Transcript explanation - mbhsbiologystaar

BIOLOGY EOC PRACTICE TEST
April 24, 2012
Yes, yes it is. 
1. Prokaryotes are considered by the scientific
community as the most ancient life-forms on Earth.
Yet, these primitive cells share many common
characteristics with the more modern eukaryotes.
However, one significant difference between these
two cell types is that only eukaryotes contain
The correct answer is
• A membrane-bound compartments to carry out specialized
functions
• B a selectively-permeable cell membrane to maintain homeostasis
• C deoxyribonucleic acid to serve as a template to produce proteins
• D a rigid cell wall which provides structure and support
EXPLANATION:
Prokaryotic cells
do not have any
membrane
organelles,
which includes
the nucleus.
WORD PARTS:
pro – before
karyo - nucleus
Choices B and C identify structures common to ALL
cells. Choice D names a structure that only some cells
have.
2. What is the most likely cause of the potato core
gaining mass when placed in the 0M sucrose solution?
The correct answer is
• A Sucrose moved into the potato core from the
solution.
• B Sucrose moved from a region of higher
concentration to a region of lower concentration.
• C Water moved down its concentration gradient.
• D Water concentrations stayed the same inside
and outside the potato core.
EXPLANATION
C is the correct answer because
- Only water is assumed to be able to
move across a cell membrane (negating
A and B)
- Water moves down its concentration
gradient (from high water
concentration to low water
concentration) so D cannot be correct
- 0M sucrose means there is no sucrose,
so A cannot be correct
- If only water can move and mass went
up, A can’t be correct, B can’t be
correct, and D can’t be correct
Potato core
0M solution
3. The isotonic point in this potato core
experiment is closest to
• A 0M sucrose because sucrose moved into the
potato core causing it to gain mass
• B 0.2M sucrose because water didn’t move
into or out of the potato core
• C 0.2M sucrose because equal amounts of
water moved into and out of the potato core
• D 1M sucrose because the potato core lost the
most mass due to water loss
EXPLANATION
• Isotonic means that the concentration of the solution
inside the cell (in this case potato cells) is the same as the
concentration of the solution outside the cell (in this case
the sucrose solution in the beaker).
• When solutions are isotonic, there is no net movement of
water (or solutes) and therefore the mass of the potato
cores (cells) won’t change.
• The only place the mass didn’t change is with the 0.2M
solution
WORD PARTS:
iso – same
hyper – above
hypo – below
tonic -
4. Viruses are considered non-living because they lack
the machinery to reproduce on their own and must rely
on a cellular host cell to survive. Structures common to
both cells and viruses include
•
•
•
•
A protein capsid
B nucleic acids
C cell wall
D nucleus
EXPLANATION
• The answer is B nucleic acid because, as you can see on
the chart above, viruses and cells both have DNA. A cell
doesn’t have a protein capsid and a virus doesn’t have a
cell wall. No viruses and only some cells have a nucleus.
5. Differences between prokaryotes and eukaryotes which
are readily observable through the light microscope include
I. prokaryotes are much smaller than eukaryotes
II. ribosomes are smaller in prokaryotes
III. prokaryotes lack nuclei
The correct answer is
• A I only
• B II only
• C I and II only
• D I and III only
EXPLANATION
• The answer is D, I and III only because you can
view the cells under the light microscope and
see that the average prokaryotic cell is smaller
than the average eukaryotic cell, as well as
that there are nuclei in the eukaryotic cells but
not in the prokaryotic cells.
• You can not see ribosomes under the light
microscope (and they wouldn’t appear
different if you viewed them under an
electron microscope even though they are
slightly different…)
6. Cells often need to take in materials from their
environment, many of which are found in lower
concentrations outside the cell compared to inside the
cell.
In order to do this, cells must use the energy from ATP to
move these materials
The correct answer is
• A against the concentration gradient through active
transport
• B with the concentration gradient through active transport
• C against the concentration gradient through passive
transport
• D with the concentration gradient through passive
transport
EXPLANATION
• A is the only correct answer. The question describes moving
a material into the cell that is in lower concentration outside
the cell. You should recognize this description as being
AGAINST the concentration gradient (low to high)
• Just like pushing a ball up a hill (from low to high) ENERGY is
required. By definition, this makes it ACTIVE transport.
DOWN/WITH, NO energy,
PASSIVE
UP/AGAINST, ENERGY,
ACTIVE
7. The cellular organelle most directly involved in maintaining
homeostasis is the?
The correct answer is
• A plasma membrane
• B cell wall
• C chloroplast
• D mitochondria
EXPLANATION
• The correct answer is A plasma membrane
because the primary role of the plasma
membrane is to regulate what comes in to and
goes out of a cell. As the environment
changes, so does what goes in and out.
• The primary functions of the other structures
are support/shape, photosynthesis, and
cellular respiration, respectively
8. Viruses are able to infect cells because they share
a common genetic code and are able to use host
cell enzymes to carry out protein synthesis.
There are some structures which are unique to viruses
and not found in cells. These include
I. Protein capsid
II. Nucleic acids
III. Cell wall
The correct answer is
• A I only
• B II only
• C I and II only
• D II and III only
EXPLANATION
• The correct answer is protein capsid only.
Both cells and viruses have nucleic acids. Only
cells have cell walls.
9. During an infection, some viruses remain inside the cell but
do not cause symptoms of disease. The graphic depicts the
The correct answer is
• A lytic cycle and the host cell is destroyed by
rapidly reproducing viral particles
• B lytic cycle and the viral nucleic acid inserts into
the host cell chromosome
• C lysogenic cycle and the viral nucleic acid
inserts into the host cell chromosome
• D lysogenic cycle and the viral nucleic acid
replicates independently of the host cell
chromosome
EXPLANATION
• The diagram on the top shows the
cycle from the question. The
diagram on the bottom shows the
other possibility. It is important that
you note that both A and D should
be immediately eliminated because
the cell is not destroyed and the
nucleic acid is not replicating
independently in the diagram.
• That narrows your choices to B and
C – lytic or lysogenic. One way you
can remember it is that it takes
much longer to go through the
lysogenic cycle, and it’s the longer
word.
10. The stage of the cell cycle pictured may be best
described as
The correct answer is
• A Cytokinesis: the cytoplasm of the cell is
divided
• B S phase: DNA is copied, resulting in
identical sister chromatids
• C G2 phase: the cell grows in size and
prepares to divide the nucleus
• D Mitotic phase: the nucleus is divided
EXPLANATION
1 nucleus
2 nuclei
• The answer is D because it is showing the
division of the nucleus.
