Review of Evolution (see the full “Evolution” PowerPoint for more details if you’re interested)

Variation and Adaptation Variation: an inherited trait that makes an individual different from other members of its species –Result from permanent changes (mutations) in an organism’s genes (DNA) –Changes in genes are inherited by offspring Adaptation: a variation that makes an organism better suited to its environment –Changes in color, shape, behavior, chemical makeup –Good examples: camouflage, defenses

Two Examples of Adaptation Having a striped coat makes these species very successful in their environments. What makes this variation an adaptation? (Why are stripes important for these animals?)

Ideas About Evolution What is meant by the term evolution? In general, the word evolution refers to any process of change over time. Examples of things evolving or changing over time: –Changes in culture: customs, languages, technology –Changes in nature: habitats, climate, environment Studies indicate that the Earth’s environments have changed greatly over millions of years. How have living things changed along with their environments and adapted to new conditions?

What is Evolution? Evolution –Refers to changes in the inherited characteristics of a species over time Theories of Evolution –Propose that existing life forms have evolved from earlier forms over long periods of time Why is evolution important in the study of life (biology)? –Explains why there are differences among the millions of species of living things on Earth –Explains why species in the past (now extinct) were very different from species found on Earth today –Explains the diversity of life on Earth (biodiversity) as well as the relationships between all living things

Lamarck’s Hypothesis: An Early Idea of Evolution In 1809, Jean Baptiste de Lamarck proposed a hypothesis for why evolution occurs: Hypothesis: Maybe characteristics (or traits) developed or acquired during life are inherited by their offspring. He called his hypothesis the “Inheritance of Acquired Characteristics” For example: muscles built by exercise giraffes stretching their necks Why was Lamarck’s idea rejected?

Darwin’s Model of Evolution In 1831, the H.M.S. Beagle sailed from England to explore the South American coast. On board was a young naturalist named Charles Darwin. Darwin was fascinated by the varieties of plants and animals he found during the voyage. During the journey, he recorded observations about the strange organisms he found in the Galapagos Islands.

Galapagos Islands Species Marine Iguana Galapagos Tortoises Darwin’s Finches Flightless Cormorant

Darwin’s Finches Darwin observed 13 similar species of finches, with variations in body size, beak shape, and eating habits. Darwin hypothesized that all 13 species descended from a similar species of finch found on the mainland. Like all living things, finches produce more offspring than could possibly survive. In a large population, there must be competition for food, habitats, and other resources. Those best adapted are most likely to survive, reproduce, and pass on their traits. Finches with the best beak shapes for the available food survive longer and therefore produce more offspring. Darwin reasoned that after many generations, these groups of finches might become separate species.

Darwin’s Finches

Principles of Natural Selection All organisms produce more offspring than can survive. Differences, or variations, occur among individuals of a species. Variations are passed on to offspring: they are inherited. Some variations are helpful. Individuals with helpful variations survive and reproduce better than those without these variations. Over time, the offspring of individuals with helpful variations make up more of a population and eventually become a separate species

Fossil Clues About Evolution Different types of fossils found in sedimentary rocks show evidence that species evolved. Examples of fossils: footprints, imprints, casts mineralized bones (like dinosaurs) frozen fossils (mammoths) insects trapped in amber (fossilized tree sap) Complex forms of life occur in younger rocks; simpler forms of life in older rocks. Fossils indicate gradual changes in living things, from simpler to more complex forms, over time.

Fossil Evidence: Feather Imprints Archaeopteryx – a primitive bird, Jurassic Period (150 million years ago)

Fossil Evidence: Dinosaur Bones Tyrannosaurus and Triceratops: Dinosaur Predator and Prey Western U.S., 70 million years ago

Fossil Evidence: Footprints Laetoli hominid footprints 3.2 million years old Tanzania, East Africa Dilophosaurus tracks 180 million years old Dinosaur State Park Hartford, Connecticut

Fossil Evidence: Amber Insects trapped in tree sap (fossilized into amber) 5 million years ago, Baltic region, Europe

Fossil Evidence: La Brea Tar Pits Extinct mammoth trapped in natural tar 40,000 years ago La Brea Tar Pits, Los Angeles, California

How Are Fossils Dated? Fossil age can be determined by two basic methods: Relative Dating –A fossil’s age depends on its location in the rock layers –Younger rock layers are found above older rock layers –“Relative” age can be determined (younger or older) Radiometric Dating –Radioactive elements in rocks decay over time –By comparing the amounts of radioactive and nonradioactive element in a rock, age can be determined: radioactivity is a kind of “clock” –Example: Carbon-14 dating

Relative Dating The limestone is known to be 200 million years old. The sandstone is known to be 350 million years old. Fossils found in the shale layer could be: a) 150 million years old b) 200 million years old c) 250 million years old d) 400 million years old That’s relative dating!!

Evolution: Direct Evidence Fossil evidence supports the idea that evolution has occurred in the past. Direct evidence supports the idea that evolution is occurring today: –Development of antibiotic-resistant bacteria (this is why antibiotics should not be overprescribed) –Rapid evolution of pesticide-resistant insects (pesticides become ineffective as time passes) –Rapid mutation of the Influenza Virus (this is why doctors need to develop a new flu vaccine every year)

Evolution: Indirect Evidence Besides fossils and modern studies of changes in species, there are many examples of indirect evidence for evolution: Embryology: the study of embryos (unborn young) and their development shows similarities among all vertebrate species (animals with backbones) Homologous structures: similar body parts in related species can indicate that two or more species share common ancestors (for example, bat’s wings and human hands) Vestigial structures: structures that don’t seem to have a function but might once have functioned in an ancestor (for example, whale leg bones and human appendix) DNA: similarities in DNA between species provides evidence for how closely related they are (for example, humans and great apes have nearly identical DNA)

General Review If you can answer these questions, you remember the basics of evolution: What is the difference between a variation and an adaptation? What is the definition of evolution? Describe Lamarck’s hypothesis for how evolution occurs. What are the five principles of natural selection? What are some different types of fossils? Describe the two methods of dating fossils. Describe four examples of indirect evidence for evolution.

References: Massachusetts Curriculum Framework Learning Standards Evolution and Biodiversity 10.Give examples of ways in which genetic variation and environmental factors are causes of evolution and the diversity of organisms. 11.Recognize that evidence drawn from geology, fossils, and comparative anatomy provide the basis of the theory of evolution. 12.Relate the extinction of a species to a mismatch of adaptation and the environment. Changes in Ecosystems Over Time 17.Identify ways in which ecosystems have changed throughout geologic time in response to physical conditions, interactions among organisms, and the actions of humans. Describe how changes may be catastrophes such as volcanic eruptions or ice storms. 18.Recognize that biological evolution accounts for the diversity of species through gradual processes over many generations. From “Life Science (Biology), Grades 6-8,” Massachusetts Science and Technology/Engineering Curriculum Framework, Massachusetts Department of Education, May 2001.