EVOLUTION UNIT 2016

EVOLUTIONARY THEORIES BEFORE DARWIN There were many important naturalists in the 18th century. Linnaeus: classification system from kingdom to species Buffon: species shared ancestors rather than arising separately E. Darwin: more-complex forms developed from less-complex forms Lamarck: environmental change leads to use or disuse of a structure

Darwin’s Observations Key Concept: Darwin’s voyage provided insight on evolution.

Darwin observed differences among island species. Variation is a difference in a physical trait. Galápagos tortoises that live in areas with tall plants have long necks and legs. Galápagos finches that live in areas with hard-shelled nuts have strong beaks.

An adaptation is a feature that allows an organism to better survive in its environment. Species are able to adapt to their environment. Adaptations can lead to genetic change in a population.

Darwin observed fossil and geologic evidence supporting an ancient Earth. Darwin found fossils of extinct animals that resemble modern animals. Darwin found fossil shells high up in the Andes mountains. It is estimated that the earth is about 4.5 billion years old.

He saw land move from underwater to above sea level due to an earthquake. Darwin extended his observations to the evolution of organisms.

Natural Selection Key Concept: Darwin proposed natural selection as a mechanism for evolution.

Several key insights led to Darwin’s idea for natural selection. Darwin noticed a lot of variation in domesticated plants and animals. Artificial selection is the process by which humans select traits through breeding. neck feathers crop tail feathers

Natural selection is a mechanism by which individuals that have inherited beneficial adaptations produce more offspring on average than do other individuals. Heritability is the ability of a trait to be passed down. There is a struggle for survival due to overpopulation and limited resources. Darwin proposed that adaptations arose over many generations.

Natural selection explains how evolution can occur. There are four main principles to the theory of natural selection. variation overproduction adaptation descent with modification Fitness is the measure of survival ability and ability to produce more offspring. ADAPTATION OVERPRODUCTION VARIATION

Natural selection acts on existing variation. Natural selection can act only on traits that already exist. Structures take on new functions in addition to their original function. wrist bone five digits

EVIDENCE OF EVOLUTION Key Concept: Evidence of common ancestry among species comes from many sources.

Evidence for evolution in Darwin’s time came from several sources. Fossils provide evidence of evolution. Fossils in older layers are more primitive than those in upper layers.

The study of geography provides evidence of evolution. island species most closely resemble the nearest mainland species populations can show variation from one island to another

Developmental similarities provide evidence of evolution. identical larvae, different adult body forms similar embryos, diverse organisms Larva Adult barnacle Adult crab

The study of anatomy provides evidence of evolution. Homologous structures are similar in structure but different in function. Homologous structures are evidence of a common ancestor. Human hand Bat wing Mole foot

Analogous structures are not evidence of a common ancestor. The study of anatomy provides evidence of evolution. Analogous structures have a similar function. Human hand Bat wing Mole foot Fly wing Analogous structures are not evidence of a common ancestor.

Structural patterns are clues to the history of a species. Vestigial structures are remnants of organs or structures that had a function in an early ancestor. Ostrich wings are examples of vestigial structures.

EVOLUTIONARY BIOLOGY TODAY Key Concept: New technology is furthering our understanding of evolution.

Fossils provide a record of evolution. Paleontology is the study of fossils or extinct organisms.

Paleontology provides evidence to support evolution.

Molecular and genetic evidence support fossil and anatomical evidence. Two closely-related organisms will have similar DNA sequences.

Pseudogenes are sequences providing evidence of evolution. no longer function carried along with functional DNA can be clues to a common ancestor

Hox genes indicate a very distant common ancestor. control the development of specific structures found in many organisms Protein comparisons, or molecular fingerprinting reveals similarities among cell types of different organisms.

Evolution unites all fields of biology. Scientist from any fields contribute to the understanding of evolution. The basic principles of evolution are used in many scientific fields.