“A change in the frequency of an allele within a gene pool.”-Wikipedia

EvolutionNotes

What does this unit (“change over time”)cover?In this unit we will study:

▫Geologic Time Scale▫Fossil Formation▫Animal Behaviors (based on fossil

evidence)▫Hypotheses' and theories about the

origins of life▫Structures, DNA, and embryology!▫Chapters 14 and 15 in your book!

To understand evolution, we must first understand…

•Evolution is based on Science.

•Science only attempts to explain the natural world – not the supernatural world.

•In science, evolution is the best explanation we have right now as to how life has changed on earth over the last few billion years.

•Evolution is not a debate in the scientific community.

•Evolution is a well researched scientific theory supported by thousands of scientific studies and many different types of evidence.

•The word “theory” in science is synonymous with the word fact. It means the idea must be supported by hundreds of thousands of pieces of evidence, gathered by many different scientists, whom over many years, reach the same conclusion.

•When scientists label an idea a theory, they are saying they are 99.9% sure this is the way it is!

•We don’t “BELIEVE” in evolution, we study it… just like photosynthesis, mitosis or any other biological process.

•Do you BELIEVE in mitosis?

So, what is evolution?•Evolution means “change over time”.•Organisms must adapt and change over

time to become better suited (live longer) to their environment.

•The key is to live long enough to pass down the “good genes” to their offspring!

•All living organisms evolve – from bacteria to humans!

How do we know evolution occurred?•Fossils•Structures in modern animals that are no

longer useful•Embryological comparisons•DNA and comparative biochemistry•Skeletal structures (comparative

anatomy)•Geographic distribution•Adaptations

Chapter 14 (Fossils)•Fossils:

▫Trace fossils (left by a soft part like a footprint) vs. cast and mold fossils (left from a hard part like a shell or bone) Both important!

▫Types of dating: Relative – general idea (older than or

younger than another fossil) Absolute – specific date, done by carbon

dating or radiometric dating▫Law of Superposition – older fossils are

lower in the rocks, younger fossils are closer to the top layer of soil

▫Strata or Stratum – layers of rock, usually different colors or made of different types of rock

▫Type of rocks fossils are found in – sedimentary

▫Whale skeletons and horse skeletons as evidence of evolution

Fossils• What is a fossil?

▫ Preserved evidence of an organism• How is a fossil formed? (page 394)

1. Organism dies and is buried in sediment2. Sediments build up and cover remains3. Minerals in water fill empty pores in hard

parts that remain4. Organism’s soft parts decay, leaves its

impression (or mineralized hard parts)5. Sediments eventually harden into rock

•Mold – impression in the rock•Cast – hard part that is mineralized (fills

up the mold)•2 types of fossils we will see in our lab

▫Trace fossil: footprints, burrows, indirect evidence

▫Cast and Mold fossil: impression/hard part that is fossilized

•4 more are found on page 393

•Geologic Time Scale – A record of what fossils showed up at what time in the past.

•Eras from oldest to most recent•Longest era? Precambrian •Current era? Cenozoic•Cambrian Explosion (many life forms

emerge, what era? Paleozoic Era)•KT Boundary provides possible evidence of

a meteorite strike (what era? Cenozoic)•Many other important events, check out

pages 397 in your book!

End of Day 1 of Guided Notes

•Handout: Geologic Time Scale WS

History of the Earth

•Estimated age of the Earth – 4.6 billion years

•Earth’s early existence – what did it look like?

Perhaps like this?

•Origins of life▫Spontaneous generation, disproved by Redi▫Biogenesis, evidence provided by Pasteur▫Primordial soup – this is an old idea and

scientists have new ideas now. They used to think lightening hit and caused the fusion of organic compounds and that was how life started.

▫Hydrothermal vents – this is the more current thinking. Life could have begun under the oceans by small bacteria that “chemosynthesized”. We have found similar organisms in the modern day.

Once life started… Cellular Evolution

•Earliest fossils found, 3.5 billion years ago•First cells – prokaryotes – like modern day

Archaea (live in hot springs and harsh environments, need no oxygen or sunlight)

•Oxygen present in early Earth bonded to iron until the iron was “full” or saturated. Then it began to accumulate in the atmosphere.

•Next to evolve – photosynthesizing prokaryotes, like cyanobacteria, these we have fossils of (3.5 bil. Yrs. Ago)

•The cyanobacteria eventually produced enough oxygen to make the ozone layer

•Once that was done, eukaryotic cells started to appear!

•Then we see many types of life forms starting to appear in the fossil record.

•Endosymboyant Theory – Margulis 1966▫States that the ancestors of eukaryotic cells

lived in close association with prokaryotic cells or even inside of each other. This was a mutualistic relationship!

•2 organelles involved (evidence)▫Chloroplast and mitochondria, why?

These organelles both have their own DNA (which is in the same shape as prokaryotic organisms), have ribosomes that are like those of prokaryotes, and they reproduce by fission (like prokaryotes).

