Theme A: Unity And Diversity

This section explores the fundamental commonalities and variations among living organisms, highlighting their molecular structures and evolutionary relationships.

Water

Water is vital for life, possessing unique properties due to its molecular structure, which significantly influences biological functions.

Nucleic Acids

This section discusses the structure, function, and significance of nucleic acids, primarily focusing on DNA and RNA.

Origins Of Cells (Hl Only)

This section explores how the first cells originated from non-living molecules through various processes on prebiotic Earth.

Cell Structure

Cell structure in living organisms is categorized into prokaryotic and eukaryotic cells, highlighting their similarities and differences.

Viruses (Hl Only)

Viruses, at the intersection of life and non-life, exhibit diverse structures and replication mechanisms that are central to understanding their role in ecosystems and human health.

Diversity Of Organisms

This section explores the classification and genetic underpinnings of the diversity of organisms across the three domains: Bacteria, Archaea, and Eukarya.

Classification And Cladistics (Hl Only)

This section explores the classification of organisms and the methodology of cladistics to understand evolutionary relationships.

Evolution And Speciation

Evolution is the accumulation of genetic changes over generations, leading to speciation and the diversity of life.

Conservation Of Biodiversity

Conservation of biodiversity is essential for ecosystem resilience and human well-being, confronting challenges posed by human activities.

A1.1 Water

This section explores the unique molecular properties of water and its essential roles in biological systems.

Molecular Structure Of Water

The molecular structure of water and its unique properties are essential for life, influencing biological processes and ecosystems.

Hydrogen Bonding And Physical Properties

This section explains hydrogen bonding in water and its significant physical properties that make it crucial for life.

Water In Biological Systems

Water is a fundamental component of life that plays crucial roles in various biological processes due to its unique properties.

A1.2 Nucleic Acids

This section discusses the structure and function of nucleic acids, focusing on nucleotides, DNA, and RNA.

Monomer Structure: Nucleotides

Nucleotides, the building blocks of nucleic acids, consist of nitrogenous bases, pentose sugars, and phosphate groups, forming essential structures for genetic information storage and transfer.

Polynucleotide Structure

This section covers the structural characteristics of nucleic acids, specifically focusing on the composition and function of DNA and RNA, along with the significance of polynucleotide chains in biological processes.

Dna (Deoxyribonucleic Acid)

DNA is a complex molecule that serves as the hereditary material in living organisms, made up of nucleotides forming a double helix structure.

Rna (Ribonucleic Acid)

This section provides a comprehensive overview of RNA, detailing its structure, types, and functions in biological systems.

Functions Of Nucleic Acids

Nucleic acids, including DNA and RNA, serve critical functions, such as storing genetic information, facilitating protein synthesis, and regulating gene expression.

A2.1 Origins Of Cells (Hl Only)

This section explores the origins of the first cells through prebiotic environments and processes leading to the emergence of life.

Prebiotic Earth Environment

This section discusses the conditions of the prebiotic Earth that led to the formation of organic molecules, paving the way for the origins of life.

Synthesis Of Organic Monomers

This section explores the processes by which organic monomers, the fundamental building blocks of life, are synthesized under primordial conditions.

Polymerization Into Macromolecules

This section discusses the polymerization processes that lead to the formation of macromolecules, focusing on nucleic acids and proteins.

Formation Of Protocells

The section explores the origin of life through the formation of protocells, highlighting the conditions and processes that led to the emergence of these primitive cell-like structures.

Rna World Hypothesis

The RNA World Hypothesis suggests that RNA was the first biomolecule to store genetic information and catalyze chemical reactions, leading to the evolution of life on Earth.

Transition To Dna–protein World

This section explores the transition from an RNA world to a DNA-protein world, focusing on the emergence of peptides and proteins, the stability of DNA, and the evolution of cellular machinery.

Endosymbiotic Theory (Origin Of Eukaryotic Cells)

The endosymbiotic theory posits that eukaryotic cells originated from free-living prokaryotes that formed symbiotic relationships.

A2.2 Cell Structure

This section covers the organization and key structural components of prokaryotic and eukaryotic cells.

Prokaryotic Cell Structure

This section explores the structure and function of prokaryotic cells, detailing their unique characteristics and components.

Cell Envelope

This section discusses the structure and functions of the prokaryotic cell envelope, including the cell wall, plasma membrane, and additional features.

Cytoplasm

The cytoplasm is the gel-like substance within cells that contains organelles, provides structural support, and facilitates biochemical processes.

Appendages

This section explores the structure and function of cellular appendages in prokaryotic cells, emphasizing their role in mobility and attachment.

Eukaryotic Cell Structure

Eukaryotic cells exhibit complexity through their distinct structure, featuring a true nucleus and various membrane-bound organelles that compartmentalize functions.

Plasma Membrane

The plasma membrane is a fundamental structure that surrounds all cells, defining their boundaries and regulating interactions with the environment.

