IB Biology Syllabus (SL & HL) as per IBO

Chapter 1: Cell

  1. Introduction to cells: 
    • A cell is the smallest functional collective unit that an organism can possess.
    • The ratio of surface area to volume determines the maximum size of a cell.
  2. Ultrastructure of cells:
    • There exist two sorts of cells: prokaryotic and eukaryotic.
    • The cell wall of prokaryotes is composed of peptidoglycan, a carbohydrate-protein compound.
  3. Membrane structure: 
    • The cell membrane is a continuous structure of phospholipids and proteins contained inside them.
    • Two different bilayer regions are known as hydrophilic (water-loving) and hydrophobic (water-hating) (water-fearing)
    • There are two types of cellular transport: passive and active transport.
  4. Cell Division: 
    • A cell cycle represents the phase of cell development and division. It consists mostly of two phases: Interphase and M phase (mitosis).
    • A tumor is a mass of malignant cells resulting from the uncontrolled division of cells.

Chapter 2: Molecular Biology 

  1. Molecules to Metabolism: 
    •  Carbohydrates, lipids, proteins, and nucleic acids are the four biochemical molecules. These four molecules work together to facilitate metabolism.
  2. Water: 
    • One Oxygen and two Hydrogen atoms form a covalently linked structure to form water.
  3. Carbohydrates and Lipids: 
    • Sugar is one form of carbohydrate. Condensation reactions combine monosaccharides (single sugar units) to generate disaccharides and polysaccharides. 
    •  Saturated fatty acids are lengthy hydrocarbon chains with a carboxyl group at one end and a methyl group at the other.
  4. Proteins: 
    • Polypeptides are formed by the condensation of amino acids during the translation process.
  5. Enzymes: 
    • Enzymes are simply proteins that catalyze the metabolic events that take place within cells.
  6. DNA replication, transcription, and translation: 
    • During cell division, DNA replication occurs and the DNA quantity is doubled.
    • RNA polymerase synthesizes mRNA from the DNA base sequences during transcription.
    • On ribosomes, translation is the production of polypeptides.
  7. Cell respiration: 
    • Cell respiration refers to the range of metabolic mechanisms that can be used to metabolize glucose in a cell.  
    • In the absence of oxygen, yeast (a single-celled fungus) is utilized.
  8. Photosynthesis: 
    • The transformation of light energy into chemical energy is known as photosynthesis.

Chapter 3: Genetics

  1. Genes: 
    • Genetics is the study of genes, variation, and inheritance.
    • The morphology of red blood cells altered from biconcave to sickle-shaped. It diminishes their oxygen-carrying capability and results in severe anemia; therefore it is also known as sickle cell anemia.
    • The entirety of an organism’s DNA base sequences is known as its genome.
  2. Chromosomes: 
    • In the nucleoid region of prokaryotes such as bacteria and archaea, DNA is a single, long, continuous, circular thread.
    • Some prokaryotes, such as Escherichia coli, have tiny DNA circles called plasmids.
  3. Meiosis: 
    • Meiosis is a specialized type of cell division in which the chromosomal content of a cell is reduced to exactly half of its initial amount after division; this process is also known as reduction division.
    • When the 21st chromosome fails to separate during Anaphase I, causing trisomy of 21st chromosomes in the baby, Down’s syndrome is one of the resulting illnesses.
  4. Inheritance: 
    • In 1865, Gregor Mendel introduced the concept of inheritance.
    • In humans, there are two types of genetic diseases: autosomal and sex-linked.
  5. Genetic Modification and biotechnology: 
    • Gene transfer is the process of transferring a gene of interest from one organism (donor organism) to another organism (host organism) to modify them for the purpose of obtaining additional benefits.

Chapter 4: Ecology

  1. Species, communities and ecosystems
    • Habitat: The natural setting in which an organism lives. 
    • Ecosystem is the sum of all biotic and abiotic components of a certain geographical region that are interconnected through energy exchange and nutrient cycle.
    • Decomposers are organisms that aid in the transformation of organic waste and dead animal and plant matter into inorganic substances.
  2. Energy flow
    • Every position inhabited by an organism in the food chain is referred to as its trophic level.
    • The interconnection of multiple food chains is known as a food web.
    • Autotrophs absorb sunlight and absorb inorganic soil nutrients to produce organic nourishment for the rest of the food chain.
  3. Carbon Cycling
    • In the carbon cycle, producers absorb carbon in the form of CO2 and transform it into glucose, an organic carbohydrate (C6H12O12 )
    • Methanogens (Archaea) create methane (CH4) as a byproduct of their metabolic processes.
    • Peat is a dark-colored, damp, organic matter-rich soil found in marshes.
  4. Climate Change
    • Greenhouse effect refers to the capacity of a planet’s atmosphere to retain heat and warmth even in the absence of sunshine.