• It is not A because it has not divided into 2
cells yet. It is not B because the S phase
happened before these pictures and is not
shown. It is not C because the nucleus is
actively dividing and the cell is not resting and
growing
Laugh break!
11. Leaves are plant organs specialized for photosynthesis.
Through the light microscope, which organelle would be
expected to be seen in greater numbers?
The correct answer is
• A mitochondrion.
• B chloroplast.
• C Golgi.
• D vesicle
EXPLANATION
• The key to this question is the
phrase “ in greater numbers”.
• The cells of the leaf of a plant are
going to have all 4 structures
mentioned. The mitochondrion is
for cellular respiration, the Golgi is
involved in protein manufacture and
transport. The vesicle is involved in
transport around the cell.
• However, because it is a leaf cell
and the leaf is the organ of
photosynthesis, you would expect
the cells to have a lot of chloroplasts
relative to other cells.
12. Each of the following statements describes the importance
of the cell cycle and mitosis to an organism EXCEPT?
The correct answer is
• A The cell cycle and mitosis are important to produce identical
new cells so that a multi-cellular eukaryote can grow larger.
• B The cell cycle and mitosis are important to produce identical
new cells so that a unicellular eukaryote can reproduce.
• C The cell cycle and mitosis are important to produce identical
new cells so that a multi-cellular eukaryote can repair
damaged tissue.
• D The cell cycle and mitosis are important to produce
identical new cells so that a multi-cellular eukaryote can
reproduce.
EXPLANATION
• Mitosis has 3 important functions:
– growth
– repair
– asexual reproduction of unicellular organisms
• Multicellular organisms can not reproduce
asexually through mitosis
– only cells can undergo mitosis, not an organism
– asexual reproduction in multicellular organisms is
referred to by other names such as fragmentation
& vegetative propagation
13. According to the illustration, adult stem cells extracted
from bone marrow tissue may be cultured to produce
different types of differentiated cells, such as liver cells,
nerve cells, and heart muscle cells. Which of the following
statements can best explain this result?
The correct answer is
• A There are different genes in each of the
individual stem cells that are cultured.
• B Environmental conditions influence which
genes are expressed.
• C Each stem cell contains only the DNA required
to make one cell type.
• D DNA can move from one stem cell to another
through the culture media.
EXPLANATION
• This diagram shows adult stem cells from bone marrow
producing a wide variety of cells, including muscle, nerve, and
liver. The key to answering this question correctly is not to get
hung up on “can they do that?” but to think about how
different kinds of cells are created.
• ALL cells have the entire set of chromosomes with all of the
genes present; however, not all of the genes are expressed in
every cell.
• Stem cells retain the ability to change which genes are being
expressed based on the signals received from outside the cell
and therefore can become different types of cells.
14. When harmful mutations occur in genes that contain the
information to make cell cycle regulatory proteins, this may
result in accelerated cell division. The result of these
mutations is most likely
The correct answer is
• A cancer
• B slower cell growth
• C a halt in mitosis
• D entry into G0 phase
EXPLANATION
CANCER – is when cells
divide uncontrollably.
• Your book explains the
functioning of the cell cycle
checkpoints using the
analogies of a stuck
accelerator and having no
brakes.
• If a signal molecule that
tells the cell “divide” gets
produced too much, it’s like
having the accelerator stuck
• If another protein is
supposed to stop or slow
down cell division, it’s like
having no brakes.
15. Which of the illustrations depicts a nucleotide,
the building block of DNA?
The correct answer is
• A guanine base only.
• B thymine base only.
• C nucleotide.
• D phosphate group.
EXPLANATION
• A nucleotide has 3 parts; if it doesn’t have all
3 parts, it’s not a nucleotide
– 5-carbon sugar (either ribose or deoxyribose)
– Nitrogen base (thymine, adenine, cytosine,
guanine, uracil)
– Phosphate group
16. Which statement most accurately describes how
deoxyribonucleic acid (DNA) carries the genetic code
for building an organism?
The correct answer is
• A The order of nitrogen bases provides the
genetic code
• B The genetic code is based on the number of
hydrogen bonds found between nitrogen bases
• C The number of deoxyribose sugars along the
sides of the DNA ladder is used to determine the
genetic code
• D The shape of the DNA molecule provides the
genetic code
EXPLANATION
• What you have learned about transcription
and translation (protein synthesis/ gene
expression) as well as mutations should be
enough to remind you that the genetic code is
in the sequence of the nucleotides of the
DNA; i.e.
– ATTCGGTAAATTGGCCC does NOT say the same
thing as ATTGCCTAAATTGGCCC because CGG
and GCC do not code for the same amino acid!
17. Which of the following structures would pair with the
nitrogen base adenine in a complementary strand of DNA?
The correct answer is
• A guanine
• B thymine
• C nucleotide.
• D phosphate group.
EXPLANATION
• The base-pairing rules, based on Chargoff’s
research, are
• A-T, G-C
18. Restriction enzymes isolated from various bacterial
species have been extensively used in the biotechnology
laboratory for cutting human genes from DNA samples to
insert into bacterial plasmids. This is made possible because
The correct answer is
• A Nitrogen bases form a common genetic code
for all organisms.
• B DNA is maintained in both bacterial and human
cells within nuclear membranes.
• C Small, circular pieces of DNA called plasmids
are common to both humans and bacteria.
• D Restriction enzymes cut at random sequences
so it does not matter that humans and bacteria
use a different genetic code.
EXPLANATION
• A is correct because there is only one genetic
code for all organisms and almost without
exception, the same sets of 3 nucleotides
(codons) code for the same amino acids,
therefore human proteins can be produced by
bacteria (we currently do this with insulin and
human growth hormone)
• The other answers are not correct because
– bacteria do not have nuclear membranes
– eukaryotic cells do not have plasmids
– restriction enzymes do not cut at random places
19. The model in the graphic illustrates translation, the
latter part of the process of protein synthesis.
Which other necessary components for
translation are absent from the graphic?
The correct answer is
• A messenger RNA and transfer RNA
• B ER membranes and ribosomes
• C ribosomal RNA and DNA
• D transfer RNA and ribosomes
EXPLANATION
• The picture on the test (above) shows just a section
of mRNA. For translation to occur, a ribosome must
be present, as well as the tRNA molecules needed to
bring the amino acids for the growing polypeptide.
More like the picture below
RIGHT: Translation in the cytoplasm at
the ribosome (structure 3)
Structure 1 - nuclear envelope
Structure 2 – mRNA
Structure 3 – ribosome
Structure 4 – polypeptide (amino acid
chain; protein)
Structure 5 – tRNA with amino acid
20. Which of the following statements is NOT correct
regarding the process in the illustration?
