Debrief of Evidence for Evolution Take notes in your packet

Station 1: Comparative Embryology Comparative embryology = the science dealing with the comparison of different organisms’ pre-birth (or pre-hatching) development. VS.

Station 1: Comparative Embryology

Station 1: Comparative Embryology

Station 1: Comparative Embryology How does this serve as evidence that supports the Theory of Evolution? Argument: the early development of these species is similar because they each evolved from a common ancestor.

Station 2A: Homologous structures

Station 2A: Homologous structures Homologous structures: structures that are similar across different species due to common ancestry.

Station 2A: Homologous structures How does this serve as evidence that supports the Theory of Evolution? Argument: even though the forelimbs have very different functions, their similar bone structure suggests that they evolved from a common ancestor.

Station 2A: Homologous structures More examples:

Station 2B: Vestigial structures

Station 2B: Vestigial structures

Station 2B: Vestigial structures Vestigial structures: homologous structures that have lost most or all of their function (vestige = “a remnant of”)

Station 2B: Vestigial structures How does this serve as evidence that supports the Theory of Evolution? Argument: these “useless” structures are remnants of structures that were once useful in an evolutionary ancestor (i.e. tailbone actually supported a tail our evolutionary ancestor) The existence of vestigial traits can be attributed to changes in the environment and behavior patterns of the organism in question. As the function of the trait is no longer beneficial for survival, the likelihood that future offspring will inherit the "normal" form of it decreases. In some cases the structure becomes detrimental to the organism (for example the eyes of a mole can become infected[6]). In many cases the structure is of no direct harm, yet all structures require extra energy in terms of development, maintenance, and weight, and are also a risk in terms of disease (e.g. infection, cancer), providing some selective pressure for the removal of parts that do not contribute to an organism's fitness. A structure that is not harmful will obviously take longer to be 'phased out' than one that is. However, some vestigial structures may persist due to limitations in development, such that complete loss of the structure could not occur without major alterations of the organism's developmental pattern, and such alterations would likely produce numerous negative side-effects. The toes of many animals such as horses, who stand on a single toe, are still evident in a vestigial form and may become evident, although rarely, from time to time in individuals. (Wikipedia)

Station 2B: Vestigial structures Other examples: - Goose bumps Talk about goose bumps and how in other mammals they cause the hair to stand up: 1) to make the organism look bigger to other threatening organisms or 2) provide extra air space that warms the animal

Station 3: Fossils

Stratigraphy – relative ages of rocks and fossils Fossil: A Fossil: B Fossil: C Which fossils were alive at the same time? Why? Which fossil(s) are the oldest? How can you tell?

But how do we know exactly how old fossils and rocks are?

Scientists can date both rocks and dead organisms Radioisotopes – elements that undergo decay at a consistent rate Carbon-14 is a radioisotope found in living things. Scientists can measure the amount of Carbon-14 and it’s decay product Carbon-12 in order to establish the age of a fossil It takes 5730 years for ½ of a sample of Carbon-14 to decay into Carbon-12 18

How does the fossil record support the Theory of Evolution?

How does the fossil record support the Theory of Evolution? There are many fossils discovered that display organisms that do not exist today!

Imagine digging and coming across this!

Or this!

Inference: There are many organisms who once roamed the Earth that are now extinct. But how do we know that they all didn’t live at the same time

Connection to evolution: Some of these fossils resemble organisms currently living on Earth. Different layers of the earth show a progression of evolution

Let’s look back at our cross-section of the earth

In review: The fossil record supports the Theory of Evolution because: Fossils show the diversity of life on earth’s timescale. We can see a progressive change in species over time.

Station 4: DNA! How many of the same genes do you think humans share with these species: Answer: mouse = 99%, yeast = 31% and worm = 40%

DNA evidence Which organism is most closely related to a human? Which is least closely related?

Station #4: DNA How does this serve as evidence that supports the Theory of Evolution? Argument: Those with more closely related DNA probably evolved from a common ancestor Argument: the structure of genetic code is the same for every organism on Earth! All organisms pass on their traits in the same way.

Exit ticket On the back of your paper, write down: The two pieces of evidence for evolution that you find most interesting and… How these two pieces of evidence support the Theory of Evolution