Good Morning!!! Today we will be finishing up GATTACA and starting some new stuff! To prepare for class please… Please get out your GATTACA question sheets

History of Life on Earth

A little information about Earth The Earth is 4.6 billion years old. Evidence shows life first evolved around 3.9 - 3.5 billion years ago. Atmosphere 3.5 bya – Hydrogen gas, water vapor, Carbon Dioxide

How did life on Earth start? Many ideas… Asteroids Recent Asteroids have been found carrying a variety of organic compounds. Hydrothermal Vents Under water vents that release very hot water and a variety of minerals/ organic materials. Hot Springs Similar to geothermal vents.

How did life originate? All living things are incredibly complex. All of the complexity did not just appear, it almost certainly originated in a series of small steps.

How did scientists get this information? Fossil Records (types of fossils, relative age, and index fossils) Radioactive dating/Half life decay

Fossil Record A fossil is the remains or evidence of any creature or plant that once lived on the Earth. Fossils can be broken up into two major categories. Type I is the remains of the dead animal or plant or the imprint left from the remains Type II something that was made by a living animal.

Earth’s oldest fossils Stromatolites- contain thousands and thousands of cyanobacteria Cyanobacteria-bacteria that is responsible for stimulating biodiversity. Possibly first organism to run photosynthesis

How do fossils form? Most fossils are formed in similar ways An animal dies and become buried under layers of sediment that are deposited by water. The organism gradually dissolves and leaves a hollow impression, or mold, in the sediment. Over time, the mold may fill with minerals, which forms a cast of an organism.

Using Fossils Principle of Superposition states that each layer of rock is older than the one on top of it. Relative dating is used to estimate ages of fossils found within the strata. Can’t give exact age but does give order to fossils laid in the strata.

Absolute Age An absolute age can be estimated by determining the amount of certain radioactive isotopes that the rock that surrounds the object contains. Known as Radiometric dating.

Geologic Time

Geologic Time The geologic time organizes geologic and evolutionary events. The geologic time scale is based on evidence in the fossil record and has been shaped by mass extinction. Geologic time is separated into the Precambrian Time, Paleozoic Era, Mesozoic Era, and Cenozoic Era.

Precambrian Time Spanned ~4.5 billion and 542 million years ago Single-celled prokaryotes and later, eukaryotes, evolved and flourished. The evolution of multicellular organisms set the stage for the evolution of modern organism. The increase of oxygen allowed organisms to get bigger and move to land. Also lead to extinction.

Paleozoic Era Spanned ~542 million to 299 million years ago. A time of great evolutionary expansion. Marine invertebrates diversified, and marine vertebrates evolved. The first land plants evolved. Some arthropods, and then some vertebrates, moved to land.

Mesozoic Era Spanned from ~250- 146 million yrs Includes Jurassic Period!! Dinosaurs RRRAAWWWWRRRRRR!!!! The animal life changed dramatically from the Paleozoic Era. Great change in the terrestrial vegetation.

Cenozoic Era ~65.5 million years ago to the present. This Era has been a period of long-time cooling. Mammals diverged from a few small, simple, generalized forms into a diverse collection of terrestrial, marine, and flying animals.