8e. Know how to analyze fossil evidence with regard to biological diversity, episodic speciation and mass extinction.

Evolution by Natural Selection –Descent With Modification Natural selection produces organisms that have different structures, establish different niches, or occupy different habitats. Each living species has descended, with changes, from other species over time. Darwin referred to this principle as _____________ _____ ______________.

Evolution by Natural Selection Descent with modification implies that all living organisms are related to one another. This is the principle known as ________________ _____________.

Darwin's Observations –Living Organisms and Fossils Darwin collected the preserved remains of ancient organisms, called ________________. Some of those fossils resembled organisms that were still alive. Others looked completely unlike any creature he had ever seen.

Evidence of Evolution What evidence of evolution did Darwin present? Evidence of Evolution –Darwin argued that living things have been evolving on Earth for millions of years. Evidence for this process could be found in the fossil record, the geographical distribution of living species, homologous structures of living organisms, and similarities in early development, or ___________________.

Evidence of Evolution –The Fossil Record Darwin saw ___________ as a record of the history of life on Earth. By comparing fossils from older rock layers with fossils from younger layers, scientists could document that life on Earth has ____________ over time.

Evidence of Evolution –Geographic Distribution of Living Species Darwin decided that all Galápagos finches could have descended with modification from a common mainland ___________________. Darwin’s theory was that species now living on different continents had each descended from different ancestors.

Evidence of Evolution However, because some animals on each continent were living under similar ecological conditions, they were exposed to similar pressures of _____________ _________________. Because of these similar selection pressures, different animals ended up evolving certain features in common.

Paleozoic Era The Paleozoic Era is divided into the following periods: Cambrian Ordovician Silurian Devonian Carboniferous Permian

Paleozoic Era –Carboniferous and Permian Periods Reptiles evolved from certain amphibians. Winged insects evolved into many forms. Giant ferns and other plants formed vast swampy forests. Remains of ancient plants formed thick deposits of sediment that changed into coal over millions of years.

Paleozoic Era –At the end of the Permian Period, there was a _____________ ________________ in which many living things became extinct at the same time. –The mass extinction at the end of the Paleozoic affected both plants and animals on land and in the seas. As much as _____% of the complex life in the oceans disappeared.

Mesozoic Era –What were the characteristic forms of life in the Mesozoic era? –During the Mesozoic Era, dinosaurs became dominant. The Mesozoic is also marked by the appearance of flowering plants. –The Mesozoic Era is often called the __________ _______ _____________

Mesozoic Era –Triassic Period Organisms that survived the Permian mass extinction became the main life forms early in the Triassic. These organisms included fishes, insects, reptiles, and cone-bearing plants. –Jurassic Period Dinosaurs became the dominant animals on land. One of the first ___________, Archaeopteryx, appeared. Many paleontologists think that birds are close relatives of dinosaurs.

Mesozoic Era Cretaceous Period Dominant animals during this period included: reptiles, birds, turtles, crocodiles, fishes, and marine invertebrates. New forms of plant life included leafy trees, shrubs, and small flowering plants. The _________________ Period ended with a mass extinction. More than ______ of all plant and animal groups were wiped out, including all of the dinosaurs.

Cenozoic Era –What were the characteristic forms of life in the Cenozoic era? –During the Cenozoic, ______________ evolved adaptations that allowed them to live in various environments—on land, in water, and even in the air. –The Cenozoic often is called the Age of Mammals. –The Cenozoic is divided into the Tertiary Period and the Quaternary Period.

Cenozoic Era –Tertiary Period The climate was generally _________ & ________. Marine mammals such as whales and dolphins evolved. Grasses evolved, providing food for grazing mammals. Some mammals became very large, as did some birds.

Cenozoic Era –Quaternary Period Earth’s climate cooled, causing a series of ice ages. About ____________ years ago, Earth’s climate began to warm and sea levels began to rise. In the oceans, algae, coral, mollusks, fishes, and mammals thrived. Insects, birds, and land mammals were common.

Cenozoic Era The fossil record suggests that the early ancestors of our species appeared about _____ million years ago. The first fossils of _________ _________ may have appeared as early as 200,000 years ago in Africa. According to one hypothesis, members of our species migrated from _________ and ultimately colonized the world.

Extinction More than ______% of all species that have ever lived are now extinct. In the past, most researchers looked for a single, major cause for each mass extinction. Many paleontologists now think that mass extinctions were caused by several factors.

Extinction –What effects have mass extinctions had on the history of life? Mass extinctions have: provided ecological opportunities for organisms that survived resulted in bursts of ________________ that produced many new species

Adaptive Radiation Adaptive radiation is the process by which a _______________ species or a small group of species evolves into ______________________ different forms that live in different ways. For example, in the adaptive radiation of Darwin's finches, more than a dozen species evolved from a single species. –Adaptive radiations can occur on a much larger scale. –The disappearance of dinosaurs then resulted in the adaptive radiation of ______________.

–Adaptive Radiation of Mammals ArtiodactylsCetaceansPerissodactylsTubulidentatesHyracoidsSireniansProboscideans Ancestral Mammals This diagram shows part of the adaptive radiation of mammals, emphasizing current hypotheses about how a group of ancestral mammals diversified over millions of years into several related living orders. Note that the dotted lines and question marks in this diagram indicate a combination of gaps in the fossil record and uncertainties about the timing of evolutionary branching.

Convergent Evolution Different organisms undergo adaptive radiation in different places or at different times but in similar environments. The process by which unrelated organisms come to resemble one another is called ____________________ evolution. Convergent evolution has resulted in sharks, dolphins, seals, and penguins.

Convergent Evolution –Structures that look and function similarly but are made up of parts that do not share a common evolutionary history are called ________________ structures. –A dolphin’s fluke and a fish’s tail fin are analogous structures.

Coevolution Sometimes organisms that are closely connected to one another by ecological interactions evolve together. The process by which two species evolve in response to changes in each other over time is called ___________________.

–Darwin felt that biological change was _________and steady, an idea known as gradualism.

Punctuated Equilibrium Punctuated equilibrium is a pattern of evolution in which long stable periods are interrupted by brief periods of more ___________ change.

Punctuated Equilibrium The concept of punctuated equilibrium has generated debate and is still controversial among some biologists today. Evolution has often proceeded at different rates for different organisms at different times during the history of life on Earth.

Developmental Genes and Body Plans It is suspected that changes in genes for growth and differentiation during embryological development could produce changes in body shape and size. Small changes in the activity of control genes can affect many other genes to produce large changes in adult animals.

Developmental Genes and Body Plans Evolution of Wings in Insects Ancient InsectTwo Types of Modern Insects Small changes in the timing of cell differentiation and gene expression can make the difference between long legs and short ones.

Summary The fossil record can tell scientists a great deal about past life. The fossil record shows that there have been periods when the number of species expanded rapidly, as well as periods when many species suddenly died off.