Adaptations over Time Unit 4

Evolution Any adaptation that has taken place over time is called evolution.

Learned Traits Any trait that is learned in ones lifetime is a learned trait. An example would be a dog learning to go to the door so that it can go outside to poop (this trait is not passed to its offspring).

Charles Darwin Darwin recorded observations he made at an island off of S. America called the Galápagos Islands. He figured the majority of plants and animals must have come from Central and S. America

Darwin Cont’d But…the island contained species that he had never seen. One of the main things he observed was finches located on different islands.

Finches There were 13 species of finches that were similar, but not exactly the same. Some had short, strong beaks Some had long, thin beaks.

Finches Cont’d Darwin figured these finches competed for food. The finches w/ the short, strong beaks were able to break open nuts. The finches with the long beaks were able to better eat insects

Separate Species Over a few generations, these finches actually became separate species.

Darwin’s Theory Darwin’s Theory is known as the Theory of Natural Selection. Natural selection means that organisms with traits best suited to their environment are more likely to survive and reproduce.

Theory of Natural Selection Basically, this theory states that those who are “fittest” will survive and pass those genes on. For example a “walking stick” insect is more likely to survive because it blends in.

Variations A variation is any permanent mutation that makes an organism different from other members of its species.

Adaptations An adaptation is any variation that makes an organism better suited to its environment. Camouflage would be an example of an adaptation.

Geographic Isolation Sometimes a small group of species is isolated from the rest of their species. This can cause the small group to have characteristics not found in the larger group.

Biodiversity The number and variety of organisms found within a specified geographic region is biodiversity.

How Fast is Evolution? Most scientists think evolution is very slow (millions of years). This is known as gradualism. Others think it can happen very fast. This is known as punctuated equilibrium. Probably both.

Very Fast Evolution An example of very fast evolution is bacteria. Just a few years ago, penecillin killed almost all bacteria, but now many are immune.

Evidence Most of the evidence for evolution comes from fossils. Most fossils are found in sedimentary rock.

What are fossils? Fossils are the petrified remains of ancient objects. Petrified – means turned to stone.

Kinds of fossils? Fossils can be of animals, plants, or other objects. Most of the time we think of dinosaurs when we hear the word fossil.

Fossils, big or small…. Fossils can be very large or very small

Where are fossils found? Fossils are mostly found in sedimentary rocks. Limestone, sandstone, and shale are all examples of sedimentary rock.

Determining Fossils Age Two basic methods—relative dating and radiometric dating—can be used, alone or together, to estimate the ages of rocks and fossils.

Relative Dating In undisturbed areas, the oldest rocks are found on bottom. Relative dating provides an estimate only.

Radiometric Dating Scientists can get more accurate dates using this method. Elements give off a certain amount of radiation. Each element gives radiation off at different rates.

Radiometric Dating Cont’d Scientists compare the amount of radioactive materials left in a rock compared to the non-radioactive materials.

Fossils and Evolution The fossil record is incomplete, or has gaps, much like a book with missing pages. The gaps exist because most organisms do not become fossils.

Extinction An species that is no longer living is extinct.

Homologous Structures Homologus structures are body parts that are similar. They often indicate that two or more species share common ancestors.

Vestigial Structures vestigial structures —structures that don’t seem to have a function. Examples include the human appendix and “tail”.

Primates Humans, monkeys, and apes belong to the group of mammals known as the primates All primates have “opposable” thumbs, binocular vision, and flexible shoulders.

Humans The fossil record indicates that Homo sapiens evolved about 400,000 years ago Homo sapiens means “wise human” or “thinking man.”

Humans The oldest recorded art has been found on the walls of caves in France, where Cro-Magnon humans first painted bison, horses, and people carrying spears.