Evolution

History of the theory of evolution James Hutton & Charles Lyell Geologist who studied fossils and the stratification (layers) in rock formations Hypothesized that geological processes happened very slowly and gradually over time

Thomas Malthus Economist who studied the growth of the human population Discovered that the human population was growing more quickly than the food supply, so eventually there would not be enough resources to support the entire population

Jean Baptiste Lamarck Hypothesized that species were able to adapt to their environment and change over time Hypothesized that organisms were able to acquire these changes during their lifetime and pass the new traits on to their offspring This hypothesis was regarded as incorrect, but recent research is providing evidence that acquired characteristics may be passed on to future generations. Theory of Inheritance of Acquired Characteristics

Example of Lamarck’s theory of inheritance of acquired characteristics

Charles Darwin English naturalist who traveled around the world on the HMS Beagle Collected many animal specimens from around the world and made detailed observations about the similarities and differences between them

Studied the organisms of the Galapagos Islands in great detail and compared them to species from the mainland, which he hypothesized were the ancestors of the island species

Darwin’s Theory of Natural Selection Darwin supported his theory with evidence he collected while on the Beagle Darwin is important for developing and demonstrating a mechanism for evolution not for inventing the theory of evolution. He called the mechanism or cause “natural selection” or “survival of the fittest” He presented his theory in a book called On the Origin of Species by means of Natural Selection

Conditions for Natural Selection Overproduction Organisms produce more offspring than their ecosystem can support Limited Resources + Too many organisms = Competition

Variation Members of the same species have genetic variations that make them different from each other

Causes of Variation Sexual Reproduction Mutations Offspring are different from their parents and from each other Independent Assortment, Crossing Over, etc. Mutations Change in the genetic material of the organism Mutations may harmful, neutral, or advantageous

Adaptation A trait that helps an organism survive and reproduce in a particular ecosystem

Selection (Natural Selection or “Survival of the Fittest”) The individual most well adapted to a particular ecosystem will have a better chance of surviving and reproducing than individuals of the same species with fewer adaptations. In other words, the most well adapted individual ‘wins’ the competition for resources and produces more offspring than the less well adapted individuals

Evolution Over time, entire species change as beneficial genes become more common in populations and detrimental genes become less common or eliminated entirely

Evidence of Evolution Fossil Evidence Fossils show that different organisms existed in the past compared to organisms that exist today

Fossils show changes in organisms over time Archaeopteryx is the oldest bird fossil. It shows the link between birds and their reptilian ancestors

Tiktaalik is a transitional form between fish and amphibians

The fossil record provides us with a history of life on Earth

Comparative Anatomy Evidence Homologous Structures: body structures that have the same basic form, but may not necessarily have a similar function Homologous structures suggest a common ancestor

Analogous Structures: body structures that serve the same function but do not have the same form

Biochemical Evidence All living things are made of the same building blocks: nucleic acids, proteins, carbohydrates, lipids ATP is used universally among living things as a source of chemical energy

Closely related organisms have similar DNA sequences

Because DNA is used to store the information cells need to make proteins, amino acid sequences can also be used to determine relationships

Example: humans share over 98% of their DNA with chimpanzees, yet only 85% with mice.