Darwinian Evolution What does evolution mean Two ways

Darwinian Evolution

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

Change in features over time… 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.

Natural Selection 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.

Theory of Evolution (by 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)

Fossil Evidence 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.

Fossils (con’t) Transitional species 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

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

Similar Structures Evidence 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

DNA 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

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.

Darwin’s Factors for the Theory of Evolution 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

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

3. Variation- differences within a species 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.

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

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

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

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.