Evolution

History of Evolutionary Thought Before 1850, most people believed… Earth formed by supernatural events and never changed Earth only a few thousand years old Each species was made to fit its environment Species never changed and did not go extinct

Early Scientists’ Ideas Darwin deserves credit for the Theory of Evolution as we know it today He was not the first to come up with the idea: Carolus Linnaeus proposed a new system of organization for plants and animals based on their similarities (noticed relationships) Erasmus Darwin considered how organisms could evolve through mechanisms such as competition Jean-Baptiste Lamarck presented evolution as occurring due to environmental change over long periods of time

Carolus Linnaeus Developed a classification system for the huge variety of living things he found Wrote book Systema Naturae in 1735 to reveal his classification system There are currently 1.9 million species that have been identified using his method Linnaeus’s system of classification reflects evolutionary relationships

Jean Baptiste Lamarck A French naturalist who proposed that populations of species evolve His idea proposed: Changes in an environment cause an organism’s behavior to change, leading to greater use or disuse of a structure or organ. The organism would pass on these acquired changes to its offspring, so a species would change in time. Idea called “Evolution by inheritance of acquired characteristics” Wrong on several accounts

- Darwin’s Theory Darwin’s Voyage Charles Darwin sailed on the Beagle, from England to the Galápagos Islands.

Darwin’s important observation The diversity of living things The remains of ancient organisms The characteristics of organisms on the Galapagos Island. He wrote a book The Origin of Species All of his observations led him to develop one of the most important scientific theories of all time: the theory of evolution by natural selection.

Species is a group of similar organisms that can mate with each other and produce fertile offspring Adaptation is a trait that helps an organism survive and reproduce.

Darwin’s Finches When Darwin traveled to the Galapagos he took interest in the finches He noticed the finch species on the islands were different, but all resembled one from S. America. Darwin thought some migrated and new species evolved.

Darwin’s Finches This is what Darwin proposed: Finches migrated from South America to the islands. Populations on different islands adapted to different environments and food sources they found. Those that could survive passed on their genes. Those that couldn’t survive perished.

Darwin’s Finches Over time different mutations accumulated in the different finch populations on the different islands. The populations diverged, or became more and more different from each other.

Darwin’s Finches The populations on the islands became so different they no longer mated if they met Several new finch species evolved from a common ancestor from S. America This is an example of macroevolution.

Evolution Darwin hypothesized, the species gradually changed over time and became better adapted to the new conditions. The gradual change in a species over time is called evolution.

Evidence supporting evolution Fossil record transition species Anatomical record homologous & vestigial structures embryology & development Molecular record protein & DNA sequence Artificial selection human-caused evolution

Fossils is the preserved remains or traces of an organism that lived in the past. Extinct: are no longer living species. Transitional species- species that have been found in the fossil record that are intermediates between two other species in the evolutionary process

Fossil record Layers of sedimentary rock contain fossils new layers cover older ones, creating a record over time fossils within layers show that a succession of organisms have populated Earth throughout a long period of time

“Dating Fossils” Relative Dating: the age of the fossil is determined by comparing its placement with that of fossils in other layers of rock.

Radioactive Dating: calculating the age of the fossil based on the amount of remaining radioactive isotopes it contains. Half-life: is the length of time required for half of the radioactive atoms in a sample to decay.

“Dating Fossils” Relative Dating Radiometric Dating

Similarities in Development All animals evolved from a common ancestor: the most recent ancestral species from which two or more different species evolved

Anatomical Evidence Anatomical evidence- evidence for evolution which is based on similarities and differences between the physical structures of different species. What can we tell about the relatedness of the three species below?

Homologous Structures: are body parts that have the same basic structure. Homologous structures in different organisms are clues that these organism evolved from a common ancestor.

Homologous structures Similar structure Similar development Different functions Evidence of close evolutionary relationship recent common ancestor

Homologous structures spines leaves succulent leaves tendrils needles colored leaves

Vestigial Structure: are body structures that seem to have no function. Evidence that it once functioned in the ancestors of the organisms that did have them.

Analogous structures Separate evolution of structures similar functions with similar external form different internal structure & development different origin no evolutionary relationship Don’t be fooled by their looks! Solving a similar problem with a similar solution

Molecular record Comparing DNA & protein structure compare common genes cytochrome C (respiration) hemoglobin (gas exchange) Closely related species have sequences that are more similar than distantly related species

Artificial selection In artificial selection, nature provided the variation, and human selected those variations that they found useful “descendants” of wild mustard “descendants” of the wolf