Evolution

The process by which species may change over time. What is evolution? A basic definition of evolution… The process by which species may change over time.

Genetic Variation and Evolution Evolution: changes through time Species accumulate difference Descendants differ from their ancestors New species arise from existing ones

DARWIN! -Made observations aboard the Beagle -Not the first to suggest evolution -Major Idea in Origin of Species: species change over time through a process called NATURAL SELECTION.

A brief history of evolution Darwin presumed that populations of individuals changed over time, and, in 1844, he developed the concept of the driving force for evolution. It wasn’t until many years later that he published his idea. “I have called this principle, by which each slight variation, if useful, is preserved, by the term Natural Selection.” —Charles Darwin from "The Origin of Species“, 1859

Voyage of the Beagle

Voyage of Beagle Dates: February 12th, 1831 Captain: Charles Darwin Ship: H.M.S. Beagle Destination: Voyage around the world. Findings: evidence to propose a revolutionary hypothesis about how life changes over time

Galapagos Finches Darwin suggested all the finches descended from South America. Modified over time and survived by eating different types of food. Beaks changed due to different types of food!

Darwin’s Finch Observations -finch beaks changed over time -the beak shape is affected by food available

Descent with modification Darwin stated that in the idea of evolution every organism descends from an ancestor with slight modification over time.

Natural selection: proposed by Darwin as the mechanism of evolution. Natural selection: mechanism of evolutionary change Natural selection: proposed by Darwin as the mechanism of evolution. Natural Selection - Process by which individuals that are better adapted to their environment survive and reproduce more successfully than less well adapted individuals do.

Natural Selection Observation 1: Organisms generally have more offspring than can survive to adulthood. Observation 2: Offspring are not identical. There is variation in their appearance, size, and other characteristics. Observation 3: Having a particular trait can make individuals more or less likely to survive. Observation 4: The traits that improve survival & reproduction will become more common.

Survival of the “fittest.” Natural Selection Inference: Those organisms that are better adapted to their environment have a greater likelihood of surviving to adulthood and passing these characteristics on to their offspring. Survival of the “fittest.”

Survival of the “fittest.” Darwin’s theory for how long necks evolved in giraffes

Survival of the fittest, what does it mean? The fittest individuals are simply the ones who have the combination of traits that allow them to survive and produce more offspring, that in turn survive to reproduce.

Selection Artificial selection: a breeder selects for desired characteristics

Five agents of evolutionary change

Patterns of Macroevolution Convergent evolution – Evolution is STRONGLY directed by the environment; adapt to your environment! Ex: develop similar structures! Coevolution – Organisms are part of one other’s environment, so they can affect one another’s evolution.

Evidence of Evolution The Fossil Record Geographic Distribution of Living Things Homologous Body Structures Similarities in Early Development

Evidence of Evolution The Fossil Record Geographic Distribution of Living Things-similar environments have similar types of organisms Homologous Body Structures Similarities in Early Development

Homologous Structures Homologous Structures – characteristics that are similar in two or more species and that have been inherited from a common ancestor of those species.

Homologous Structures

modifies homologous structures Adaptive Radiation - Modifies homologous structures

Convergent Evolution -Similarities evolve in groups that are NOT closely related to one another, because the groups become adapted to similar habitats. -These similarities are called analogous characters.

Darwin’s ideas explained… Biogeography The Fossil Record Similar environments shape the evolution of organisms in similar ways. Scientists can infer where and when ancient organisms lived on earth

Similarities in Early Development