Chapter 15•Examples of topics scientists study and

use as evidence of Evolution:▫Embryology▫Comparative Biochemistry

(Macromolecules)▫Biogeography▫Vestigial Structures▫Homologous Structures▫Analogous Structures

• Acquired Traits – things you acquired and are not genetically passed down to you (like large muscles or good handwriting skills)▫ These are NOT examples of evolutionary genetic

changes.

A man named Charlie D…

•Background about Charles Darwin…

One of Charles Darwin’s most famous studies was on the Galapagos Islands (I’ve been there!!!).He collected a lot of information on Finches.

•Darwin’s 2 Conclusions▫Decent with Modification: The newer forms

appearing in the fossil record are actually the modified descendants of older species.

▫Modification by Natural Selection: The process by which organisms with favorable variations reproduce at higher rates than those without such variations.

•Darwin info…▫Beagle (his ship), Finches (the birds he studied),

Galapagos (famous islands), his book (The Origin of Species), his life (we will watch a video about it!)

Definition:

•Biological Fitness – high fitness means you can create a high number of viable offspring (they don’t die)

•Divergent Evolution – one species looks more and more different (finches)

•Convergent Evolution – 2 species look more and more similar (shark and dolphin)

•Types of Selection▫Artificial - breeding organisms on purpose,

done by humans – dog breeders▫Natural - 4 contributing factors: Variation,

Heritability, Overproduction, and Reproductive Advantage. (page 421)

▫Sexual – the male and female organisms look drastically different (peacocks)

•Camouflage – blending in (Chameleon)•Mimicry – looking like another organism

(snakes)•“Favorable Traits” – things that are helpful

traits that have evolved from our ancestors•Bacterial Evolution

▫Mutations are “mess ups” in the DNA▫Cause bacteria to change and become

resistant to antibiotics▫Also seen in virus’ like HIV which can evolve

in minutes or hours!•Cladograms – diagrams that show

evolutionary relationships

Cladogram - Example

End of Day 2 Guided Notes

Now let’s look at…▫Embryology▫Comparative Biochemistry

(Macromolecules)▫Biogeography▫Vestigial Structures▫Homologous Structures▫Analogous Structures

Embryology

•Scientists can look at the very beginning stages of development for an organism and compare it to other organisms to determine how similar (closely related) those organisms are to each other.

•Let’s take a look!

Can you tell what is what?Can you identify

the:ChickenRabbitFish

HumanTortoise

CowSalamander

Pig

How about now?Can you identify

the:ChickenRabbitFish

HumanTortoise

CowSalamander

Pig

Ok, here’s the last one!Can you identify

the:ChickenRabbitFish

HumanTortoise

CowSalamander

Pig

Answers!

Comparative Biochemistry (Macromolecules)

•Scientists now know the DNA sequence of humans (and many other living organisms)

•We can compare our DNA or other biological molecules to see how closely they match up with other organisms. The closer the match, the more recent the common ancestor.

•Let’s see an example…

Human Cytochrome Chttp://bioweb.cs.earlham.edu/9-12/evolution/HTML/live.html

• Biochemistry also reveals similarities between organisms of different species.

• For example, the metabolism of vastly different organisms is based on the same complex biochemical compounds. The protein cytochrome c, essential for aerobic respiration, is one such universal compound.

• The universality of cytochrome c is evidence that all aerobic organisms probably descended from a common ancestor that used this compound for respiration.

• Certain blood proteins found in almost all organisms give additional evidence that these organisms descended form a common ancestor.

• Such biochemical compounds, including cytochrome c and blood proteins, are so complex it is unlikely that almost identical compounds would have evolved independently in widely different organisms.

• Further studies of cytochrome c in different species reveal variations in the amino acid sequence of this molecule. For example, the cytochrome c of monkeys and cows is more similar than the cytochrome c of monkeys and fish.

• Such similarities and differences suggest that monkeys and cows are more closely related than are monkeys and fish.

• Scientists have similarly compared the biochemistry of universal blood proteins. Their studies reveal evidence of degrees of relatedness between different species. This evidence implies that some species share a more recent common ancestor than other species do.

Biogeography•Some animals look similar to other

animals in different parts of the world•Migration!•Evolution is linked with climate and

geological forces (plate tectonics).

Vestigial Structures

•“Stuff we don’t need anymore but we must have needed it way back in the past”

•Definition: Structures that are reduced forms of functional structures in other organisms.

•Gives us a clue as to how that organism has changed over time!!!

•Examples:

Examples of Vestigial Structures• Snakes have tiny pelvic

bones!• Whales have tiny pelvic

bones, even today! ▫Why?

• Kiwi wings – much to small, can’t fly. ▫Why would a bird have

wings if it can’t fly?• Appendix – important in

digestion for many mammals, but not humans!

Human Vestigial Structures

Homologous Structures•Anatomically similar

structures inherited from a common ancestor

•“Same setup” – the limbs of many organisms have the same basic anatomy

Analogous Structures•Anatomically similar but not evidence of evolution•Can be used for the same purpose and similar in

construction but not inherited from a common ancestor