Chapter 5: Evolution and Biodiversity

  1. Evidence for evolution: 
    • Speciation is the process through which one or more new species develop from preexisting ones.
    • Evolution is described as the accumulated gradual or abrupt change in a population’s heritable characteristics.
    • Adaptive Radiation refers to the evolution of various functional structures from a common ancestor.
    • In asexual reproduction, the children are formed from a single parent; thus there is a small probability that variation will occur. However, in sexual reproduction, two parents are involved, and the gametes from each parent are combined to form a zygote, therefore variety occurs.
  2. Natural selection
    • This theory is supported by Alfred Wallace and Charles Darwin as a mechanism for the evolution of species over time.
    • The creature that has successfully adapted to its environment has a greater probability of surviving than the one that has not.
  3. Classification of biodiversity
    • The system of always identifying an organism with two names is known as binomial nomenclature.
    • Except for viruses, which are regarded non-living, all living and extinct organisms are divided into three domains: the Archaea domain, the Eubacteria domain, and the Eukaryote domain.
  4. Cladistics
    • Cladistics is a type of natural classification that groups taxa based on the features that have evolved most recently.

Chapter 6: Human Physiology: 

  1. Digestion and Absorption
    • With the aid of enzymes, digestion is a set of processes that breakdown of ingested food into smaller molecular forms.
    • The largest organ in the human body is the liver.
    • The pancreas generates the hormones insulin and glucagon, which metabolize glucose, as well as pancreatic juice, which contains the enzymes lipase (for digestion of lipids), amylase (for digestion of starch), and endopeptidase (for digestion of proteins) (for protein digestion).
  2. The Blood System
    • The heart is a double-pump organ that pumps blood to all of the body’s organs via the arteries and veins.
    • In order to supply and receive blood, pressure fluctuations in the chambers of the heart occupy the cardiac cycle.
  3. Defence against infectious diseases
    • Pathogens are the most likely hazard to humans, and to prevent them from entering the body, the first line of defence is activated.
    • After pathogens have breached the major physical barriers, this secondary defence comes into play.
    • Antibodies are Y-shaped protein molecules that aid the immune system in combating invading foreign cells.
    • Gas exchnagezternal intercostal muscles).
  4. Neurons and synapses
    • Neurons are the essential cells of the brain and nervous system, and they are designed to send information as electrical impulses to other nerve cells.
    • The action potential comprises depolarization and repolarization and is the nerve impulse.
  5. Hormones, homeostasis and reproduction
    • Homeostasis is the human body’s tendency to maintain a stable equilibrium of physiological variables such as blood pH, body temperature, blood-glucose concentration, blood-CO2 concentration, and osmotic balance within tissues.
    • Hormones are non-nutritive chemical messengers produced in minute quantities.
    • In human reproduction, male gamete (sperm) and female gamete (egg) fuse to generate a zygote.

Chapter 7: Nucleic Acids 

  1. DNA structure and replication (HL ONLY)
    • In 1952, Alfred Hershey and Martha Chase confirmed DNA as the genetic material through an experiment with radioisotopes.
    • DNA is a double-stranded structure, with deoxyribose sugar and phosphate molecules serving as the backbone of each strand.
    • DNA During cell division, replication occurs as the DNA content is doubled.
    • Slicing is the post-transcriptional process of removing non-coding sequences known as introns from pre-mRNA, leaving only exons.
  2. Transcription and gene expression (HL ONLY)
    • RNA polymerase synthesises mRNA from the DNA base sequences during transcription.
    • Together, two or more polypeptides that bind to perform a certain function are designated a protein.
  3. Translation (HL ONLY)
    • On ribosomes, translation is the production of polypeptides.

