ESAT Biology: Revision Notes

B1.1

This topic covers the essential components, or organelles, inside eukaryotic cells, which form the basis of all animal and plant life. Understanding the specific role of each part is key to answering questions on how cells live, get energy, and are structured.

B1.2

Prokaryotic cells, such as bacteria, are simple cellular structures defined by the absence of a true nucleus. Understanding their key components is crucial for distinguishing them from more complex eukaryotic cells.

B1.3

This topic covers the hierarchical structure of multicellular organisms, explaining how simple, specialised cells are progressively organised into more complex tissues, organs, and systems to carry out life functions.

B2.1

This topic covers the essential mechanisms by which substances cross biological membranes, a fundamental process for cell survival, communication, and function. Understanding these passive (no energy) and active (energy required) transport methods is key to solving problems in physiology and cell biology.

B3.1

This topic covers mitosis, the process by which most body cells divide to create genetically identical copies for growth, repair, and replacement. Understanding the stages of the cell cycle and the consequences of its failure, such as cancer, is key.

B3.2

Meiosis is a specialized type of cell division that reduces the chromosome number by half, creating four genetically unique haploid cells (gametes). This process is fundamental to sexual reproduction, ensuring that the offspring receives a complete, diploid set of chromosomes upon fertilisation.

B3.3

This topic contrasts asexual and sexual reproduction, focusing on the number of parents involved and the resulting genetic variation in offspring. Understanding this is crucial for questions on inheritance, population dynamics, and evolution.

B3.4

This topic covers how sex is determined in mammals by the X and Y sex chromosomes. It focuses on using genetic diagrams, such as Punnett squares, to predict the probability and expected ratios of male and female offspring.

B4.1

This topic establishes the fundamental principle that in eukaryotic organisms, like animals and plants, the genetic blueprint (DNA) is stored and protected within a specialised compartment called the nucleus. Understanding this is key to how inheritance and cell control work.

B4.2

This topic covers the fundamental vocabulary of genetics, explaining how traits are encoded in DNA and passed from one generation to the next. Mastering these terms is crucial for interpreting genetic diagrams and solving inheritance problems.

B4.3

This topic covers monohybrid inheritance, which is the prediction of genetic outcomes for a single trait. You will use Punnett squares and family pedigrees to calculate probabilities and ratios, which are essential for understanding how traits and genetic conditions are passed down through generations.

B5.1

This topic covers the fundamental organisation of an organism's genetic material. It defines the hierarchy from the complete genetic blueprint (the genome) down to the structures that hold it (chromosomes) and the molecule itself (DNA).

B5.2

DNA is a large polymer molecule that carries an organism's genetic instructions. Understanding its structure, from the nucleotide building blocks to the double helix, is fundamental to biology and often tested with simple percentage calculations.

B5.3

This topic covers the fundamental process of protein synthesis, explaining how the genetic information encoded in a DNA sequence of nucleotide bases is translated into a specific sequence of amino acids to build a functional protein.

B5.4

A gene mutation is a change to the sequence of bases in DNA. This can alter the protein produced, which may in turn affect an organism's observable traits (phenotype), but often these changes have no effect at all.

B6.1

Genetic engineering involves transferring a gene from one organism to another to create recombinant DNA. For ESAT, you must understand the process, the key enzymes involved, and be able to weigh the medical benefits against the potential risks.

B6.2

Stem cells are undifferentiated cells that can develop into specialised cell types. Their varying potential (potency) underpins their use in regenerative medicine, but also creates significant ethical and practical challenges.

B6.3

This topic contrasts selective breeding, where humans direct the evolution of a species for desired traits, with natural selection, where the environment is the driving force. Understanding the mechanisms and consequences, particularly the impact on genetic diversity, is key for the ESAT.

B7.1

This topic explains how genetic differences within a species' population provide the raw material for evolution. It details the mechanism of natural selection, where environmental pressures favour certain traits, leading to changes in the population's characteristics over time.

B7.2

This topic explains the two fundamental sources of differences we see among individuals in a species: inherited genetic factors and external environmental influences. Understanding this distinction is crucial for grasping how natural selection and evolution operate.

B8.1

Enzymes are essential protein molecules that act as biological catalysts. They dramatically accelerate the rate of specific chemical reactions necessary for life, which would otherwise happen too slowly.

B8.2

Enzymes are protein catalysts that dramatically speed up specific biochemical reactions. Their function depends on a unique region called the active site, which binds to a specific reactant molecule.

B8.3

Enzymes are biological catalysts whose activity is highly sensitive to their environment. For the ESAT, you must understand how temperature and pH changes alter the rate of enzyme-catalysed reactions by affecting the enzyme's structure and the kinetic energy of molecules.

B8.4

Digestive enzymes are biological catalysts that break down large, insoluble food molecules into smaller, soluble molecules that can be absorbed into the bloodstream. The ESAT requires you to know the specific roles of the three main types of digestive enzymes.

B9.1

Cellular respiration is the chemical process that all living cells use to break down glucose and release energy in the form of ATP for essential life functions. It is a metabolic process within cells, distinct from the physical act of breathing.

B9.2

This topic covers the structure and function of key animal organ systems, including the nervous, respiratory, circulatory, digestive, and excretory systems. It explains how these systems work together to enable response, gas exchange, transport, nutrition, and waste removal, which are fundamental to understanding multicellular life.

B9.3

Homeostasis is the active regulation of an animal's internal environment, such as temperature and blood sugar, to maintain stable conditions necessary for enzyme function and cell survival. This topic covers the negative feedback mechanisms that control these vital internal states.

B9.4

This topic covers how hormones act as chemical messengers in the body, focusing on adrenaline's role in the 'fight or flight' response and the complex hormonal control of the human menstrual cycle and contraception.

B9.5

This topic covers the distinction between communicable diseases, caused by pathogens and fought with treatments like vaccines, and non-communicable diseases, which arise from multiple factors and require long-term management.

B10.1

This topic covers the hierarchical organisation of life, from individual organisms to entire ecosystems. It explains how populations interact with each other and their non-living environment, and the factors that cause their numbers to change over time.

B10.2

This topic covers how essential materials like carbon and water are continuously recycled through ecosystems. ESAT questions test your understanding of the key biological and physical processes involved, and how they interact to maintain a balance.

B10.3

This topic covers how we measure the variety and number of organisms in an ecosystem using sampling techniques, and how to analyse the effects of human activities like farming and pollution on this biodiversity.

B11.1

Photosynthesis is the fundamental process by which plants convert light energy into chemical energy, creating their own food. The rate of this vital reaction is not constant; it is controlled by the most scarce environmental resource, known as the limiting factor.

B11.2

Plants possess a sophisticated vascular system to transport water, minerals, and sugars. This topic examines the structure and function of xylem and phloem, the process of water uptake, and the factors influencing transpiration.