Where did all this diversity come from?!

Why do these organisms look so similar? What has shaped their appearance over time?

Why are all these animals white?

Why are Lemurs found only on Madagascar?

How does something like THIS come about?!!

The Facts…. 99% of everything that has ever lived no longer exists on the Earth – it is extinct Some modern organisms look very similar to other unrelated organisms (ex. Ant-eaters & Echidnas) Some modern organisms look very similar to ancient organisms that are now extinct (ex. fossils) For centuries, people looked at these fossils and tried to EXPLAIN what they are, and what they mean What hypotheses could you propose for the diversity of life? What evidence could you gather? What do you ALREADY KNOW about inheritance?

“EVOLUTION” – what’s all the fuss about?! Theory = “a scientific explanation of natural phenomena, based on empirical evidence” A theory brings together all the research into a single cohesive, testable explanation Evolution = “change over time” A scientific explanation for the origin, diversity and continued change observed within living things Defined more specifically in Biology as “descent with modification” (ie. The things alive today are modified versions of their ancestors…just like you and me!) Physical traits are passed-on to offspring Some traits are beneficial, others aren’t The beneficial traits remain in the population, and become more common over time – THIS IS “EVOLUTION”…

Let’s back up: “In The Beginning…” Most scientists in the early 1600’s believed that life was a force carried in the air, and that life was spontaneously generated from non-living matter Redi’s simple experiment with maggots and meat proved this to be false… Pasteur filled a flask with growth medium, heated it to kill all life, and then drew out the neck of the flask into a long S. This prevented dust & microorganisms in the air from entering the flask, but allowed air to flow freely. If the swan neck was broken, microbes could enter the flask and grow The Result? Bacteria only grew in the broken flasks… Therefore, microbes come from OTHER microbes…

ALEXANDER OPARIN - FORMATION OF MACROMOLECULES WITHOUT OXYGEN STANLEY MILLER AND HAROLD UREY EXPERIMENT “Created” amino acids from simulated early Earth conditions… http://en.wikipedia.org/wiki/Image:Miller-Urey_experiment_en.png creative commons copyright

THE FIRST CELLS!!! FIRST SIMPLE BACTERIA APPEARED AROUND 3.5 BILLION YEARS AGO SOME ARE CYANOBACTERIA - THESE ARE PHOTOSYNTHETIC BACTERIA (Stromatolites…) WHAT GAS DID THESE BACTERIA PRODUCE? ATMOS. WAS ALMOST 10% O2 ABOUT 2.5 BILLION YEARS AGO WHAT TYPE OF CELLS ARE BACTERIA? WHAT TYPE OF CELLS ARE ALL OTHER ORGANISMS? WHERE DID EUKARYOTIC CELLS COME FROM? ENDOSYMBIOSIS… Dr Gordon Beakes © University of Newcastle upon Tynelicensed for use through the Centre for Bioscience ImageBank,http://www.bioscience.heacademy.ac.uk/imagebank/"

ENDOSYMBIONT THEORY THE BEGINNING OF THE EUKARYOTIC CELLS EVIDENCE FOR ENDOSYMBIOSIS DNA & structural similarities evolution.berkeley.edu/evolibrary/article/0_0_0/endosymbiosis_03

HOW Does Life Change?

Summary of Darwin’s Theory of Evolution 1. Individual organisms in nature differ from one another

2. Organisms produce more offspring than can survive. Turtle eggs Lobster eggs Turtle eggs: Lobster eggs: 8,000-100,000 for maine lobster; up to Insect eggs Frog eggs

3. Members of each species must compete for limited resources.

4. Each organism has different advantages and disadvantages for the struggle of existence.

5. Individuals best-suited to their environment survive and reproduce 5. Individuals best-suited to their environment survive and reproduce. Those not suited will be less likely to breed Survival of the fittest!

Nature (the environment) will determine which organism is the fittest to Survive

6. Species change over time, by passing on their useful (and harmful) traits to their offspring

7. All species alive today have therefore descended with modifications from ancient ancestors

Fossil record of the camel

8. Ultimately, ALL organisms on Earth are united into a single tree of life… Darwin’s original sketchbook drawing

Darwin’s Theory is supported by…. ARTIFICIAL SELECTION Nature provides variation but humans decide what traits are selected and passed on. Hybridization brings about new variations

Descent with Modification Darwin proposed that after long periods of time, offspring of ancient organisms spread out through the environment, and natural selection then results in organisms with traits that are very different from their ancestor Different structures Different niches Different habitats We call this Adaptive Radiation

Is There Any Evidence For This Theory?

Evidence of Evolution Did you know???? Fossil Records-fossils being discovered were evidence that the world was much older that once thought. Did you know???? Some fossils were very similar to modern day creatures 99% of species that once lived are now extinct!!!!!!

Fossils show history of life on Earth Relative Dating -The layering of rock can show which fossils are older.

Fossils show history of life on Earth Radioactive Dating -using the half-life of radioactive elements scientists can tell approx. how old a fossil is…

What Does The Fossil Record Tell Us About Evolution? Sedimentary rocks can be dated by studying the decay of radioactive isotopes they contain. In some cases, successive layers of rocks of different ages are so well-preserved that families of similar fossils can be traced through the layers, over several million years of history This apparent transition suggests a pattern of development, and allows scientists to infer changes from one form to another and construct a diagram called a Phylogenetic Tree…

Trilobite Evolution Phylogenetic trees show the evolutionary ancestry of organisms, based on their inferred relationships to ancestral species

The History Of Life The fossil record has allowed scientists to locate the “first appearance” of different organisms within rocks of a specific age The pattern of change & progression suggests that recent organisms might be modified forms of ancient organisms that previously existed

The Geological Timescale Based ONLY on the fossil evidence, it appears that the nature and diversity of life on our planet has changed dramatically throughout Earth’s history But HOW have these changes occurred? How? We’ll look at Macroevolution on Wednesday