycerol. Villi absorb nutrients.
- Large Intestine: Absorbs water; undigested material is excreted via the anus.
- Dental Caries: Tooth decay due to bacterial acid production from sugars, forming plaque. Brushing prevents this.
Activity 5.3: Saliva Action
Test starch solution with/without saliva. Saliva-treated solution shows no starch (due to amylase), indicating saliva breaks down starch.
Questions:
- What are the differences between autotrophic and heterotrophic nutrition?
- Where do plants get each of the raw materials required for photosynthesis?
- What is the role of the acid in our stomach?
- What is the function of digestive enzymes?
- How is the small intestine designed to absorb digested food?
5.2 Respiration
Respiration is the process of acquiring oxygen to break down food for cellular energy needs, producing ATP.
- Glucose Breakdown: Glucose (6-carbon) is broken into pyruvate (3-carbon) in the cytoplasm.
- Types of Respiration:
- Aerobic: In mitochondria, pyruvate is broken into CO₂ and H₂O using O₂, releasing more energy.
- Anaerobic: In the absence of O₂, pyruvate forms ethanol and CO₂ (e.g., yeast fermentation) or lactic acid (e.g., muscle cramps).
- ATP: The energy currency of cells, synthesized from ADP and phosphate during respiration. Each ATP releases 30.5 kJ/mol when broken down.
Activity 5.4: CO₂ in Exhaled Air
Blow air through lime water; it turns milky faster than air passed via syringe, indicating higher CO₂ in exhaled air.
Activity 5.5: Fermentation
Yeast in sugar solution produces CO₂, turning lime water milky, confirming CO₂ as a fermentation product.
Respiration in Organisms
- Plants: Exchange gases via stomata and intercellular spaces. CO₂ is used in photosynthesis during the day, and O₂ is released.
- Aquatic Animals: Use dissolved O₂ via gills (e.g., fish, Activity 5.6).
- Terrestrial Animals: Use atmospheric O₂ via specialized organs (e.g., lungs in humans).
- Human Respiration:
- Air enters through nostrils, filtered by hairs and mucus.
- Lungs contain alveoli (large surface area for gas exchange).
- Haemoglobin in red blood cells transports O₂; CO₂ is dissolved in plasma.
Activity 5.6: Fish Respiration
Observe fish mouth and gill movements, noting faster breathing rates due to low dissolved O₂ in water.
Questions:
- What advantage does a terrestrial organism have over an aquatic organism in obtaining oxygen?
- What are the different ways glucose is oxidized to provide energy?
- How are oxygen and carbon dioxide transported in humans?
- How are lungs designed to maximize gas exchange?
5.3 Transportation
5.3.1 Transportation in Human Beings
- Circulatory System: Comprises heart, blood, and blood vessels.
- Blood Components:
- Plasma: Transports food, CO₂, and wastes.
- Red Blood Cells: Carry O₂ via haemoglobin.
- Platelets: Aid clotting to prevent blood loss.
- Heart Function: Double circulation ensures oxygenated and deoxygenated blood are separated, pumping blood efficiently to the body and lungs.
- Blood Vessels:
- Arteries: Thick-walled, carry blood from the heart.
- Veins: Thin-walled with valves, return blood to the heart.
- Capillaries: Thin-walled, facilitate exchange with cells.
- Lymph: Tissue fluid that drains excess fluid and fats back to the blood.
Activity 5.7: Haemoglobin Levels
Compare haemoglobin levels in humans (men, women, children) and animals (e.g., buffalo), noting variations due to physiological needs.
5.3.2 Transportation in Plants
- Xylem: Transports water and minerals from roots to leaves via root pressure and transpiration pull (Activity 5.8).
- Phloem: Transports photosynthetic products (e.g., sucrose) using ATP-driven osmotic pressure.
Activity 5.8: Transpiration
Compare water loss in a potted plant vs. a stick, showing transpiration’s role in water movement.
Questions:
- What are the components of the human transport system and their functions?
- Why is it necessary to separate oxygenated and deoxygenated blood in mammals and birds?
- What are the components of the plant transport system?
- How are water and minerals transported in plants?
- How is food transported in plants?
5.4 Excretion
Excretion is the removal of harmful metabolic wastes, primarily nitrogenous compounds.
5.4.1 Excretion in Human Beings
- Excretory System: Includes kidneys, ureters, urinary bladder, and urethra.
- Nephron Function: Filters blood in Bowman’s capsule, reabsorbs useful substances, and forms urine.
- Urine Regulation: Controlled by water and waste levels, stored in the bladder, and released via the urethra.
- Artificial Kidney: Hemodialysis removes wastes via diffusion in kidney failure cases.
5.4.2 Excretion in Plants
- Methods: Excess water via transpiration, O₂ from photosynthesis, and storage of wastes in vacuoles, resins, gums, or falling leaves.
Questions:
- Describe the structure and functioning of nephrons.
- What are the methods used by plants to get rid of excretory products?
- How is the amount of urine produced regulated?
Key Learnings
- Life processes include nutrition, respiration, transportation, and excretion.
- Autotrophic nutrition uses photosynthesis; heterotrophic nutrition relies on complex organic intake.
- Respiration produces ATP via aerobic or anaerobic pathways.
- Human circulation involves double circulation; plant transport uses xylem and phloem.
- Excretion removes nitrogenous wastes via nephrons in humans and various methods in plants.
Exercises
- The kidneys in human beings are a part of the system for (a) nutrition, (b) respiration, (c) excretion, (d) transportation.
- The xylem in plants are responsible for (a) transport of water, (b) transport of food, (c) transport of amino acids, (d) transport of oxygen.
- The autotrophic mode of nutrition requires (a) carbon dioxide and water, (b) chlorophyll, (c) sunlight, (d) all of the above.
- The breakdown of pyruvate to give carbon dioxide, water, and energy takes place in (a) cytoplasm, (b) mitochondria, (c) chloroplast, (d) nucleus.
- How are fats digested in our bodies? Where does this process take place?
- What is the role of saliva in the digestion of food?
- What are the necessary conditions for autotrophic nutrition and its byproducts?
- What are the differences between aerobic and anaerobic respiration? Name some organisms that use anaerobic respiration.
- How are the alveoli designed to maximize the exchange of gases?
- What would be the consequences of a deficiency of haemoglobin in our bodies?
- Describe double circulation of blood in human beings. Why is it necessary?
- What are the differences between the transport of materials in xylem and phloem?
- Compare the functioning of alveoli in the lungs and nephrons in the kidneys with respect to their structure and functioning.