The correct answer is
• A I must be complementary to an mRNA
codon.
• B This process occurs in the nucleus of a cell.
• C III shows the first two amino acids of a
growing polypeptide chain.
• D The process shown is translation.
EXPLANATION
• The question wants to know which statement is
NOT true – this IS showing translation, Roman
numeral I is pointing to the anticodon, which
must be complementary to a codon, and Roman
numeral III is pointing to the first 2 amino acids in
the chain
• HOWEVER, translation occurs in the cytoplasm at
the ribosome, NOT in the nucleus. Transcription
(DNA RNA) is in the nucleus
Ever feel this way?
21. Bacterial species’ genomes are arranged somewhat
differently than those of eukaryotes. Their circular
chromosome contains clusters of genes which code for
proteins that work together to accomplish a series of
related tasks. In this way, groups of genes can be turned
on when the gene product(s) are needed, and turned off
when they aren’t needed. This confirms the fact that
The correct answer is
• A gene expression is a regulated process.
• B genes are arranged similarly in prokaryotes and
eukaryotes.
• C eukaryotes have circular chromosomes.
• D bacterial genomes are much larger than those
of eukaryotes.
EXPLANATION
• This is a tough question. The answer is that gene
expression is a regulated process. You might have
discussed the lac and trp operons in your Biology class and
remembered that the genes that code for the breakdown
of lactose or the synthesis of tryptophan can be turned on
and off as the cell needs those things to be done.
• If not, here are some other things you might have known:
– Genes are on linear chromosomes in eukaryotes (like you); think
about the karyotypes we looked at in the genetics unit
– Bacterial genomes (the one big ring) are MUCH smaller than all
of the chromosomes in a eukaryote combined, which is what a
genome is – all of the genetic material in an organism
22. Changes in DNA sequences are called mutations.
Mutations may affect only one nitrogen base in the sequence,
or may affect large regions of a chromosome. The particular
type of gene mutation that is illustrated is called a
The correct answer is
• A point mutation
• B insertion mutation
• C frameshift mutation
• D nonsense mutation
EXPLANATION
• On this question, you must
remember that you are
looking for the BEST answer.
• Frameshift mutation is the
BEST answer because it is the
most specific and accurate
– It is a point mutation, but that is
less specific
– It is NOT an insertion, it’s the
opposite, a deletion
– It is not a nonsense mutation
because it did not result in a
premature stop codon that can
be seen on the page
23. The significance of this gene mutation is that
The correct answer is
• A A different amino acid sequence results which
is likely to affect the functioning of the final
protein product.
• B A different amino acid sequence results which
is not likely to affect the functioning of the final
protein product.
• C No protein product will be produced.
• D The protein product is unaffected
EXPLANATION
• This question refers to the same diagram we were
just looking at. Let’s start with the WRONG
answers.
– D is clearly wrong because if you look at the 2 amino
acid sequences, there is a change
– C is wrong because a protein is forming (a chain of
amino acids is a protein), it’s just not the same one
– B is wrong because protein function is VERY closely
related to protein structure and it is NOT LIKELY that you
can make changes and it still function normally. Think
about the one amino acid change that results in sickle
cell anemia or how important enzyme structure is to
enzyme function
24. Maize is a variety of corn that is often used to illustrate
genetic crosses. Since each kernel of corn on a cob is an
offspring, much data can be obtained from observing a single
corn cob. Kernels are found as one of two colors; either
purple (P) which is dominant, or yellow (p) which is recessive.
If two heterozygous purple plants were crossed, what would
be the predicted phenotype ratio of the resulting offspring?
The correct answer is
• A 1PP:2Pp:1pp
• B all PP
• C 3 purple:1 yellow
• D all purple
EXPLANATION
• You may have done a lab in
class where you counted the
corn kernels to work genetics
problems. In this problem, you
are told you have 2 purple
heterozygotes. This means
both the “mom” and the “dad”
are Pp. If we put this in a
Punnett square we will get PP,
Pp, Pp, and pp as our possible
offspring. This means that 3
out of every 4 will be purple or
the phenotypic ratio is 3:1
PP
Pp
Pp
pp
25. Lentil seeds can be found in two varieties based on the
different sizes of spots which may be observed on their outer
surface. Seeds with larger spots are called spotted, while
seeds with smaller spots are called dotted. The different-sized
spots are inherited in a co-dominant pattern. Predict the
resulting phenotype of offspring if a lentil with spotted seeds
were crossed with a lentil that has dotted seeds.
The correct answer is
• A Seeds are both spotted and dotted.
• B Seeds have intermediate size spots.
• C Seeds have no spots.
• D Seeds are all spotted.
EXPLANATION
... .. .
….. ….
SPOTTED SEED
• Recall that codominant means that
DOTTED SEED
both of the alleles are expressed
equally, like in type AB blood.
Therefore, lentils must have the
following alleles:
– S – spotted
D – dotted
o – neither spots nor dots
– A spotted parent could be SS or So
– A dotted parent could be DD or Do
– Crossing an S- parent with a D- parent
is going to result in some spotted and
dotted seeds (SD)
26. In pea plants, tall (T) is dominant over short (t), and purple
flowers (P) are dominant to white flowers (p). Given two
parent plants which are heterozygous for both of these traits,
what is the probability of producing tall offspring with white
flowers?
The correct answer is
• A 9/16
• B 3/16
• C 1/16
• D0
EXPLANATION
• This is a true dihybrid cross of TtPp with TtPp.
There are 4 possible phenotypes:
– tall purple (dominant dominant)
– tall white (dominant recessive)
– short purple (recessive dominant)
– Short white (recessive recessive)
These are ALWAYS in a 9:3:3:1 ratio; therefore, 3 out of
16 (9+3+3+1=16) will be tall and white
You can verify with a 16-box Punnett square, or with two
4-box Punnett squares
27. Variation is the raw material for change in organisms,
providing a mechanism by which populations may evolve and
adapt to changing environmental conditions. Meiosis
provides a number of opportunities for increased variation in
sexually reproducing populations through each of the
following events EXCEPT
The correct answer is
• A crossing over
• B independent assortment of alleles
• C random distribution of homologous
chromosomes
• D fertilization
EXPLANATION
• The BEST answer is D fertilization because:
– crossing over (the exchange of genes during prophase I of meiosis)
– independent assortment of alleles (the fact that just because the gene
for red flowers was inherited doesn’t mean that the gene for tall stems
also has to be inherited with it, even though they’re both dominant or
both present in the same parent); this is Mendel’s law of independent
assortment p. 169 in your text
– random distribution of homologous chromosomes (just because
chromosome number 1 from your mom enters a particular gamete,
doesn’t meant that it has to have all chromosomes from your mom;
which direction each chromosome from each parent goes is
completely random each time gametes are formed); this is Mendel’s
law of segregation p.169 in your text
ARE all events in meiosis
Fertilization is NOT an event in meiosis. If the question was about
sources of genetic variation in sexually reproducing organisms, then C
would be the NOT answer and A, B, and D would all be sources.
