Evolution Test Study Guide!
For your test on Monday you should be able to:
1. Name the scientist who first proposed the theory of “evolution by natural
Charles Darwin and Alfred Russell Wallace (his lesser known co-author)
2. Give examples of evidence for evolution such as the fossil record and vestigial
Comparative Anatomy: Comparing body structures such as bones in animals
today as well as in fossils. The fact that so many different organisms share
homologous traits (like arm bones in a human, a whale and a frog, or like DNA
in all living things) points to the idea that we evolved from common ancestors.
Embryo comparisons: The embryos of vertebrates are very similar at early
stages. For example, all vertebrates go through a stage where they have gills.
Vestigial structures: Human tail bones and hip bones in whales are structures
that no longer serve a useful function. Eyes in blind cave fish and blind cave
crayfish are another example.
3. Name the process that drives evolution. Natural Selection
4. List the four steps of natural selection.
Overproduction: Organisms tend to produce more offspring than an
environment can support. This is also sometimes called “overpopulation.”
Genetic Variation: Offspring have minor differences in their genes. This
can mean that some of them are different colors, move slower or faster,
have better or worse eyesight, or many many other differences. The
sources of these differences are:
i. Mutations: Copying mistakes in their DNA
ii. Sexual reproduction: Mixing of different combinations of genes.
iii. In bacteria: Plasmid transfer –the passing of DNA amongst
Struggle for survival: Since there are more organisms than an
environment can support, they must compete for limited resources such as
food, water, shelter/territory/habitat, sunlight (plants), or even air. They
also must compete to avoid becoming food (being eaten). They also have
to compete to find a mate. The genetic variations in their population mean
that some have a better chance of succeeding in this struggle for survival
Successful reproduction: Those organisms whose genetic variations
helped them survive in the struggle for survival have a chance to
reproduce. If they reproduce, then they pass their DNA on to the next
Over time, the conditions of environment (NATURE) select some traits for survival
and other traits for extinction, pushing evolutionary change in species.
5. Correctly define the following terms: Evolution, adaptation, design, trait, natural
selection, species, cladogram, mutation, node, homology, analogy, phylogeny,
clade, genetic variation, and ‘survival of the fittest’.
Evolution: Inherited changes in a species over time.
Adaptation: The process in which natural selection pushes change in
species when environments change. Traits that are best matched to an
environment are adapted to that environment. Sometimes environments
change, and natural selection removes organisms that are not adapted to
the environment. Organisms whose trait are better matched to the new
environment are adapted to the new environment.
Design: Another way of saying the general structure of an organism.
Example: A tetrapod design is a skull and backbone with four limbs.
Trait: A physical or behavioral characteristic of an organism. Long ears
in a rabbit is a physical trait. Aggression in a male beta fish is a behavior
Natural Selection: The main process that drives evolutionary change.
Natural conditions select organisms and species for survival or extinction
depending on how well genetic variations help or hurt their success in the
struggle for survival and successful reproduction.
Species: There are several definitions for species. For our purposes, this
definition works for everything but bacteria and archaea: Species are
organisms that can breed and produce offspring that can also breed and
reproduce. A Siamese cat and a calico cat can breed and produce
offspring that are also capable of producing offspring. They are part of the
same species. A tiger and a lion can breed and produce a “liger” hybrid,
but ligers cannot breed and have offspring. Tigers and lions are
genetically too different to be considered species, even if they are closely
Cladogram: A diagram of the branches of the tree of life. “Clados” means
“branch” in Greek. Cladograms are a great way to organize a tree of life
according to shared and unique traits. “What Did T Rex Taste Like” is a
great way to review what a cladogram is and how it can be read.
Mutation: A copying mistake in DNA. Most mutations are harmful or
make no difference. A few can be helpful. We and all life on Earth are
the product of 4 billion years of successful mistakes: 4 billion years of
mutations that were selected for survival by natural selection.
Node: The point on a cladogram where it branches. The point represents
the most recent common ancestor of all the organisms beyond that
Homology: A trait that is shared by different organisms because they
came from a common ancestor that also had that trait.
Analogy: If different organisms have similar traits that came from
DIFFERENT ancestors, they are called Analogies. Analogies serve
similar functions: Bird wings and bat wings allow birds and bats to fly,
but come from different ancestors.
Phylogeny: A tree of life. It shows the historical lines of life. A
cladogram is a phylogeny. Phylogenies show the connections amongst
organisms according to their homologies (shared traits) and unique traits.
Clade: A part of a cladogram that includes a node (most recent common
ancestor) and all of the descendants of that common ancestor.
Genetic Variation: Differences in individuals that are caused by slight
differences in the genes they have inherited from their parents. These
differences give some individuals advantages in the struggle for survival
as well as in success in reproduction.
‘Survival of the Fittest’: Those organisms which have traits that are well
matched to their environment are the ones most fit to survive.
6. Identify that organisms pass their traits on to their offspring. Be prepared to
explain the implication of this: If different organisms have similar traits it makes
sense to assume they share a common ancestor
For example: Bats and hyenas and duckbilled dinosaurs all have jaws and
four limbs. These are physical traits that they pass on to their offspring.
Since they all have the same bone structures, we can also propose that they
inherited them from common ancestors. Four limbs they all inherited
from a common ancestor back in the Devonian Period. Jaws were
inherited from a common ancestor in the Ordovician Period when the first
fish with jaws evolved.
7. Read a cladogram to see which organisms have a more recent common ancestor
and more shared traits.
Review the What did T Rex Taste Like website for help on this.
8. Read a cladogram to identify the shared traits of organisms.
Review the What did T Rex Taste Like website for help on this.
9. Identify why bacteria are able to evolve faster than larger species of life
Most bacteria reproduce very quickly. E.Coli typically divides every 20
minutes. Rapid reproduction Rapid evolution.
Bacteria can easily share DNA with each other, even with different
species. They can pass “Plasmids” (loops of DNA) to each other and pick
up new traits. This way, a new trait can quickly spread a large number of
10. Explain why it is important to finish all of a given course of antibiotics.
First, a course of antibiotics is a prescription of antibiotics. Example: A
prescription might say take an antibiotic in the morning and evening for 14
days. The entire prescription is a course of 14 days of antibiotics twice a
If a patient takes the antibiotics for only part of the time, some of the
bacterial infection may still be present. If it is, the bacteria that are still
around are going to be the most resistant ones because they are the ones
that have survived the longest.
There are genetic variations amongst the more resistant surviving bacteria.
Some of them may have even stronger resistance. Stopping early means
you are selecting the most resistant bacteria for survival. You may be
helping superbacteria evolve.
11. Draw a simple cladogram based on shared and unique traits of organisms.
Use the “What Did T Rex Taste Like” website AND “Reconstructing