Evolution

Course Details: BSC2010 Spring 2026 Unit 3: Evolution Section
- Instructor: Dr. Mary Hart
- Office: 316A Bartram Hall
- Office hours: Period 4 (Contact via Canvas email for alternative times)

Objectives:
- Define scientific theory: Understanding the distinction between the scientific use of 'theory' and general usage.
- Evolution as a scientific theory: Explanation of why evolution fits this classification.
- Contributions to evolutionary theory: Key individuals and their contributions to the progression of the theory of evolution.
- Darwin's natural selection: Elaboration on Darwin’s concepts and the evidence supporting them.
- Key lines of evidence for evolution: Overview of significant supporting data.

Definition:
- Evolution: The change in the genetic composition of populations over time. This is classified as microevolution.
Broader implications:
- These genetic changes lead to the origin and extinction of species, as well as the diversification of life—a concept known as macroevolution.

Observations of Evolution:
- Evolutionary changes have been documented across various domains:
- Laboratory Experiments
- Natural Populations
- Fossil Record

Applications and Importance:
- Disease Study and Treatment: Understanding evolution is crucial for combating diseases.
- Crop Development: Implementation of evolutionary understanding in the improvement of agricultural practices.
- Industrial Processes: Evolutionary principles are used to enhance industrial applications.
- Understanding Biodiversity: Comprehending how life diversifies contributes to biological science.

Quote: “Nothing in Biology Makes Sense Except in the Light of Evolution” (1973)
- Implication: Evolution is central to understanding life—from biological functions to complexities in structures.

Mechanisms of Evolution:
- Our understanding of genetic changes operates through evolutionary theory, allowing us to generate testable hypotheses regarding biological patterns.

Pre-Darwinian Ideas:
- Erasmus Darwin: Early notions of species change expressed in his work, Zoonomia (1794), hint at a common origin for warm-blooded animals.
- Key Quote: Suggests that organisms improve through inherent activity and generational transmission of modifications.
Missing Mechanism: Erasmus's ideas lacked a concrete evolutionary mechanism, notably being Charles Darwin's grandfather.

Jean-Baptiste Lamarck: Proposed inheritance of acquired characteristics in 1809.
- Quote: “All acquisitions or losses wrought by nature on individuals, through the influence of the environment … are preserved by reproduction.”

Darwin's Background:
- Born in 1809, focused on geology and natural history, trained for the clergy.
Influence of Literature:
- Lyell’s Principles of Geology (1830): Emphasizes that current geological forces shaped the Earth's features and posited that the Earth is “indefinitely old.”
- Malthus’s An Essay on the Principle of Population (1798): Proposed that rapid population increase is limited by resource availability, leading to a struggle for existence.

Artificial Selection:
- Darwin’s farming of pigeons showcased similarities between natural and artificial selection methods—both increase trait frequency.
- Observations of resource limitations and offspring overproduction generated Darwin's insight that individuals better suited to their environment are more likely to survive and reproduce.

Darwin's Expedition:
- Set sail on the H.M.S. Beagle on December 27, 1831, and returned on October 2, 1836.
- Key observations made during the voyage were crucial in developing his scientific theories.

Definition of Natural Selection: Summarized insights derived from the Beagle voyage and breeding experiments, resulting in:
- Species change over time
- Divergent species share a common ancestor (termed descent with modification)
- Natural Selection as the mechanism of evolutionary change.
Darwin’s Description:
- “Owing to this struggle for life, any variation, however slight … will tend to the preservation of that individual and will generally be inherited by its offspring.”

Variation in Trait: A population must exhibit variation.
Heritability: The variations must be heritable.
Fitness: Some variants must have higher survival and reproductive rates, termed higher fitness.

Outcome: If these conditions are satisfied, the trait frequency increases in successive generations, indicative of evolution by natural selection.

Independent Discovery: Wallace reached the concept of evolution through natural selection concurrently and co-published with Darwin in 1858, leading to the joint credit for this idea.
Documentary Resource: Recommended viewing: The Making of a Theory: Darwin, Wallace, and Natural Selection.

Types of Evidence:
- Distributions of species
- Selection experiments
- Direct observations of natural selection and speciation
- Shared traits reflecting a nested hierarchy indicative of a common ancestor
- Comparative morphology
- Developmental biology (embryology)
- Fossil record
- Molecular biology (DNA comparisons)
Cetacean Case Study: Focus on whales, dolphins, and their evolutionary significance.

Similarities to Other Mammals:
- Presence of placenta, whiskers, and nasal passages.
Comparative Morphology:
- Homologous Structures: Bone structures in tetrapods show evolutionary connections.
- Vestigial Structures: Whales possess vestigial hind limbs, indicative of their terrestrial ancestors.

Embryonic Development:
- Comparisons of arm and leg buds between dolphin and human embryos show significant similarities, demonstrating shared ancestry in embryological development.
Developmental Stages:
- Documented stages from early to mature dolphin provide insights into evolutionary processes.

Maiacetus Inuus:
- Dating roughly 47.5 million years ago, fossil remains offer insights into early cetaceans.
Basilosaurid Whales:
- Existing approximately 34 to 40 million years ago, fossils provide critical information on the morphology of early whales, some showcasing hind limbs.

Molecular Data and Phylogeny:
- Analysis suggests a common ancestor around 54 million years ago, reinforcing evolutionary connections through mitochondrial DNA comparisons.