Evidence for Evolution

I. Clues From Fossils Paleontologist are scientists who study the past by collecting and examining fossils When these organisms died, they were covered with silt and mud Over millions of years, many of them became fossils

II. Five Types of Fossils Most evidence for evolution comes from fossils A fossil is the ancient remains of a once-living organism Most fossils are found in sedimentary rock Sedimentary rock is formed when layers of sand, silt, clay or mud are compacted together, like cement Examples: Limestone, sandstone, shale

The fossil record provides evidence that living things evolved over time. They reveal the age, size, shape and other characteristics of life forms from the past. Specimens can be compared with each other and with living creatures in order to better understand evolutionary history.

II. Five Types of Fossils 1. AMBER 1. AMBER Insects get stuck in resin of trees Insects get stuck in resin of trees Resin hardens into amber Resin hardens into amber Amber is hard, yellow, & transparent Amber is hard, yellow, & transparent

II. Five Types of Fossils 2. FROZEN 2. FROZEN Fossils found with flesh and hair Fossils found with flesh and hair The cold helps preserve proteins The cold helps preserve proteins

3. MINERALIZATION Shells, bones, & teeth Shells, bones, & teeth Minerals can replace wood or bone Minerals can replace wood or bone Called “petrifaction” Called “petrifaction” II. Five Types of Fossils

4. IMPRINT Leaves, feathers, bones Leaves, feathers, bones Leave markings in sediment Leave markings in sediment Sediment then hardens into rock Sediment then hardens into rock II. Five Types of Fossils

II. Five types of Fossils 5. CAST Minerals fill in hollow parts of an organism Minerals fill in hollow parts of an organism

III. Determining a Fossils’ Age Paleontologists can use clues provided by rock layers and fossils to determine the age of fossils Paleontologists can use clues provided by rock layers and fossils to determine the age of fossils These clues provide information about the geology, weather and life forms that must have been present. These clues provide information about the geology, weather and life forms that must have been present. Two methods: relative dating and radiometric dating Two methods: relative dating and radiometric dating

Age by Fossil and Rock Layers

1. Relative Dating Compares undisturbed rock layers and provides an estimate of the fossil’s age The deeper the layer, the older the fossil The deeper the layer, the older the fossil Younger fossils would lie closer to the surface Younger fossils would lie closer to the surface 2. Radiometric Dating (Absolute Dating) A more accurate way of dating the fossil is called radiometric dating (aka absolute dating)

Radioactive element is an unstable atom that gives off a steady amount of radiation. Scientists can estimate the age of the rock by comparing the amount of radioactive element found in rock to the amount of nonradioactive element. Half life radio active element to decay into another element. Half life : The amount of time it takes half of the radio active element to decay into another element.

IV. Fossils and Evolution The fossil record is incomplete, there are gaps because not all organisms become fossilized when they die The fossil record is incomplete, there are gaps because not all organisms become fossilized when they die By looking at the fossils record, scientists conclude that many, simpler forms of life existed early in Earth’s history and more complex forms appeared later By looking at the fossils record, scientists conclude that many, simpler forms of life existed early in Earth’s history and more complex forms appeared later

IV. Fossils and Evolution Fossils provide indirect evidence of evolution Fossils provide indirect evidence of evolution More than 99% of all organisms that ever lived are extinct More than 99% of all organisms that ever lived are extinct

V. More Clues About Evolution Direct evidence: Cross-breeding plants, antibiotic resistance, pesticide resistance in insects Direct evidence: Cross-breeding plants, antibiotic resistance, pesticide resistance in insects Indirect evidence: Similarities in embryos, similarities in DNA, Similar structures Indirect evidence: Similarities in embryos, similarities in DNA, Similar structures

Image Bank Embryo Evidence

Embryology 1. The study of embryos and their development is called embryology 1. The study of embryos and their development is called embryology 2. An embryo is the earliest growth stage of an organism 2. An embryo is the earliest growth stage of an organism 3. The embryos of fish, reptiles, birds, and mammals all have a tail and brachial pouches 3. The embryos of fish, reptiles, birds, and mammals all have a tail and brachial pouches

Image Bank Homologous Body Parts

Homologous Structures Body parts that are similar in origin, structure and function are called homologous. Body parts that are similar in origin, structure and function are called homologous. Examples: Frog’s forelimb, bat’s wing, human arm Examples: Frog’s forelimb, bat’s wing, human arm Often indicate common ancestor Often indicate common ancestor Homologous: similar but not identical Homologous: similar but not identical

Vestigial Structures Vestigial structures are structures that don’t seem to have any function Vestigial structures are structures that don’t seem to have any function For example, manatees, snakes, and whales no longer have back legs, but they have a pelvic bone. Scientists believe that vestigial structures are structures that once had a function in an ancestor For example, manatees, snakes, and whales no longer have back legs, but they have a pelvic bone. Scientists believe that vestigial structures are structures that once had a function in an ancestor

DNA evidence 1. Scientists compare DNA among organisms to identify similarities among species. By looking at DNA, scientists can determine how closely related organisms are. For example, DNA evidence suggests that dogs are the closest relatives of bears 1. Scientists compare DNA among organisms to identify similarities among species. By looking at DNA, scientists can determine how closely related organisms are. For example, DNA evidence suggests that dogs are the closest relatives of bears 2. DNA evidence shows similarities in humans and chimpanzees 2. DNA evidence shows similarities in humans and chimpanzees Monkeys, apes, chimpanzees are all primates Monkeys, apes, chimpanzees are all primates

EVIDENCE OF EVOLUTION DIRECT EVIDENCE Direct proof of evolution Cross bred plants to produce genetic changes Antibiotic Resistant Bacteria Pesticide Resistant Insects

INDIRECT EVIDENCE: Supports evolution but is not direct proof Fossils: Embryology Vestigial Structures Homologous Structures DNA

13.1 Section Review (evidence)p. 265(1-9) 13.2 Section Review(ideas)p. 270(1-7) 13.3 Section Review(ideas)p. 275(1-7) 13 Chapter Assessment p. 279Vocab (1-8), Concepts (1-12)