  Two ways to describe evolution:  1. Change in features over time  2. The history of life on earth What does evolution mean?

  Can be observed with short-lived species where many generations can be quickly observed  Ex. Bacteria (strep throat, bronchitis, pneumonia…)  Antibiotic resistance has developed because the bacteria has changed and become stronger. Change in features over time…

  Process by which individuals possessing a set of traits that have a survival advantage in a given environment tend to leave more offspring that survive to reproduce in the next generation.  Ex. Sea stars that develop offspring that match the coloration of their environment are more likely to survive and have their populations increase. Natural Selection

  History of life on earth  All life on earth started from a common ancestor  Based on evidence including fossils, body structures, observable similarities, genetic observations (DNA comparison) Theory of Evolution (by natural selection)

  Give us information about organisms that lived in the past.  Can indicate whether some fossils are older or younger than others.  Suggests relative ages of the organisms.  Introduce us to species that have become extinct.  May illustrate changes in organisms that have occurred within species or groups of species over time. Fossil Evidence

  organisms that are “in between” ancient and modern forms  Is extinct but may represent a link to modern groups  Ex. Archeopteryx- seen as the link between birds and reptiles Fossils (con’t) Transitional species

  Ex. Tiktaalik- transitional species between fish and four-legged land animals

  Homologous structures- scientists have observed similar bone elements in the limbs of many closely related animals which they believe indicates that the species share a common ancestor Similar Structures Evidence

  DNA= “the blueprint of life” contained in cells of every living thing. The order of the base pairs determines the characteristics of an organism.  Tiny differences in the sequence of the DNA changes the genes which can change the outward appearance, internal structure or even viability of an organism DNA Evidence

  Mutations - changes that occur in genes; source of differences within populations and the reason why species can change over time  The greater the percentage of similarity in DNA sequences between two organisms, the more closely related they are.

  1. Overproduction - species generally produce a larger number of offspring than is necessary to prevent them from becoming extinct.  Those that survive have a high level of fitness Darwin’s Factors for the Theory of Evolution

  2. Competition - offspring compete for limited space and food  Leads to some individuals and species surviving over others

  Examples: swimming ability, size, shape, etc.  Occur randomly due to mutation  Some may not affect the organism, some may benefit and some may harm an organism. 3. Variation- differences within a species

  4. Adaptation - characteristics or genetic traits that enhance an organism’s survival and reproductive success.  Characteristics are adaptations only if they are in an organism’s DNA  Two types: Behavioral & structural

  Behaviors such as how an organism moves, responds to danger, finds nutrients and reproduces can be adaptations Behavioral adaptations

  Ex. Migration- allows the animal to find the best food sources available so they can take the best care of their young (ex. Whales & albatross)

 Ex. Sponges are sessile and have adapted strategies for reproduction by releasing egg and sperm on the same night so there is a greater chance of fertilization and larvae development

  Example: diatoms  Have clear walls with spiny plates  Spiny plates help them float  Clear walls help them photosynthesize in their habitat. Structural Adaptations

  5. fitness- characteristic that says that organisms within the population that are best genetically suited will be the most successful and survive to reproduce and pass on their genes  Takes into account the ability to survive in a specific environment, find mates, and produce offspring

  6. Speciation- changes in a population that lead to a new species  Ex. Populations of finches that Darwin observed on the Galapagos Islands became so different from the finches on the mainland that they could no longer reproduce with one another.