Mitochondria are membrane-bound cell organelles that generate most of the chemical energy needed to power the cell's biochemical reactions.
C is the correct answer.

Fungi are the major decomposers of nature; they break down organic matter which would otherwise not be recycled, and make it possible for members of the other kingdoms to be supplied with nutrients.
NB: bacteria are prokaryotic organisms.
B is the correct answer.

Urea causes the denaturation of Ribonuclease enzyme. Thus, the latter completely loses its activity.
B is the correct answer.

During anaphase I, homologous chromosomes are pulled apart and move to opposite ends of the cell. At the end of meiosis I, each daughter cell has one copy of homologous chromosomes (4 chromosomes) and sister chromatids are joined together at the level of the centromere (each chromosome has two chromatids)
D is the correct answer.

Habituation occurs when animals are repeatedly exposed to the same stimuli, and eventually stop responding to that stimulus.
D is the correct answer.

Structures that have no apparent function and appear to be residual parts from a past ancestor are called vestigial structures. Thus B, D and E are incorrect.
Structures that are similar in unrelated organisms are called analogous structures because they have separate evolutionary origins.
Structures that are similar in related organisms (similar embryonic origin) are called homologous structures. They are inherited from a common ancestor.
So, C is the correct answer.

10% of the energy at any trophic level is transferred to the next level. In a 4 step trophic level, the energy is transferred 3 times from the first trophic level to the fourth. That means that 10% of the energy is lost 3 times.
The amount of energy transferred from the lowest to the highest trophic level in a 4 step trophic level pyramid is 700 x (10%)³ = 0.7 kcal.
D is the correct answer.

Ionic and covalent bonds are intramolecular forces that hold atoms together within a molecule (I and III). Hydrogen bonds and the Van der Waals force are intermolecular forces are forces that exist between molecules (II and IV).
Thus, D is the correct answer.

Gel electrophoresis is a technique used to separate DNA fragments according to their size.
The solubility of fragments, the sequence of nucleotides and the composition of nitrogenous bases don’t affect the separation in an electrophoresis technique.
D is the correct answer.

A hypotonic solution has a lower solute concentration than the cytosol.
When a red blood cell is placed in a hypotonic solution, water flows from the solution into the cell due to osmosis. Therefore, the cell swells and bursts.
A is the correct answer.

Centrioles do not exist in plant cells. In plants, mitosis takes place with microtubules forming spindle fibers but without the help of centrioles.
In an animal cell, a cleavage furrow forms at the equatorial cortex after anaphase. In plants, a rigid “cell plate” is formed in the middle of the cell to form two cells.
C is the correct answer.

During strenuous exercise, your respiratory and cardiovascular systems cannot transport enough oxygen to your muscle cells. Thus the alternative pathway is lactic acid fermentation because it’s a type of anaerobic respiration that occurs when muscles have too little oxygen for aerobic respiration to continue.
Alcoholic fermentation doesn’t occur in human cells.
Calvin cycle occurs in plant cells.
Glycolysis is the first step in the breakdown of glucose to extract energy for cellular metabolism and it’s not an alternative pathway for aerobic respiration. Krebs cycle (aerobic) is a central driver of cellular respiration.
Therefore B is the correct answer.

Glycolysis is a series of reactions that extract energy from glucose by splitting it into two molecules of pyruvates.
During lactic acid fermentation pyruvate is transformed into lactate.
During alcoholic fermentation pyruvate is transformed into ethanol.
Krebs cycle occurs in the mitochondria.
Calvin cycle is a part of photosynthesis.
Therefore C is the correct answer.

Polymerase Chain Reaction (PCR) is a fast technique used to "amplify" small segments of DNA.
C is the correct answer.

Speciation occurs when a group within a species separates from other members of its species and develops its own unique characteristics.
Temporal isolation occurs when two populations differ in their periods of activity or reproductive cycles. Geographic isolation occurs when two populations occupy different habitats or separate niches within a common region. These two isolation lead to speciation.
D is the correct answer.

The right part of the heart has deoxygenated blood while the left part of the heart has oxygenated blood. The left atrium receives the oxygenated blood by the pulmonary vein. The left ventricle receives the blood from the atrium and pumps it to all the cells of the organism. While the right ventricle pumps the deoxygenate blood to the lungs by the pulmonary artery.
E is the correct answer.