28. Gel electrophoresis (DNA fingerprinting ) is NOT a
useful method for confirming
The correct answer is
• A the order of nitrogen bases in DNA
• B family relationships such as paternity
• C a person’s identity
• D genes that cause genetic disorders
EXPLANATION
D is the correct choice because a DNA fingerprint
does not give you an exact sequence
• Gel electrophoresis spreads out bands of DNA from large to
small by size. The bands are created when an enzyme chops
up a large sample at a particular sequence.
• Therefore the same DNA sample will always produce the
same banding pattern and you can determine
– C a person’s identity with ease.
– B family relationships because they will share common DNA
sequences, so a parent and child should have half of their bands in
common
– D genes for a genetic disorder because you would be searching for a
particular sequence and would know where the band breaks would be
in a normal gene verses a mutated gene
29. The process of meiosis occurs in sexually reproducing
eukaryotes and is important for the continuation of these
species because of all of the following EXCEPT
The correct answer is
• A chromosome number is halved in the
daughter cells.
• B crossing over during Prophase I provides
increased variation.
• C diploid chromosome number is maintained
in the zygote.
• D gametes produced are 2n.
EXPLANATION
• Meiosis is a reduction division of a diploid cell into haploid
gametes (eggs and sperm). In humans, this means that a cell
with 46 chromosomes is divided into gametes with 23
chromosomes. This is important because when an egg and a
sperm fuse to form a zygote the zygote has 46 chromosomes
again to continue dividing into a multicellular organism.
• During meiosis, pieces of the chromosomes are exchanged.
This is called crossing over and helps increase genetic
variability (different mixes of traits) within a population.
30. A baby is born with phenotypic characteristics of
Down’s syndrome; a rounded face, small chin, almondshaped eyes, and shorter limbs. Evidence from which of
these techniques would best confirm the child has an
extra chromosome 21?
The correct answer is
• A gel electrophoresis
• B DNA fingerprinting
• C karyotype analysis
• D gene therapy
EXPLANATION
• The correct answer is karyotype
analysis because looking at a
picture of a person’s
chromosomes laid out in order,
biggest to smallest, would allow
for a chromosomal disorder to
be detected.
• Gel electrophoresis was
described on question 28. The
DNA fingerprint is what results.
Gene therapy involves
introducing “normal” genes to
someone with a genetic disorder,
such as cystic fibrosis, in hopes
of “curing” them.
What a great game!
31. The complete amino acid sequence was determined for a
protein shared by all primate groups. The data provided in the
graph shows the percentage of amino acids each
primate protein shared with the human protein. According to
this molecular homology data,
The correct answer is
• A The gorilla is least related to humans.
• B The gorilla and gibbon are most closely related.
• C The chimpanzee is most closely related to
humans.
• D The chimpanzee is least related to the lemur.
EXPLANATION
• The data shows that the gorilla version of the
protein and the chimpanzee version of the
protein are almost 100% identical to the
human version of the protein.
• This means that if you were to look at the
amino acid sequence of all 3 proteins there
would be very few differences.
32. The rock strata were excavated in an area as illustrated
above and the fossil remains examined. According to this
information, the most likely scenario is that
The correct answer is
• A Layer I is the oldest, followed by Layer II, III, and
IV.
• B Fish suddenly appeared on Earth at the time of
Layer III.
• C A marine environment gradually filled with
sediment and became a terrestrial environment.
• D A terrestrial environment was covered by a
shallow sea for a period of time.
EXPLANATION
• Recall that the newest
fossils are on top and the
oldest fossils are on the
bottom (so A is wrong)
• The most likely thing to
have occurred is that a
terrestrial (land)
environment was covered
by an ocean. This is
indicated by the leaf in
layer IV being in the oldest
layer while the fish are in
the newer layers on top of
it. This is what choice D
says, and is the opposite of
choice C.
• B is not likely
33. How does competition for limited resources within and
between species drive evolutionary change?
The correct answer is
• A Individuals with favorable adaptations will
out-compete others and produce more
offspring.
• B Competition makes some individuals stronger
than others, and more of the stronger individuals
survive.
• C Stronger individuals develop different
adaptations than weaker individuals.
• D Competition produces variation between
populations.
EXPLANATION
• The best answer is A. Evolutionary
change occurs at the level of the
population and requires that more
(fertile) offspring be produced by those
with the best adaptations for a particular
environment.
• Choices B and C are focusing on strength
of an individual. That is not necessarily
passed on. (Recall that just because you
work out, does not mean your offspring
will be “buff” when born)
• Choice D does not answer the question.
Natural Selection
34. Each of the finch varieties pictured evolved from a
common ancestral finch species. This diversity of species
likely developed due to
The correct answer is
• A individuals evolving different traits during their
lifetime living longer than others
• B finches being born with beneficial variations
reproducing more successfully
• C immigration of finch species providing a greater
variety of traits in the population
• D selective predation of one particular variety of
finch
EXPLANATION
• A is not correct because living longer doesn’t have
anything to do with passing on traits to enough
offspring to change a population
• C is not correct because it is not probable that birds
would immigrate in large numbers that were
perfectly adapted
• D is even less likely than C
• B accurately describes the theory of evolution by
natural selection and is the only correct answer.
35. Cheetahs are the fastest land mammals, yet they can only
maintain their top speed of about 70 mph for a few seconds.
Since all cheetahs are nearly genetically identical due to a past
bottleneck event, development of future diversity in this
species is most likely to occur by
The correct answer is
• A gene flow
• B immigration
• C emigration
• D mutation
EXPLANATION
• First, it’s important to note that this graph is a
distractor on this question. It has nothing to do with
the question.
• Choices A, B, and C are all the same – gene flow is
the movement of genes in and out of a population,
which is what immigration and emigration are
(organisms moving in and out of a population)
• D mutation is the only way that new genes will be
introduced into the population to increase genetic
variation
36. The importance of a uniform taxonomic system to
the scientific community includes all of the following
EXCEPT
The correct answer is
• A binomial nomenclature provides common
language.
• B species names are descriptive words.
• C ambiguity of common names is introduced.
