L1_OverviewEvoBio_W2025_ClassSlides (1)

Lecture Overview

• Lecture Topic: An Overview of Evolutionary Biology

• Key Figures/Topics: Gibbon, Orang, Chimpanzee, Gorilla, Human Skeletons

Learning Objectives 1.1: Introduction to Evolution

• Evolutionary Biology: Study of the origin and diversity of life.

• Evolution Defined: Change in the heritable characteristics of biological populations over successive generations.

• Natural vs Artificial Selection:

  • Natural Selection: Process where organisms better adapted to their environment tend to survive and produce more offspring.

  • Artificial Selection: Intentional reproduction of individuals with desired traits.

Learning Objectives 1.2: Research Approaches

• Empirical Research: Based on observation and experimentation.

• Theoretical Research: Based on mathematical models to explain biological phenomena.

The Advent of Natural Selection

• Darwin's Contribution: Shifted understanding from supernatural explanations of biodiversity to natural processes.

• Quote: "Nothing in biology makes sense, except in the light of evolution." - Theodosius Dobzhansky (1973).

• Importance of Evolution: Unites various biological disciplines, helps understand organism similarities, functionalities, and origins.

What is Evolutionary Biology?

• Objective: Understand life's origin, maintenance, and diversity.

• Key Aspects:

  • Classification of species (living and extinct).

  • Inferring relationships and adaptations among species.

  • Investigating genetic variation and extinction mechanisms.

What is Evolution?

• Core Components:

  • Survival of the Fittest: Organisms best suited to their environment tend to survive.

  • Descent with Modification: Changes in species over time linked to ancestral forms.

• Evolutionary Processes:

  • Natural Selection

  • Non-random Mating

  • Mutation

  • Migration

  • Genetic Drift

Natural Selection

• Definition: Better-adapted forms increase in frequency within a population.

• Mechanism: Beneficial alleles lead to increased survival and reproduction.

• Nature of Process: Gradual, occurring over long timescales.

Descent with Modification via Natural Selection

• Key Features:

  • Genetic variation within populations.

  • Mutations affecting fitness (positive, negative, neutral).

  • Advantageous traits lead to increased reproductive success.

• Result: Evolutionary changes become more common through natural selection over time.

Additional Mechanisms Influencing Evolution

• Besides Natural Selection, other mechanisms include:

  • Non-random Mating

  • Mutation

  • Migration

  • Genetic Drift

Artificial Selection

• Concept: Human-driven selection for specific traits in reproductive individuals.

• Examples:

  • Selective breeding in agriculture.

  • Domestication of various animal species.

Example of Antibiotic Resistance

• Context: Fast reproduction rates of bacteria lead to increased resistance to antibiotics.

• Question: Do antibiotics impose artificial or natural selective forces on bacteria?

Example of Trophy Hunting

• Subject: Mountain sheep (Ovis canadensis) hunting regulations (1972-1995).

• Findings: Hunting led to reduced horn length desirable traits over time.

• Question: Did trophy hunting impose artificial or natural selective forces on sheep?

Anthropogenic Evolution

• Impact of Humans:

  • Human actions influence natural selection processes.

  • Definitions:

    • Anthropogenic Evolution: Evolutionary changes induced by human activities (e.g., climate change, habitat destruction).

Phylogenetic Trees as Hypotheses

• Concept: All living beings share a common ancestor.

• Importance: Phylogenetic trees illustrate historical relationships and serve as hypotheses for evolutionary biology.

• Components of Phylogenetic Trees:

  • Branches

  • Branch tips

  • Internal nodes (points of divergence)

Approaches to Studying Evolution

• Two Main Approaches:

  1. Theoretical Research: Utilizes models to explain biological systems.

  2. Empirical Research: Based on observation and data collection to support theoretical models.

Theoretical Approach: Understanding Sex Ratio

• Hypothetical Model: Investigates the dynamics of sex ratio in populations.

• Outcomes: 1:1 male-female ratio as an equilibrium evolved due to selective pressures.

Testing the 1:1 Sex Ratio

• Prediction Confirmation: Examined through variations in the sex ratio in Blue Moon butterflies.

• Result: Population sex ratio returned to 1:1 within 10 generations.

Empirical Approach: Observational Research

• Historical Context: Darwin and Huxley noted that humans share common ancestors with great apes.

• Supporting Evidence: Genetic sequencing shows minimal differences between human and chimpanzee genomes.

Understanding Differences in Chimps and Humans

• Gene Expression Differences: Variability in gene expression in different organs contributes to phenotypic differences.

• Natural Selection's Role: Notable for specific variables, especially related to reproductive functions.

Key Terms to Know

• Evolutionary biology, Evolution, Descent with modification, Genetic variation, Phenotype, Fitness, Natural selection, Artificial selection, Anthropogenic evolution, Phylogeny, Empirical vs. theoretical research: These terms will be further explored as the course progresses.