The gene for color blindness is carried on the non-homologous segment of X chromosome. Since males (XY) always only inherit the Y from their fathers, sons cannot inherit color blindness from their fathers. Additionally, they only have one X chromosome inherited from their mothers, and will then only require one copy of the allele on X for the disease to affect them, even if the gene is recessive.
Assuming the allele for colorblindness is ‘d’, and the allele for ‘normal vision’ is ‘N’, we can conclude that all boys of a color blind mother (X^d X^d) are affected (X^d Y).
The chance for a carrier mother (X^N X^d) and a normal father (X^NY) to have color blind boys is 50% of boys (or 25% of children).
The chance for a carrier mother (X^N X^d) and a color blind father (X^d Y) to have color blind girls is 50% of girls or 25% of children.
E is the correct answer.

Evidence for evolution comes from many different areas of biology: anatomy, molecular biology, biogeography, fossils and direct observation. Since I, II and III belong to those areas, E would be the correct answer.

• Glycolysis occurs in the cytoplasm.
• Krebs cycle occurs in the mitochondrial matrix.
• Electron transport chain occurs in the inner membrane of the mitochondria.
• Calvin cycle occurs in the chloroplast.
• Fermentation occurs in the cytoplasm.

C is the correct answer

At the end of mitosis (at the end of telophase) the amount of DNA is 3.3 a.u in each daughter cell obtained. Each daughter cell will undergo interphase to be prepared for another mitosis. Following one of these daughter cells, it will then start G1 with 3.3 a.u. After G1, during S phase, the amount of DNA will be duplicated to 6.6 a.u. (at the end of S phase). The cell will start phase G2 with 6.6 a.u..
A is the correct answer.

Parents are normal but they carry the allele for albinism (recessive). The fetus carries two alleles for albinism (double band). Therefore, he/ she will have the condition.
C is the correct answer.

According to the graph, enzyme A is active at an acidic pH (0 < pH < 4.5), and enzyme B is active at an alkaline pH (6 < pH < 11).
The pH is highly acidic in the stomach and becomes alkaline in the small intestine.
Therefore, enzyme A is found in the stomach and enzyme B in the small intestine.
C is the correct answer.

According to the graph, the activity of enzyme A becomes 0% above pH = 4.5, thus its activity is 0% at pH = 7. While enzyme B is active at 6 < pH < 11, therefore, at pH=7 its activity is 50%.
C is the correct answer.

Each pigment has a specific color. Chlorophyll b has a green color and fucoxanthin has a brown color.
B is the correct answer.

There are five stages in the nitrogen cycle:

1. Nitrogen fixation
2. Mineralization
3. Nitrification
4. Immobilization
5. Denitrification

During the first stage, nitrogen moves from the atmosphere into the soil by nitrogen fixing bacteria.
A is the correct answer.

Imprinting is a simple and highly specific type of learning that occurs at a particular life stage. For example, when ducklings hatch, they imprint on the first adult animal they see, typically their mother.
C is the correct answer.

A, B and C are three types of symbiotic relationships. Among these relationships, mutualism represents the relationship described in the given. Mutualism is defined as: two organisms of different species "work together," each benefiting from the relationship.
C is the correct answer.

Physical and chemical barriers form the first line of defense (innate immunity). Non-specific immunity forms the second line of defense and involves in general phagocytes. Specific immunity is the third line of defense and involves in general lymphocytes. The figure represents the phagocytosis of bacteria entering the skin due to an injury. B is the correct answer.

Redness: due to the additional number of erythrocytes passing through the area.
Heat: caused by the increased movement of blood through dilated vessels into the environmentally cooled extremities.
Swelling is the result of increased passage of fluid into the surrounding tissues, the infiltration of cells and the deposition of connective tissues.
C is the correct answer.

Every food chain starts with a primary producer (autotrophs like plants…). The second trophic level, one step away from the primary producer, consists of organisms that eat the producer. They are herbivores. The third trophic level, two steps away from the primary producer, consists of organisms that eat herbivores. These are the first carnivores.
B is the correct answer.

