KEY CONCEPT There were theories of biological and geologic change before Darwin. Chapter 10: Evolution and Natural Selection

Early scientists proposed ideas about evolution. Evolution is the biological change process by which descendants come to differ from their ancestors. A species is a group of organisms that can reproduce and have fertile offspring.

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. Inheritance of Acquired Characteristics

KEY CONCEPT Darwin’s voyage provided insight on evolution.

Charles Darwin’s trip… Selected as naturalist for HMS Beagle Collected specimens, made many crucial observations about the natural world helped map S.A. Coast

Darwin observed differences among island species. Variation is a difference in a physical trait. Adaptation – a feature that allows an organism to better survive

Darwin’s Finches Darwin noted variations of finches Each finch had distinct niche (food, nesting, region) Different birds filled same niche on different islands Big bills=tough seeds Fine bills=small seed/insects

Galapagos Tortoises Several variations of shell shape, found on different islands and habitats Dome shelled tortoises =good at getting into cactus foods, low lying brush, short legs Saddle-backed shells=neck clearance to get high vegetation, have long legs

Darwin found fossils of extinct animals that resemble modern animals. Giant armadillos, sloths like current ones Darwin observed fossil and geologic evidence supporting an ancient Earth.

Darwin found fossil sea shells high up in the Andes mountains… How did they get there? He saw land move from underwater to above sea level due to an earthquake. Hmm…if land can move up, perhaps mountain tops were once at sea-level?

These observations of geology and living/fossilized organisms suggested that: Species change over time!! Isn’t Evolution Just a Theory? How do we know Evolution Happens?

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

There are four main principles to the theory of natural selection. –variation Natural selection explains how evolution can occur. – overproduction – adaptation – descent with modification Fitness is the measure of survival ability and ability to produce more offspring. How Does Natural Selection Work?

Natural Selection Case Study How can natural selection explain the development of drug resistant bacteria?

KEY CONCEPT Evidence of common ancestry among species comes from many sources and 10.5 Evidence for Evolution

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 the upper layers.

Paleontology provides evidence to support evolution.

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

Embryology provides evidence of evolution. Larva Adult barnacle Adult crab –identical larvae, different adult body forms –similar embryos, diverse organisms

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

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

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

KEY CONCEPT New technology is furthering our understanding of evolution.

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

Protein comparisons, or molecular fingerprinting reveals similarities among cell types of different organisms.

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