Evolution and Speciation (Topic A4.1.1-4.1.7)
Page 1: Evolution as Change
Definition of Evolution: Change in heritable characteristics of a population over time.
Page 2: Evolution of Whales
Odontoceti (Toothed Whales): Key species in the evolutionary lineage of modern whales.
Transition Timeline: Various species and their ages:
Pakicetus inachus: 47 million years ago
Ambulocetus natans: 47-41 million years ago
Malacetus inuus: 41 million years ago
Rodhocetus kasrani: 4130 years ago
Dorudon atrox: 4034 years ago
Basilosaurus cetoides: 10 million years ago
Orcinus orca: 11 million years ago
Page 3: Fundamental Definition of Evolution
Evolution fundamentally describes the change over time.
Page 4: Change in Organisms
In organisms, evolution refers to heritable changes in populations, not individuals.
Page 5: Importance of Genetic Change
Biological Evolution: Continuous change must be at the genetic level; changes that are non-genetic are not considered evolutionary.
Page 6: Historical Perspective on Evolution
Adaptation: Organisms appear to fit their environment well. Example: Fennec fox adaptations for desert survival.
Theories: Contrast between Darwinian evolution and Lamarckism.
Page 7: Charles Darwin vs. Jean-Baptiste Lamarck
Darwinian Evolution: Recognized as correct by modern science; bases on natural selection.
Contrasting Theories: Lamarck's ideas proposed that traits acquired during a lifetime could be passed on.
Page 8: Lamarckism Explained
Proposed by Lamarck: Traits can be acquired and inherited (e.g., giraffes stretching necks).
Pre-darwinian acceptance of this theory.
Page 9: Darwinian Natural Selection
Mechanism of Natural Selection:
Variation within species.
Beneficial traits enhance survival and reproductive success.
Less adapted individuals are less likely to reproduce.
Page 10: Lamarck's Giraffe Explanation
Lamarck's view: Giraffes stretch necks to reach food, leading to longer necks in offspring.
Page 11: Darwin's Giraffe Explanation
Darwin’s view: Some giraffes are born with longer necks due to natural variation.
Advantage of longer necks leads to increased reproductive success over time.
Page 12: Definition of Theory in Science
Scientific Theory: Represents the highest level of understanding; it explains phenomena and is repeatedly tested.
Page 13: Distinction of Laws and Theories
Scientific Laws: Describe what happens; theories explain how and why.
Page 14: Quote on Evolution
Theodosius Dobzhansky: "Nothing in biology makes sense except in the light of evolution."
Page 15: Limitations of Proving Evolution
The theory cannot be formally proven due to varying universal scenarios. Requires ongoing scientific validation.
Page 16: Evolution vs. Gravity
Richard Dawkins Quote: Comparison of evolution with gravity to illustrate widespread acceptance despite being "just a theory".
Page 17: Human Lineage
Human ancestors include: Australopithecus afarensis, Homo erectus, Homo neanderthalensis, Homo habilis, Homo sapiens.
Page 18: Evidence from Fossils
Fossil Evidence: Provides insight into evolution and Earth's age (4.5 billion years).
Page 19: Defining Fossils
Fossils: Evidence of past life; includes remains, impressions, carbon residues, and other imprints.
Page 20: Fossil Record Significance
Fossils provide evidence for time and evolutionary history; aquatic organisms fossilize more readily than land organisms.
Page 21: Evolutionary Trends from Fossils
Fossils allow paleontologists to track evolutionary changes and identify intermediate species.
Page 22: Age of Earth
Approximate age: 4.5 billion years. Previous beliefs suggested a much younger Earth, insufficient for Darwinian evolution.
Page 23: Relative Dating of Fossils
Relative Dating: Technique to assess the age of fossils compared to others without specific ages.
Page 24: Radioactive Dating
Radioactive Dating: Measures decay of radioactive elements. Key isotopes: Uranium-238, Potassium-40, Carbon-14.
Page 25: Carbon-14 Dating
Used for dating much younger samples (up to 50,000 years); important for archaeological findings.
Sample Calculation: Example of determining the age based on Carbon-14 to Nitrogen-14 ratio.
Page 26: Determining Fossil Age
Example Analysis: Calculating the age of a bone sample using the C-14 decay formula.
Page 27: Half-life Calculation Example
C-14 Half-life: 5770 years; illustrates how to derive age from sample ratios over half-lives.
Page 28: Common Ancestry Evidence
DNA Evidence: Technological advancements in sequencing DNA provide deeper insights into evolutionary relationships.
Page 29: Importance of DNA Sequencing
DNA sequencing alters the perception of evolutionary ancestry, allowing for better classification beyond physical traits.
Page 30: Tools for Evolutionary Analysis
Genome sequencing and tools like Clustal Omega help uncover species' evolutionary history and relationships.
Page 31: Cladograms
Diagrams based on DNA sequence similarities illustrate evolutionary relationships.
Page 32: Genetic Similarities
DNA comparison reveals common ancestry and levels of relatedness among species.
Page 33: Sequencing 2.3 Million Species
Collation of DNA sequences enhances understanding of species divergence from a common ancestor.
Page 34: Universal Genetic Code
All organisms utilize DNA similarly, providing a basis for comparison of amino acids and sequences.