Transcription involves the formation of mRNA. Translation involves the formation of peptide. Replication involves the formation of DNA. During RNA processing, introns are removed and exons are joined together.
A is the correct answer.

I1 has affected children. The disease is recessive which means his children both have two copies of the diseased allele, and got one copy from each parent.
Therefore, I1 has at least one copy of the disease allele ‘d’.
Since he is normal, he also carries the normal allele ‘N’.
Therefore, his genotype is Nd.
B is the correct answer.

II2 is affected and since the disease is recessive, II2 has both copies of the allele and the genotype is definitely dd.
C is the correct answer.

II4 is normal but with affected siblings so she definitely has one allele N inherited from a parent. Her parents (I1 and I2) have affected children while being normal themselves, which means they are both carriers with a Nd genotype. Doing the Punnett square, II4 has 50% chance of being Nd and 25% chance of being NN.
Since we don’t know the phenotypes of her children, her genotype cannot be known definitively.
E is the correct answer.

The ablation of the pituitary gland causes a decrease in the size of the ovaries and uterus and puts a stop to the sexual cycle. However, LH and FSH injections reverse the effects of the ablation, return the sexual cycle to normal and both the ovaries and uterus to normal development.
This means that the pituitary gland controls the development of the uterus, ovaries and sexual cycle through secretion of LH and FSH in the bloodstream (I and III).
Since grafting the pituitary gland was only effective on site (not in the abdomen), this gland only works in its site (IV).
Answer D is correct.

FSH hormone is a follicle-stimulating hormone that triggers, at a specific level, the development of follicles. While an acute rise of LH hormone level triggers ovulation.
C is the correct answer.

%G = 35%; G is complementary to C therefore there are the same amount of G and C bases: %G = %C → %C= 35%. 70% of the bases are G and C, which leaves 30% of the bases to be A and T. ( %A + %T = 100 - 70 = 30%)
A is complementary to T, there is an equal amount of A and T bases => %A = %T = 30/2 = 15%.
A is the correct answer.

A lysosome is a membrane-bound cell organelle that contains digestive enzymes. It’s involved with various cell processes. If the cell is damaged beyond repair, lysosomes can help it to self-destruct in a process called programmed cell death or apoptosis.
E is the correct answer.

In cross I, 100% of the progeny have long stem, despite one parent having short stem; we can conclude that long stem is dominant over short stem.
In cross III, parents are both long stem, so they each have at least one L allele.
However, 20 out of 80 of F1 in cross III have short stem (equivalent of 25% of F1). The short stem allele being recessive, this means they have two copies of the s allele and inherited one s allele from a parent and another s allele from the other parent. Therefore, both parents are Ls.
B is the correct answer.

A test cross can be used to determine whether a dominant phenotype (long stem) is homozygous or heterozygous by crossing it with a known phenotype (short stem, ss, recessive homozygous).
In cross IV, we obtained offsprings with 50% long stem plants (80) and 50% short stem plants (79). Working with Punnett squares done where the long stem plants are homozygous in one and hybrid in another, this phenotype percentage is obtained when the long stem parent is Ls.
Therefore, the long stem plant is hybrid.
D is the correct answer.

Plants obtained from cross I have Ls genotype. Plants obtained from cross II have ss genotype. The results of a cross between Ls and ss are as follow: 50% Ls and 50% ss

Parathyroid hormone helps prevent low calcium levels by acting on the bones, intestine and kidneys. It stimulates the release of calcium by bones into the bloodstream, the absorption of calcium by the intestine and the conservation of calcium by the kidneys.
C is the correct answer.

Antidiuretic hormone stimulates water reabsorption at the level of kidneys.
B is the correct answer.

Glucagon and insulin are two hormones secreted by the pancreas to regulate blood glucose level. Glucagon increases blood glucose level, while insulin decreases blood glucose level.
E is the correct answer.

Dorsal nerve roots carry sensory neural signals to the central nervous system. If this root is destroyed, the frog will not feel the stimulation and the message can’t reach the central nervous system. The frog wouldn’t be able to respond to the stimulus via a reflex. Therefore, the frog will not feel the stimulation and won’t react to it.
B is the correct answer.

