These notes are highlighted from our A-level Biology exam focus textbook, for complete study materials on this course, refer to the textbook. For effective preparation, practice past questions on this course as much as possible.
Lecture 1: Origin of Living Things
Biology is the scientific study of living organisms. It covers how they are structured, how they function, how they grow, and how they relate to their environment. Biology is important because it helps us understand and improve healthcare, farming, food production, and our natural world.
Science works through a process called the Scientific Method. A scientist first observes something and asks a question. Then a hypothesis is formed, which is simply an educated guess about the answer. The hypothesis is then tested through experiments. Data is collected, analyzed, and a conclusion is drawn. This same process is applied in biology experiments in the laboratory.
Biology has a close relationship with medicine because understanding living things helps doctors treat diseases. It also connects with agriculture because biological knowledge helps farmers grow better crops and raise healthier animals.
Lecture 2: Living Things and Biological Molecules
Living things are grouped into five major kingdoms which are Monera, Protista, Fungi, Plantae, and Animalia. Each kingdom has its own unique set of characteristics that define its members.
All living things are made up of biological molecules. Carbohydrates are molecules that supply the body with energy and glucose is a common example. Lipids are fats and oils that store energy and help form cell membranes. Proteins are responsible for building and repairing body tissues and they also work as enzymes and hormones. Nucleic acids, which include DNA and RNA, are responsible for storing and transferring genetic information from one generation to the next.
Lecture 3: Cell Organization, Structure and Function
The cell is the smallest and most basic unit of life. Everything a living organism does happens at the cellular level. Cells are studied using a microscope, and students are expected to make biological drawings of what they observe.
There are two main types of cells. Plant cells have a cell wall, chloroplasts for making food, and a large vacuole for storing water. Animal cells do not have a cell wall or chloroplasts, and their vacuoles are very small. Both cell types share common structures like the nucleus, which controls the cell, the mitochondria, which produce energy, the ribosomes, which make proteins, the cytoplasm, which fills the cell, and the cell membrane, which controls what enters and leaves the cell.
When making biological drawings, lines must be clean and continuous, labels must be horizontal, titles must be written, and there must be no shading or colouring.
Lecture 4: Cell Division, Genetics and Heredity
Genetics is the study of how characteristics are passed from parents to offspring. A chromosome is a thread-like structure found in the nucleus that carries genes. A gene is a unit of inheritance that determines a specific trait. An allele is one of the different forms a gene can take.
When a trait is dominant it will always show in the organism even if only one copy is present. A recessive trait only shows when two copies are present. The genotype refers to the actual genetic makeup of an organism while the phenotype refers to the physical appearance that results from that genotype.
Cells divide in two major ways. Mitosis produces two identical cells and is used for growth and repair of body tissues. Meiosis produces four sex cells and is used in reproduction. The stages of meiosis can be identified under a microscope.
Gregor Mendel was the scientist who discovered the basic laws of inheritance. His laws explain how traits are inherited and can be verified in practical class using coloured seeds or beads. Some traits like blood groups and eye colour are controlled by multiple alleles, meaning more than two allele options exist for those traits.
Lecture 5: Systematics, Taxonomy and Nomenclature
Taxonomy is the science of identifying, naming, and classifying living organisms into groups based on their shared features. Systematics is broader and also studies the evolutionary relationships between organisms.
Every organism is given a scientific name made up of two parts, which is called binomial nomenclature. The first part is the genus and the second part is the species. For example, humans are called Homo sapiens. These names are written in Latin and are used worldwide so that scientists everywhere refer to the same organism by the same name.
In practical class, students identify and classify different specimens and also study the adaptive features that help each organism survive in its environment.
Lecture 6: Ecology
Ecology is the study of how living organisms interact with one another and with their physical environment. These interactions can be cooperative or harmful depending on the relationship involved.
Symbiosis is a general term for when two different organisms live closely together. Within symbiosis there are different types of relationships. In mutualism both organisms benefit from the relationship. In parasitism one organism benefits while the other is harmed. In commensalism one organism benefits while the other is neither helped nor harmed.
Ecology also involves studying populations within specific habitats, understanding how environmental conditions change over time, and examining how climate change is affecting living organisms and their ecosystems today.
Lecture 7: Evolution
Evolution is the process by which living organisms change gradually over very long periods of time, leading to the development of new species. These changes happen through natural selection, where organisms that are better suited to their environment survive and reproduce more successfully.
There are different types of evolution. Convergent evolution occurs when unrelated organisms develop similar features because they live in similar environments. Divergent evolution is when organisms from a common ancestor develop different characteristics over time. Parallel evolution is when two related organisms evolve similar traits independently.
Understanding evolution is very important in taxonomy because it helps explain why organisms are grouped the way they are. Both plants and animals are classified partly based on their evolutionary history and the features they have inherited from common ancestors.