Chapter 8: Metabolism, Cell respiration and photosynthesis

  1. Metabolism (HL ONLY)
    • Metabolism is the sum of all chemical reactions occurring within a live organism, the vast majority of which are enzyme-mediated.
    • The suppression of an enzyme’s activity is caused by changes in pH, temperature, and substrate concentration, among others. The modification of the active site’s conformation or the presence of a foreign molecule may also result in inhibition.
  2. Cell respiration (HL ONLY)
    • The cellular respiration route is catabolic.
    • Glycolysis: During this process of glucose breakdown, four molecules of ATP are produced and two are utilized to conduct the process.
  3. Photosynthesis (HL ONLY)
    • The transformation of light energy into chemical energy is referred to as photosynthesis.
    • Photosystem types include Photosystem I and Photosystem II.

Chapter 9: Plant Biology: 

  1. Transport in the xylem and phloem of plants (HL ONLY)
    • Cohesion is the attractive force between molecules of the same substance, such as water.
    • Adhesion is the attractive force between the molecules of dissimilar substances.
    • Xylem is responsible for plant support and is the water-conducting tissue of terrestrial plants.
    • Phloem is composed of living cells and aids in organic chemical movement.
  2. Growth in plants (HL ONLY)
    • The growth pattern of plants is indeterminate, i.e., they grow throughout their lifetime (with exceptions in some).
    • Phototropism is the development of a plant in reaction to light.
  3. Reproduction in plants (HL ONLY)
    • The term for flowering plants is angiosperms. The reproductive organs of plants are the flowers.
    • Pollination is the process by which pollen grains from the anther of the same or a different flower settle on the stigma of the same or a different bloom via wind, insects, water, birds, etc.
    • Fertilization is the process of male and female sex cells coming together to form a zygote.

Chapter 10: Genetics and Evolution

  1. Meiosis (HL ONLY)
    • Replication of chromosomes and the joining of two chromosome copies by the centromere.
  2. Inheritance (HL ONLY)
    • The Segregation Act: It claims that the pair of alleles for a certain trait segregate during the creation of gametes, such that kids inherit one allele from each parent. One of the results of the dihybrid cross is this law.
    • When two genes are located on the same chromosome, or very close to one another, they are referred to as linked.
    • Continuous and discrete or discontinuous variation are the two types.
  3. Gene pools and speciation (HL ONLY)
    • All the genetic information contained in the reproducing individuals of a population at a particular time is the gene pool.
    • Gradualism is characterized by small, continual, and rapid change. Charles Darwin utilized this concept while developing his theories on natural selection.

Chapter 11: Animal Physiology

  1. Antibody production and vaccination (HL ONLY)
    • Through antigens, the immune system detects all alien cells.
    • Monoclonal antibodies are antibodies specific to a single type of antigen.
  2. Movement (HL ONLY)
    • The term “skeleton” refers to a structure composed of bones or chitin.
    • Muscles work antagonistically in pairs to simultaneously contract and relax, generating bone movement.
    • Muscular comprises many muscle fiber cells. They are multinucleated and have an endoplasmic reticulum with specific components.
  3. The kidney and osmoregulation (HL ONLY)
    • Osmoregulators are organisms that have differing solute concentrations than their surroundings.
  4. Sexual reproduction (HL ONLY)
    • Spermatogenesis refers to the development of spermatozoa (sperm cells).
    • The process of ovum production is known as oogenesis.
    • Fertilization describes the union of male and female gametes.

Chapter 12: Biotechnology and Bioinformatics 

  1. Microbiology: organisms in industry
    • Microorganisms are small, develop rapidly, and have different metabolic processes.
    • There are two distinct types of fermentation: fed-batch and continuous.
    • It is a method for distinguishing between the gram-negative and gram-positive bacterial groupings. Their respective cell wall structures distinguish these two groups.
  2. Biotechnology in agriculture
    • Biotechnology allows for the cultivation of genetically engineered crops (GM crops).
  3. Bioremediation
    • Bioremediation is the process of removing contaminants using organisms, particularly microbes.
    • A biofilm is a layer of microbial aggregation that adheres to the surface due to the cooperation of individual cells.
    • In biotechnology, Polymerase Chain Reaction is the most prominent method for amplifying any DNA strand. Gene therapy — utilizing viral vectors – also found a place in the detection of markers.
  4. Biopharming
    • The concept behind biopharmaceutics was that if edible vaccines could be manufactured (similar to vaccinations in crops), then antigens could be produced that promote the release of antibiotics and confer protection.
  5. Bioinformatics
    • In genomics, bioinformatics is prominent. It employs information technology and computer to aid in the comprehension of biological processes.

