Unit 9 Evidence of Evolution

How can we tell the difference between a rock and a fossil? Why do we care about

fossils in the first place?

Paleontologists trained to recognize structures and patterns of anatomical features (trained in both anatomy and geology). Fossils are also used as evidence for evolution and fossils give useful information about environments and the ways past organisms lived.

How do fossils form? How does this affect what organisms (or what parts of organisms) are more or less likely to become fossils?

Fossils form in sedimentary rock. Remains must avoid being trampled, scavenged, and decomposed. Being buried in dry, anoxic environments are best. Hard part>Soft parts and Large bones>Small bones. Occurs through impression or mineralization.

What are the three main types of rock? Which one is most likely to have fossils in it, and why?

Sedimentary(Layers of Sediment-ex: limestone, sandstone), Metaphoric (Heat+Pressure), Igneous (ex. cooled lava/magma). Sedimentary is the most likely to have fossils in it because it is being layered around sediment and isn’t being exposed to heat or other factors.

What is the principle of superposition? What is the principle of faunal succession? How

can we use these to determine the age of a given fossil?

The principle of superposition describes how the older layers are on the bottom and the newest laters are on the top in a sequence of sediment. The principle of faunal succession describes how fossil animals succeed one another in a specific, recognizable order in rock layers. We can use both of these to determine the age of a given fossil relative to how high or low it is in a sequence of sediment and determine whether or not one fossil animal is younger or older than another.

What is radiometric dating? What kind of rocks does it work on? How can we use these to determine the age of a given fossil?

Radiometric dating uses the rate of decay of radioactive isotopes to assign numerical ages to fossils. It works on igneous rocks. By determining the percentage of the parental isotopes that has decayed its daughter isotopes we can determine how many half lives have occurred. In knowing the relative half-life of an isotope we can then determine a fossils age.

What is a half-life? Be able to go from # of half-lives to expected % of parent isotope

remaining (or expected ratio of parent:daughter isotopes), and vice-versa.

A half life is the amount of time it takes for half of the parental isotope to decay into the daughter isotope. For 1 half life-50% parent isotope remaining, 2→1/4, 3→1/8, 4→1/16…

What are transitional fossils? What are some examples of transitional fossils (or

transitional series) in the fossil record, and why are they considered transitional?

Transitional fossils are fossils that exhibit intermediate traits between an ancestral forma and its later descendants. Example of transitional fossils are Tiktaalik (between fish and tetrapods) and Archaopteryx (between reptiles and birds)

Be able to define and recognize homologous traits

Definition: A structure present in a common ancestor and its descendants (even if modified), or the same structure under every variety of form and function

Ex. The bones in the forelimb of a horse are homologous to the bones in the fin of a fish.

What are vestigial structures and what do they tell us about the history of life?

Vestigial structures are structures inherited from an ancestor that no longer serves a clear function. They tell us that life has a shared history and has changed over time

How old is the Earth?

4.5 billion years

How long has life existed on Earth?

3.5 billion years

What was the earliest life on
What was the earliest life on Earth like?

Prokaryotes, later evolved primitive photosynthesis

When did eukaryotes evolve? Multicellular?

1.5 billion year ago, 1.2 billion years ago

What is the structure of the geologic time scale? (___ subdivided into ____) How did we determine the boundaries between these divisions?

Eras are subdivided into periods. Boundaries between eras are determined by major changes in life forms, specifically mass extinctions where many species disappear and new ones emerge. 

What event marked the beginning of the Paleozoic?

The Cambrian Explosion in which multicellular eukaryotic animals diversified. Most major animal phyla appeared for the first time in the fossil record. All animals still marine. (Approximately 540 mya)

What event marked the end of the Paleozoic and the start of the Mesozoic?

Permian Extinction/Great Dying, wiped out 96% of marine species and 70% of terrestrial vertebrate species (approximately 250 mya)

What events marked the end of the Mesozoic and the start of the Cenozoic?

K/T Boundary (Cretaceous-Tertiary Period) or End-Cretaceous Extinction (approximately 65 mya), dust stopped photosynthesis, Chicxulub Crater, birds and mammals diversify afterwards.

Approximately when were the two biggest mass extinction events in the history of life on Earth? Which one was bigger? What are believed to be the causes of each?

1.End-Permian extinction, approximately 250 mya, biggest extinction, causes: massive volcanoes, glaciers formed, sea level drops, less oxygen in the air and in the oceans

2.End Cretaceous extinction (K/T Boundary), 65 mya, 2nd biggest extinction, causes: meteorite (Chicxulub Crater) created dust and stopped photosynthesis

In many of the streams around Gainesville, you can find fossilized shark teeth that are loose on the stream bottoms (i.e., they are no longer embedded in rock.) The presence of these teeth gives strong evidence that

most or all of Florida was once under water

The presence of different types of fossils at different positions (depths) in a geological formation indicate a change in the age of the fossils. The area where the fossils change from one type to another is termed a:

boundary layer

Evidence for Evolution

similarities in anatomy and development, the presence of a fossil record, similarities in DNA sequence