Charles Darwin and Evolution Changes Over Time Charles Darwin and Evolution

Charles Darwin

Charles Darwin 1831 When he was 22 years old he set sail aboard a British Naval Ship called the HMS Beagle. 5 year long trip around the world He was a naturalist: a person who studies the natural world. Darwin’s observations led him to develop one of the most important scientific theories of all time: the theory of evolution by natural selection.

Observations During the voyage Darwin observed plants and animals he had never seen before. He wondered why they were so different than the ones he had seen in England. He was amazed by the tremendous diversity or variety of living things he saw.

Diversity Today scientists know that living things are even more diverse than Darwin could ever have imagined. Scientists have identified more than 1.7 million species of organisms on Earth.

Species A species is a group of similar organisms that can mate with each other and produce fertile offspring. What is the difference between a species and a breed?

South America

The Galapagos Islands

Finch Beaks

The Galapagos Darwin observed some of the greatest diversity of life forms. Giant tortoises, land tortoises Seals Lizards Flightless birds 13 species of finches

Island differences Darwin observed that you could determine what island a tortoise was from based on the shape of its shell. Finches were noticeably different from one island to another. The most obvious difference was the various sizes and shapes of their beaks. Adaptation: a trait that helps an organism survive and reproduce. The beaks were an adaptation related to the foods the finches ate.

Evolution Species gradually changed over many generations and became better adapted to the new conditions. The gradual change in a species over time is called evolution.

Scientific Theory Darwin’s ideas are often referred to as the theory of evolution. A scientific theory is a well-tested concept that explains a wide range of observations.

Natural Selection In 1858, Darwin and another British Biologist, Alfred Russel Wallace, proposed an explanation for how evolution occurs. The next year Darwin published The Origin of the Species. Natural selection is the process by which individuals that are better adapted to their environment are more likely to survive and reproduce than other members of the same species.

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Factors that Affect Natural Selection Overproduction Competition Variation

Overproduction Most species produce far more offspring than can possibly survive. Each year a female sea turtle lays over 100 eggs. Why isn’t the sea full of sea turtles?

Competition Since food and other resources are limited, the offspring must compete with each other to survive. Only a few turtles will survive long enough to reproduce.

Variations A difference between individuals of the same species is called a variation. For example, some newly hatched turtles are able to swim faster than other turtles. Some variations make certain individuals better adapted to their environment. Those individuals are more likely to survive and reproduce. Without variation a species can become extinct. Extinct meaning no longer and living members of that species

Selection Over a long period of time, natural selection can lead to evolution. Helpful variations gradually accumulate in a species, while unfavorable ones disappear. lizard

Speed of evolution Gradualism- Described as a slow ongoing process by which one species changes to a new species Punctuated Equilibrium- One species suddenly changes to another.

What role do genes play in evolution? Only traits that are controlled by genes can be acted on by natural selection Elephant Evolution

Peppered Moth The Industrial Revolution began in England in the late 1700s. Smoke from the factories blackened the tree trunks of trees. Light colored moths were no longer camouflaged. What color was more suited for the new environment?

How do New Species Form? Geographic Isolation Continental Drift A new species may form when a group of individuals remains separated from the rest of its species long enough to evolve different traits. A group is separated from the rest of the species

Continental Drift

Pangea Pangea

Examples of New species: 10,000 years to change Kaibab squirrel/Abert’s squirrel North American White Tailed Deer/Fire Island Deer

Kaibab Squirrel Abert's Squirrel

Kaibab Squirrel Abert’s Squirrel

Used to determine the evolutionary relationships among species Supporting Evidence Fossil Records Embryology Homologous structures Vestigial structures Fossils Body structure Early development DNA Protein structures

Fossil A fossil is the preserved remains or traces of an organism that lived in the past. A fossil can be formed from parts of live organisms, foot prints, or burrows left in mud. Actual age of fossils is determined by radioactive dating

How do they form? Most fossils form when organisms that die become buried in sediments. Sediments are particles of soil and rock. Over millions of years layers harden to become sedimentary rock. Some remains get buried in the sediment and are actually changed into rock. Fossils that form in this way are called petrified fossils. Minerals replace all or part of an organism

Preserved Remains Ice preservation Tar pit Tree sap hardens to form amber. Imprint fossils Cast fossils Mineralized fossils

What can fossils tell you? How do they form? The Fossil Record What can fossils tell you? How do they form?

Branching Trees: Cladograms A branching tree is a diagram that shows how scientists think different groups of organisms are related.

Embryology The study of embryos and their development The similarities suggest an evolutionary relationship among all vertebrate species.

Homologous Structure Bird’s wing Dolphins flipper Dog’s leg All of their bones are arranged in a similar pattern. These similarities provide evidence that these organisms all evolved from a common ancestor. Similar structures that related species have inherited from a common ancestor are known as homologous structures.

Vestigial Structures Structures that don’t seem to have a function. Example: Manatees, snakes, and whales no longer have back legs, but, like all animals with legs, they still have pelvic bones. Humans: appendix, tailbone, wisdom teeth, and goosebumps