Theme A: Unity and Diversity - IB 11 Biology
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Theme A: Unity and Diversity

Theme A: Unity and Diversity

The exploration of unity and diversity among living organisms reveals fundamental molecular structures, cellular architectures, and evolutionary histories shared across various life forms. By investigating the principles of water, nucleic acids, and cell origins, the chapter underscores the significance of genetic, species, and ecosystem diversity. Furthermore, the urgent need for conservation due to human impact on biodiversity is highlighted, emphasizing the interconnectedness of ecological systems.

67 sections

Sections

Navigate through the learning materials and practice exercises.

  1. 1
    Theme A: Unity And Diversity

    This section explores the fundamental commonalities and variations among...

  2. 1.1

    Water is vital for life, possessing unique properties due to its molecular...

  3. 1.2
    Nucleic Acids

    This section discusses the structure, function, and significance of nucleic...

  4. 1.3
    Origins Of Cells (Hl Only)

    This section explores how the first cells originated from non-living...

  5. 1.4
    Cell Structure

    Cell structure in living organisms is categorized into prokaryotic and...

  6. 1.5
    Viruses (Hl Only)

    Viruses, at the intersection of life and non-life, exhibit diverse...

  7. 1.6
    Diversity Of Organisms

    This section explores the classification and genetic underpinnings of the...

  8. 1.7
    Classification And Cladistics (Hl Only)

    This section explores the classification of organisms and the methodology of...

  9. 1.8
    Evolution And Speciation

    Evolution is the accumulation of genetic changes over generations, leading...

  10. 1.9
    Conservation Of Biodiversity

    Conservation of biodiversity is essential for ecosystem resilience and human...

  11. 2

    This section explores the unique molecular properties of water and its...

  12. 2.1
    Molecular Structure Of Water

    The molecular structure of water and its unique properties are essential for...

  13. 2.2
    Hydrogen Bonding And Physical Properties

    This section explains hydrogen bonding in water and its significant physical...

  14. 2.3
    Water In Biological Systems

    Water is a fundamental component of life that plays crucial roles in various...

  15. 3
    A1.2 Nucleic Acids

    This section discusses the structure and function of nucleic acids, focusing...

  16. 3.1
    Monomer Structure: Nucleotides

    Nucleotides, the building blocks of nucleic acids, consist of nitrogenous...

  17. 3.2
    Polynucleotide Structure

    This section covers the structural characteristics of nucleic acids,...

  18. 3.3
    Dna (Deoxyribonucleic Acid)

    DNA is a complex molecule that serves as the hereditary material in living...

  19. 3.4
    Rna (Ribonucleic Acid)

    This section provides a comprehensive overview of RNA, detailing its...

  20. 3.5
    Functions Of Nucleic Acids

    Nucleic acids, including DNA and RNA, serve critical functions, such as...

  21. 4
    A2.1 Origins Of Cells (Hl Only)

    This section explores the origins of the first cells through prebiotic...

  22. 4.1
    Prebiotic Earth Environment

    This section discusses the conditions of the prebiotic Earth that led to the...

  23. 4.2
    Synthesis Of Organic Monomers

    This section explores the processes by which organic monomers, the...

  24. 4.3
    Polymerization Into Macromolecules

    This section discusses the polymerization processes that lead to the...

  25. 4.4
    Formation Of Protocells

    The section explores the origin of life through the formation of protocells,...

  26. 4.5
    Rna World Hypothesis

    The RNA World Hypothesis suggests that RNA was the first biomolecule to...

  27. 4.6
    Transition To Dna–protein World

    This section explores the transition from an RNA world to a DNA-protein...

  28. 4.7
    Endosymbiotic Theory (Origin Of Eukaryotic Cells)

    The endosymbiotic theory posits that eukaryotic cells originated from...

  29. 5
    A2.2 Cell Structure

    This section covers the organization and key structural components of...

  30. 5.1
    Prokaryotic Cell Structure

    This section explores the structure and function of prokaryotic cells,...

  31. 5.1.1
    Cell Envelope

    This section discusses the structure and functions of the prokaryotic cell...

  32. 5.1.2

    The cytoplasm is the gel-like substance within cells that contains...

  33. 5.1.3

    This section explores the structure and function of cellular appendages in...

  34. 5.2
    Eukaryotic Cell Structure

    Eukaryotic cells exhibit complexity through their distinct structure,...

  35. 5.2.1
    Plasma Membrane

    The plasma membrane is a fundamental structure that surrounds all cells,...

