Evidence for Evolution Biogeography Fossil Records Comparative anatomy Comparative embryology Molecular biology Evolution is consistent with all scientific observations!

Biogeography Species are most closely related to those near them Rain forests in different parts of the world have very different species Species tend to be very similar to the fossils found in there area – but with some changes

Fossil Records The age of different fossils matches what we would expect I.e. we find that brain size has increased over time

Fossils Con. Oldest vertebrate fossils are fish, then amphibians, reptiles, mammals and birds Many hypothesized intermediate species have been found, i.e. Artie, Lucy, fish with legs

Comparative Anatomy The anatomies of related species are similar, even if they are used differently i.e. bones of humans, cats whales and bats are similar It seems unlikely a designer would make a bat's wing similar to a whale's fin Homologous Structures

Vestigial Organs Leftover body parts that do not help a species i.e. whales still have pelvises and remnants of leg bones These structures serve no purpose in the modern animal

Comparative Embryology Similar species develop in very similar ways Especially early in development, before lots of specialization has occurred

Molecular Biology Closely related species are closely related in their genetic codes Also supports idea that all species are related- all species share DNA and some proteins

The “Theory” of Evolution The closely related nature of all life is really not debatable Natural selection is really the theory Well documented and thoroughly supported- like the “Theory” of Gravity

Macroevolution and Speciation Microevolution explains how populations can change over time But how do new species or other taxonomic groups arise?

Geographic Speciation The formation of new species usually occurs when 2 populations are separated and evolve differently Eventually the species have changed so much that they can no longer reproduce

Reproductive Isolation A byproduct of genetic differences Different: Mating behaviors Mating times Mating locations Mating “structures” Gametes Or offspring that are infertile- no mixing of genes

Reproductive Isolation  Speciation With no gene flow between the population, they become more and more different This usually takes thousands to millions of years

Exception - Polyploidy Occasionally plants end up combing their full genomes (instead of half) leading to a doubling of the chromosome # Instantly forms a new species Extremely significant in plant evolution

Biological Definition of Species 2 populations that cannot naturally mix genes Due to any of the reproductive isolation methods Not a perfect system

Evolution is Always Occurring Usually just slowly Bacteria and viruses change over time – we must constantly come up with new antibiotics and new vaccines

Changing Environments Accelerate Evolution New habitats open up opportunities for evolution Leads to adaptive radiations – where many groups evolve from a single ancestor i.e. after the fall of dinosaurs- many mammal groups evolved

One Major Change leads to many New Adaptive Radiations Imagine the first species that could breath in air Many new species would quickly evolve – lots of territories to take over! Then evolution would slow down once there is competition for space

Extinction Is the norm Most species go extinct- but new ones survive There have been at least 5 major mass extinctions

Phylogeny and Taxonomy Tracing Evolutionary History

Phylogenetic Trees Show how each species is related to other closely related species Shows common ancestors Use fossils and other evidence to reconstruct an organisms history

Monophyletic Taxa We want to trace species to a single common ancestor for each taxa, and include every species that descended from that ancestor i.e. all mammals can be traced to a single mammalian ancestor

Monophyletic Taxa Includes a species and every single one of it’s descendents I.e. Primates – include the primate ancestor and all of it’s descendents (including us!)

NOT a Monophyletic Taxa Plants and Animals (because fungi and other species share the same common ancestor) Grouping all monkeys/apes together BUT not including humans Reptiles (birds share the same common ancestor and should be included in reptiles!)

Comparing fossils/anatomies/structure/devel opment How Do We Make Trees? Comparing DNA Comparing fossils/anatomies/structure/devel opment

Molecular Biology Provides Great Evidence for Classification Similarities in DNA sequence Comparison of proteins The more DNA changes/protein differences, the less closely related the species

Molecular Analysis Advantages Disadvantages Most accurate Large numbers of traits/proteins to analyze Allows us to differentiate between closely related species that appear very similar Individuals of the same species differ in DNA Can be confusing

DNA Base Pair Differences 1 2 3 4 5 x 10 20 30 40

1 2 3 4 5 x 10 20 30 40

Practice (# of base pair differences in a gene) Cat Dog Wolf Skunk Otter x 28 26 15 14 2 10 9 8

Phylogenetic Tree Time

Homology/Anatomy Analysis Find an adaptation that is present in one lineage, but not in another The phylogenetic tree branches when these new features evolved

Cladistic Tables Different Species 1 2 3 4 5 Character A? Character B? Yes Character B? No Character C? Character D? Character E?

1 2 3 4 5 Character A? Character B? Character C? Character D? Yes Character B? No Character C? Character D? Character E?

Practice Reptiles Plants Mammals Bacteria Amphibians Y N DNA Organelles Cell Walls Amnion Hair Reptiles Y N Plants Mammals Bacteria Amphibians

Ancestral reptile Time Ancestral fish Ancestral animal

Anatomy Analysis Homologous structures show relationships Advantages Disadvantages Homologous structures show relationships Allows us to determine when changes occurred (using fossils) Best way to analyze extinct species Analogous structures do not and can be confused Not all species leave fossils The fossils we have collected are incomplete

Homology vs. Analogy Homology means two features are similar due to ancestry Wings in bats, arms in humans, fins in whales Called homologous structures Caused by divergent evolution Analogy is when two organisms have similar features but are not closely related Wings in bats and birds Caused by convergent evolution Evolved the same solution

Embryology Analysis Advantages Disadvantages Allows us to see similarities even when adults of the species look very different I.e. reptiles and birds look more closely related Often similarities are lost later in development i.e. We have gills early on in development

We did not evolve from chimpanzees!