Evidence for Evolution Review (what we’ve learned so far) Mutations and sexual reproduction/ crossing over provide variability within species. Some traits.

Evidence for Evidence for EvolutionEvolution

Review (what we’ve learned so far)Review (what we’ve learned so far) Mutations and sexual reproduction/ Mutations and sexual reproduction/

crossing over provide variability within crossing over provide variability within species.species.

Some traits give individuals within a Some traits give individuals within a species an advantage - those species an advantage - those organisms live longer and/or reproduce organisms live longer and/or reproduce more = natural selectionmore = natural selection

Over time, the population shifts so that Over time, the population shifts so that all (or most) individuals have this trait = all (or most) individuals have this trait = adaptationadaptation

Evolution of a whole new species Evolution of a whole new species (speciation) takes long periods of time(speciation) takes long periods of time

Main evidence for evolutionMain evidence for evolution

FossilsFossils

Geographic distribution of organisms Geographic distribution of organisms around the worldaround the world

Artificial selectionArtificial selection

Homologous structuresHomologous structures

Vestigial structuresVestigial structures

EmbryologyEmbryology

Comparative analysis of DNAComparative analysis of DNA

FossilsFossils

The bulk of our The bulk of our understanding about understanding about ancient lifeancient life

Bacterial cells to complete Bacterial cells to complete T-Rex skeletonsT-Rex skeletons

How are fossils formed? How are fossils formed? (Short video)(Short video)

http://www.teachersdomain.org/6-8/sci/life/div/becfossil/index.html

http://kcts9.pbslearningmedia.org/resource/tdc02.sci.life.evo.becfossil/becoming-a-fossil/

Fossil QuestionsFossil Questions

How are fossils formed?How are fossils formed?

Organism dies and is covered by sediments Organism dies and is covered by sediments (mud, sand, silt, clay, ash)(mud, sand, silt, clay, ash)

Calcium in bones replaced by minerals in Calcium in bones replaced by minerals in the sediments over timethe sediments over time

Sometimes imprints can also be preserved Sometimes imprints can also be preserved (tracks, leaf impressions, etc.)(tracks, leaf impressions, etc.)

It’s a pretty rare event to find complete fossils in good condition. After millions of years any number of things could happen to destroy fossils before they are discovered and documented by scientists, if the animal even fossilizes at all. Finding well preserved baby animals is particularly hard, since they are more likely to have gotten trampled or eaten after their death. Phillip Currie from the

University of Alberta has recently uncovered a juvenile Chasmosaurus belli that was so complete and intact, he was actually able to speculate about the cause

of death.The fossil was found in what used to be a riverbed. This has led Currie and his

research team to believe that the baby didn’t die at the hands of a larger creature. It most likely wandered out

too far into the water and got caught in the current. Unable to save itself, it drowned and settled at the bottom of the river, where it would eventually

become fossilized in the sediment. The body was so well preserved, Currie was actually able to see impressions from the baby’s skin in the surrounding rock.

Why do most living things not Why do most living things not leave fossils behind?leave fossils behind?

Organism was eatenOrganism was eaten Didn’t die in correct environment to be Didn’t die in correct environment to be

preserved preserved Body has no ‘hard parts’ (shell, skeleton)Body has no ‘hard parts’ (shell, skeleton)

• Virtually absent from fossil record: flatworms, Virtually absent from fossil record: flatworms, jellyfish, sea slugs, etc.jellyfish, sea slugs, etc.

How are fossils uncovered?How are fossils uncovered?

Erosion brings fossils back to surfaceErosion brings fossils back to surface Humans dig to find fossilsHumans dig to find fossils

• Determine specific locations that are likely spots Determine specific locations that are likely spots to hold fossilsto hold fossils

How do scientists determine the How do scientists determine the age of fossils?age of fossils?

Technique known as:Technique known as:

Radiometric DatingRadiometric Dating

http://www.teachersdomain.org/6-8/sci/life/div/radiodating/index.html

http://kcts9.pbslearningmedia.org/resource/tdc02.sci.phys.matter.radiodating/radiometric-dating/

Transitional Transitional FossilsFossils

a.k.a. Intermediate a.k.a. Intermediate fossilsfossils

Important because they:Important because they: Provide a link Provide a link

between past forms of between past forms of an organisman organism

Transitional Fossils: Orca exampleTransitional Fossils: Orca example

We’ve believed for a long time that We’ve believed for a long time that whales (and seals, otters, etc) were whales (and seals, otters, etc) were mammals because they share COMMON mammals because they share COMMON FEATURES with land mammalsFEATURES with land mammals

1.1. Warm-blooded (endothermic)Warm-blooded (endothermic)2.2. Give live birth and provide milk for youngGive live birth and provide milk for young3.3. Have hairHave hair4.4. Similar respiratory, circulatory, nervous, Similar respiratory, circulatory, nervous,

and digestive systemsand digestive systems

Transitional FossilsTransitional Fossilswhales evolution example:whales evolution example:

Modern whaleModern whale – – totally aquatictotally aquatic Nostrils on top of head = blowholeNostrils on top of head = blowhole Tail evolved into flipperTail evolved into flipper Ears modified directional hearing underwaterEars modified directional hearing underwater

BasilosaurusBasilosaurus – – aquatic aquatic flippers & long, flexible bodyflippers & long, flexible body small, weak hind legssmall, weak hind legs Nostrils on top of headNostrils on top of head

AmbulocetusAmbulocetus – – amphibious (both land and water)amphibious (both land and water) Forelimbs equipped with fingers/small hoovesForelimbs equipped with fingers/small hooves Hind feet & tail adapted for swimmingHind feet & tail adapted for swimming Nostrils on top of snoutNostrils on top of snout

Mesocynids– Mesocynids– terrestrialterrestrial Tetrapod – limbs adapted to moving on landTetrapod – limbs adapted to moving on land Ears adapted to hearing in airEars adapted to hearing in air Nostrils in front of snoutNostrils in front of snout

What is this picture of??What is this picture of??