Nucleus

The section discusses the structure and function of the cell nucleus, highlighting its components and significance in cellular processes such as gene expression and cell division.

Endomembrane System

The endomembrane system comprises a series of interconnected membranes within eukaryotic cells that are essential for the synthesis, processing, and transport of proteins and lipids.

Mitochondria

Mitochondria are essential organelles involved in aerobic respiration, facilitating the production of ATP through oxidative phosphorylation.

Chloroplasts (In Photosynthetic Eukaryotes)

This section discusses the structure and function of chloroplasts, the organelles responsible for photosynthesis in eukaryotic plants and algae.

Peroxisomes

Peroxisomes are small, membrane-bound organelles containing oxidative enzymes that play crucial roles in cellular metabolism, including the detoxification of hydrogen peroxide and the metabolism of fatty acids.

Cytoskeleton

The cytoskeleton is a dynamic network of protein fibers that plays a critical role in maintaining cell shape, providing structural support, and facilitating intracellular transport and cell division.

Other Organelles And Features

This section discusses the various organelles and features found in eukaryotic cells, emphasizing their structure and functions within the cellular architecture.

A2.3 Viruses (Hl Only)

Viruses are unique entities at the intersection of life and non-life, characterized by their inability to replicate independently and their genetic material, which permits rapid evolution.

Basic Viral Structure

This section covers the fundamental structure of viruses, including their genetic material, capsid, and envelope.

Classification Of Viruses

This section explains the classification of viruses based on their structure, nucleic acid type, and replication strategies.

Viral Replication Cycles

This section explores the intricate cycles through which viruses replicate, highlighting the steps of attachment, entry, uncoating, genome replication, and release.

Lytic Vs. Lysogenic Cycles (Bacteriophages)

Bacteriophages can undergo two distinct cycles of infection: the lytic and lysogenic cycles, each with unique processes and outcomes.

Viral Pathogenesis And Host–virus Interactions

This section discusses the interactions between viruses and their hosts, exploring viral structure, replication, immune responses, and implications in evolution and ecology.

Viruses In Evolution And Ecology

This section explores the role of viruses in evolution and ecology, examining their genetic impact, ecological significance, and co-evolution with hosts.

A3.1 Diversity Of Organisms

This section covers the classification of life into three domains based on molecular differences and explores species definition, genetic variation, and levels of biological diversity.

Definition Of Species

The section provides various definitions and concepts related to the classification of species within biological diversity.

Genetic Variation As The Basis Of Diversity

Genetic variation, driven by mutations, sexual reproduction, and gene flow, forms the foundation for biological diversity among species.

Levels Of Biological Organization And Diversity

This section discusses the various levels of biological organization, including molecular, cellular, organismal, and ecosystem levels, while highlighting the diversity among living organisms.

Chromosome Numbers And Karyotype Variation

This section discusses the significance of chromosome numbers and karyotype analysis in understanding organismal diversity and genetic abnormalities.

A3.2 Classification And Cladistics (Hl Only)

This section focuses on classification systems that organize biological diversity and describes cladistics as a method for inferring evolutionary relationships.

Taxonomy: Hierarchical Classification

This section outlines the hierarchical classification of living organisms, emphasizing the importance of taxonomy in understanding the unity and diversity of life.

Cladistics: Inferring Evolutionary Relationships

Cladistics is a method used to classify organisms based on shared derived characters to reconstruct their evolutionary relationships.

A4.1 Evolution And Speciation

The section examines how populations undergo genetic changes over generations, leading to the emergence of new species and the mechanisms of speciation.

Mechanisms Of Evolutionary Change

This section covers the mechanisms driving evolutionary change, including mutations, natural selection, genetic drift, and gene flow.

Evidence For Evolution

This section explores the various types of evidence that support the theory of evolution, including fossil records, comparative anatomy, and molecular biology.

Speciation: Formation Of New Species

This section explores the process of speciation, detailing the mechanisms that lead to the formation of new species, including genetic isolation and natural selection.

Reproductive Isolating Mechanisms

Reproductive isolating mechanisms prevent gene flow between populations, playing a crucial role in speciation.

Patterns Of Evolution

Patterns of evolution highlight the various mechanisms driving the diversification of life forms on Earth.

A4.2 Conservation Of Biodiversity

Conservation of biodiversity is crucial for ecosystem resilience and human well-being, but human activities have accelerated biodiversity loss.

Levels Of Biodiversity

This section discusses the various levels of biodiversity, including genetic, species, and ecosystem diversity, and their significance in understanding biological resilience and conservation.

Threats To Biodiversity

This section discusses various threats to biodiversity including habitat loss, pollution, climate change, invasive species, and overexploitation.

Conservation Strategies

Conservation strategies aim to protect biodiversity through various approaches that address species, genetic, and ecosystem diversity.