L16 2025 - The Selection Process I - Tagged
Page 1: Introduction
Title: The Selection Process in Evolution
Key Concepts:
The engines of evolution
The fuel of evolution
Reference: Campbell’s Biology: Unit 4
Page 2: Defining Evolution
What is Evolution?
Pattern: Change over time
Examples of modern mammals over millions of years
Geological periods: Permian, Triassic, Jurassic, Cretaceous, and Cenozoic
Fossil examples include Dimetrodon and Megazostrodon
Page 3: Evolution as a Mechanism
Two perspectives:
William Paley: Design Argument
Charles Darwin: Theory of Evolution
Page 4: Lecture Content Overview
Main Questions:
What causes evolution?
Does evolution lead to perfection?
Page 5: Mechanisms of Evolution
Five mechanisms that cause change over time:
Natural selection
Non-random mating
Genetic drift
Gene flow
Mutation
Darwin's insights in 'Origin of Species' encompass all these factors.
Page 6: Natural Selection Defined
Definition: Natural selection involves three conditions:
Variation
Differential success (fitness)
Inheritance
Outcome: The most successful variant increases in frequency; leads to evolution.
Population growth often exceeds available resources (Malthus, 1798).
Page 7: Evidence of Natural Selection
Example: Observations by Albert Farn on colour morphs of the Annulet Moth
Variability linked to habitat and survival, supporting Darwin's theory.
Page 8: Industrial Melanism
Case Study: Peppered Moth
Observations of dark colourations due to industrialization reflect natural selection.
Page 9: Conditions of Natural Selection
Reiterating the conditions for natural selection:
Variation
Differential success
Inheritance
Page 10: The Pre-Industrial Period
Data: % of black forms of Peppered Moths from 1800-2000 (not shown in detail)
Page 11: The Industrial Period
Data: Changes in Peppered Moth population dynamics during industrialization
Page 12: Post-Industrial Recovery
Data: Recovery of Peppered Moth population post-industrialization reflected in % changes.
Page 13: Rapid Evolution Case Study
Case Study: Tusklessness in elephants due to selective pressures (civil war effects illustrated).
Page 14: Biochemical Evolution in Laboratory
Experimental Evidence: Adaptations observed in biochemical pathways through gradual changes.
Page 15: Focus of Natural Selection
Nature of Selection:
Concentrates on self-interest of individuals promoting their own genes.
Kin selection illustrates cooperation among related individuals.
Page 16: Pace of Change in Evolution
Gradualism vs. Rapid Evolution:
Gradualism suggests continuous small changes; examples include the ancient Coelacanth.
Recognition of punctuated equilibrium (Eldridge & Gould) explains rapid changes in some instances.
Page 17: Speed of Evolution
Continued discussion on gradualism vs. rapid evolutionary changes.
Page 18: Influence of Body Size on Selection
Variation in Body Size: The influence of selection intensity on evolution speed is examined.
Page 19: The Origin of Species
Concept: Natural selection as non-random survival mechanism of variation (Dawkins).
Page 20: Evolutionary Timeframes
Complexity of Evolution: Reference to vast timeframes required for potential evolutionary changes.
Page 21: Complexity of Evolution (continued)
Additional hypothetical complexities of evolution shown in statistical modeling.
Page 22: Recap of Causes of Evolution
Summarization of five causes of evolution as part of accidental toolkit.
Page 23-24: Non-Random Mating
Concept:
Non-random mating also known as sexual selection.
Particular traits increase mating success.
Page 25: Sexual Selection Dynamics
Characteristics Enhanced: Traits that make individuals more attractive or dominant in mating contexts.
Page 26: Chance in Evolution
Genetic Drift: Random changes affecting trait frequencies, particularly in small populations.
Page 27-30: Genetic Drift Effects
Simulation Example: Demonstration of genetic drift through population simulation scenarios.
Founder Effect: Small group diverging genetically (e.g., Porphyria in King George III).
Bottleneck Effect: Example of lions in the Ngorogoro Crater surviving a crash, becoming genetically different.
Page 31-32: Bottleneck Effect Cont.
Continuation of the bottleneck effect case study illustrating population changes over time.
Page 33: Gene Flow Mechanism
Definition: Movement of genes between populations contributing to genetic changes.
Page 34-35: Gene Flow Examples
Example: Dispersal under environmental influences, illustrated via Agrostis grass in a copper mine.
Page 36: Mechanisms of Evolution Recap
Reflection on various causes of evolution discussed so far.
Page 37: Evolution Does Not Lead to Perfection
Adaptations: Specific features that enhance survival but do not necessarily imply perfection.
Page 38: Not All Features are Adaptations
Banana anatomy: Illustrates functional design for human consumption while challenging perceptions of adaptations.
Page 39: Perceptions of Adaptation
Just-so stories: Addressing imaginative explanations and the role of adaptations in organisms' characteristics.
Page 40: Adaptation Evidence
Kettlewell’s Experiment: Dark vs. light Peppered Moth survival rates under different environmental conditions in the 1950s.
Page 41: Evolution and Perfect Organisms
Summary on the limitations of evolution to fashioning perfect organisms due to the whimsical nature of the toolkit and historical constraints.
Page 42: Design Limitations in Evolution
Continued exploration of why evolution does not guarantee perfection due to variation, compromises, and historical constraints.
Page 43: Evolution Reiterated
Repeated information on adaptations and the evidence of evolutionary change over time.
Page 44: Take Home Message
Summary: Evolution results from natural mechanisms rather than intelligent design.
Page 45: Lecture Summary
Key Points:
Evolution as descent with modification leads to complex adaptations without a specific goal.
Natural selection plays a key role along with genetic drift and gene flow in evolutionary change.