EVOLUTION Ms. Muneer

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Black Widow – Evil????

Evolution…. Do we really need to know this?  To understand how _________________________________________  To provide answers to questions ________________________________  To apply to our understandings of health sciences, agriculture, industry, and conservation

Hmmm…. Controversies?  Evolution: The process in which significant changes in the inheritable traits of a species occur over time  Many cultures and religions believe or have believed that life is immutable  Immutable: life forms are unchanged and unchanging since the beginning of time  Today most people understand the world is dynamic and change is a constant  500 years ago most people thought that their natural world changed very little  Part of the confusion was that people thought the Earth was very young  In 1650 Archbishop James Ussher of Armagh declared that the Earth was created on Sunday, October 23, 4004 B.C.

What is Evolution?  Evolution is change over time caused by the accumulation of inherited characteristics over many generations.  A characteristic that helps an organism to survive and reproduce in its environment is called an adaptation.  Similarities in DNA and physical structures indicate that all organisms are related to common ancestors.

What evidence do we really have?  FOSSILS!  Fossils are preserved remains or traces of an organism or its activity; hardened body parts such as bones  An organism may simply leave an impression in hardened material, or, if the rate of decomposition is very slow, the organism’s cells may be replaced by minerals, resulting in permineralized fossil  Ideal conditions for fossilization are rare

Process of Fossilization A fish returns to its birth place to spawn.Having spawned the fish dies and shortly after sinks to the seafloor.

Process of Fossilization After several weeks the soft body tissues have mostly decayed. Tectonic activity induces nearby sediment to mobilise, burying the fish in the event.

Process of Fossilization Several months pass and all that remains of the buried fish is its skeleton. As times passes more sediment accumulates above the fish and the skeleton is gradually compressed and permineralised.

Process of Fossilization Over time the rock is distorted and uplifted by geological forces associated with continental movement, raising it above sea level. The uplifted rock is exposed to weathering and gradually erodes away, eventually exposing the tip of the fish's skull at the surface.

Name: Lucy Discovered: October 1 st 2009 The find reveals that our forebears underwent a previously unknown stage of evolution more than a million years before Lucy, the iconic early human ancestor specimen that walked the Earth 3.2 million years ago. Oldest Human fossil!

Study of Fossils  Also known as Palaeontology  Today’s fossil records comprise of more than species  Less than 1% of species in the fossil record are living today  Cuvier observed that fossils of simple organisms could be found at all depths, more complex forms were found in the shallower deposits  His theory – Catastrophism stated that local catastrophes could cause extinction, extinct forms are then replaced by different newly created species  Cuvier determined the relative age of fossils by assuming a chronology for rock strata (eg. Deeper fossils are older)  There was still no method for determining the absolute age of a rock or fossil Baron Georges Cuvier

What exactly is a species?  A species is a group of organisms that can mate and produce viable offspring.

Earth’s Birthday

Old theory …..  Lord William Thomas Kelvin was the first to try to determine the age of Earth in 1866  He assumed that Earth was gradually cooling down  Absolute age according to Kelvin: 400 million years  Kelvin’s Revised Absolution age: million years

Current Theory …  Pierre Curie!!!!  In 1903 discovered radioactive decay  Radioactive decay is the release of subatomic particles from the nucleus of an atom, which results in the change of a radioactive parent isotope into a daughter isotope  Remember: number of protons determines the element  New absolute age of Earth: 4.6 billion years!

Radioactive Decay 14C 6 Protons 8 Neutrons 14N 7 Protons 7 Neutrons Proton Neutron Electron

Oldest Rock Found Canadian Shield north of Yellowknife – 3.9 billion years

Radiometric Dating  Calculation of the age of rock based on the decay of radioisotops in the rock  Radioisotopes – atoms with an unstable nuclear arrangement that undergoes radioactive decay  Parent isotope decays into daughter isotope  eg. 40 K can change into 40 Ar or 40 Ca

Radiometric Dating  Half Life – decay is measured in half-life (time it takes for 50% of parent isotope to decay)

Radiometric Dating  14 C Dating – carbon is found in all living things (1/2 life of 5730 years)  Can be used to test objects years  Ideal for testing human remains

How Old?????  Example: A sample of rock contains radioactive uranium and lead. If 25% of the parent isotope remains, how old is the rock? (Half-life of uranium to lead is 713 million years)  The half-life of uranium to lead is 713 million years, and for 25% of the parent isotope to remain, 2 half-lives have occurred.  So, the rock is (2 x 713) = x 10 9 years old.

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