Guard cells use osmotic pressure to open and close stomata allowing plants to regulate the amount of water and solutes within them. To open, the guard cell becomes turgid, and to close, it becomes flaccid to stop transpiration. In a dry area the plant conserves water and stops the transpiration.
Therefore E is the correct answer.

The tendency of individuals that are better adapted to a particular environment to be more successful at surviving and producing offspring is called the survival of the fittest. Therefore the given example corresponds to the survival of the fittest (answer C).

Extremely cold climate, low biotic diversity, simple vegetation structure, short season of growth and reproduction, energy and nutrients in the form of dead organic material form some of tundra characteristics.
Answer C is correct

In reference to the given table, when the amount of light decreases (the distance from light increases), the amount of oxygen produced decreases. III is correct.
At a distance of 10 cm from the light, 39 bubbles of oxygen are produced per minute, therefore at a distance of 15 cm from the light (distance increases), there would be less bubbles of oxygen produced than at 10 cm (amount of oxygen produced decreases). IV is correct.
Answer E is correct.

In the presence of light, plants undergo photosynthesis. During photosynthesis, plants release oxygen. Thus, if the rate of photosynthesis increases, the amount of oxygen produced increases. As the plant gets closer to light, the rate of photosynthesis increases.
Answer A is correct.

The five alternatives are cellular processes. Among these processes, pinocytosis is defined as a biological process of taking in fluid together with its contents into the cell.
B is the correct answer.

Digestive enzymes include:

• amylase produced in the mouth to break down large starch molecules.
• pepsin produced in the stomach to break down proteins.
• trypsin produced in the pancreas and released in the small intestine to break down proteins.
• lipase produced in the pancreas and released in the small intestine to break down fats.

In reference to the bar graph, we can conclude that the digestion of food X starts in the stomach (by pepsin enzyme) and continues in the small intestine (by trypsin enzyme). Therefore, the correct answer is D.

q corresponds to the frequency of the recessive allele ‘s’. The frequency of affected individuals (ss) will then correspond to q².
In a population of 10000, 36 individuals are affected, therefore:
q² = 36/ 10000 = 3.6x10^-3
q = √(q²) = 0.06= 6%

p + q = 1
q= 0.06 => p= 0.94 = 94%

p corresponds to the frequency of the dominant allele ‘S’.
The frequency of homozygous dominant individuals (SS) will then correspond to p².
p² = 0.94 = 0.8836= 88.36%

q² = 36/ 10000= 3.6 x 10^-3 = 0.36%

The frequency of hybrid individuals (Ss) corresponds to 2pq.
Applying Hardy-Weinberg equation: p² + 2pq + q² = 1
2pq = 1- 0.8836- 3.6 x 10^-3 = 0.1128 = 11.28%

During metaphase, chromosomes line up at the equatorial plate and sister chromatids of each chromosome are captured by microtubules from opposite spindle poles.
The correct answer is C.

Each cell starts its cycle with interphase during which DNA is duplicated to obtain chromosomes with 2 chromatids each ready to be separated during mitosis.
A cell that undergoes mitosis gives at the end of the division two identical daughter cells. The cell shown in the figure started with 2n= 4 (4 chromosomes of 2 chromatids each) and will end with 2 cells each contains 2n= 4 (4 chromosomes of 1 chromatid each).
B is the correct answer.

Bacteria are prokaryotes and have been the very first organisms to live on Earth. So the first cells were prokaryotes. The primordial atmosphere was oxygen-free so there were only anaerobic heterotrophic bacteria.
Answer A is correct.

m-RNA is complementary to the transcribed DNA with the substitution of T by U.
Answer B is correct.

Experiment 1 shows that the voice of the predator didn’t cause the cockroach to run away. Experiments 2, 3 and 4 show that only the feeling of air produced by the predator causes the cockroach to run away.
C is the correct answer.

When the antennae are insulated with a petroleum based jelly, the cockroach runs away because it can still feel the air. Therefore, antenna are not the sense organs that receive the stimulus (air). But when the legs are covered with a petroleum based jelly, the cockroach does not run away because it cannot feel the air anymore. We can conclude that the legs are the sense organs that receive the stimulus (air) and the correct answer is B.