Page 35: Mutation Accumulation
Over time, mutations lead to genetic variation, which helps understand evolutionary divergence.
Page 36: DNA Comparison Scope
More genetic differences correlate with longer times since divergence among species; fewer suggest closer relationships.
Page 37: Comparing Molecular Sequences
Use of non-coding DNA, gene sequences, amino acid sequences tailored based on species relationship distance.
Page 38: Appropriate Context for Comparison
Amino Acid Usage: Best for distantly related species.
Base Sequences: Preferred for closely related organisms.
Page 39: Example of Selective Breeding
Selective Breeding: Manipulation by humans to enhance desired traits in dogs, representing an evolutionary process.
Page 40: Artificial Selection Process
Traits become common through selective breeding, not limited to animals as it applies to plants too.
Page 41: Brassica Example
Plants like Brassica have been bred for different foods via artificial selection to modify various attributes.
Page 42: Domesticated Fox Experiment
Dmitry Belyaev's experiment on foxes showcases rapid evolution through selective breeding for tameness.
Page 43: Domesticated Fox Results
The domestication project resulted in friendly foxes showing dog-like behaviors, continuing research under Lyudmila Trut.
Page 44: Evolutionary Speed Examples
Evolutionary changes can happen quickly as seen with dogs, plants, and foxes through human intervention.
Page 45: Early Dog Domestication
Dogs domesticated around 15,000 years ago; reasons for domestication remain speculative, but include hunting and protection.
Page 46: Breeding for Specific Traits
Different dog breeds arose for specific purposes: hunting, herding, racing, and toy sizes highlight artificial selection's efficacy.
Page 47: Rapid Evolution Evidence
Showcases how selective breeding leads to observable evolutionary changes across species.
Page 48: Homologous Structures Evidence
Homologous Structures: Anatomically similar features across different species indicating shared ancestry.
Page 49: Speciation Defined
Speciation: Diverging evolutionary process leading to distinct species from a common ancestor.
Page 50: Common Adaptations
Consideration of whether species share evolutionary ancestry despite physical similarities.
Page 51: Pentadactyl Limb Example
Classical example of homologous structures; evidence of common ancestry through similarity in limb structure.
Page 52: Function of the Pentadactyl Limb
Despite similar underlying bone structures, limbs have evolved for varied functions based on the species’ habitat and behaviors.
Page 53: Bone Structures in the Pentadactyl Limb
Includes humerus, radius, ulna, carpals, metacarpals, and phalanges seen across species (humans, cats, horses, bats, dolphins).
Page 54: Analogous Structures Defined
Analogous Structures: Similar function but different evolutionary origins; e.g., wings of birds vs. wings of insects.
Page 55: Evolutionary Product of Analogous Structures
Analogous traits arise through convergent evolution due to adaptation to similar environments without recent common ancestors.
Page 56: Example of Convergent Evolution
Dolphins and sharks share similar traits (e.g., fins) despite not having common ancestors exemplifying convergent evolution.
Page 57: Vestigial Structures Definition
Vestigial Structures: Functionless remnants of organs from ancestors showing evolutionary divergence.
Page 58: Vestigial Structures Examples
Goosebumps, wisdom teeth as examples of vestigial structures in modern organisms.
Page 59: Speciation Explained
Definition: Separate species arise when populations can no longer interbreed and produce viable offspring.
Page 60: Models of Speciation Overview
Two models:
Gradualism: Slow, continuous evolution.
Punctuated Equilibrium: Rapid changes followed by stability.
Page 61: Gradualism Explained
Evolution happens gradually over long periods; changes may not be evident in short timeframes.
Page 62: Example of Gradualism
Horse evolution illustrates gradualism with numerous intermediates in the fossil record.
Page 63: Distinction of Speciation and Gradualism
Speciation occurs when populations diverge and cannot reproduce after significant changes over time.
Page 64: Punctuated Equilibrium Defined
Punctuated Equilibrium: Characterized by sudden evolution followed by stasis in change.
Page 65: Example of Punctuated Equilibrium
Kingfisher birds in Papua New Guinea rapidly evolving during geographic shifts in habitats.
Page 66: Reproductive Isolation Defined
Reproductive Isolation: Barriers preventing interbreeding, preserving distinct gene pools between populations.
Page 67: Divergence Over Time
Geographic separation increases divergence over time, leading to speciation.
Page 68: Differential Selection Defined
Selection by environmental pressures favors certain traits, leading to evolutionary changes in populations.
Page 69: Chimpanzee and Bonobo Divergence
Example of divergence due to differential selection influenced by geographic barriers like the Congo River.
Page 70: Adaptations in Bonobos vs. Chimpanzees
Bonobos adapted for forests; physical differences reflect distinct survival strategies in their environments.
Page 71: Bonobo Behavior Insights
Unique traits (helpfulness, non-violent behavior) observed in bonobos provide insights into evolution and social structures.
Page 72: Evolutionary Relationship Clarity
While closely related to humans, bonobos are more closely related to chimpanzees than to humans, highlighting evolution paths.
Page 73: Guiding Questions on Evolution
Consider the evidence supporting evolution and how various structures reflect commonality and diversity in species.
Page 74: References
Various sources cited for further reading and verification on evolutionary topics.