Common Decent & Evolutionary Trees

Evolutionary Relationships depicted in an evolutionary tree Evolutionary relationships in branching trees

Evolutionary Relationships depicted in an evolutionary tree Nodes show that groups share a common ancestor & evolved from this ancestor

Each branch point represents the divergence of two species Branching

Carnivora Panthera pardus (leopard) Mephitis mephitis (striped skunk) Lutra lutra (European otter) Canis familiaris (domestic dog) Canis lupus (wolf) Species Genus Family Order FelidaeMustelidaeCanidae PantheraMephitisLutraCanis This evolutionary tree shows that leopards, skunks, otters, dogs, wolves all share a common ancestor. What other conclusions can you make form this phylogenic tree? Common Ancestor

How many common ancestors does G and H have? FOUR How many common ancestors does G and E have? TWO Which pair are more closely related G and H OR G and E? G and H share more ancestors.

In the below evolutionary tree which groups are more closely related J and K OR J and H? J and K are more closely related because they share two common ancestors I, A. And J and H only share one common ancestor, A

Reptiles is a groups that includes Crocodiles, lizards, tortoises and turtles. They all share a common ancestor However one of them is more closely related to birds? Can you guess which one?

Simple evolutionary tree of vertebrate groups

Evolutionary Tree Summary

Complicated Evolutionary Tree

How do we determine Evolutionary Relationships? – Physical characteristics Similarities and differences – Biochemical evidence DNA Similarities and differences Similarities in other molecules (example: ATP, Hemoglobin protein)

Evolutionary tree made based on phyical characteristics

Basing Evolutionary Trees on DNA DNA is a molecule All living things have DNA All DNA molecules have the same general structure DNA contains our genes. The more similarities we have in our DNA the closer we are related.

ALL DNA molecules have the same basic structure DNA Double Helix

The Components and Structure of DNA Watson and Crick discovered that hydrogen bonds can form only between certain base pairs — adenine only with thymine — guanine only with cytosine. This principle is called base pairing. P P P O O O P P P O O O G C TA

BASE-PAIRINGS CG H-bonds T A

Evolutionary Trees and DNA We looking at similarities between organisms scientists look at the base sequence of DNA. That is the sequence of ATCG

LE 25-15ab Sites in DNA sequence I Species 1 Base-change event Bases at site 1 for each species II III IV IIIIIIIV Biochemical evidence (DNA Similarities) can be used instead of physical characteristics

Common Decent Lab Today you are going to compare DNA segments with several primate species: – Gorillas – Chimpanzees – Humans – Unknown Common ancestors

Characteristics we share with primates Developed upright walk and extensive head rotation

Limbs/ Mobile Arms The arrangement of bones at shoulder permits brachiation movement – the bones of the shoulder girdle allow weight to be transferred via the arms

Characteristics we share with primates Hands/ Grasping Limbs – with long fingers and a separate opposable thumb

Characteristics we share with primates Reduction in nose and teeth Flattened noses – decrease ability to smell – Reduced in number of teeth

Based on your knowledge of the following animals select which hypothesis you think is correct. G = Gorilla C- Chimpanzee H= Human A = Common Ancestor Then give a clear reason for why you made your choice.