• D two or more different kinds of organisms
may not have the same name.
EXPLANATION
• The current system of binomial nomenclature
has many advantages, but the correct answer,
C is NOT one of those. The current system
eliminates ambiguity by removing reliance on
common names.
• A – the common language is Latin
• B – the names are somewhat descriptive
• D – 2 organisms can’t have the same name
37. Which is the best description of how the fossil record
provides evidence of common ancestry?
The correct answer is
• A Analogous structures can be identified between
related groups of organisms.
• B Homologous structures can be identified
between related groups of organisms.
• C Molecular homologies can be identified
through trace remains.
• D Developmental homologies can be identified
through fossilized soft tissues.
EXPLANATION
• An analogous structure is one
that is similar in function but
does not have the same
evolutionary origin. A good
example is the wing of a
butterfly and the wing of a
bird.
• Homologies are things that
share an evolutionary origin.
Homologies can be
anatomical (like looking at
similar fossils or skeletons),
embryological, or molecular
(similar proteins or DNA)
38. Duck feet are especially well-adapted for life in the water.
Sharp claws allow them to better navigate the wet, slippery
environment and webbed toes aid in their swimming ability.
These adaptations probably came about as a result of
The correct answer is
• A one duck developing these favorable traits over
its lifetime and passing them to its offspring
• B variation in the duck population; ducks born
with one or more of these traits were more
reproductively successful
• C nature selecting against these adaptations
• D selective breeding of ducks with these
favorable traits over many generations
EXPLANATION
• The correct answer, B, is describing how
adaptations lead to changes in populations
through natural selection and is therefore the
correct answer.
• Choice A is not possible- organisms don’t
develop adaptations in a lifetime and they
can’t pass things on that aren’t genetic
• Choice C is the opposite of what is true
• Choice D is implying that humans bred these
traits into ducks.
We’re halfway through…
here’s a little comic relief 
39. The finch beak adaptations in the graphic most likely
evolved through the mechanism of
The correct answer is
• A stabilizing selection
• B adaptive radiation
• C genetic drift
• D non-random mating
EXPLANATION
• The correct answer is B adaptive radiation because when an
organism arrives in a new environment, such as the Galapagos
Islands were, it adapts through natural selection to fill all of
the available niches, resulting in a variety of related species
• Stabilizing selection is when there is less variation in a trait
due to natural selection. A example of this is human birth
weight. Babies below and above a certain weight don’t
survive, so you get a narrow curve on the graph.
• Genetic drift is change in gene frequency in a population due
to chance, such as in founder effect or population bottleneck.
• Non-random mating refers to there being a preference for
certain traits in mates.
40. Species become more diverse to
I. Occupy available niches
II. Reduce competition
III. Adapt to changing environmental conditions
The correct answer is
• A I and II only
• B I and III only
• C II and III only
• D I, II, and III
EXPLANATION
• The answer is D, I, II, and III because all three
of those explain why there is diversity or
variation within a species.
– An available niche is a habitat that is available,
including resources in which an organism can
“make a living”
– Reducing competition means that an organism is
one of a very few if not the only one wanting a
particular resource like food, water, or space
– Adapting to changing environmental conditions
refers to the process of natural selection that
results in change in gene frequency
Laugh Break!
We hope you have no days like this:
41. Given the characteristics described in the information
box , this species belongs in kingdom
The correct answer is
• A Archaebacteria
• B Fungi
• C Eubacteria
• D Protista
EXPLANATION
Characteristics of species
Unicellular
Nucleated cells
Microscopic
Motile
Inhabits aquatic environments
Protista is the correct answer by default because it
can’t be any of the other three. Archaebacteria and
Eubacteria are the 2 kingdoms of prokaryotes and
they don’t have nucleated cells. Fungi aren’t motile
and are rarely unicellular (only the yeast are).
Remember – it’s the junk drawer of classification!
42. The organism pictured, Escherichia coli,
is a common symbiont in mammalian digestive systems.
This organism has a circular chromosome located in a
region of the cell called the nucleoid (A), a rigid outer
cell wall (B), and a semi-permeable cell membrane (C).
To which kingdom does this organism belong?
The correct answer is
• A Archaebacteria
• B Eubacteria
• C Protista
• D Fungi
EXPLANATION
• The correct answer is B Eubacteria because
– Archaebacteria aren’t known symbionts, and
– Protista and Fungi are eukaryotes, which means
they will have linear chromosomes in a nucleus,
not a circular chromosome in the nucleoid region.
43. Fungi are unique among eukaryotes in that they are
The correct answer is
• A unicellular
• B multicellular
• C autotrophic
• D decomposers
EXPLANATION
• The key word here is “unique”. In the eukaryotes,
the protists are also unicellular; both animals and
plants as well as some protists are multicellular, and
some protists and all plants are autotrophs (which
fungi aren’t, by the way, they’re heterotrophic by
absorption). Only fungi are decomposers (along with
the prokaryotic bacteria!)
44. The animal species in the illustration has the following
characteristics; it breathes with lungs, maintains a constant
body temperature, has hair, gives live birth, and nurses young
with milk. These characteristics place the animal in the class
The correct answer is
• A Amphibia
• B Aves
• C Mammalia
• D Osteichthyes
EXPLANATION
Amphibia
(amphibians)
Cold- blooded
Smooth skin
Gills in young,
adults respire
through lungs, skin
Aves
(birds)
Warm-blooded
Body covered in
feathers
lungs
Mammalia
(mammals)
Warmblooded
Body covered lungs
in hair
Osteichthyes
(bony fish)
Cold-blooded
Body covered in
scales
gills
Chondrichthyes
(cartilaginous fish)
Cold-blooded
Body covered in
scales
gills
Reptilia
(reptiles)
Cold-blooded
Body covered in
scales
lungs
SCIENCE!
45. The simple sugar glucose, C6H12O6 , is formed
through the process of photosynthesis as depicted in the
chemical equation. Simple sugars are unique among biomolecules in that
The correct answer is
• A they are used by the body for long-term energy
storage.
• B they do not dissolve readily in water.
• C carbon, hydrogen, and oxygen atoms are
always found in a 1:2:1 ratio.
• D they are the building blocks of proteins.
EXPLANATION
• A is incorrect because it’s FAT that is used for
long-term energy storage
• B is incorrect because sugar will dissolve in
water
• D is incorrect because it is AMINO ACIDS that
are the building blocks of proteins.
• C is correct because 6:12:6 reduces to 1:2:1
46. When comparing the reactants and products of
photosynthesis and cellular respiration, which statement
is true?
The correct answer is
• A Carbon dioxide is a product of
photosynthesis.
