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

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 0 M 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

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 G
0 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

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.

SPOTTED SEED
EXPLANATION
. . . . . .
….. ….
DOTTED SEED
• Recall that codominant means that 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
• D 0

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.

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.

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.



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

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
Cold- blooded Amphibia
(amphibians)
Aves
(birds)
Mammalia
(mammals)
Osteichthyes
(bony fish)
Chondrichthyes
(cartilaginous fish)
Reptilia
(reptiles)
Warm-blooded
Warmblooded
Cold-blooded
Cold-blooded
Cold-blooded
Smooth skin Gills in young, adults respire through lungs, skin
Body covered in feathers lungs
Body covered lungs in hair
Body covered in scales gills
Body covered in scales gills
Body covered in scales lungs

45. The simple sugar glucose, C
6
H
12
O
6
, 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. CO
2
III. O
2
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)



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.

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 CO reproduction.
2 through stoma in the leaves to build all of the macromolecules needed for
• 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

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.

EXPLANATION
• A and D are true 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 CO
2 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 2 nd 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

A
EXPLANATION
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 given

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
4
Typical Animal Cell
6
7
5
• 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.