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Chapter 7 Changes Over Time Section 1: Darwin’s Theory What important observations did Darwin make on his voyage? How did Darwin account for the diversity of species and the differences between similar species? How does natural selection lead to evolution? Chapter 7 Changes Over Time Darwin’s Voyage Charles Darwin sailed on the HMS Beagle, from England to the Galápagos Islands and back, for 5 years starting in 1831. Chapter 7 Changes Over Time Galápagos Islands Located 525 miles west of Ecuador. Was visited by Darwin in 1835. Chapter 7 Changes Over Time Galápagos Finches Darwin noticed that on each island, the finches had adapted to the local environment. Adaptation: a trait that helps an organism survive and reproduce in its environment Chapter 7 Changes Over Time Galápagos Finches Chapter 7 Changes Over Time Overproduction and Variation Natural selection is the process by which individuals who are better adapted to their environment are more likely to survive and reproduce than other members of the same species. Chapter 7 Changes Over Time Competition and Selection Variations among turtles make some of them better able to survive. Turtles that survive to become adults will be able to reproduce. Chapter 7 Changes Over Time Competition and Selection Variations among turtles make some of them better able to survive. Turtles that survive to become adults will be able to reproduce. Chapter 7 Changes Over Time Factors that Affect Natural Selection Overproduction Animals (including humans), plants, and other organisms tend to produce too many offspring, and there may not be enough food, water, or shelter to protect them all. Chapter 7 Changes Over Time Factors that Affect Natural Selection Variation Members of the same species differ from one another in many of their traits Example: You may be faster than your sibling, but your sibling may be taller, or have a better immune system, or have better reflexes. Chapter 7 Changes Over Time Factors that Affect Natural Selection Competition All living things struggle to survive. Sometimes they compete for more food, or running away from a predator, or fighting off a disease. Chapter 7 Changes Over Time Factors that Affect Natural Selection Overproduction + Variation + Competition = Natural Selection The environment “selects” which members of a species lives long enough to have offspring. Some members have lots of offspring, others have few, and some have no offspring. Over time, helpful traits (like speed, camouflage, and disease-resistance) will show up more often in a species. Eventually, most members will have this trait. Chapter 7 Changes Over Time Things to Remember • Species: a group of similar organisms that can mate with each other and produce offspring • Overproduction: species creating more offspring than can possibly survive • Adaptation: a trait that can help an organism survive Chapter 7 Changes Over Time Section 2: Evidence of Evolution What evidence supports the theory of evolution? How do fossils form? What do scientists learn from fossils? Chapter 7 Changes Over Time Homologous Structures The structure of the bones in a dolphin’s flipper, a bird’s wing, and a dog’s leg is similar. Homologous bones are shown in the same color. Chapter 7 Changes Over Time Similarities in Early Development Chapter 7 Changes Over Time Similarities in DNA and Protein Chapter 7 Changes Over Time How Do Fossils Form? Most fossils form when organisms that die become buried in sediments. Chapter 7 Changes Over Time Types of Fossils Molds and Casts: Most common fossil; organism dies and gets buried in sediment, creating a mold; more sediment later fills in this mold to create a cast Chapter 7 Changes Over Time Types of Fossils Petrified: rock minerals replace parts of the organism, turning the fossil into a hard, rock-like state Chapter 7 Changes Over Time Types of Fossils Trace: evidence of activity, such as footprints or cave paintings Chapter 7 Changes Over Time Types of Fossils Preserved Remains: organism trapped in amber, tar or ice; produces the best fossils Chapter 7 Changes Over Time Section 3: Evolution of Species What factors have contributed to the diversity of species? How do new species form? How do scientists infer evolutionary relationships among species? What causes the extinction of species? Chapter 7 Changes Over Time Evolution in Progress There are over 150 major breeds of dogs and hundreds of other crossbreeds. All of these dog breeds (and wolves) came from the same ancestral animal Chapter 7 Changes Over Time Kaibab and Abert’s Squirrels These two kinds of squirrels have been isolated from one another for a long time. Eventually this isolation may result in two different species. Kaibab Squirrel Abert’s Squirrel Chapter 7 Changes Over Time A Branching Tree This branching tree shows how scientists now think that raccoons, lesser pandas, giant pandas, and bears are related. Chapter 7 Changes Over Time Extinction of Species Extinction is caused by a change in species' environment. The members of a species may not have adaptations that allow them to survive and reproduce in the changed environment. Baiji River Dolphin Thylacine Woolly Mammoth Chapter 7 Changes Over Time Things to Remember • Extinct: no more members of a particular species exist; occurs when a species does not have the right adaptations to survive and reproduce Chapter 7 Changes Over Time End of Section: Evolution of Species Chapter 7 Changes Over Time Section 4: Classifying Organisms Why do biologists organize living things into groups? What do the levels of classification indicate about the relationship between organisms? What characteristics are used to classify organisms into domains and kingdoms? Chapter 7 Changes Over Time Classification through Names Kingdom: Phylum: Class: Order: Family: Genus: Species: Animalia Chordata Mammalia Primates Hominidae Homo H. sapiens Animalia Chordata Mammalia Carnivora Felidae Felis F. domesticus Chapter 7 Changes Over Time Classification through Names Kingdom: Phylum: Class: Order: Family: Genus: Species: Animalia Chordata Mammalia Carnivora Felidae Felis F. domesticus Animalia Chordata Mammalia Carnivora Felidae Felis F. chaus Chapter 7 Changes Over Time Three Domains of Life In the three-domain system of classifications, all known organisms belong to one of three domains–Bacteria, Archaea, or Eukarya. Bacteria Archaea Eukarya Protists Fungi Plants Animals Chapter 7 Changes Over Time Levels of Classification As you move down the levels of classification, the number of organisms decreases. The organisms at lower levels share more characteristics with each other. Chapter 7 Changes Over Time End of Section: Classifying Organisms Chapter 7 Changes Over Time Section 5: Branching Trees How does a branching tree diagram show evolutionary relationships? Chapter 7 Changes Over Time A Branching Tree Branching trees such as this show relationships between groups of organisms. It also shows the order in which specific characteristics may have evolved. Chapter 7 Changes Over Time Shared Derived Characteristics A branching tree diagram shows evolutionary relationships by grouping organisms according to shared derived characteristics. Amphibians Fishes Reptiles Egg with shell Invertebrates Four limbs Backbone Ancestor of animals Chapter 7 Changes Over Time End of Section: Branching Trees