Between 1994 and 2000 (6 years) the volume lost was 300 gigatons: 300/6= 50
Between 2002 and 2006 (4 years) the volume lost was 250 gigatons: 250/4= 62.5
Between 2008 and 2016 (8 years) the volume lost was 1500 gigatons: 1500/8= 187.5
Between 2002 and 2016 (14 years) the volume lost was 2000 gigatons: 2000/14= 142.85
Between 1994 and 2016 (22 years) the volume lost was 2500 gigatons: 2500/22= 113.63
The highest ratio corresponds to alternative C. Therefore, answer C is correct.

Glaciers provide a scientific record of how climate has changed over time. Through studying glaciers, we gain valuable information about the extent to which the planet is rapidly warming. They provide scientists a record of how climate has changed over time. The rise of earth’s temperature causes the ice melting. Therefore, B is the correct answer.

In reference to the bar graph E is the correct answer.

The blood circulatory system delivers nutrients and oxygen to all cells in the body. Oxygenated blood coming from lungs arrives to the left atrium. The latter pumps blood to the left ventricle, and this action requires a small amount of energy, thus, a small amount of mitochondria. The left ventricle pumps blood to all body cells, and this action requires a high amount of energy, thus, a high amount of mitochondria. Therefore, D is the correct answer.

When resources are available (I), yeasts reproduce rapidly (II) and few yeasts die (IV). This leads to a rapid growth of the population. On the other hand, if the medium contains a low quantity of resources, many yeasts will die. Therefore, E is the correct answer.

Due to a high rate of reproduction in phase A, resources won’t be available for the high number of yeasts (IV). Thus, the birth rate decreases and the death rate increases (I). Therefore, the growth of yeast population slows down.
C is the correct answer.

Experiment 2 shows that bile emulsifies lipids but can’t digest them into fatty acid and glycerol. But when pancreatic juice is added (experiment 3), oil drops are digested into fatty acids and glycerol. Therefore, B is the correct answer.

• Pancreatic amylase: breaks down starch molecules
• Trypsin: breaks down proteins in the small intestine
• Maltase: breaks down maltose molecules
• Lipase: breaks down fats
• Pepsin: breaks down proteins in the stomach

D is the correct answer

Leaf A is magnolia (leaf edge is smooth) and leaf B is walnut (leaflets attached at multiple points).
C is the correct answer.

Leaf F is white oak (leaf edge is lobed) and leaf G is chestnut (leaflets attached at one single point).
B is the correct answer.

The first cell contains DNA labeled with heavy nitrogen (N¹⁵). After the first cycle, two cells are obtained containing a hybrid DNA. After the second cycle, four cells are obtained: 2 cells contain hybrid DNA (labeled with both N¹⁵ and N¹⁴) and 2 cells contain light DNA (N¹⁴). Therefore, A is the correct answer.

Water molecules are capable to flow through a selectively permeable membrane. This process is called osmosis. It takes place from a hypotonic medium (low on solute) to a hypertonic medium (high on solute), thus, from medium 2 to medium 1. Therefore, C is the correct answer

As the exercise intensity increases, oxygen consumption increases then remains constant. The body tries to find another energetic source so it relies on lactic acid fermentation to supply the muscles with more energy. Therefore, A is the correct answer.

Aerobic pathway supplies the body with a high amount of energy. Oxygen consumption increases as a function of exercise intensity. At a high level of intensity, red blood cells become saturated with oxygen and can’t bind more oxygen molecules. Thus the body relies on other energetic pathways (lactic acid fermentation).
B is the correct answer.

In reference to the table, the productivity of green plants increases to reach 7 a.u. as the amount of fertilizers increases from 0 to 80 a.u. Above 80 a.u., the productivity decreases to 5.2 a.u. Thus, fertilizers are a necessary component for plant growth but in a specific quantity. Therefore, D is the correct answer.

In reference to the table, the speed of conduction increases as the diameter of the nerve fiber increases (from 1 to 15 a.u. in myelinated nerve fibers, and from 0.2 to 5 a.u. in non-myelinated nerve fibers). With the same diameter (1 µm), the speed of conduction of nerve impulses is faster in myelinated nerve fibers (1 a.u. in myelinated nerve fibers and 0.2 a.u. in non-myelinated nerve fibers).
A is the correct answer.

The figure shows one factor that affects transpiration: humidity, in the form of water droplets.
D is the correct answer.