Exhaustive Study Guide on Life Processes and Maintenance Systems
Introduction to Life Processes and Movement
Criteria for Being Alive: Traditional observations of living beings include visible movements, such as a dog running, a cow chewing cud, or a human shouting. However, these are insufficient as defining characteristics.
Visible vs. Invisible Movement: Sleep presents a case where visible actions cease, but breathing continues. Plants may show growth-related movement, but a plant that is not visibly growing or an animal breathing without visible movement is still alive.
Molecular Movement: Professional biologists assert that invisible molecular movement is necessary for life. This is the movement of molecules within the organized structure of a living being.
The Virus Controversy: Viruses do not show molecular movement until they infect a host cell, leading to a scientific controversy over whether they are truly alive.
The Necessity of Maintenance and Repair
Organized Nature of Life: Living organisms are well-organized structures consisting of tissues, cells, and smaller components.
Entropy and Breakdown: Environmental effects can cause this organized nature to break down over time. If order breaks down, the organism dies.
Maintenance Processes: Living creatures must constantly repair and maintain their structures. Because these structures are made of molecules, they require the constant movement of molecules.
Definition of Life Processes: The processes which together perform the maintenance job of living organisms, even when the organism is inactive (e.g., sitting or sleeping), are called life processes.
Basic Requirements: Energy and Raw Materials
Energy Consumption: Maintenance requires work, and work requires energy. This energy must come from outside the organism's body.
Nutrition: The process of transferring a source of energy (food) from the outside to the inside of the body is called nutrition.
Carbon-Based Life: Most food sources are carbon-based because life on Earth depends on carbon-based molecules.
Growth Requirements: If an organism is to grow in size, it requires additional raw materials from the environment.
Chemical Reactions: Energy sources must be broken down or built up in the body to be converted into a uniform source of energy. This involves a series of chemical reactions, primarily oxidising-reducing reactions.
Respiration and Complexity
Respiration Definition: The process of acquiring oxygen from outside the body and using it to break down food sources for cellular needs is called respiration.
Single-Celled Organisms: No specific organs for gas exchange or waste removal are needed because the entire surface is in contact with the environment.
Multi-Cellular Organisms:
As body size and complexity increase, simple diffusion cannot meet the requirements of all cells because they are not all in direct contact with the environment.
Specialised tissues perform specific functions like uptake of food and oxygen.
Transportation: A system is needed to carry food and oxygen from the site of uptake to all parts of the body.
Excretion: Chemical reactions create useless or harmful by-products (waste). The process of removing these wastes is called excretion. Specialized excretory tissues require the transportation system to move waste away from cells.
Nutrition: Autotrophic and Heterotrophic
General Requirement: All organisms need energy and materials to maintain order, grow, and synthesize proteins.
Autotrophic Nutrition:
Definition: Organisms that use simple food materials from inorganic sources ( and ).
Examples: Green plants and some bacteria.
Storage: Plants store unused carbohydrates as starch. Humans store energy as glycogen.
Heterotrophic Nutrition:
Definition: Organisms that utilize complex substances produced by autotrophs (directly or indirectly).
Bio-catalysts: Enzymes are used to break down complex substances into simpler ones.
Strategies:
External Digestion: Breaking down food outside the body before absorption (e.g., fungi like bread moulds, yeast, mushrooms).
Internal Digestion: Taking in whole material and breaking it down inside (e.g., most animals).
Parasitic: Deriving nutrition without killing the host (e.g., Cuscuta/Amar-bel, ticks, lice, leeches, tape-worms).
The Process of Photosynthesis
Equation Components: Photosynthesis converts carbon dioxide and water into carbohydrates in the presence of sunlight and chlorophyll.
Main Events:
Absorption of light energy by chlorophyll.
Conversion of light energy to chemical energy and the splitting of water molecules () into hydrogen and oxygen ().
Reduction of carbon dioxide () to carbohydrates.
Timing: Steps do not always occur sequentially. Desert plants take up at night, forming an intermediate that is processed during the day using energy absorbed by chlorophyll.
Chloroplasts: These are cell organelles containing chlorophyll, identifiable as green dots in a leaf cross-section.
Gaseous Exchange: Occurs through stomata (tiny pores) on leaves, and also across stems and roots.
Guard Cells: Control the opening and closing of stomatal pores. They swell when water flows into them (opening the pore) and shrink when water leaves (closing the pore).
Other Raw Materials: Roots take up water, nitrogen, phosphorus, iron, and magnesium from the soil.
Nitrogen: Essential for protein synthesis. Taken up as inorganic nitrates/nitrites or organic compounds prepared by bacteria.
Nutrition in Humans
Alimentary Canal: A long tube from mouth to anus with specialized regions.
The Mouth:
Mechanical: Crushing food with teeth.
Saliva: Secreted by salivary glands; contains the enzyme salivary amylase, which breaks down starch (complex) into simple sugar.
Tongue: Mixes food with saliva and moves it around.
The Oesophagus: Moves food to the stomach via peristaltic movements (rhythmic muscle contractions).
The Stomach:
A large muscular organ that expands when food enters.
Gastric Glands: Secret hydrochloric acid (), pepsin (protein-digesting enzyme), and mucus.
Acid Function: Creates an acidic medium for pepsin and kills bacteria.
Mucus Function: Protects the stomach lining from the acid.
The Small Intestine:
The longest part of the canal, coiled for compactness.
Length Variations: Herbivores (e.g., cows) have longer small intestines to digest cellulose; carnivores (e.g., tigers) have shorter ones as meat is easier to digest.
