Evidence of Evolution FOR EVOLUTION

1. Fossils 2. Geographic Distribution 3. Homologies Evidence of Evolution 1. Fossils 2. Geographic Distribution 3. Homologies

1st type of Evidence FOSSILS

Fossil Record What is a fossil? -The preserved remains of a once-living organism. How do fossils help scientists? 1. Tells us what organisms lived long ago 2. Shows how the Earth’s surface has changed. 3. Help us understand what past environments may have been like.

How do we get fossils? Fossils are formed in SEDIMENTARY ROCK. If an organism dies and is buried by sediment rock, it’s bones are protected from rotting. Over time, more sediment layers build on top of the remains. Minerals replace all or part of the organism’s body. The preserved remains may later become exposed by erosion or the Earth’s movement.

How do we know the age of fossils? You have to DATE them!

Which fossil came first? Relative Dating Age of fossils RELATIVE to other rocks or fossils. 2. Radioactive dating ACTUAL age of fossils using the half life of radioactive isotopes

How does Relative Dating work? Rock layers form in order of age – the oldest layers on the bottom and the youngest on the top. Scientists use index fossils to compare the ages of fossils. Index fossil: a species easily recognizable, existed for a short period of time, and wide geographic range. *** Does NOT give age in years*** A B C D E

How does Relative Dating work? Looking at this mountain, where would you expect to find the oldest fossils? B C D E

Which is older B or D? Index Fossils Found Fossils SAME AGE

How Does Radioactive Dating Work? Throughout an organism’s life, it takes in Carbon-14. Once the organism dies it no longer takes in Carbon-14. The C-14 present in the plant or animal begins to decay at a certain rate called half-life. Half-life: the length of time required for half the radioactive atoms in an organism to decay. Carbon-14 half life: 5,730 years

What do you notice about the percent of original C-14 remaining? Decay of Carbon-14 Years from Present 5,730 11,460 17,190 22,920 28,650 34,380 40,110 45,840 51,570 Percent of Original C14 Remaining 100 50 25 12.5 6.25 3.13 1.56 0.78 0.39 0.20 What do you notice about the percent of original C-14 remaining?

What are the scientific explanations for data showing periods of stasis and sudden appearance in the fossil record? The fossil record suggests that evolution has proceeded at different rates for different organisms at different times.

Gradualism The idea that evolution involves a slow, steady change in a particular line of descent.

Showing very little change over time Example: Horseshoe crabs STASIS Showing very little change over time Example: Horseshoe crabs

Punctuated equilibrium Definition-Stable periods interrupted by rapid changes Rapid Evolution may occur because: A) small pop becomes isolated from the large population B)small group migrates to a new environment--FINCHES

2nd type of Evidence Geographic Distribution

Geographical Distribution Similar animals living in different locations are the product of different lines of evolutionary descent.

3rd type of Evidence Homologies 3 types of Homologies Anatomical Molecular Developmental (embryology)

Homologous Structures Homologous Structure: structures that have different mature forms but develop from the same embryonic tissues. Homologous structures provide strong evidence that all four-limbed vertebrates have descended, with modifications, from common ancestors.

Homologous Structures Not all homologous structures serve important functions. Vestigial organs: Organs in animals that are reduced in size to where they are just traces of homologous organs in other species.

Which structures are analogous? Homologous? Analogous Structures Analogous Structure: the similarity of structure between two species that are not closely related. Which structures are analogous? Homologous? Answer: Analogous- Bird to Insect, Bat to Insect Homologous- bird and bat wings

How do Analogous Structures Occur? Convergent Evolution: Species from different evolutionary branches may come to resemble one another if they live in very similar environments. Natural Selection may result in body structures and even whole organisms that look very similar without having the same common ancestor.

Embryology Pig Cow Rabbit Human Comparative Embryology: the comparison of early stages of development Pharyngeal (throat) pouches in embryotic stages shows one sign that vertebrates evolved from a common ancestor.

Molecular Biology Molecular Biology studies amino acid sequences of similar proteins in different species to discover the molecular history of evolution and common ancestor.

Molecular Biology Molecular Biology is the BEST WAY to determine how closely species are related to one another. Which two species are most closely related based on these nucleotide sequences? Species 1 ATGTAGCTG Species 2 ATCTGACTC Species 3 AGGTACCAG Species 4 AGGCGGCAG