History of Life on Earth http://www.youtube.com/watch?v=0SCjhI86grU History of Life on Earth

How did life on earth begin? Scientist currently believe that life was first seen in oceans (an aquatic environment). According to fossil record, for about 90% of its existence, life was limited to aquatic environments. Popular theory states that the earliest organisms that were able to survive were prokaryotic organisms that resemble modern-day bacteria. Pangea: a huge continent made up of all the land masses on Earth

Biodiversity and Speciation Speciation: the evolution of a new species from an existing species Cooler environment leads to animals with the inherited trait for thicker fur to be better able to survive, reproduce, and pass this trait on to offspring. Biodiversity: the variety of organisms, their genetic information, and the communities in which they live

Adaptations and Species Change Adaptation: any trait that improves an organism’ chances for survival and reproduction in its environment Variations may result from mutations or from how genetic material is rearranged during sexual reproduction. Mutations occur randomly, but are not always harmful and do not always cause organisms to evolve (must occur in germ cells to be passed on)! Camouflage is a positive adaptation!

Genetic Variation Gene flow: the introduction of genes from one population into the gene pool of another population Effected by mobility Gene pool: the combined genetic information of all members of a population

Extinction Throughout the history of life, events occurred that have caused more than 99% of all species to die out: extinction. Although extinctions usually happen at a fairly constant rate, sometime huge numbers disappeared in periodic mass extinctions.

Ancestry Ancestry: the history of an organism’s development Phylogenetic trees: use DNA analysis, fossil evidence, and patterns of early development to construct these trees Can be represented by a branching tree The base of the tree represents a common ancestor, which the branches show how different groups of organisms are related

Rate of Evolution Theories Gradualism Punctuated Equilibrium Description Biological change results from a slow and steady process over a long period of time. Biological change results from a quick, sporadic process over a short period of time followed by long periods of little or no change. Mechanism Tiny changes in a species gradually add up to major changes over time. The mutations of a few genes result in the appearance of a new species. Evidence Intermediate forms are found in the fossil record for some species. Gaps occur in the fossil record.