Secretions: Receives bile juice (from liver) and pancreatic juice (from pancreas).
Bile Functions: Makes acidic food alkaline for pancreatic enzymes and emulsifies fats (breaks large fat globules into smaller ones).
Pancreatic Enzymes: Trypsin (digests proteins) and Lipase (breaks down emulsified fats).
Intestinal Secretions: Convert proteins into amino acids, complex carbohydrates into glucose, and fats into fatty acids and glycerol.
Absorption: Managed by villi (finger-like projections) which increase surface area and are rich in blood vessels.
The Large Intestine and Anus: Unabsorbed food moves to the large intestine for water absorption; the remainder is expelled via the anus, regulated by the anal sphincter.
Respiration Pathways and Energy
First Step: Breakdown of glucose (6-carbon molecule) into pyruvate (3-carbon molecule) in the cytoplasm.
Pathways of Pyruvate Breakdown:
Anaerobic (Absence of ): Occurs in yeast (fermentation). Produces ethanol, , and energy.
Lack of (Muscle Cells): Occurs during sudden activity. Produces lactic acid (3-carbon molecule) and energy. Lactic acid build-up causes cramps.
Aerobic (Presence of ): Occurs in mitochondria. Produces , , and a high amount of energy.
ATP (Adenosine Triphosphate):
The energy currency for cellular processes.
Formed from ADP and inorganic phosphate using energy from respiration.
Energy release: Breaking the terminal phosphate linkage using water releases .
Human Respiratory System
Passage: Nostrils $\rightarrow$ Nasal passage (filtered by hair and mucus) $\rightarrow$ Throat (contains rings of cartilage to prevent collapse) $\rightarrow$ Lungs.
Alveoli: Balloon-like structures that provide a surface for gas exchange. They are surrounded by an extensive network of blood vessels.
Mechanism of Breathing:
Inhalation: Ribs lift, diaphragm flattens, chest cavity expands, air is sucked into alveoli.
Exhalation: is brought by blood to alveoli and released.
Residual Volume: A volume of air that always remains in the lungs to allow time for gas exchange.
Respiratory Pigment: In humans, it is haemoglobin, which has a high affinity for oxygen and is found in Red Blood Corpuscles (RBCs).
Solubility: is more soluble in water than oxygen, so it is mostly transported in dissolved form in plasma.
Transportation
Blood Composition: Plasma (fluid medium transporting food, , nitrogenous wastes) and cells (RBCs, WBCs, platelets).
The Heart (The Pump):
A muscular organ the size of a fist.
Chambers: 4 chambers (Left/Right Atria, Left/Right Ventricles) to prevent mixing of oxygenated and deoxygenated blood.
Pathway: Oxygenated blood (Lungs $\rightarrow$ Pulmonary Vein $\rightarrow$ Left Atrium $\rightarrow$ Left Ventricle $\rightarrow$ Aorta $\rightarrow$ Body). Deoxygenated blood (Body $\rightarrow$ Vena Cava $\rightarrow$ Right Atrium $\rightarrow$ Right Ventricle $\rightarrow$ Pulmonary Artery $\rightarrow$ Lungs).
Valves: Ensure one-way flow.
Ventricles: Thicker walls because they pump blood further away.
Comparative Circulation:
Birds/Mammals: 4 chambers; high energy efficiency for body temperature maintenance.
Amphibians/Reptiles: 3 chambers; tolerate some mixing; temperature depends on environment.
Fish: 2 chambers; blood oxygenated in gills; single circulation.
Double Circulation: Blood passes through the heart twice in one cycle (common in vertebrates).
Blood Vessels and Pressure
Arteries: Carry blood away from the heart at high pressure; thick, elastic walls.
Veins: Collect blood and return it to the heart; thinner walls; contain valves.
Capillaries: Smallest vessels, one-cell thick; site of material exchange.
Blood Pressure: The force exerted against vessel walls.
Systolic: (during ventricular contraction).
Diastolic: (during ventricular relaxation).
Hypertension: High blood pressure caused by constriction of arterioles.
Platelets: Circulate to plug leaks and clot blood at injury sites.
Lymph: Tissue fluid that escapes from capillaries; colourless, contains less protein; carries digested fat and drains excess fluid back into the blood.
Transportation in Plants
Xylem: Transports water and minerals from roots to leaves.
Mechanism: Active ion uptake creates a concentration gradient (water moves into roots). Transpiration pull (evaporation from leaves) creates suction to pull water upwards.
Phloem: Transports products of photosynthesis (translocation of sucrose, amino acids).
Mechanism: Uses energy from ATP to increase osmotic pressure, moving material to tissues with lower pressure.
Excretion
Human Excretory System: Pair of kidneys, pair of ureters, urinary bladder, urethra.
The Nephron: The basic filtration unit of the kidney.
Bowman’s Capsule: Cup-shaped end that collects filtrate from capillary clusters.
Selective Re-absorption: Glucose, amino acids, salts, and water are re-absorbed as filtrate moves through the tubules.
Urine Production: Healthy adults produce of initial filtrate daily, but only is excreted as urine; the rest is re-absorbed.
Haemodialysis (Artificial Kidney): A device using semi-permeable tubes in dialysing fluid to remove nitrogenous wastes from the blood in case of kidney failure. Unlike natural kidneys, no re-absorption occurs.
Plant Excretion:
Oxygen released during photosynthesis.
Excess water via transpiration.
Storage in cellular vacuoles, resins, or gums (old xylem).
Shedding of leaves containing waste.
Excretion into the surrounding soil.