Biology: Characteristics and Classification of Living Organisms
Chapter 1: Characteristics and Classification of Living Organisms
Technical Notes:
The 7 Characteristics of Life (MRS GREN):
Movement: Action by an organism or part of an organism causing a change of position or place.
Respiration: Chemical reactions in cells that break down nutrient molecules to release energy for metabolism.
Sensitivity: Ability to detect or sense stimuli in the internal or external environment and to make appropriate responses.
Growth: Permanent increase in size and dry mass by an increase in cell number or cell size or both.
Reproduction: Processes that make more of the same kind of organism.
Excretion: Removal from organisms of the waste products of metabolism, toxic materials, and substances in excess of requirements.
Nutrition: Taking in of materials for energy, growth, and development.
Binomial System: Organisms are named by their Genus (capitalized) and species (lowercase).
Classification:
Traditionally based on morphology (shape) and anatomy, but modern classification uses DNA base sequences.
Similarities in DNA sequences indicate more recent common ancestors.
Important Questions:
Q: Define a species.
A: A group of organisms that can reproduce to produce fertile offspring.Q: List the features of all living cells.
A: Cytoplasm, cell membrane, DNA as genetic material, and ribosomes for protein synthesis.
Chapter 2: Organization of the Organism
Technical Notes:
Organelles:
Nucleus: Contains genetic material.
Mitochondria: Site of aerobic respiration to release energy.
Ribosomes: Site of protein synthesis.
Rough Endoplasmic Reticulum (RER): Studded with ribosomes; transports proteins.
Chloroplasts (Plants only): Site of photosynthesis; contains chlorophyll.
Vacuole (Plants only): Large and permanent; contains cell sap and maintains turgidity.
Cell Wall (Plants only): Made of cellulose; prevents bursting.
Specialized Cells:
Ciliated cells: Move mucus in the trachea.
Root hair cells: Increase surface area for water absorption.
Red blood cells: Biconcave, no nucleus, contains hemoglobin to transport oxygen.
Important Questions:
Q: Calculate the magnification if the image is 50 mm and the actual size is 0.05 mm.
A: M = I/A = 50/0.05 = ×1000.Q: Why do bacterial cells lack mitochondria?
A: Bacteria are prokaryotes; they do not have membrane-bound organelles.
Chapter 3: Movement in and out of Cells
Technical Notes:
Diffusion: Net movement of particles from a region of higher concentration to lower concentration down a concentration gradient, as a result of their random movement.
Osmosis: Net movement of water molecules from a region of higher water potential to lower water potential across a partially permeable membrane.
Active Transport: Movement of particles through a cell membrane from a region of lower concentration to higher concentration (against a gradient) using energy from respiration and protein carriers.
Important Questions:
Q: What happens to an animal cell in pure water?
A: Water enters by osmosis. The cell swells and eventually bursts (lysis) because it lacks a cell wall.Q: Define "turgid."
A: A plant cell that is tight and firm due to high internal water pressure against the cell wall.
Chapter 4: Biological Molecules
Technical Notes:
Chemical Elements:
Carbohydrates and Fats: C, H, O.
Proteins: C, H, O, N (sometimes S).
Food Tests:
Starch: Iodine solution (Brown → Blue-black).
Reducing Sugars: Benedict's solution + Heat (Blue → Brick red).
Proteins: Biuret test (Blue → Purple).
Lipids: Ethanol emulsion (Clear → Milky white).
Vitamin C: DCPIP (Blue → Colorless).
Important Questions:
Q: Describe the structure of DNA.
A: Two strands coiled to form a double helix, with paired bases (A-T and C-G) held by cross-links.
Chapter 5: Enzymes
Technical Notes:
Definition: Biological catalysts that speed up chemical reactions without being changed.
Mechanism: Lock and Key.
The substrate is complementary to the active site. They bind to form an enzyme-substrate complex.
Factors affecting enzymes:
Temperature: Increasing temp increases kinetic energy and collisions. Above the optimum, the active site changes shape; the enzyme is denatured.
pH: Extreme pH changes the shape of the active site.
Important Questions:
Q: Why does the rate of reaction decrease after the optimum temperature?
A: The enzyme molecule vibrates too much, breaking bonds that maintain the active site's shape. The substrate can no longer fit.
Chapter 6: Plant Nutrition
Technical Notes:
Equation:
Leaf Anatomy:
Palisade mesophyll: Packed with chloroplasts at the top for maximum light absorption.
Spongy mesophyll: Large air spaces for gas exchange (CO2 diffusion).
Stomata: Pores that allow gas exchange, controlled by guard cells.
Important Questions:
Q: What is the fate of glucose made in photosynthesis?
A: Used for respiration, stored as starch, converted to cellulose for walls, or nectar to attract insects.
Chapter 7: Human Nutrition
Technical Notes:
Diet: Needs balanced carbs, fats, proteins, vitamins (C and D), minerals (Calcium and Iron), fiber, and water.
Alimentary Canal:
Mouth: Mechanical digestion and amylase (chemical).
Stomach: Protease (Pepsin) and Hydrochloric acid (kills bacteria/optimal pH).
Pancreas: Secretes amylase, protease (trypsin), and lipase.
Liver: Produces Bile, which emulsifies fats (increasing surface area) and neutralizes stomach acid.
Important Questions:
Q: Where does most absorption of digested food occur?
A: In the ileum (small intestine).Q: Define "Ingestion."
A: Taking in of substances into the body through the mouth.
Chapter 8: Transport in Plants
Technical Notes:
Xylem: Transports water and minerals from roots to leaves. Walls are lignified (dead/waterproof).
Phloem: Transports sucrose and amino acids from sources to sinks (Translocation).