• B Oxygen is a product of cellular respiration.
• C Solar energy is converted to chemical
energy in the process of photosynthesis.
• D Energy is stored in the bonds of glucose in
the process of cellular respiration.
EXPLANATION
• As you can see, the light energy that powers
photosynthesis is ultimately stored in the
bonds of ATP for cellular use.
47. When compared to the process of photosynthesis,
cellular respiration produces more
I. ATP
II. CO2
III. O2
The correct answer is
• A I only
• B II only
• C I and II only
• D I and III only
EXPLANATION
48. Enzymes are proteins which function in both catabolic
and anabolic pathways in living things. Which of the following
is NOT a characteristic of enzymes?
The correct answer is
• A Enzymes act as biological catalysts.
• B Enzymes slow down chemical reactions.
• C Enzymes reduce activation energy needed
for a chemical reaction to proceed.
• D Enzymes are re-usable.
EXPLANATION
• We typically describe
enzymes as speeding up
reactions, which is why B
is NOT a characteristic.
• Enzymes are catalysts,
which by definition are
not changed or used up
(A and D); see picture
above
• Enzymes reduce
activation energy (C); see
graph
49. Polymers such as proteins, lipids, amino acids, and
carbohydrates are formed when individual monomers are
joined through the process of dehydration synthesis.
Dehydration synthesis requires the
The correct answer is
• A loss of a water molecule
• B destruction of a water molecule
• C evaporation of a water molecule
• D addition of a water molecule
EXPLANATION
• Word Parts:
– de – to remove
– hydro – water
– syn – together
Dehydration synthesis reactions lose a molecule of
water when a bond is formed between 2
molecules.
Dehydration synthesis reactions can form
polysaccharides (carbohydrates), nucleic acids,
proteins, and some lipids
50. Which of these best describes how human body systems
interact to protect the body from injury or illness?
The correct answer is
• A The skeletal system releases calcium ions into the
organs of the respiratory system to encapsulate
bacteria and viruses in the lungs.
• B Immune system B-cells are produced in the bone
marrow of the skeletal system and introduced into
the blood stream.
• C The nervous system stimulates the digestive system
to release toxins that kill invading microbes.
• D Hormones released by viruses increase both blood
pressure and body temperature which work to
inactivate them.
EXPLANATION
• A, C, and D all
describe things
that do not
happen in the
human body.
• B describes an
immune response
such as is
pictured
(swelling,
redness, arrival
of WBCs, etc)
We love you 
51. Which is the best description of how the organ system
pictured interacts with the circulatory system to
deliver nutrients to cells?
The correct answer is
• A Nutrients are taken in through the respiratory system and are
picked up by the thin walls of capillaries in the lungs for delivery to
the rest of the body’s cells.
• B The digestive system processes food into smaller molecules
which are picked up for delivery to the body’s cells by the
circulatory system through capillaries in the small intestine.
• C The circulatory system moves the secretions from the liver,
gallbladder, and pancreas through the bloodstream for delivery to
the stomach where they are used to break down large particles.
• D Water recovered from the large intestine is picked up by
capillaries and delivered to the stomach to aid in digestion.
EXPLANATION
• A is incorrect because nutrients are not taken
in through the respiratory system
• C is incorrect because the products of those
accessory organs do not enter the circulatory
system and do not enter the stomach (they go
to the small intestine through a duct)
• D is incorrect because the water is not
delivered to the stomach
• All of choice B is accurate.
52. Which is the best explanation of how the muscular system
aids in delivering nutrients to cells?
The correct answer is
• A Layers of smooth muscle line the organs of the digestive
system, pushing the meal through the system by
involuntary contractions known as peristalsis.
• B Teeth mechanically break down food into smaller pieces
so enzymes in the digestive system have a larger surface
area to work on.
• C Microvilli in the small intestine have a large surface area
for small molecules to diffuse from the digestive system
into the bloodstream.
• D Large muscles require large amounts of energy to do
work.
EXPLANATION
• What’s tricky here is that
all 4 answer choices are
correct statements;
however, only A answers
the question!
• To the right is a picture of
peristalsis – the rhythmic
contractions of
involuntary muscle to
move particles along a
tract
53. Which is the best description of the interactions of plant
organ systems to produce the response illustrated?
The correct answer is
• A Stem tips produce a growth hormone which travels through
phloem tissues to other parts of the plant where it causes
elongation of cells on the dark side of a stem.
• B Leaves which receive excess sunlight produce a wilting hormone
that travels to other parts of the plant through vascular tissues.
• C Bright days cause leaves to lose water rapidly, which draws water
up from the roots through vascular tissues at such a pace that
stems bend due to the increased water weight.
• D Certain chemical substances in the air are taken into leaves
through stoma and as they are carried downward through vascular
tissues in the stem the increased weight causes stems to bend.
Laugh Break!
EXPLANATION
• The picture illustrates phototropism – a plant’s response to light.
Other tropisms include:
– Geotropism or gravitropism – roots grow down and shoots grow up
– Thigmotropism – vines cling and coil in response to touch
• Choice A accurately describes what happens when a plant is exposed
to light.
– Photo – light
– Tropism – response to a stimulus
– Positive – toward the stimulus
– Negative – away from the stimulus
There is no wilting hormone, that’s just a lack of water; water and chemicals do
not weigh plants down
54. Glucose produced by photosynthesis is
stored as starch in storage organs such as potatoes,
onions, and carrots. Which of these is NOT part
of the plant system interactions involved in this process?
The correct answer is
• A Leaves produce the sugar glucose through
photosynthesis.
• B Sugars produced by leaves are moved from
sink to source by xylem vessels.
• C Sugars produced by leaves are moved from
source to sink by phloem vessels.
• D Root systems store glucose as starch.
EXPLANATION
• B is an incorrect
statement because
sugar does not move in
xylem and because it
moves from the source
to the sink, not sink to
source.
• Water is carried in
Xylem – WXY
• Phloem carries phood
(food)
55. Which is the most correct description of two plant systems
interacting to perform the function of reproduction in
angiosperms?
The correct answer is
• A Carbon is obtained from the air as CO2 through stoma in
the leaves to build all of the macromolecules needed for
reproduction.
• B Carbon is obtained from the soil through the root systems
and delivered with water and other nutrients to
reproductive organs.
• C Most water is obtained in the form of water vapor
through leaf pores and delivered through phloem tissues to
reproductive organs.
• D Most water is absorbed directly through stoma during
rain events and transferred to all parts of the plant by
phloem tissues.
