BLG 144 Evolution by natural selection

Special creation

The original theory, based on religion, says that species are independent and unrelated, that the earth is only 6000 years old and young, and that species don’t change over time.

Composition of a scientific theory

Pattern (whats observed in the natural world) and Process (mechanism that explains patterns)

Plato

Greek philosopher; believed that every organism is a perfect type made by god. Each type doesn’t change. believed in typological thinking

Typological thinking

Doesn’t give importance to variation, assumes variation is misleading or unimportant. focuses of type of organisms. “Cookie cutter”. categorizes organisms.

Aristotle

Believed in fixed types, but creates chain hierarchy based on size/complexity.

Lamarckian

Progressive. Evolution creates better and more complex species over time

Inheritance of acquired characters

Certain traits are acquired during the lifespan of an organism and then passed onto offspring.

Darwin/Wallace

Believed that changes over time do occur, there’s no hierarchy, not intentional or progressive. Emphasized variation. Natural selection acts on variation

Population thinking

Focuses on differences between organisms of the same species.

Descent with modification

Over time organisms are slightly different and eventually different from ancestors although still related. Evidence: fossils (traces of organisms from the past)

Earth is old evidence

earliest organism found in the fossil record was 3.8 billion years old

species change evidence

fossils have been found that species are extinct

law of succession

beneficial traits succeed

transitional features

intermediate between ancestor and modern features.

Vestigial trait

trait thats reduced or incompletely developed. no function but resembles other functioning traits. Could mean that species are related if structure is similar

bipedal

ability to stand on two feet. allows for ability to look behind better. this made the tail used for balance obsolete, which is why its a vestigial trait in humans

Homology

Similar but not the same

Genetic homology

Dna sequence of two species are similar. causes developmental homology

Developmental homology

Similarities in embryos of different species. causes structural homology

Structural homology

Similar bone structure among different species

Internal consistency

Different case studies must have the same outcome. Data from different sources agree and support the same theory.