Biology II

 Evidence for the nature and rates of evolution can be found in the anatomical, molecular characteristics and in the fossil record.

 Fossil Record: The fossil record provides evidence about the history of life on Earth. ◦ Shows how groups of organisms have changed over time

 Relative Dating: the age of the fossil is determined by comparing its placement with that of fossils in other layers of rock ◦ Helps estimate fossils age ◦ Oldest layers on the bottom ◦ Most recent is at the top

 Radioactive elements “break-down”  Half-life: the length of time required for half of the radioactive atoms in a sample to decay  Different Radioactive elements have different half-lives  Ex. Carbon years  Ex. Potassium Billion years  Radioactive Dating: the use of half-lives to determine the age of a sample

 Geographic Distribution ◦ Species now living on different continents had each descended from different ancestors.

Similar, But Unrelated Species and

 Homologous Body Structures: structures that have different mature forms but develop from the same embryonic tissues  All develop from the same cells in the embryo  Evidence of descended, with modifications from common ancestors.

Turtle Alligator Bird Mammal Ancient, lobe- finned fish

 Not all homologous structures serve important functions.  The organs of many animals are so reduced in size that they are just vestiges, or traces, of homologous organs in other species. ◦ These organs are called vestigial organs.

1. Individual organisms differ, and some of this variation is heritable 2. Organisms produce more offspring than can survive, and many that do survive do not reproduce 3. Each unique organism has different advantages and disadvantages in the struggle for existence. 4. Species alive today are descended with modification from ancestral species that lived in the distant past.

 Geological Time Scale: is used to represent evolutionary time:  Paleontologists use this information to:  Place Earth’s rocks to their relative age

 There are two Era’s: 1.Pre-Cambrian 2.Modern a)Paleozoic b)Mesozoic c)Cenozoic

 Precambrian Time (4.6 Billion Yrs-500 Million Yrs.) ◦ Covers 90% of Earth’s History ◦ Anaerobic Forms of life appeared ◦ Followed by Photosynthetic Forms of life ◦ Few fossils (because all were soft-bodied) ◦ All lived in sea

 Paleozoic Era: (500 Million Yrs-250 Million Yrs.) ◦ Fossil evidence shows rich diversity of MARINE life ◦ “Cambrian Explosion”: diversification of life  Shells  Outer skeletons ◦ Vertebrates started to invade the land (amphibians) ◦ Rich Vegetation on land ◦ Mass Extinction occurred at the end of the Paleozoic (95% of life was extinct)

 Mesozoic Era: (250 Million Yrs-65 Million Yrs.) ◦ Increased dominance of dinosaurs ◦ Appearance of flowering plants ◦ Mammals appeared ◦ Mass Extinction at the end of Mesozoic Era  “Meek inherit the Earth”

 Cenozoic Era: (65 Million Yrs.-Present) ◦ Mammals evolved adaptations that allowed them to live in various environments

 Clock Model of Earth’s History First humans First prokaryotes Cenozoic Era Mesozoic Era Paleozoic Era Precambrian Time First land plants First multicellular organisms First eukaryotes Radiation of mammals Accumulation of atmospheric oxygen

Biology II

 How is the age of the Earth important to the study of biological evolution?

 Macroevolution: large-scale evolutionary patterns and processes that occur over LONG periods of time ◦ Extinction ◦ Adaptive Radiation ◦ Convergent Evolution ◦ Coevolution ◦ Punctuated Equilibrium ◦ Changes in developmental Genes