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I. History of evolutionary thought. In the 1830 ’ s an English Naturalist named Charles Darwin took a trip around the world on a ship called the HMS Beagle . He was fascinated by diverse and unique organisms, such as tortoises of the Galapagos Islands. . A. The Idea of evolution.
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I. History of evolutionary thought • In the 1830’s an English Naturalist named Charles Darwin took a trip around the world on a ship called the HMS Beagle. • He was fascinated by diverse and unique organisms, such as tortoises of the Galapagos Islands.
A. The Idea of evolution • After his trip, he noted that groups of animals varied from island to island. • Ex. Tortoises on the same island looked alike, while the tortoises on neighboring islands were different. • He noted similarities and differences as he traveled. He was convinced that organisms had changed over time and he wondered why.
He came up with the theory of EVOLUTION. Evolution is the change over time.
i. Ideas of Darwin’s time • In the 18th century, most scientists thought all species were permanent and unchanging. • Thought was that the Earth was only thousands of years old, not billions.
ii. Darwin’s ideas • In the mid 1800’s, Darwin and Alfred Russell Wallace formed a new theory to explain how evolution may take place. • 2 GOALS: • 1. Present large amounts of evidence that evolution occurs. • 2. Explain variety and distribution of organisms on Earth in terms of natural processes that are observable every day.
A. Descent with modification • 1st to argue that ALL species had descended from only 1 or a few original kinds of life. • Ex. Islands are home to 13 similar species of finches. Each with a different beak that is adapted for certain food. • Darwin suspected that all 13 species descended from just a few ancestral finches. They adapted different beaks based on diet or available food.
b. Natural selection • Natural Selection is the process by which individuals are better suited to survive in their environment.
4 main parts of darwin’s reasoning • 1. Overproduction: more offspring can be produced than can survive to maturity. It is possible for species to reproduce over and over, but the environment limits this by causing death or limiting births. • 2. Genetic Variation: Within a population, individuals have different traits. Ex. some deer have thicker fur than others. These traits can be inherited.
3. Struggle to Survive: Individuals must compete. Darwin called it ”struggle for existence”. Some variations give individuals an advantage called :Adaptations. Ex. thick fur in winter may make individuals successful. • 4. Differential Reproduction: Those with the best adaptations are most likely to survive and reproduce. “Survival of the Fittest”.
Darwin also referred to the measure of of an individual’s hereditary contribution to the next generation as: FITNESS. • Fitness is more than just living long. It refers to one’s ability to reproduce successfully to pass on the genetic trait that makes it successful.
Adaptation vs. acclimation • In evolutionary theory, Adaptation refers to changes in traits in populations over long periods of time. • Ex. populations of animals adapt thicker fur over long periods of time due to climate changes. Long term. • Acclimation refers to changes made by a single being in one’s own lifetime. • Ex. Animal grows thicker fur during Winter months because it is better during that time period.
Evidence of evolution • Age of Fossils • 1669- Danish Scientist Nicolaus Steno came up with the principle of SUPERPOSITION. • This basically states that if rock strata is undisturbed, the lower levels are older than the above layers.
Today’s geologists often can tell fossil’s RELATIVE AGE by comparing with known fossil records. • Can find ABSOLUTE AGE by using radiometric dating.
Distribution of Fossils • Many inferences can be made from fossil record: • 1. Different organisms lived at different times. • 2. Today’s organisms are different from those of the past. • Ex. Tribolites
3. Fossils found in adjacent layers are more like each other than fossils found deeper or higher layers. • 4. Comparing fossils and rocks from around the planet, we can infer when and where different organisms existed.
Transitional Species • We can infer that species have differed in a gradual sequence based on TRANSITIONAL SPECIES. • They are intermediate organisms between ancestor and descendents. • One of the common arguments given is that within evolution you find transitional species, that is, organisms or species that bridge the gap from one species to another.
Tiktaalik is a cross between a fish and a four-legged animal (“tetrapod”). This organism set the stage for amphibians to adapt into the oxygen-poor shallow waters of the coastline.
Biogeography • Study of the locations of organisms around the world. • Ex. Australia has animals that resemble wolves, cats, mice, moles or anteaters, but in Australia they are marsupials (pouch to carry young). Possible explanation- isolation of Australian continent.
Anatomy and Embryology • Descent with modification predicts findings of ANATOMY and EMBRYOLOGY. • Anatomy- body structure • Embryology- how organisms develop
HOMOLOGOUS STRUCTURES: Same structure that occurs in different species with different functions.
Biologists define HOMOLOGOUS STRUCTURES as anatomical structures that occur in different species. • Often have different FUNCTIONS. • ANALOGOUS STRUCTURES have similar function, but often come from different structures.
VESTIGIAL STRUCTURES: structures that seem to serve NO function, but resemble structures with functional roles in related organisms. • Ex. Human coccyx (tailbone)- made up of 4 fused vertebrae resemble animal tail. • Ex. Appendix • Ex. Pelvic bones of whales
