Theory of Evolution “Nothing in biology makes sense EXCEPT in the light of evolution.” -Theodosius Dobzhansky

Early Evolutionary Thought James Hutton Suggested Gradualism Gradual change over a long period of time leads to species formation

Early Evolutionary Thought Gould and Eldredge Suggested Punctuated Equilibrium A successful species may stay unchanged for long periods of time. Major environmental changes may have caused evolution to occur in spurts

Early Evolutionary Thought Jean-Baptiste Lamarck, 1809 Suggested the Law of Use and Disuse One Of First Scientists To Understand That Change Occurs Over Time Organisms Could Change The Size Or Shape Of Organs By Using Them Or Not Using Them

Early Evolutionary Thought Lamark Stated that Changes Are Adaptations To Environment acquired in an organism’s lifetime Said acquired changes were passed to offspring If body part NOT used, it deteriorated

Early Evolutionary Thought Thomas Malthus Wrote that human populations are able to increase faster than what the food supply can. We do not because of disease, war and famine.

Early Evolutionary Thought Charles Darwin Naturalist aboard the HMS Beagle Traveled for 5 years around the world Made observations and collected samples Eventually landed on the Galapagos Islands where he made several observations that impacted his Theory of “Descent with Modification”.

The Galapagos Islands Very Different Climates Small Group of Islands 1000 km West of South America Very Different Climates

The Galapagos Islands Animals On Islands Tortoises Iguanas Finches

Natural Selection When visiting on the Galapagos Islands Darwin noticed: Individuals that have physical or behavioral traits that better suite their environment are more likely to survive and reproduce. This theory is called Natural Selection

Natural Selection Finches Darwin noticed that there were a number of different types of finches All finches had physical traits that allowed them to adapt to their environment. For example if a finch lived on a part of the island that was abundant in flowering plants then the finches beak would be long and thin so that it could drink nectar.

Natural vs. Artificial Selection Natural Selection A mechanism for change in populations. Occurs when organisms with favorable variations survive, reproduce, and pass their variations to the next generation. Organisms without these variations are less likely to survive and reproduce. Artificial Selection Breeding organisms with specific traits in order to produce offspring with identical traits

Evidence of Evolution Anatomy Homologous Structures Structural features with a common evolutionary origin Can be similar in arrangement, in function, or in both.

Evidence of Evolution Analogous Structures Body parts of organisms that do not have a common evolutionary origin but are similar in function

Evidence of Evolution Vestigial Structures Body structure in a present-day organism that no longer serves its original purpose, but was probably useful to an ancestor.

Evidence of Evolution Embryology Study of the earliest stage of growth and development of both plants and animals The embryos of a fish, a reptile, a bird, and a mammal have a tail and pharyngeal pouches suggest evolution from a distant, common ancestor Pharyngeal pouches Pharyngeal pouches Tail Tail Fish Reptile Bird Mammal

Evidence of Evolution Biochemistry Provides strong evidence for evolution. Comparing the same hemoglobin protein in several species reveals a pattern. Species that share a common ancestor more recently have fewer amino acid differences.

Adaptations Mimicry Three major adaptations exist in nature: A structural adaptation that enables one species to resemble another species. Because a yellow jacket looks so much like a honeybee it’s predators often mistake it for it’s twin and stay away.

Adaptations Camouflage Adaptation that enables species to blend with their surroundings Because well-camouflaged organisms are not easily found by predators, they survive to reproduce.

Adaptations Physiological Adaptations Changes in an organism’s metabolic processes Evolve much more rapidly. For example, some of the medicines developed during the twentieth century to fight bacterial diseases are no longer effective

Antibiotic Resistance The bacteria in a population vary in their ability to resist antibiotics. When the population is exposed to an antibiotic, only the resistant bacteria survive. The resistant bacteria live and produce more resistant bacteria.

Formation of a New Species Speciation Process by which new species form Reproductive Isolation Two populations of the same species do not breed with one another because: Geographic separation Difference in mating periods Other barrier to reproduction.