EVOLUTIONMs. Muneer

Video

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: LucyDiscovered: October 1st 2009The 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 250 000

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: 15-20 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 Decay14C

6 Protons8 Neutrons

14N

7 Protons7 Neutrons

ProtonNeutronElectron

Oldest Rock FoundCanadian 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. 40K can change into 40Ar or 40Ca

Radiometric Dating Half Life – decay is measured in half-life

(time it takes for 50% of parent isotope to decay)

Radiometric Dating 14C Dating – carbon is found in all living

things (1/2 life of 5730 years) Can be used to test objects 100-100 000

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) = 1.426 x 109 years old.

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