EXPLANATION
• A is the correct answer
because CO2 enters through
the stomata
• B is incorrect because
carbon comes from CO2 not
from the soil
• C is incorrect because very
little if any water comes
from water vapor and it
moves in xylem
• D is incorrect because water
doesn’t enter during rain
events and moves in xylem
56. Which term contains all of the others?
The correct answer is
• A tissue
• B organ
• C organ system
• D cell
EXPLANATION
• “contains all the others” means they want to know if you
choose one of those four things, which one would give you
all of them
• If you choose organ system, you will have organs in your
system, you will have tissues making up your organs, and
you will have cells making up your tissues
57. Which of the following statements is least accurate in
describing internal feedback mechanisms?
The correct answer is
• A The excretory system plays a major role in controlling water
balance, salt concentrations in the blood, and removing
nitrogenous wastes.
• B An imbalance in blood sugar regulation by the competing
hormones insulin and glucagon may result in the disease diabetes.
• C Cold-blooded organisms expend less energy than warm-blooded
organisms because they lack control mechanisms to maintain body
temperature.
• D Positive feedback mechanisms work to maintain levels within a
narrow window of parameters, whereas negative feedback
mechanisms push levels beyond the normal range.
EXPLANATION
• Negative feedback is like how a thermometer works. You set it to
produce air at a certain temperature and when the air is hotter or
colder than that, it will come on and work to return the air to the
temperature you set it at. Your body temperature is regulated in a
similar way. Your blood sugar level is regulated through negative
feedback, too.
• Positive feedback is like how praise is supposed to work. You do
something good and somebody gives you praise and you want to do
more good so you get more praise so you do more good… A
biological example is childbirth. Pressure on the cervix releases
hormones that cause contractions that put pressure on the cervix
that release hormones that cause contractions…
• D is exactly the opposite of this so it is the LEAST accurate
• A, B, and C all relate to feedback mechanisms in the bodies of
animals
58. Microorganisms such as E. coli inhabit the
digestive systems of a variety of higher organisms,
including humans. These endosymbionts help their
hosts maintain health by all of these EXCEPT
The correct answer is
• A breaking down food
• B producing key nutrients
• C infecting adjoining tissues
• D competing with harmful microorganisms
EXPLANATION
• E. coli are very important to our digestive
health. One of the most important things
they do is aid in vitamin K synthesis, which is
essential for blood clotting.
• All of our natural symbionts, such as E. coli,
help to outcomplete pathogenic
microorganisms
• Our natural symbionts do not cause infection
in healthy individuals
59. As the process of ecological succession
progresses with time, species diversity tends to
The correct answer is
• A gradually decrease from colonization to climax
community
• B be limited in early stages and increase over
time
• C increase during intermediate stages, then
rapidly decrease during the climax community
stage
• D be highest in the colonization stages
EXPLANATION
• Ecological succession is the theory that species replace
other species over time as the environment changes
until a stable ecosystem is developed. The stability
comes from the interaction of a diverse and large
number of organisms in the climax community.
• Diversity increases with succession, it does not
decrease
60. Which of these statements best summarizes the change in
populations which has occurred during the stages of
succession illustrated above?
The correct answer is
• A Populations of freshwater fish and aquatic
plants are gradually replaced by populations of
weeds and grasses as a pond fills with silt.
• B A terrestrial ecosystem is replaced by a
freshwater ecosystem.
• C A marine ecosystem is replaced by a terrestrial
ecosystem.
• D Populations of freshwater fish and aquatic
plants die off as their habit becomes filled with
silt.
EXPLANATION
• A is correct because what you see is a pond with
fish and aquatic plants that gets shallower and
shallower until it is filled with dirt (silt) and different
plants are growing there
• B and C are completely inaccurate and not
supported by the diagram
• D is not the right answer because it is incomplete
Your parents love you, too!
61. Eliminating microorganisms from an ecosystem
would have all of the following effects EXCEPT
The correct answer is
• A increased carbon dioxide available to
plants
• B plants starved of key nitrogen-containing
nutrients
• C food chains disrupted
• D decomposition would halt
EXPLANATION
• the key word is EXCEPT
• If microorganisms are eliminated :
– the nitrogen cycle would be interrupted because bacteria are the
key to the nitrogen cycle processes
– Food chains would be disrupted because the smallest organisms
feed on the microorganisms, so they would die, which means the
larger ones would die; AND the plants would die because of the
lack of nitrogen in the soil so the herbivores would die
– Bacteria are principal decomposers (along with the fungi) so there
would be a tremendous impact on this process
The CO2 available to plants would not change or would actually
decrease because of the lack of decomposition, but it would not
increase
62. Termites are incapable of digesting the wood fibers they
ingest, but maintain a population of symbiotic bacteria in their
gut which break down the wood fiber for them.
This relationship is best described as
The correct answer is
• A parasitism
• B mutualism
• C predation
• D commensalism
EXPLANATION
• Parasitism:  on host
• Mutualism:  on host
• Predation: one organism eats another
organism (predator and prey)
• Commensalism: no effect on host
This relationship is mutualism because both the
host (termite) and the bacteria are benefitting
from the relationship
63. The deer tick must feed on the blood of warmblooded mammals in order to survive. At times, as the tick
feeds it also transmits harmful bacteria to the host which
cause lyme disease. This relationship is an example of
The correct answer is
• A parasitism
• B mutualism
• C predation
• D commensalism
EXPLANATION
• Ticks suck the blood from their host to steal
nutrients from them – this is a negative effect
• Ticks that cause diseases like Lyme disease
have an even more negative effect
• When the host is negatively impacted  the
relationship is parasitism
64. Based on the adaptations listed in the table above, which
organism is best suited for life in the tropical rainforest
ecosystem?
The correct answer is
• Snowshoe hare
• Kangaroo rat
• Prairie dog
• Tarsier
EXPLANATION
• Fur, reduced ears, and changing colors in seasons
are adaptations of animals that live through long
cold winters, not tropical rainforests
• Small bodies, large ears, burrowing, and
concentrated urine are adaptations of desert
animals
• Eating grass, burrows, strong hind legs, and water
from food are adaptations for a temperate
grassland
• Living in trees, eating bugs at night, and having
excellent climbing and jumping skills are
adaptations suitable for tropical rainforests
65. In the food web, which organisms are most likely
to become overpopulated if there were a larger than
average production of seeds during a growing season?
The correct answer is
• A grouse
• B chipmunk
• C elk
• D grizzly bear
EXPLANATION
• Grouse is correct because it eats the seeds,
but has no predators keeping its population in
check, unlike the chipmunks.
66. What is the best explanation of why the numbers of
organisms at each trophic level decrease from the bottom
of the pyramid to the top?
