Do Now Do you think these two organisms evolved from a common ancestor? What evidence would you need to convince yourself?

Do Now: Gather the following... Evidence for Evolution handout in front (everyone) 1 laptop per table Open to our Schoology page PowerPoint and Notes Folder Evidence for Evolution WebQuest Links Folder

Evidence for Evolution

Group Work: Fossil Record

Fossil Record Layers of rock contain fossils Newer layers of rock cover older ones Creates a timeline Fossils can show a record of organisms that lived on Earth over a long period of time

What can you infer from this illustration??? Is there a transitional fossil? Punctuated equilibrium Is this gradualism or punctuated equilibrium?

Fossil Record Many fossils link early extinct species with species living today Example: Tiktaalik- “missing” link between land and sea animals.

A transitional species: Tiktaalik

Tiktaalik (2006) Like a fish complete with scales and gills Flattened crocodile head with unusual fins sturdy interior bones that would have allowed Tiktaalik to prop itself up in shallow water and use its limbs for support as most four-legged animals do.

Transitional Species: Aetiocetus

Horse Lineage

Transitional Species: Thrinaxodon Ancient reptile Thrinaxodon ancient mammal

Group Work: Embryological Evidence

Embryological similarities Embryos of related species show similar patterns of development in early stages Ex. Pharyngeal slits = evidence for common ancestor Pharyngeal slits Pharyngeal slits Hox genes- homeobox genes- group of related genes that control the body plan of an embryo along the head-tail axis Genes give information for segment identity, but do not form actual segment themselves Discovered Hox genes because of mutations: UBX gene (ultabithorax) duplicates thorax and gives you two AntP (antennapedia gene)- grow legs out of the head of fruit fly Pharyngeal slits- In fish- turn into gills In mammals- develop into eustacian tube, middle ear, tonsils, parathyroid and thymus = same structures in embryo turn into different functions in different species

Hox Genes

Group Work: Homology

Comparative anatomy Refers to structural similarities found between related organisms Homologous structures – Limbs that perform different functions but are built from the same bones Human Cat Whale Bat

Convergent Evolution: Analogous Structures Similar function but different structure Structures that resemble each other due to similar selective pressures and not to recent common ancestry

Convergent Evolution Species that are only distantly related (do not share a recent common ancestor) develop similar adaptations and resemble each other They live in similar environment and are exposed to similar selective pressures

Group Work: Vestigial Structures

Vestigial Structure: cavefish Remains of structures that were functional in ancestors Eyes on a blind cave fish

Vestigial Structure: EMU

Vestigial Structure: Whale Remains of structures that were important to the organisms’ ancestors but are not to the existing organisms

What about vestigial structures in humans? Long tail used for balance Ears more alert to predators Goosebumps make hair stand up, keep warm, scare predators Little toe was used for balance Wisdom teeth: used for grinding hard foods/leaves

Group Work: Comparative Biochemistry

Comparative Biochemistry Similarities in DNA and proteins Amino acid sequences can be compared among various species for minor changes The more similar the code, the closer related

Biochemical/Molecular Data Types of Organisms human monkey pig duck turtle fish moth yeast (Candida) 10 20 Number of Amino Acid Differences Compared to Human Cytochrome c 30 Branch points tell the number of amino acids that differ between human cytochrome c and the organisms depicted 40 50

Percent Agreement between Beta Globin of Various Species Human Chimp Gorilla Red fox Dog Polar bear Horse Rat Chicken 100. 99.3 91.1 89.7 83.6 81.5 69.2 91.8 90.4 82.9 80.8 68.5 98.6 95.2 80.1 72.6 94.5 79.5 71.2 71.9 76.0 67.8 65.8

Biogeography Geographic distribution of species How could this be evidence? Darwin notes that tortoise species in tropical Galapagos more closely resembled tortoises on the mainland than those on distant tropical islands Similar species = descendents of immigrants There was a closer match between geographically nearby species, even when the environments for the two differed THAN there was between that species and other species living in the same type of environment but geographically distant

SUMMARY SHEET What do you think? Of these four (in your packet), which do you think is the strongest evidence for evolution?