  36. 5.2.2

    The section discusses the structure and function of the cell nucleus,...

  37. 5.2.3
    Endomembrane System

    The endomembrane system comprises a series of interconnected membranes...

  38. 5.2.4
    Mitochondria

    Mitochondria are essential organelles involved in aerobic respiration,...

  39. 5.2.5
    Chloroplasts (In Photosynthetic Eukaryotes)

    This section discusses the structure and function of chloroplasts, the...

  40. 5.2.6

    Peroxisomes are small, membrane-bound organelles containing oxidative...

  41. 5.2.7
    Cytoskeleton

    The cytoskeleton is a dynamic network of protein fibers that plays a...

  42. 5.2.8
    Other Organelles And Features
  43. 6
    A2.3 Viruses (Hl Only)

    Viruses are unique entities at the intersection of life and non-life,...

  44. 6.1
    Basic Viral Structure

    This section covers the fundamental structure of viruses, including their...

  45. 6.2
    Classification Of Viruses

    This section explains the classification of viruses based on their...

  46. 6.3
    Viral Replication Cycles

    This section explores the intricate cycles through which viruses replicate,...

  47. 6.4
    Lytic Vs. Lysogenic Cycles (Bacteriophages)

    Bacteriophages can undergo two distinct cycles of infection: the lytic and...

  48. 6.5
    Viral Pathogenesis And Host–virus Interactions

    This section discusses the interactions between viruses and their hosts,...

  49. 6.6
    Viruses In Evolution And Ecology

    This section explores the role of viruses in evolution and ecology,...

  50. 7
    A3.1 Diversity Of Organisms

    This section covers the classification of life into three domains based on...

  51. 7.1
    Definition Of Species

    The section provides various definitions and concepts related to the...

  52. 7.2
    Genetic Variation As The Basis Of Diversity

    Genetic variation, driven by mutations, sexual reproduction, and gene flow,...

  53. 7.3
    Levels Of Biological Organization And Diversity

    This section discusses the various levels of biological organization,...

  54. 7.4
    Chromosome Numbers And Karyotype Variation

    This section discusses the significance of chromosome numbers and karyotype...

  55. 8
    A3.2 Classification And Cladistics (Hl Only)

    This section focuses on classification systems that organize biological...

  56. 8.1
    Taxonomy: Hierarchical Classification

    This section outlines the hierarchical classification of living organisms,...

  57. 8.2
    Cladistics: Inferring Evolutionary Relationships

    Cladistics is a method used to classify organisms based on shared derived...

  58. 9
    A4.1 Evolution And Speciation

    The section examines how populations undergo genetic changes over...

  59. 9.1
    Mechanisms Of Evolutionary Change

    This section covers the mechanisms driving evolutionary change, including...

  60. 9.2
    Evidence For Evolution

    This section explores the various types of evidence that support the theory...

  61. 9.3
    Speciation: Formation Of New Species

    This section explores the process of speciation, detailing the mechanisms...

  62. 9.4
    Reproductive Isolating Mechanisms

    Reproductive isolating mechanisms prevent gene flow between populations,...

  63. 9.5
    Patterns Of Evolution

    Patterns of evolution highlight the various mechanisms driving the...

  64. 10
    A4.2 Conservation Of Biodiversity

    Conservation of biodiversity is crucial for ecosystem resilience and human...

  65. 10.1
    Levels Of Biodiversity

    This section discusses the various levels of biodiversity, including...

  66. 10.2
    Threats To Biodiversity

    This section discusses various threats to biodiversity including habitat...

  67. 10.3
    Conservation Strategies

    Conservation strategies aim to protect biodiversity through various...

What we have learnt

  • All living organisms share fundamental molecular building blocks.
  • Diverse life forms arise from shared evolutionary histories, leading to a rich variety of species.
  • Conservation of biodiversity is critical for ecosystem resilience and human well-being.

Key Concepts

-- Unity and Diversity
The concept that all living organisms have common molecular and cellular foundations yet exhibit vast differences due to evolutionary processes.
-- Endosymbiotic Theory
A widely accepted hypothesis for the origin of eukaryotic cells, suggesting that key organelles originated from free-living bacteria engulfed by primitive host cells.
-- Speciation
The process through which new and distinct species emerge, often due to reproductive isolation and genetic divergence.
-- Biodiversity
The variety of life on Earth, encompassing genetic, species, and ecosystem diversity, vital for ecological health and resilience.

Additional Learning Materials

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