Evolution: the evidence pt 2. (7)

What is the theory of Evolution

• Things evolve | populations change over time

• Evolution usually happens gradually | populations change over hundreds to thousands of years

• Speciation occurs | one species splits into two or more species

• All species share common ancestry | splitting of lineages from one ancestral form

• Much of evolutionary change was caused by natural selection | the sole process producing adaptation, the ‘appearance’ of design

When does speciation usually occur?

In isolation and no gene exchange between species

What is the DNA difference between chimps and humans?

1-4%

When did humans and apes split?

5-7 million yrs ago

What are hominins 

human side of split since the human and chimp common ancestry

What does a cladogram show?

• See what is closely related and distantly related 

• Diverged in the distant past --> distantly related 

What is a karyotype?

organized profile of an individual's chromosomes, displaying their number, size, and shape, often presented as a laboratory-produced image

What is the difference between chimps and humans in karyotype?

• humans- 23 pairs of chromosomes (46)

• Chimps- 24 pairs of chromosomes (48)

What is one prediction of what happened to the extra chromosome between humans and chimps?

• It was lost, we didn’t need those genes

• Unlikely prediction

  • Unlikely to lose tons of genes --> usually conserved (doesn't code much but still need them) 

What is Prediction 2 of what happened to the extra chromosome between humans and chimps?

•A Creator distributed the genes differently, didn’t need as many chromosomes

• unlikely

What is Prediction 3 of what happened to the extra chromosome between humans and chimps?

• There was a fusion event

• most likely

What causes a formation event?

• Mutations can occur 

• Chromosomal rearrangment:

  • chromosomes may not align correctly , replicated incorrectly, or break apart —> might lead to death (some important genes were messed up) —>changes does not manifest in population 

• Death doesn’t always occur

What is the evidence for a fusion event?

• conservation of gene structure/order 

  • all same genes are basically there (arranged by nucleotides) --> fusion events probable

• common ancestry

What happened to the extra chromosome between humans and chimps?

• Human chromosome (2) and chimp chromosome: in the past --> telomerase (end of chromosomes) fused together between 2A and 2B 

  • One lineage humans: fusion event --> happened only once 

    • Individual survived (all genes there but just rearranged) 

    • Arrangement was very adaptive --> passed through generations until all humans have 23 chromosome pairs 

  • Fusion event happened before ancestors started radiating around the world (5-6 million years ago) 

What are primates?

• members of order of mammals

• distinguished by large brains, nails instead of claw,

• front facing eyes,

• opposable thumbs in some

What should we see in fossil records if evolutionary theory is true?

• First detectable traces of life on earth should be simple forms and only later would more complex forms appear

Why should life get more complex as time goes on?

more time for organisms to develop adaptations and variation

Does life always get more complex?

No

What is a fossil?

• remains of a once living orgnaims preserved in sedimentary rock

When do fossils occur?

when organismal features are preserved long after death

How complete is the fossil record?

Incomplete

Why is the fossil record incomplete?

• • Soft-bodies preserved less than hard

• Rare species even rarer

• Lack of sedimentation

• Highly dependent on conditions – few were fossilized

What is permineralization? 

Organism is buried, filled with mineral rich waters, turns tissue to stone; in some cases, in exceptional detail (cellular level)

What allows for multiple fossils to be captured at once?

Mass extinction event

What conditions allow for fossils to form?

• Found in anoxic/anarobic environment (no oxygen): 

  • Usually wet depressed area 

    • Organism quickly covered in mud, clay that blocks oxygen in that space --> limits what could decompose 

  • Animal tissues change form organic to stone (inorganic)  (individual cells are replaced) 

What are trace fossils?

• fossils of trails

• preserve record of anatomy and behavior

Why is it important to cover organism quickly with sediment for fossil to form?

limits what bacteria/ other organisms can decompose of the body

What groups rarely form fossils?

• bacteria

• single celled eukaryotes

How are plants/wood petrified?

• Earthquake / volcanoes bury’s forest 

• Organic tissue (plant tissue) --> converted to stone 

How does wood petrification help discover Earth’s history?

• count the rings

• see what environmental conditions were back then

  • size, color, width, etc change based on environmental factors around them

What is the Messel Shale?

