WARM UP Three brothers share a family sport: A non-stop marathon The oldest one is fat and short And trudges slowly on The middle brothers tall and slim And keeps a steady pace The youngest runs just like the wind, Speeding through the race "Hes young in years, we let him run," The other brothers say "Cause though hes surely number one, Hes second, in a way.“What is this object?
CHAPTER 6: CHANGES OVER TIMESection 1: Darwin’s Theory
DARWIN’S BACKGROUND Born in England, 1809 Studied Medicine at Edinburgh University Transferred to Cambridge University Studied to be a MinisterLibrary of Congress, Prints andPhotographs Division [reproductionnumber, e.g., LC-USZ61-104].
DARWIN’S EXPEDITION - 1831 Hired as Naturalist on H.M.S. Beagle Sailed on Five Year Scientific Expedition Down East Coast of South America Up Pacific Coast to Galapagos Islands Made Stops on Mainland and Islands Observed Variety of Life and Habitats
DARWIN’S OBSERVATIONS While traveling Darwin studied the things around him during the course of his travels. Darwin observed the diversity of living things, the remains of ancient organisms, and the characteristics of organisms on the Galapagos Islands. What is diversity?
DARWIN’S OBSERVATIONS There are over 1.7 million species of organisms on Earth. A species is a group of similar organisms that can mate with each other and produce fertile offspring. While traveling Darwin found the bones of dead animals. These bones are called fossils. Some of these fossils confused Darwin because they were bigger then they should have been. Darwin wanted to know why these animals were smaller now. A fossil is the preserved remains or traces of an organism that lived in the past.
GALAPAGOS ORGANISMS Notice how isolated the Galapagos Islands are.
GALAPAGOS ORGANISMS When Darwin was in the Galapagos Islands he noticed many different life forms. Some of the animals he had seen before were much different then they were back in England. After noticing these differences Darwin began to compare the animals found in the Galapagos Islands to those found elsewhere. Darwin found many similarities between these animals and ones found in South America. Why was there this similarity?
GALAPAGOS ORGANISMS The animals in South America weren’t identical, for example, the animals in South America had smaller claws compared to the ones in the Galapagos Islands. Darwin believed that some of the species found in the Galapagos Islands had actually come from the mainland of South America. He believed that over time, the animals on the islands changed and became different then the ones on the mainland.
GALAPAGOS ORGANISMS The differences between animals wasn’t just between the mainland and the islands. There were even differences between animals on one island and the next. The size and shape of bird’s beaks differed depending on which island they were located on. When Darwin looked at the beaks and the location he found that the beak suited the location perfectly. The bird’s beaks of that area were made to eat the food found in that location.
GALAPAGOS ORGANISMS The shape of a beak is an example of one type of adaptation. An adaptation is a trait that helps an organism survive and reproduce. What are some examples of adaptations?
EVOLUTION When Darwin returned to England after his voyage he continued studying the things he had observed during his trip. Darwin finally came to the conclusion that plants or animals that arrived on the Galapagos Islands faced conditions that were different from those on the mainland. Perhaps, Darwin hypothesized, the species gradually changed over many generations and became better adapted to the new conditions.
EVOLUTION Evolution is the gradual change in species over time.
EVOLUTION Darwin’s beliefs are called the scientific theory of evolution. A scientific theory is a well tested concept that explains a wide range of observations. Darwin studied other living things to help him understand how evolution might occur. One thing he studied was the offspring of animals produced by selective breeding.
EVOLUTION According to the theory of evolution, two processes are necessary for populations to change over time. These are mutations and natural selection. Natural Selection is the process by which individuals that are adapted to their environment are more likely to survive and reproduce than other members of the same species. Darwin described his research in a book entitled The Origin of Species.
EVOLUTION Proposed Evolution Resulting from Natural Selection: Organisms Produce Many Offspring Competition for Food, Territory, Mates, etc. Those With Best Traits Survive Organisms Change Over Many Generations Time Frame: Millions of Years
EVOLUTION The different ways natural selection occur are: Overproduction – there are too many offspring to survive Variations – animals have different abilities Competition – animals compete with one another to survive Selection – some variations make animals better suited to an environment Environmental change – a change in environment can make it easier or harder for an animal to survive Genes and natural selection – there can be certain mutations or traits inherited that make survival harder for an animal
EVOLUTION A variation is any difference between individuals of the same species. Certain species might eat meat where others only eat plants. Darwin believed that over a long period of time natural selection can lead to change. Helpful variations may gradually accumulate (add up) in a species, while unfavorable (unwanted) ones may disappear.