Are you 100% Are you 100% sure?sure?

What is this picture of??What is this picture of??

Are you still Are you still 100% sure?100% sure?

Can we ever Can we ever truly fill in all truly fill in all of the gaps??of the gaps??

Gaps in Fossil RecordGaps in Fossil Record

We have fossils for 350,000 species of We have fossils for 350,000 species of ancient organisms…ancient organisms… That’s only a tiny fraction of total number of That’s only a tiny fraction of total number of

species that have ever lived!!!!!species that have ever lived!!!!!

We fill in the ‘gaps’ using logical reasoning We fill in the ‘gaps’ using logical reasoning as well as other lines of evidenceas well as other lines of evidence

EmbryologyEmbryology

Early stages of related animals are very Early stages of related animals are very similarsimilar

Similarity in the development from egg to Similarity in the development from egg to adult form (ontogeny) is evidence of adult form (ontogeny) is evidence of common ancestrycommon ancestry More similarity in ontogeny = more recent More similarity in ontogeny = more recent

common ancestor (more closely related)common ancestor (more closely related)

Comparative Embryology of VertebratesComparative Embryology of Vertebrates

Which one is the human? The rabbit? The fish? The salamander? The tortoise? The hog? The calf?

Comparative Embryology of VertebratesComparative Embryology of Vertebrates

So when do organisms begin to look different? During _______?

HUMAN

Comparative Embryology of VertebratesComparative Embryology of VertebratesWhich two seem more genetically related/separate from the others?? How do you know?

Geographic Distribution on Geographic Distribution on Organisms around the worldOrganisms around the world

Similar environments around Similar environments around the world contain organisms the world contain organisms that are DIFFERENT species that are DIFFERENT species but have similar anatomies but have similar anatomies and/or behaviors because…and/or behaviors because…

similar selective pressures similar selective pressures lead to common structures lead to common structures and or behaviors that aid and or behaviors that aid survival and/or reproductionsurvival and/or reproduction

Example: Example: meerkats and meerkats and prairie dogsprairie dogs

Another example of Another example of similar geography similar geography resulting in similar resulting in similar structure in unrelated structure in unrelated organisms:organisms:

beavers,beavers,muskrats,muskrats,coypus,coypus,& capybaras& capybaras

Beaver

Muskrat

Beaver and Muskrat

Coypu

Capybara

Coypu and Capabara

Geographic Distribution, cont.Geographic Distribution, cont.

Additionally, Additionally, organisms from a organisms from a common ancestor will common ancestor will change in structure change in structure and function to adapt and function to adapt to a new, specific to a new, specific environment (niche)environment (niche)

Prime example: Prime example: islands!islands! the more isolated the the more isolated the

island, the more island, the more distinct its organismsdistinct its organisms

Artificial SelectionArtificial Selection When humans breed organisms with desired When humans breed organisms with desired

trait repeatedly until desired characteristic is trait repeatedly until desired characteristic is obtained.obtained.

Plant and animal breeders have long taken Plant and animal breeders have long taken advantage of the heritability of traits to improve advantage of the heritability of traits to improve crops and livestock and petscrops and livestock and pets

Humans use the same mechanisms to change Humans use the same mechanisms to change organisms that nature usesorganisms that nature uses Artificial – Artificial – humanshumans ‘select’ the best traits ‘select’ the best traits Natural – Natural – naturenature ‘selects’ best, or ‘most fit’ traits ‘selects’ best, or ‘most fit’ traits

Artificial Selection ExamplesArtificial Selection Examples

Hundreds of varieties of peppers – all originated from an initial species

Different breeds of dogs and cats ‘created’ by man by selecting for desirable traits (fast, sociable, good smell, short fur, etc.)

Homologous StructuresHomologous Structures

Similar structures in a variety of different Similar structures in a variety of different organisms organisms

Shared trait(structure) provides evidence that Shared trait(structure) provides evidence that the organisms had a shared common ancestor the organisms had a shared common ancestor with that traitwith that trait

Example:Example:

Homologous Homologous bone bone structure in structure in forelimbs of forelimbs of all mammalsall mammals

Vestigial StructuresVestigial Structures As species evolve over time… some structures become As species evolve over time… some structures become

unnecessary to survival of organismunnecessary to survival of organism Over time become reduced (vestiges) Over time become reduced (vestiges) Eventually disappearEventually disappear

ExamplesExamples: :

Human Tailbone Human Tailbone (coccyx)(coccyx) - These fused vertebrae are the only vestiges that

are left of the tail that other mammals still use for balance, communication, and in some primates, as a prehensile limb. As our ancestors were learning to walk upright, their tail became useless, and it slowly disappeared.

Hind Leg Bones in WhalesHind Leg Bones in Whales

Comparative Analysis of DNAComparative Analysis of DNA

If all organisms evolved from same original If all organisms evolved from same original ancestors (3.5 bya), then all should share ancestors (3.5 bya), then all should share some common DNAsome common DNA

YES! all life shares same general YES! all life shares same general machinery for regulation of cell division, machinery for regulation of cell division, building cell parts, etc.building cell parts, etc.

Greater DNA similarity between 2 species Greater DNA similarity between 2 species = more recent common ancestor= more recent common ancestor