Download 1 - About Phelan

Evolution Review
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Learning Target: Describe how Darwin arrived at his idea about species variation, and the
concept of natural selection.
1. Give one example of variation that Darwin observed on the Galapagos Islands.
Darwin observed various finches with different shaped beaks.
a. How were these variations related to the environment?
Finches had beaks that matched the food source available on their island.
b. What was Darwin’s conclusion about how these variations occurred?
Organisms that had a beak shape that allowed them to get enough food to survive and have
offspring, passed those traits for a particular beak type to their offspring. Over time, that
specific phenotype (trait) became dominant in the population.
2. Describe two other observations Darwin made that lead to his ideas about species
variation.
Tortoises have different leg and neck differences depending on the type of plants available.
Fossil shells proved that land changed and therefore organisms died or adapted to the new land
(earthquake proved this on his voyage.)
Learning Target: Compare and Contrast Artificial Selection and Natural Selection
3. What is Artificial selection?
Humans change a species to breed a particular set of traits.
a. What must be true about a trait for artificial selection to occur?
Inheritable
b. What is the “selective agent” in artificial selection?
Humans are the selective agent, and pick traits they deem most favorable.
What is Natural selection?
Organisms inherit traits that allow them to produce more offspring on average and become
more fit to for their environment.
c. What must be true about a trait for natural selection to occur?
Inheritable
d. What is the “selective agent” in natural selection?
The environment is the selective agent.
e. How is natural selection similar to artificial selection? How is it different?
Similar: Organisms inherit traits from their parents and pass traits to offspring, therefore
increasing the frequency of a trait.
Different: AS- humans decide what trait is beneficial, even if that organism might die in the wild.
NS- the environment decides what traits will survive and allows organisms to survive.
Learning Target: Explain how variations occur in individuals and in populations.
4. Does natural selection cause a change in the traits of existing individuals? Explain your
answer.
No, natural selection does not change the traits in an existing individual. Natural selection
changes the frequency of traits in a population over time. These changes are often genetic
mutations that allow an organism a better chance to survive. Those changes are then passed to
offspring where they are inherited.
5. What causes variation in individual organisms?
Variation in individual organism is due to a set of traits that allow them better adapt to their
environment. Eventually, adaptations can lead to genetic change in a population over time.
Also, organism inherit traits from their parents. This often accompanies genetic mutations and
therefore diversity in a species.
6. Explain how natural selection causes a change in a population over time. Be sure to
include biological fitness in your answer.
Over time, organisms that are able to reach reproduction maturity, pass desirable traits to their
offspring. These traits allow the organism, and their offspring, to survive until the next
generation reaches reproduction maturity. This is biological fitness. To be fit, organisms need
to have offspring, and their offspring need to survive and produce more offspring so that traits
and genes continue to be inherited.
Learning Target: Summarize how the four principles of natural selection are related to the
evolution of a population.
7. List and describe the four main principles of natural selection.
Variation: organism have genetic variation as a result of obtaining genetic material from their
parents, occasionally with mutation.
Overproduction: organisms produce many offspring to ensure that some reach maturity and
reproduce. Having many offspring also allow for competition between offspring and increases
the frequency of desirable traits.
Adaptation: successful organisms are “naturally selected” to survive in their environment and
therefore pass along those traits.
Descent with Modification: over time, organisms more suited for survival will pass those traits to
their offspring and possibly alter the genetic make-up of an entire species.
8. Think back to the Natural Selection lab. Use the four principles of natural selection to
explain how this lab shows the process of natural selection.
Organisms that blended into their environment were able to survive and produce offspring.
These organisms are considered fit for their environment because they also are able to
reproduce offspring with the same traits that allow for survival. Over time, the frequency of
organisms with that particular trait increases and becomes the “norm.” Fossil evidence will
show that organisms with the undesirable trait died off. Occasionally fossils will also indicate
environmental conditions that allowed for extinct organism to survive during that time.
Learning Target: Explain the different types of evidence that support evolution.
9. List and describe the five main types of evidence for evolution.
Fossil record: fossils are traces of organisms. Fossils deeper in the Earth are different from
fossils in upper layers, indicating that organisms changed over time to adapt to their
environment.
Geography: Different ecosystems give rise to organisms that are able to survive and produce
offspring. Similarities in ecosystems might indicate a common historical past and therefore
similar but different species that have adapted to better fit their environment.
Embryology: embryos of vertebrates are hard to tell apart. Similar features suggest a common
ancestor.
Anatomy: Homologous and analogous structures provide evidence of a common ancestor.
Homologous structures have similar structures and perhaps different function. Analogous
structures have different structure but similar function perhaps indicating they evolved
separately.
Genetics: Mapping out the genome demonstrates that many organisms, although they appear
very different, have similar gene sequences and perhaps a common ancestor.
10. Give an example of homologous, analogous, and vestigial structures. Describe how each
supports/relates to the theory of natural selection.
Homologous structures: structures with similar bone structures; may or may not have similar
functions. Example: human arm, forearm, and hand with that of a cat; both have a long
humerus, radius and ulna, cluster of bones, and phalanges. Shows link to a recent common
ancestor.
Analogous structures: structures have similar function, but not different structure. Example: fish
fin and whale flipper. Both are used for swimming, but a whale flipper has bones that look
similar to other vertebrates including humans. Fish fins do not have the same internal structure.
This indicates NO common ancestor.
Vestigial structures: Structures that may have reduced or no function, but show a common
ancestor. Example: Cavefish and salamanders have eyes, but they are not able to see from
them. Emus and ostriches have wings but are flightless birds. These structures link them to
their ancestors even though they may no longer serve their function.
11. How does paleontology support the theory of natural selection?
Paleontology studies the fossil record and provides evidence that organisms a long time ago
share structures that are similar to organisms living today. These structures may be categorized
as homologous, analogous, or vestigial. The fossil record also allows us a glimpse into Earth’s
history, prior environmental conditions that may have affected the process of natural selection
and evolution.
12. List two specific pieces of genetic and/or molecular evidence for evolution.
Fetal development of many different organisms show that many different organisms started off
the same, in terms of their development. But during development, their bodies specialize to fit
their environment according to their DNA.
The genome project has allowed for the ability to map out entire genome sequences.
Organisms that are unrelated, such as fruit flies and humans, have a relatively similar set of
chromosomes and share a lot of similar sequences.