• gap in earth that opens to cavern filled with mud, dirt, clay 

• hot bed for fossils

Why the Messel Shale a hot bed for fossils?

• animals drop in gap —> creates layer cake of animals and sediments

• well preserved conditions —> imprint of fur remains

• Deeper you go the older the animals

What does resin/sap turn into?

• amber

Is amber a form of permineralization?

No

How do fossils form with sap?

• resin and sap flow out of tree —> collects overtop of insect

• falls into anoxic environment —> turns into amber

Within fossils, what usually stays intact?

• hard parts

• DNA often does not remain intact —> but some DNA proteins can still be analyzed

What are the strengths of fossils?

• show evolutioning linkages through dinosaurs

What fossils have been preserved from the recent times?

• Baby mammoth – 40,000 ya

• Otzi – 3300 BCE

• Tollund Man 405-380 BCE

How does ice preserve fossils?

• organic material can be preserved (ex: collect food last eaten)

  • slows down decomposition

How was the Tollund Man preserved?

• Imbedded in peep bog (very acidic) 

• Thrown in bog --> preserved in acidification of bog 

• Not undergoing perminierlization--> will decompose and is not a rock currently 

What is a geological timescale?

series of time divisions that mark Earth’s long history

What can be found at the bottom of an open face rock/mountain?

• made of mud

• deposited by sea 500 mil yrs ago

• contains oldest fossils of arthropods called trilobites

What can be found in the middle of an open face rock/mountain?

• red=limestone

• deposited by oceans 335 million yrs ago

• traps marine fossiles

What can be found at the top an open face rock/mountain?

• white beds = terrestrial land

• deposited 260 million years ago

• find footprints of vertebrate animals

how are geological strata arranged?

• • Oldest = Deepest

• Geological processes may move strata after formation

• Fossils in particular strata represent relative age

What is an isotope?

each of two or more forms of the same element that contain equal numbers of protons but different numbers of neutrons in their nuclei

What is radiometric dating?

Dating ancient materials using the decay of radioisotopes as a yardstick

What gives absolute age?

Radiometric age

What do fossils in particular strata represent?

relative age

What is half-life?

The time it takes for an amount of a substance to reach half its original value. Radioactive half-life is the time it takes for half of the atoms in a given sample of a substance to decay.

What isotopes are used for radiometric dating?

• Recent (-50,000 years) - Carbon, 14C

• Far back (millions of years) – Potassium-Argon

• Older (millions to billions years) – Uranium –> Lead

How is Uranium 235/238 used for radioactive dating?

• at Half- life turns Uranium turns into lead

• Find proportion in fossil and estimate how much was in that environment when it was alive

• used to time calibrate 

What is the process of radiocarbon dating?

1. Sun emits cosmic radiation --> excites neutrons--> collides with elementals in atmosphere (oxygen, nitrogen, carbon etc) 

2. Neutrons collide with Nitrogen 14 (14N) (most common in atmosphere) —> kicks out protein —> turns it into Carbon 14 

3. Carbon 14 in atmosphere connect with oxygen --> forms CO2 

4. CO2 absorbed by plants and photosynthesis to create energy 

5. Plants absorb Carbon 14 (formerly nitrogen)+ oxygen

6. Something eats plan  --> carbon 14 is now part of the animals (tissues and bones metabolized) 

7. Animal dies or plant dies and buried —> 14C decays to more stable 14N

What is 14C half-life?

• 14 C turns in 14N in 5730 yrs

• in another 5730 yrs, half of remaining 14C decays to 14N and so on

how is radiocarbon dating used?

• The level of 14C in plants and animals when they die approximately equals the level of 14C in the atmosphere at that time

• Gives template : how much Carbon 14 in fossil --> how much carbon existed in the past in the atmosphere --> can link to time period that it would have been alive 

What has radiocarbon dating directly compared with?

• Directly compared with known year-by-year data from tree-ring data (~13,000 years),

• ocean and lake sediments, corals and stalagmites (now ~55,000 years)

What does the level of 14C in plants and animals show?

• The level of 14C in plants and animals when they die approximately equals the level of 14C in the atmosphere at that time.

What is the error in Uranium-lead radioactive dating?

