KEY CONCEPT There were theories of biological and geologic change before Darwin.

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

Theories of geologic change set the stage for Darwin’s theory. There were three theories of geologic change. catastrophism gradualism uniformitarianism

Uniformitarianism is the prevailing theory of geologic change.

What term describes the theory that natural disasters shaped Earth's landforms and caused species to become extinct? Which scientist developed a classification system based on similarities? Which theory of geologic change is accepted by today's scientists? Human effects on evo Posters

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 adaptations is a feature that allow 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.

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

https://my.hrw.com/content/hmof/science/high_school_sci/na/gr9-12/hmd_bio_9780547688442_/dlo/onlinemediagallery/course/asset/Animations/60263.swf

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.

https://my.hrw.com/content/hmof/science/high_school_sci/na/gr9-12/hmd_bio_9780547688442_/dlo/onlinemediagallery/course/asset/Animations/bio_ch10_0321_ab_natrlsel.swf

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. DESCENT with MODIFICATION 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

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 the upper layers.

The Fossil Record, continued Section 2 Evidence of Evolution Chapter 15 The Fossil Record, continued Transitional Species Fossils of transitional species show evidence of descent with modification.

Evidence of Whale Evolution Section 2 Evidence of Evolution Chapter 15 Evidence of Whale 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. 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

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.

What term describes features that are similar in structure but different in function? In which rock layer would you expect to find the most primitive fossils?—Top, middle, bottom The embryos of many kinds of animals have gill slits. Gill slits develop into gills in fish and into ears of mammals. What do these common structures indicate? Describe analogous structures?

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.

What is a transitional fossil? What can be learned about evolution from DNA sequencing? Why is the fossil record incomplete? Suppose scientists found a fossil of a dinosaur that had feathers. What evolutionary information can be inferred from this fossil?

KEY CONCEPT Modern classification is based on evolutionary relationships.

Cladistics is classification based on common ancestry. Phylogeny is the evolutionary history for a group of species. evidence from living species, fossil record, and molecular data shown with branching tree diagrams

Cladistics is a common method to make evolutionary trees. classification based on common ancestry species placed in order that they descended from common ancestor

A cladogram is an evolutionary tree made using cladistics. A clade is a group of species that shares a common ancestor. Each species in a clade shares some traits with the ancestor. Each species in a clade has traits that have changed.

basis of arranging species in cladogram Derived characters are traits shared in different degrees by clade members. FOUR LIMBS WITH DIGITS Tetrapoda clade 1 Amniota clade 2 Reptilia clade 3 Diapsida clade 4 Archosauria clade 5 EMBRYO PROTECTED BY AMNIOTIC FLUID OPENING IN THE SIDE OF THE SKULL SKULL OPENINGS IN FRONT OF THE EYE & IN THE JAW FEATHERS & TOOTHLESS BEAKS. SKULL OPENINGS BEHIND THE EYE DERIVED CHARACTER basis of arranging species in cladogram more closely related species share more derived characters represented on cladogram as hash marks

Nodes represent the most recent common ancestor of a clade. FOUR LIMBS WITH DIGITS CLADE Tetrapoda clade 1 Amniota clade 2 Reptilia clade 3 Diapsida clade 4 Archosauria clade 5 Clades can be identified by snipping a branch under a node. FEATHERS AND TOOTHLESS BEAKS. SKULL OPENINGS IN FRONT OF THE EYE AND IN THE JAW OPENING IN THE SIDE OF THE SKULL SKULL OPENINGS BEHIND THE EYE EMBRYO PROTECTED BY AMNIOTIC FLUID DERIVED CHARACTER NODE

Molecular evidence reveals species’ relatedness. Molecular data may confirm classification based on physical similarities. Molecular data may lead scientists to propose a new classification. DNA is usually given the last word by scientists.

What does a cladogram show? What is true about two organisms that share the same common ancestor? What is true about the organisms that branch off after a hash mark on a cladogram? What does a node represent on a cladogram?