The correct answer is
• A The organisms increase in size as you move
up the pyramid.
• B Energy is used for life processes and lost as
heat at each trophic level.
• C Energy is wasted at each trophic level.
• D There is more sunlight available to the first
trophic level.
•
A
and
D
are
true
EXPLANATION
statements, but do not
explain the pyramid.
• C is not a true statement
• B is the correct answer .
Recall that only 10% of
the energy on the
previous trophic level is
passed to the next, so
with less energy available,
fewer organisms are
supported
67. Carbon flows cyclically through organisms and the
environment. Which of the following descriptions
of the carbon cycle is NOT correct?
The correct answer is
• A Major reservoirs of carbon include tropical
forests, oceans and fossil fuels.
• B Carbon dioxide is produced through
photosynthesis and used in cellular respiration.
• C Humans may disrupt the carbon cycle by
burning fossil fuels which may result in global
warming.
• D Carbon is released to the atmosphere in the
form of CO2 through respiration in living things.
EXPLANATION
• A, C, and D are all true statements about carbon and the carbon
cycle; B is the correct answer because it is the reverse of that – CO2
is produced in respiration and used in photosynthesis
68. In an ecosystem, the simple food chain above shows the
movement of matter and energy from one organism to the
next. If disease reduced the number of organisms at the
producer level, which other organism would feel the greatest
effect?
The correct answer is
• A the mouse because it is a producer
• B the mouse because it eats producers
• C the cat since it is a 2nd order consumer
• D the coyote because it is the top consumer
in the food chain
EXPLANATION
• Because the coyote is receiving less energy than any other
organism in the food chain because only 10% is passed up
at each level, it would be the most impacted.
• If there are fewer plants, fewer mice will survive, but some
will. If a few mice survive, very few cats will survive, but
some will; and finally, if a very few cats survive, very very
few coyotes will.
• Don’t overthink the question. It is asking about THIS
FOODCHAIN, not any other organism that may or may not
exist in the ecosystem.
69. The graph depicts the growth of a population of yeast cells
over time. The dotted line labeled A most likely represents
The correct answer is
• A the limit of tolerance of the yeast cells to
environmental conditions
• B the highest number of yeast cells the
population can achieve
• C the carrying capacity of the environment
• D population size of a predator which preys on
the yeast
EXPLANATION
A
B
• On a population graph, a horizontal line typically
represents carrying capacity (K). Carrying capacity
is the number of organisms of one species the
resources in an environment can support.
• A is incorrect because it says the limit of tolerance,
and that’s not what carrying capacity measures;
highest number of yeast cells the population can
achieve is not accurate either
• D has nothing to do with the graph
Use the information in the following paragraph for the next question
Throughout the decade of the 1930’s, a series of severe dust storms blew
across the prairie lands of the United States, causing extreme ecological and
agricultural damage. Years of poor farming practices and drought resulted in
the loss of tons of topsoil to prevailing winds. Millions of acres of land became
barren and uninhabitable.
70. Which is the best description of how this event likely
impacted the natural prairie ecosystem that inhabited
the area?
The correct answer is
• A Carrying capacity of the environment
increased.
• B The mature prairie community was replaced
with weedy species.
• C Biodiversity increased.
• D Primary succession occurred.
EXPLANATION
• In the information given, it is stated that “Years of
poor farming practices and drought resulted in the loss of
tons of topsoil to prevailing winds. Millions of acres of land
became barren and uninhabitable.”
• The loss of topsoil will require D, primary
succession.
• B can be argued, but the question states that the
land was barren and uninhabitable – that means
not even weeds would grow. They might have
during the process, but the final result would have
been nothing left.
• A and C do not make sense with the information
You can do this! We know you can!
71. Which of the following most accurately shows diffusion ?
The correct answer is
• A
EXPLANATION
• Diffusion is the movement of particles from an
area of high concentration to an area of low
concentration.
• B is showing the reverse of that (which can’t
happen in nature); C & D are not showing
anything happening.
72. The rough ER is represented by which letter ?
The correct answer is
• A. 2
B. 3
C. 5
D. 6
73. The organelle where cellular respiration
takes place and glucose is converted
into ATP energy is represented by
The correct answer is
• A. 2
B. 4
C. 5
D. 6
EXPLANATION
1
2
3
5
4
6
7
Typical Animal Cell
• 1 – cell/plasma membrane –
homeostasis
• 2 – rough ER – transport of
materials through cell;
protein synthesis
• 3 nucleus – protects the DNA
• 4 ribosome – site of protein
synthesis; made in nucleolus
• 5 smooth ER – lipid synthesis
• 6 mitochondria – cellular
respiration; ATP production
• 7 vacuole – storage OR
vesicle – moving things
from one organelle to
another; endo- and
exocytosis
74. A herbicide is sprayed on foliage to eliminate weedy
plants. This herbicide remains on the leaves of sprayed
plants, is ingested by grasshoppers and accumulates in
their tissues. Songbirds then feed on the grasshoppers
and the herbicide accumulates in their tissues. Finally, the
coyote feeds on songbirds and the herbicide accumulates
in the coyote’s body. At which trophic level do the toxins
become most concentrated?
The correct answer is
• A producers
• B primary consumers
• C secondary consumers
• D top consumers
EXPLANATION
• This phenomenon is called biological magnification.
• When a toxin like DDT or a heavy metal like lead or
mercury gets into the environment, only a few
molecules enter the bodies of microorganisms, but
the larger animals consume multiple organisms at
the level below them, increasing the concentration
of those molecules in their bodies.
• Since these are substances that can’t be excreted,
they build up to tremendous levels at the top of the
food chain
75. A butterfly population has 2 alleles for wing color, pink
(gg) and green (GG or Gg). The butterflies spend most of
their time during the day in the canopies of trees. As a
result the pink butterflies are much less common than the
green butterflies due to predation by birds, lizards, and
other predators. This is an example of
The correct answer is
• A development of the butterfly due to hormonal action
• B natural selection due to varying survival rates of the two
colors of butterflies in the population
• C maturation of the butterfly as it metamorphosis into a
sexually mature adult
• D extinction as the pink butterfly becomes rarer and rarer
EXPLANATION
• Choices A and C are not correct because there
is nothing in the question to indicate that the
butterfly is developing or maturing.
• D is not correct because the pink butterfly is
unlikely to become extinct due to the fact that
the recessive allele is maintained in the
heterozygote
• B explains why the green butterflies are
common and the pink ones are rarer.
We would LOVE for you to know
everything!
This is how we hope you feel
during the EOC!
The End!