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Evolution The process in which species change over time. Charles Darwin Was a British naturalist. He was hired to travel on the HMS Beagle to learn as much as he could about the living things he saw on the voyage. The HMS Beagle Traveling with the ship, Darwin observed many different plants and animals. He was very curious about why these living things were so different from the ones he studied in England. This curiosity led to develop: The theory of _______________ by natural selection. The Galapagos Islands The Beagle traveled to the Galapagos Islands of South America. Here, Darwin made some of his most important observations! The Galapagos Islands Darwin observed that the __________ of the Galapagos were very different from one island to the next. The beaks of the birds varied in shape and size. Darwin’s Finches As Darwin studied his finches, he noticed that each species was well suited to the life it led. Insect eaters: sharp, needlelike beaks Seed eaters: strong, wide beaks The Galapagos Islands Darwin also noticed that the iguanas that lived on the island were different from the iguanas on the mainland. Island Iguanas had large claws. Mainland Iguanas had small claws. The Galapagos Iguanas Darwin realized that the claws of the iguana were also beneficial to the life it led. The large claws of the island iguanas kept them from slipping off of the rocks. The small claws of the mainland iguanas allowed them to climb trees where they ate leaves. Galapagos Iguanas Life After the Beagle ________________ are traits that help organisms survive and reproduce. Beak shape and claw length are examples of this. When Darwin returned home from life on the Beagle, he tried to understand how these specific traits arose. Darwin’s Conclusion Darwin reasoned that arrived on one of the Galapagos Islands faced conditions that were different from the mainland. He came up with the conclusion that species must gradually change over many generations to become better adapted to their environment. This change over time is called _____________. The Theory of Evolution What is a scientific theory? A well-tested concept that explains a wide range of observations. The theory of evolution is what scientists have determined to be true based on significant amounts of research, observations, and evidence to back this up. How does evolution happen? Darwin still didn’t know one thing: how does evolution happen? Darwin bred pigeons. He allowed only pigeons with many tail feathers to mate. This produced pigeons with two or three times the usual number of feathers. This process is called ___________ ______________. Maybe, he thought, something happens like this in nature! Selective Breeding in Nature Why are certain traits selected for (and how) in nature? ____________ _____________ 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. The Origin of Species Charles Darwin, along with biologist Alfred Russel Wallace, published his explanation in a book called The Origin of Species. Natural Selection Factors that affect the process of natural selection: 1. Overproduction 2. Competition 3. Variations Overproduction Most species produce far more offspring that can possibly survive. Sea turtles lay more than 100 eggs. If all of the young turtles survived, the sea would be full of turtles! But this is not the case… not all of the offspring will survive. Overproduction Sea Turtles are organisms that overproduce Natural Selection Factors that affect the process of natural selection: 1. Overproduction 2. Competition 3. Variations Competition Offspring must compete with each other to survive. Offspring compete for resources- food, water, living space, etc. Only some will escape from predators. Only a few offspring will survive long enough to reproduce. Competition Sea Turtle hatchlings compete for space. Natural Selection Factors that affect the process of natural selection: 1. Overproduction 2. Competition 3. Variations Variations Any difference between individuals in the same species is called a variation. We know that this is a result of genetics. Some variations make certain individuals better adapted to their environment. Variations Some newly hatched turtles are able to swim faster than others. Natural Selection Individuals that are better adapted to their environment are more likely to survive and reproduce. When these well-adapted individuals reproduce, their offspring inherit the alleles for these adaptations. Thus… Natural Selection The environment has “selected” these welladapted organisms to be the parents of the next generation. Nature… has selected… natural selection Over a long period of time, natural selection can lead to evolution (the changing of a species). Helpful variations gradually accumulate in a species, while unfavorable ones disappear.