BIOL 100: Topic 13 - Evolution

Evolution

A heritable change in the characteristics of a population over time

Microevolution

Small-scale evolution within a population; changes in allele frequency

Macroevolution

Large-scale evolutionary change that leads to the formation of new species or groups

Population

A group of individuals of the same species living in a shared geographic area

Charles Darwin

Scientist who proposed natural selection as a mechanism for evolution based on evidence from his travels

Darwin’s Voyage

Darwin traveled aboard the HMS Beagle and made observations in the Galápagos Islands

Galápagos Finches

Example of adaptive radiation; different beak shapes evolved to suit specific food sources

Natural Selection

Mechanism of evolution where individuals with favorable traits are more likely to survive and reproduce

4 Conditions for Natural Selection

Variation, Heritability, Differential Survival and Reproduction, and Accumulation of Favorable Traits

Adaptation

A heritable trait that increases an organism's ability to survive and reproduce in a particular environment

Fitness

The reproductive success of an individual relative to others in the population

Artificial Selection

Selective breeding of domesticated species to promote desired traits by humans

Inherited Traits

Traits passed genetically from parent to offspring; subject to natural selection

Environmental Traits

Non-heritable traits influenced by environmental factors (e.g., tanning)

Descent with Modification

The idea that modern species have evolved from ancestral species, accumulating changes over time

Common Descent

The principle that all living organisms share a common ancestor

Fossil Record

Chronological collection of life’s remains in sedimentary rock layers

Transitional Fossils

Fossils that show intermediary forms between ancestral and derived species (e.g., Tiktaalik)

Homologous Structures

Anatomically similar structures inherited from a common ancestor (e.g., vertebrate forelimbs)

Analogous Structures

Structures with similar function but different evolutionary origin (e.g., bird wing vs insect wing)

Vestigial Structures

Reduced or non-functional remnants of features that served a function in ancestral species (e.g., human appendix)

Embryological Evidence

Similar early developmental stages in vertebrates suggest common ancestry

Comparative Embryology

Study of embryo development stages across species to identify shared evolutionary history

Molecular Evidence

Similarities in DNA or protein sequences across species indicate shared ancestry

Cytochrome c

Protein often used in molecular comparisons to show evolutionary relationships

Biogeography

The study of geographic distribution of species; closely related species often found in the same region

Island Species

Species on islands often evolve uniquely due to isolation and selective pressures

Continental Drift

Past movement of continents explains the fossil and evolutionary history of now-separated species

Evolutionary Tree

Diagram showing evolutionary relationships among species based on shared traits and ancestry

Branch Point

On an evolutionary tree, represents the last common ancestor of descendant groups

Clade

A group of organisms that includes an ancestor and all its descendants

Natural Selection Summary

Leads to adaptation; acts on existing variation; does not create new traits

Mutation

Source of new genetic variation; can be neutral, harmful, or beneficial

Variation in Traits

Results from genetic differences and is essential for natural selection

Inherited vs Acquired Traits

Inherited traits are passed down genetically; acquired traits (e.g., muscle growth) are not

What Fossils Tell Us

Provide evidence of change over time and show intermediate forms

Evolution Is Not Goal-Oriented

Evolution does not work toward a perfect form; it responds to current environmental pressures

Tree of Life

Represents all life forms as descendants from a single common ancestor