Lecture 1- evolution overview

What is evolution?

Change in genetic composition of populations over time

Microevolution

Genetic changes within populations over time

Macroevolution

Large-scale evolutionary changes, such as speciation and extinction

Darwin’s three conditions for natural selection

Variation exists, variation is heritable, and affects fitness

What did Jean-Baptiste Lamarck propose?

Inheritance of acquired characteristics (now discredited)

Why was Lamarck’s mechanism incorrect?

It assumed traits acquired during life are passed on genetically

Darwin's insight from artificial selection

Nature can similarly select traits that improve fitness

What leads to "struggle for existence"?

Limited resources and overproduction of offspring

What happens if Darwin's three conditions are met?

The favored trait increases in frequency across generations

Lamarck vs. Darwin

Lamarck: acquired traits passed on; Darwin: heritable variation + selection

Vestigial structures

Evolutionary remnants, like whale hind limbs, that indicate common ancestry

Homologous structures

Similar structures in different species due to common ancestry

Example of microevolution

Changes in beak size in Galápagos finches due to drought

Why is evolution considered both a fact and a theory?

Evolutionary change is observable (fact); the mechanisms are explained by theory