Chapter 14.1 Evolution

Evolution-  is all of the changes that have transformed life over an immense time. In a sense, evolution is the biological history of life on Earth.

Although humans and chimpanzees separated six million years ago, we still share 96 % of our genome Adaptation- an inherited characteristic that improves an organism's ability to survive and reproduce in a particular environment.Ex: The kangaroo's hind legs, giraffe’s long neck

Scientists & Theories

- Georges Buffon, 1749, Earth might be much older than a few thousand years.  Fossils & living animals were similar but not exactly alike

- Jean Baptiste Lamarck, early 1800's built on Buffon, said life evolves or changes.  Species are not permanent, evolution is a process of adaptation. (bad rap because he said that organism's had an effect on what was passed on, giraffe)

Charles Darwin Author of “ The Origin of Species" published in 1859After a 22 year old Darwin joined the voyage of the Beagle, 5 year Major Findings occurred on Galapagos Islands-  group of islands off the coast of South America.   He studied the geology, plants & animals.

Darwin believed the earth was very old based on his geological observations (inspired by Lyell)1.Deep river canyons that would have taken millions of years to have been carved by erosion

2.Marine fossils at the top of the Andes Mountains

Darwin noticed that the plants and animals throughout the continents all had a distinct characteristics. South American’s species were quite distinct from the species of Europe. Even the fossils that Darwin found were uniquely different from continent to continent. 

Upon returning home Darwin continued to think about the question of how species change, he read an essay on human populations written a few decades earlier by Thomas Malthus. Malthus concluded that populations can grow much faster than the rate at which supplies of food and other resources 

can be produced. 

Darwin’s two main points1. Descent with modification  Darwin proposed that the descendants of the earliest organisms spread into various habitats over millions of years. In these habitats, they accumulated different modifications, or adaptations, to diverse ways of life. Long ears of the Jack Rabbit are adapted to help cool the body in hot weather & the white fur of snowshoe hare are examples of this.

2. Natural Selection the Mechanism for EvolutionThe variation observed in wild populations would produce some individuals that were slightly better equipped to thrive and reproduce under the particular conditions in that environment. Those individuals would tend to leave more offspring than their fellows, and over many generations their traits would come to dominate the population.

14.2Evolution Evidence

Fossil Record: Rock strata, or layers, form when the rates of sedimentation or the types of particles forming the sediments vary over time. Aquatic organisms can become fossils when they die and are buried in sediments in a way that preserves some of their structure. Land organisms can become fossils in a similar way, if they are swept into rivers, lakes, swamps, and seas. Other remains of land dwellers may become fossils after being covered by windblown dust, sand, or volcanic ash.

Younger rock strata usually are layered on top of older ones, as illustrated in Figure 14-10. Thus, the positions of fossils in the rock strata can reveal their relative age. The fossil record is this chronological collection of life's remains in the rock layers, recorded during the passage of time.

Of certain animals:Australia marsupials: isolated from other kinds of animals & mammals, very few placental mammals.

Geographic Distribution

Similarities in StructureHomologous structures – similar structures in species, suggest sharing of a common ancestor.  (homo – same) 

i.e. forelimbs

Vestigial structures – remnants of structures that may have had important functions in an ancestral species – but no clear function in modern descendents 

Ex.  Whale:  some have hip bones, human – tail bone

Developmental similarities:Vertebrate embryonic stages look 

very similar

DNA sequence – determine amino acid sequence to build a protein

Greater the similarity, closer related in ancestry.

4-5% difference in total DNA between humans & chimpsBut what does that mean?

http://genome.cshlp.org/content/15/12/1746.long

Molecular Biology