2 million years in 2.5 billion yrs

How were rocks in the beginning of Earth formed?

• Bacterial appear 3.5 billions years ago 

• Rock formed by bacteria growing and exuding slime --> gets covered in mud --> fossilzes --> creates rock 

What are planktonic diatom (rhizosolenia)?

• free floating algae in ocean

• have a support scaffolding system

How did rhizosolenia diverge?

• Magnetic cores of the Earth flip once in a while —> changes environment (weather, ocean structure)

• Causes sediment columns to diverge

  • one stays at 4mm

  • others go down to 1mm

What were early horses (Hyracotherium) like?

• lived in America 

• Lived in forests

• size of foxes

• had fingers

• eat soft vegetation

How did the modern form of a horse form?

• Marshal’s reconstruction

• leave the forest —> speciation in more open environment

How did leaving the forest speciate early horeses?

• Fingers become less valuable --> better for one hoof (no need to creep around roots) 

• Become larger to avoid predators 

• Change mouth --> molars become flat (eating grasses and not bugs on trees) 

• Become even larger --> leave north America to Russia and Asia 

  • Increased Diversity in that region 

What happened to the New World horses?

• ice age wiped out horses in North America

  • only lived in Asia

How did modern horses return to NA?

• Horses came back through colonization after being extinct

  • only domesticated left

• No wild horses left (except one artificial kept?)

  • Only Eqqus

What shape does changes in species occur in?

• branching pattern (not linear)

  • different distinct groups going extinct and others going on 

What should transitional forms show?

connections between modern groups with their common ancestor

What traits do intermediate species show?

traits of both the common ancestor and new descendent

• ex: transitional form of birds and dinosaurs —> structure similar to birds and dinosaurs

Where did terrestrial salamanders come from?

• became terrestrial from marine ancestor

What does Tiktaalik show?

• Transitional early form of life leaving water

What is retrodiction?

Something that make sense only in light of evolution, but is not necessarily predicted by evolution

Which vestigial trait do wales have?

• Hind limbs and pelvis

• shows atavism?

What is atavism

• Vestigial structure that showed its true form

• reappearance of an ancestral trait that was lost during evolution

What vestigial structure shows in dolphins?

• hind limbs

• Some Dolphins have mutation where hind limbs actually grow (hind fins)

What are vestigial genes?

Dead genes (silent)

What does the human fetal yolk sac show?

• Vestigial genes: genes to produce a yoc sac, but they are silent

  • humans have genes for making yolk proteins —> 3 genes —> they are nonfunctional (silenced)

• human fetal yolk sac - empty

Why can’t humans make vitamin C?

• vestigial character

• Could get vitamin C from outside sources due to new diet —> NS said it was too expensive to create

What are endemic animals?

species that naturally occur only within a specific geographic area, such as an island, region, or country, and are not found anywhere else in the world

What is there a lack of in Oceanic islands?

• mammals

• Lord Howe, Galapagos

• mammals on continental islands (Madagascar) but not oceanic islands

What species are more often found in oceanic islands?

• endemic plants, birds, and insects

Why are there more endemic plants, birds, and insects on oceanic isands?

They are better at dispersal 

What do mass extinctions enable?

provides evolutionary opportunities for survivors on a grand scale

When did the Earth form? 

4.6 billions yrs ago

When was the first evidence of oxygen-rich environment? 

• proterozoic eon

• 2500 million years ago

When was the first evidence of life?

• Archean eon

• 4025 million years ago

When was the first animal fossil appear?

• proterzoic eon

• 680/541 million years ago

When was the first eukaryotic microfossile appear?

• proterzoic eon

• 2000 million years ago

When was the Archean eon?

4 billion - 2.5 billion years ago

When is the first evidence of lfie?

• Archean era

• closer to 4 billion years ago

When was the proterozoic era

2.5 billion - 541 million years ago 

What happened in the beginning of the Proterzoic era?

First eukaryotic microfossiles

What happened near the end of the proteerozoic eon?

major diversification of eukaryotic organisms

What happened near the very end of the proteerozoic eon?

first animal fossiles 

When is the phanoerozoic era?

541 million yrs ago to now

What is biogeography?

• the study of the geographic distribution of plants, animals, and other forms of life.

• gives geographical data