Transpiration:
Evaporation of water at the surfaces of mesophyll cells followed by loss of water vapor from plant leaves through stomata.
Important Questions:
Q: How does water move up the xylem?
A: By a transpiration pull created by cohesion (water molecules sticking together) and adhesion.
Chapter 9: Transport in Animals
Technical Notes:
Heart:
Right side: Pumps deoxygenated blood to lungs.
Left side: Pumps oxygenated blood to body (Thick muscular wall).
Vessels:
Arteries: Thick elastic walls, high pressure.
Veins: Thin walls, low pressure, have valves.
Capillaries: One cell thick for efficient diffusion.
Important Questions:
Q: Name the blood vessel that carries oxygenated blood to the liver.
A: Hepatic artery.
Chapter 10: Diseases and Immunity
Technical Notes:
Pathogen: A disease-causing organism.
Defense mechanisms:
Mechanical: Skin, nose hairs.
Chemical: Stomach acid, mucus.
Cells: Phagocytes (engulf) and Lymphocytes (produce antibodies).
Immunity: Memory cells are produced after infection/vaccination for a faster future response.
Important Questions:
Q: Define "Active Immunity."
A: Defense against a pathogen by antibody production in the body.
Chapter 11: Gas Exchange in Humans
Technical Notes:
Alveoli Features:
Thin (one cell thick), large surface area, moist, good blood supply.
Breathing In:
External intercostals contract, ribs move up/out, diaphragm flattens, volume increases, pressure decreases.
Important Questions:
Q: How does the composition of inspired vs expired air differ?
A: Expired air has less oxygen, more CO2, and more water vapor.
Chapter 12: Respiration
Technical Notes:
Aerobic respiration:
Anaerobic respiration:
Humans: Glucose → Lactic acid (Occurs during vigorous exercise; causes oxygen debt).
Yeast: Glucose → Ethanol + CO2.
Important Questions:
Q: Why is less energy released in anaerobic respiration?
A: The glucose is not completely broken down.
Chapter 13: Excretion in Humans
Technical Notes:
Kidney Functions:
Ultrafiltration: Small molecules (glucose, urea, water) forced into the tubule.
Selective Reabsorption: All glucose and some salts/water reabsorbed into blood.
Urea: Formed in the liver from excess amino acids (Deamination).
Important Questions:
Q: What is the function of the bladder?
A: To store urine before it is excreted through the urethra.
Chapter 14: Coordination and Response
Technical Notes:
Nervous System: Central (CNS) and Peripheral.
Reflex Arc:
Receptor → Sensory neurone → Relay neurone → Motor neurone → Effector.
The Eye: Accommodation.
Near object: Ciliary muscles contract, suspensory ligaments slacken, lens becomes fat (thick).
Important Questions:
Q: Define "Hormone."
A: A chemical substance produced by a gland and carried by the blood, which alters the activity of specific target organs.
Chapter 15: Drugs
Technical Notes:
Antibiotics: Chemicals that kill bacteria. They do not work on viruses because viruses have no cell wall or metabolism.
Resistance: Overuse leads to the survival of resistant strains (Natural Selection).
Important Questions:
Q: Why shouldn't you stop a course of antibiotics early?
A: It leaves resistant bacteria alive to multiply.
Chapter 16: Reproduction
Technical Notes:
Sexual Reproduction: Fusion of haploid nuclei to form a diploid zygote. Increases variation.
Hormones:
FSH: Matures egg.
LH: Triggers ovulation.
Estrogen: Repairs lining.
Progesterone: Maintains lining.
Important Questions:
Q: List three functions of the placenta.
A: Exchange of nutrients, exchange of oxygen, and removal of fetal waste (urea/CO2).
Chapter 17: Inheritance
Technical Notes:
Definitions:
Genotype: Genetic makeup.
Phenotype: Observable features.
Homozygous: Two identical alleles.
Mitosis: Division resulting in genetically identical cells.
Meiosis: Division resulting in genetically different haploid cells (gametes).
Important Questions:
Q: If two heterozygous (Bb) brown-eyed parents have a child, what is the chance of a blue-eyed (bb) child?
A: 25% (1 in 4).
Chapter 18: Variation and Selection
Technical Notes:
Natural Selection: Variation exists → Struggle for survival → Survival of the fittest → Reproduction → Alleles passed on.
Selective Breeding: Humans choosing individuals with desired traits to breed.
Important Questions:
Q: Give an example of continuous variation.
A: Height or weight.
Chapter 19: Organisms and Their Environment
Technical Notes:
Trophic Levels: Energy is lost (90%) at each level through respiration, heat, and waste.
Nitrogen Cycle:
Nitrogen-fixing: Gas → Nitrates.
Nitrifying: Ammonia → Nitrates.
Denitrifying: Nitrates → Gas.
Chapter 20: Biotechnology and Genetic Modification
Technical Notes:
Yeast: Used in bread (produces CO2) and biofuel (produces ethanol).
Genetic Engineering Process:
Cut gene with restriction enzyme (sticky ends).
Cut plasmid with the same enzyme.
Join with ligase.
Important Questions:
Q: Why are bacteria used in biotechnology?
A: Rapid reproduction, share the same genetic code as humans, no ethical concerns.
Chapter 21: Human Influences on Ecosystems
Technical Notes:
Eutrophication:
Fertilizer runoff → Algal bloom → Bacteria decompose dead algae and use up all oxygen → Fish die.
Global Warming: Greenhouse gases (CO2 and methane) trap heat in the atmosphere.
Important Questions:
Q: Define "Sustainable development."
A: Providing for the needs of an increasing human population without harming the environment.