Evolution SG KEY

Evolution Study Guide
Evolution Study Guide
1. What is evolution?
– the process by which modern organisms changed over time from ancient common
2. What is artificial selection?
– nature provides variation (variety) in organisms’ traits, but humans choose
to breed those organisms that have the most useful traits.
– Give an example.
i. Example: humans breed cows that produce the most milk.
ii. Example: humans breed trees that create the most fruit.
3. What is another name for natural selection?
– AKA: “survival of the fittest”
4. Describe an animal that is very fit in its habitat.
– finches on the Galapagos islands have a beak size adapted to the type of food
that they eat.
5. Name the 3 parameters of evolution by natural selection.
• 1. Struggle for existence – more organisms are produced than can survive.
2. Variation and adaptation – some variations are better suited.
3. Survival of the fittest – individuals with adaptations that are well suited to
their environment survive and reproduce.
• Fitness – measure of how well an organism survives/reproduces.
6. What is an adaptation?
– – heritable characteristic that increases an organism’s ability to survive
and reproduce.
7. What is competition? What types of resources do organisms compete over?
– Competition – individuals or groups of organisms compete for similar
resources (territory, mates, food, water, etc.) in the same environment.
8. What is common descent?
– Common descent – all species (living and extinct) descended from a common
– Over many generations, adaptations caused a successful species to evolve into
a new species.
9. What provides evidence for this “descent with modification”?
– The fossil record provides evidence for this “descent with modification”.
What is Divergent Evolution?
a. single species or group of species evolve over a short period of time into
different forms living in different ways due to a change in environment that
makes new resources available.
b. Ex. Dinosaurs, Darwin’s finches.
What is Convergent Evolution?
– similar structures are produced in distantly related organisms.
• Ex. Mammals that feed on ants/termites evolved independently 5 times.
1. Geographic
 Species
 Similar
and describe the 7 pieces of evidence for evolution.
Distribution of Species
of animals on different continents had similar structures and behaviors.
selection pressures caused animals to evolve common features.
2. Fossils
 A fossil is the preserved or mineralized remains (bone, tooth, shell) or trace
of an organism that lived long ago.
3. Anatomy
 Homologous Structures – parts of different organisms (that are often quite
dissimilar) that developed from the same ancestral body parts.
o Are similar in structure but differ in function!
4. Physiology
 Analogous structures -- structures that are similar in appearance and function
but have different origins and usually different internal structures.
o Differ in structure, similar in function.
 Vestigial structures – any body structure that has reduced or no body function.
o As species adapt to environments the change in form and behavior and
continue to inherit these structures as part of the body, even though they
have no function.
5. Embryology
 Embryos of different species in early development are indistinguishable from
each other.
 Illustrates descent from a common ancestor.
6. Universal Genetic Code
 The genetic code of all organisms on Earth (bacteria, yeast, fruit flies,
humans) is the same!
o Example: the AUG codon always codes for the amino acid methionine.
7. Biochemical Homology
 Similar DNA, RNA, and amino acid sequences amongst species in same taxonomic
In a population of wooly worms, the number of green individuals increased
over time. What happened to the allele frequency of the allele for green color?
– -the allele frequency for green color increased
What is the main source of genetic variations in populations?
These mutations occur randomly.
Not all mutations affect an organism’s fitness.
If a mutation occurs in a skin cell, does that mutation get passed on to the
offspring of that individual?
– no- Only heritable mutations matter for evolution.
Name and describe the 3 types of selection in populations.
Directional Selection – organisms at one end of the curve have a higher fitness
than those in the middle or at the other end.
Stabilizing Selection – organisms in the center have highest fitness.
Disruptive Selection – organisms at the ends of curve have highest fitness.
Name and describe the 3 other sources of changes in allele frequencies.
• Genetic drift – change in allele frequency that occurs in small populations due to
random chance.
• Genetic bottleneck – change in allele frequency following a dramatic reduction in
population size.
• Founder effect – change in allele frequency following migration of a small subgroup
out of the population to start a new population.
What is speciation?
• Species – population of organisms that can interbreed and produce fertile offspring
• Speciation – evolution/formation of a new species.
What is reproductive isolation?
Reproductive isolation occurs when 2 populations can’t interbreed - causes
Once reproductive isolation occurs, natural selection increases the
differences between the separated populations.
Name and describe the 5 Mechanisms of reproductive isolation.
1. Behavioral isolation – different courtship.
2. Ecological/habitat isolation – can only mate in specific or preferred
3. Mechanical isolation – no sperm is transferred.
4. Gametic isolation – no fertilization of egg occurs.
5. Temporal isolation – reproduce at different times.
What is geographic isolation?
– population becomes divided (isolated) by a physical barrier.
What is gradualism?
Gradualism – slow, steady change leading to new species.
What is punctuated equilibrium?
Punctuated equilibrium – brief periods of rapid change leads to the formation
of new species.