Chapter 13: Neurobiology and Behavior 

  1. Neurobiology
    • Neurobiology is the study of the complex information processing system, which consists of the brain and nervous system.
    • Embryogenesis is the study of the embryo’s growth into a newborn.
    • Neurogenesis is the production or synthesis of neurons through the development of neuroblast cells.
  2. The human eye
    • When there are no movements of the extremities, such as the legs and arms, no eye movement, lack of corneal reflex, absence of pupil reflex, absence of gag reflex, and absence of respiration, a person is called brain-dead.
  3. Memory
    • Memory is the process of storing and encoding the information and then accessing it while putting into use.
  4. Psychoactive drugs
    • Psychoactive medications modify the post-synaptic transmission and consequently the synaptic function.
    • Anesthetics are the molecules that can block sensory reception and result in a lack of sensation in any portion of the body or the entire body.
    • Ethology is the study of animal behaviour under natural situations.

Chapter 14: Ecology and Conservation

  1. Species and Communities
    • Species refers to the group of organisms that share a habitat, share similar characteristics, and are capable of interbreeding.
    • Sometimes, abiotic and biotic elements operate as limiting factors, resulting in the distribution of species according to their tolerance for those factors.
    • All the conditions in which an organism lives, such as its habitat, diet, and interactions with other species, are referred to as its niche.
    • In parasitism, one organism is the host and the other is a parasite that resides in or on the host’s body.
    • Mutualism is a partnership in which two species live in close association and mutually benefit.
    • Commensalism: In this connection, one creature benefits from another organism that is neither damaged nor helped.
  2. Communities and ecosystems
    • Pyramids of energy illustrate the energy available at each trophic level.
    • Succession is the process by which living organisms and their abiotic elements coexist in a region.
  3. Biomagnification
    • Any species brought by humans into an area containing endemic species (native species) is referred to as an alien species.
    • Biomagnification is the process through which chemical compounds accumulate at higher trophic levels.
    • There are two types of plastic present in the water that are thought to be particularly hazardous to marine life: microscopic plastic and macroplastic.
  4. Biodiversity
    • Biodiversity is the degree of variation in life forms within an ecosystem. It can be described by its two components: diversity (the number of species presents) and distribution (the closeness or relatedness of the species with each other).
  5. Population
    • The population of a region depends on four factors: births, deaths, immigration, and emigration.
    • When a habitat has a restricted quantity of resources, the population graph displays an S-shaped (sigmoid) curve. Also known as the logistic growth curve.
  6. Nitrogen and phosphorus cycles
    • It is predominantly governed by the following bacteria:
      • There are microbes that repair atmospheric nitrogen. Example: (symbiotic) Rhizobium with Azotobacter (free living).
      • Another type of bacteria converts ammonia to nitrites through the process of nitrification. Ex – Nitrosomonas.

Chapter 15: Human Physiology

  1. Human Nutrition
    • If the necessary nutrients are synthesised by the body’s metabolism, they are referred to as non-essential nutrients. Essential nutrients are those that cannot be synthesised by the body and must be consumed as part of the diet.
    • Malnutrition is the result of an incorrect or imbalanced diet.
  2. Digestion
    • Exocrine gland secretions are important for digesting.
    • The gastric pits produce three glandular secretions, HCl, pepsin, and mucus, which are produced by three glandular cells.
    • The villi-lined small intestine is responsible for food absorption.
  3. Functions of the liver
    • Only one of the liver’s two primary blood veins, the hepatic portal vein and the hepatic artery, leads to the liver’s exit (hepatic vein).
    • Hepatocytes remove toxins from the plasma, modify them into weaker molecules, and render them water-soluble so that the kidney can excrete them.
  4. The Heart 
    • The entirety of the heart consists of cardiac muscles.
    • Defibrillators could be utilized when the heart has stopped pumping (cardiac arrest) or when the electrical impulses of a cardiac cycle are no longer in sequence (arrhythmia).
  5. Hormones and metabolism
    • Hormones are secreted directly into the bloodstream, where they are absorbed by the receptor molecules of the target cells.
  6. Transport of respiratory gases
    • Each haemoglobin molecule within an erythrocyte cell may accommodate a maximum of four oxygen molecules and one CO2 molecule.
    • Bohr Shift: It is noticed when the partial pressure of CO2 (pCO2) exceeds the partial pressure of oxygen (pO2). In this circumstance, haemoglobin releases oxygen molecules for cellular respiration, causing a change in the curves.
    • The respiratory centre in the medulla oblongata regulates the rate of ventilation.


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