The Theory of Evolution

Charles Darwin (Working off the information and data collected from other scientists)

Charles Darwin and Natural Selection Charles Darwin (1809-1882): studied evolution. Evolution is the change in populations over time. Fossil evidence formed the basis of the early evolutionary concepts.

Many explanations about how species evolve have been proposed, but the ideas first published by Charles Darwin are the basis of modern evolutionary theory.

Charles Darwin sailed off on the HMS Beagle at the age of 21, which journey for five years. There he was the ships naturalist, studying and collecting species along the route. Darwin became curious about the possible relationships among the species he collected.

On the Galapagos Islands Darwin made several observations which led him to believe that species can change over time. After several years of studying and researching other scientist methods and experiments as well as conducting his own he realized that several individuals struggle to survive.

Darwin gained insight into the mechanism that determined which organisms survive in nature from his pigeon-breeding experiments. Breeding organisms with specific traits in order to produce offspring with identical traits is called artificial selection. Darwin believed there was a force in nature acting like artificial selection.

Natural Selection is a mechanism for change in populations Natural Selection is a mechanism for change in populations. It occurs when organisms with certain variations survive, reproduce, and pass their variations to the next generation. Organisms without there variations are less likely to survive and reproduce. As a result, each generation consists largely of offspring from parents with these variations that aide survival.

Darwin published the first book about evolution called The Origin of Species by Natural Selection. Interpreting evidence after Darwin: One of the problems if that evolutionary processes are difficult for humans to observe directly. The short scale of human life spans makes it difficult to comprehend evolutionary processes that occur over millions of years. Evolution is more commonly defined by modern biologists as any change in the gene pool of a population.

Adaptations: Evidence for Evolution Adaptation is any variation that aids an organism’s chances of survival in its environment. For example, thorns are an adaptation of some plants and distinctive colorings are an adaptation of some animals.

Peppered Moths

According to Darwin’s theory adaptations in species develop over many generations. Structural adaptations for mole rats to survive underground are large teeth and claws. Mimicry is a structural adaptation that enables one species to resemble another species. One form of mimicry is to acquire physical features to resemble a harmful species. Predators will then avoid them, fearing that they are dangerous.

Camouflage is another adaptation that enables a species to blend with their ___________________. Because well-camouflaged organisms are not easily found by predators, they survive to reproduce.

Physiological adaptations can develop rapidly Physiological adaptations can develop rapidly. For example, medicines can evolve very rapidly. Physiological adaptations are changes in an organism’s metabolic processes. Besides bacteria what’s another example of a species who has underwent physiological adaptations? ________________________________

Other Evidence for Evolution Fossils are an important source of evolutionary evidence because they provide a record of early life and evolutionary history. Even though paleontologists have missing pieces in their fossil record, they still understand the overall picture. As the fossil record becomes more complete, the sequences of evolution become more clear.

Structural features with common evolutionary origin are called homologous structures. Homologous structures can be similar in arrangement, in function, or in both. Evolutionary biologists view homologous structures as evidence that organisms evolved from a common ancestor. You can compare the butterfly wing with a bird. They are not similar in structure, but they are similar in function. EX. Bat wing, whale flipper, and dog paw

The body parts of organisms that do not have common evolutionary origin but are similar in function are called analogous structures. Example: Bird wing & bat wing are both for flight but they are structurally different

Another type of body feature that suggests evolutionary relationships is a vestigial structure. This is a body structure that has no function in a present-day organism but was probably useful to an ancestor. Ex. Human tailbone, whale pelvis

An embryo is the earliest stage of growth and development of both plants and animals. Similarities among the young embryos suggest evolution from a distant, common ancestor.

Today many scientists use the results of biochemical studies to help determine the evolutionary relationships of species. Since Darwin’s time, scientists have constructed evolutionary diagrams that show levels of relationships among species.