Evidence of Evolution Answer Key
I.
II.
III.
IV.
Fossils
1. 1 (the bottom layer)
2. 7, technically. 6 has the youngest layer with organisms in it
3. 6. We would assume that the last organisms in the evolutionary chain would be the
most complex.
4. 1. We would assume the earliest known version of an organism is the least complex
5. It’s only through the comparison between organisms in layers of different ages that one
could see a gradual evolution of traits/complexity. Some only show in a few layers, ones
that are believed to have gone extinct, and others show up through many layers.
Biogeography
1. It is believed that the Gastornis is the ancient ancestor of all ratites (flightless birds like
the emu, rhea, and ostrich). When Pangaea broke apart populations of the Gastornis
were isolated from one another, each struggling with its own unique set of natural
selection pressures. These different pressures forced the Gastornis to evolve into
different modern forms, which we see today. There are many other examples of this.
One such example is the camelid (camels, llamas, alpaca, etc.)
Embryology
1. It appears that most, if not all, animals develop from an embryo. What is interesting is
that all the animals have a strikingly similar embryonic stage. This is used to support
evolution from the perspective that development is made possible by genes; genes
which all animals share.
Homologous Structures
1. (2) directive
2. (3) directive
i. Functions
Table 1
Animal
Functions
Human
Grasping
Climbing
Whale
Movement
Stabilization
Cat
Digging
Walking
Bat
Flying
Turning in flight
Bird
Flying
Turning in flight
Crocodile
Walking
Digging
iii. No. They are not arranged the exact same way but based upon the same
template.
“homo” means alike or similar.
3. (4) Comparative morphology is what you just did. It is the process of comparing the
structure (morphology) of different species in order to determine how similar they are.
IV.
IV.
Analogous Structures: Structures that do not show evolutionary relationships even though
they perform the same function.
a. Flight
b. Internally, the bird wing is supported by bones whereas the butterfly wing is not.
Externally, bird wings are covered in feathers and butterfly wings are made of chitin.
Bird wings are one structure whereas butterfly wings are two. Others?
c. Not really. There structures are very different from one another. The goal here is to
understand that structure is more important for determining evolutionary relationships
than function.
d. There are many. Platypus, alligator, frog, and duck webbed feet. Webbed feet are better
for swimming that toed or hooved feet. You find that organisms that spend a significant
amount of time in the water have them where land animals do not.
e. Convergent evolution (evolution that leads very distant relatives to reach similar
adaptations because they live similar lives).
Vestigial Structures
a. There is no light so a light gathering organ like an eye is not necessary.
b. They are built very similarly so yes.
Structure
Possible Function(s)
Why it is considered vestigial
Muscles that make
hair stand up
Create more depth for warmth
We accommodate cold by wearing clothes.
Besides, we don’t have enough hair for this
function to work.
Coccyx (tail bone)
Once was a tail
We no longer have tails. No it’s merely a
nuisance when we fall on them!
Muscles that move
ears
Hear predators from different
angles.
We no longer need to hear predators in the
same way. We move our heads instead, if
even needed at all.
V.
VI.
Natural Selection Observed.
1. Ones that have the genetic material that confers (gives) the bug resistances.
2. Over time (many generations) the passing of the resistance genes has changed
the genetic makeup of the bug populations forming new versions (some could
argue species) that are different, genetically, from the originals.
Biochemistry
1. Mammals: Dog, chimpanzee, mouse
2. Dog (81%), chimpanzee (98%), mouse (79%)
3. Mine are exactly the same. Hopefully yours are too. If not, why? What made your
list in number 1 different? What was the criteria you used to make the list?
1. Cytochrome c
2. The larger the gap in organisms evolutionary relationships the larger the difference
in amino acid sequences that give rise to the trait.
3. Biochemistry allows scientists a new perspective on evolution. What is found is that
mutations accumulate and occur at a predictable rate. Since mutations are the
source of variation that natural selection acts of then more differences in genetics
naturally gives rise to different species.
Analysis and Interpretations
1. Fossils are created by organisms getting trapped in some sort of material (amber, mud, ash)
that freezes them in time. They are protected from erosion or other degrading influences.
Fossils are created in a variety of ways, which gives rise to the various types of fossils found.
Some are impressions left behind, like casts. Some organisms go through chemical
replacement steps that replace their organic remains with more permanent compounds, like
silica or minerals. Fossils are useful though because one can date the ground around the
fossil, creating an age for the fossil itself. Be examining the fossils of organisms in different
ages it has been repeated found that there is a progression in complexity over time.
2. Homologous structure, or being built similarly, is a string piece of evidence. It strongly
suggests that the common ancestor to organisms that are built similarly had an older more
primitive form. Because the different organisms had different natural selection working on
them, they evolved into different species but they are still dependent upon the original
frame.
3. Fish fins and whale flippers are both homologues to an extent but more analogous as the
actual structure of a fin is much different than the flipper of a whale.
4. Embryology tells us that that organisms that evolved from a common ancestor develop in
similar away to the original ancestor. This homology suggest evolution from a specific source
ancestor.
5. The list above really summarizes this but there are others. Tonsils, wisdom teeth, body hair
these are all examples of structures that are not needed by modern man. They are left overs
that evolution hasn’t eliminated from our current structure.
6. You would expect that their genetics would be similar as well, considering genetics
determines structure. We have two arms because our genetics says so.