Urea is derived from which of the following?

The correct answer is Gram-positive Staphylococcus.

The image shows the bacteria as round cells arranged in a cluster of four, which is a key clue. In bacterial classification:

• Cocci are spherical bacteria
• Staphylococcus commonly appears in clusters
• The flow chart specifically places “Round in clusters & Tetrads: Staphylococcus, Micrococcus” under the Cocci branch associated with Gram Positive

Since the bacteria shown are:

1. round
2. arranged in a cluster/tetrad
3. matched by the flow chart to Staphylococcus

the best answer is Gram-positive Staphylococcus.

Step-by-Step Reasoning from the Flow Chart

1. Identify the shape

The bacteria in the image are circular, not rod-shaped or spiral-shaped.

That means they are cocci.

2. Identify the arrangement

The cocci are arranged in a cluster of four, also called a tetrad.

The flow chart shows:

• Round in clusters & Tetrads: Staphylococcus, Micrococcus
• Oval Shape in Chains: Streptococcus, Enterococcus

Because the image is not a chain, we eliminate Streptococcus-type organisms.

3. Match with answer choices

Now compare the answer choices:

• Gram-negative Micrococcus → incorrect, because the flow chart places Micrococcus with Gram-positive cocci
• Gram-negative Lactobacillus → incorrect, because Lactobacillus is rod-shaped, not cocci, and not gram-negative here
• Gram-positive Staphylococcus → correct
• Gram-positive Streptomyces → incorrect, because Streptomyces is not round clustered cocci

So the correct answer is C. Gram-positive Staphylococcus.

Why the Other Choices Are Incorrect

A. Gram-negative Micrococcus

This is incorrect because Micrococcus is associated with round clusters/tetrads, but it is not listed as gram-negative on the chart. The chart places that cocci grouping under Gram Positive.

B. Gram-negative Lactobacillus

This is incorrect because Lactobacillus is not spherical cocci. It is associated with a rod-like bacterial form, and the image clearly shows round bacteria.

C. Gram-positive Staphylococcus

This is correct because:

• the cells are cocci
• they are arranged in a cluster/tetrad
• the flow chart matches this arrangement with Staphylococcus

D. Gram-positive Streptomyces

This is incorrect because Streptomyces does not match the spherical clustered appearance shown. It is not the cocci arrangement in the diagram.

Key Concept

This question tests two major microbiology ideas:

1. Bacterial shape

Common bacterial shapes include:

• Cocci = spherical
• Bacilli = rod-shaped
• Spirilla/Vibrio = spiral or curved

2. Bacterial arrangement

Bacteria can also be identified by how they are arranged:

• Clusters → often suggests Staphylococcus
• Chains → often suggests Streptococcus
• Tetrads → groups of four cocci

A useful exam shortcut is:

• Staph = clusters
• Strep = chains

That helps with many TEAS microbiology questions.

Take Away Points

• Cocci are round bacteria.
• Staphylococcus is typically found in clusters.
• Streptococcus is typically found in chains.
• The pictured bacteria are round and clustered, matching Staphylococcus.
• Based on the flow chart, the correct identification is Gram-positive Staphylococcus.

This question refers to the structure of neurons and how nerve signals (action potentials) travel quickly through the nervous system.

The key phrase in the question is:

“insulating sheath that facilitates rapid movement of the action potential down the axon.”

This structure is the myelin sheath, which is made of myelin.

1. What is Myelin?

Myelin is a fatty insulating substance that surrounds the axon of many neurons.

It forms a covering called the myelin sheath.

This sheath helps:

• Protect the axon
• Insulate the electrical signal
• Speed up nerve impulse transmission

2. How Myelin Speeds Up Nerve Signals

Normally, an electrical impulse moves continuously along an axon.

However, when the axon is covered with myelin, the signal jumps between small gaps called Nodes of Ranvier.

This process is called:

Saltatory Conduction

Instead of traveling slowly along the entire axon, the impulse jumps from node to node, greatly increasing the speed of transmission.

Example speeds:

• Unmyelinated neuron: ~1 m/s
• Myelinated neuron: up to ~120 m/s

3. Cells that Produce Myelin

Different cells produce myelin depending on the part of the nervous system.

Why the Other Options Are Incorrect

Myosin

Myosin is a motor protein found in muscle cells that works with actin to cause muscle contraction.

It has nothing to do with nerve insulation.

Actin

Actin is a structural protein involved in:

• muscle contraction
• cell shape
• cytoskeleton structure

It is not part of nerve insulation.

Sarcomere

A sarcomere is the functional unit of muscle fibers responsible for muscle contraction.

It is unrelated to neuron signal conduction.

Key Takeaway Points

Myelin insulates axons

The myelin sheath surrounds axons and helps speed up nerve impulse transmission.

Myelin enables saltatory conduction

Electrical signals jump between nodes of Ranvier, making nerve impulses travel faster.

Damage to myelin affects nerve signals

Diseases like Multiple Sclerosis (MS) occur when myelin is damaged, slowing nerve signal transmission.

Myelin is made by glial cells

• Schwann cells (peripheral nervous system)
• Oligodendrocytes (central nervous system)

TEAS Exam Memory Trick

Remember:

Myelin = insulation for neurons

Just like insulation on an electrical wire helps electricity travel efficiently, myelin helps nerve signals travel quickly.

This question involves Mendelian genetics, specifically dominant and recessive alleles.

The problem describes two separate traits:

1️⃣ Ear type
2️⃣ Hair length

We must determine the genotype that produces attached ears and short hair.

Step 1: Ear Type Genetics

The question states:

• F = Free ears (dominant)
• f = Attached ears (recessive)

Because attached ears are recessive, the dog must inherit two recessive alleles to show this trait.

Therefore the genotype must be:

ff

If even one F allele were present (Ff), the dog would have free ears.

Step 2: Hair Length Genetics

The question also states:

• S = Short hair (dominant)
• s = Long hair (recessive)

Since short hair is dominant, the dog only needs at least one S allele to show short hair.

Possible genotypes for short hair are:

• SS
• Ss

Among the answer choices, the genotype that includes short hair is Ss.

Step 3: Combine Both Traits

We combine the two genotypes:

Final genotype:

ffSs

Why the Other Options Are Incorrect

FfSs

This would produce free ears, because F is dominant.

ffss

This would produce attached ears AND long hair, because ss causes long hair.

Ffss

This would produce free ears and long hair, which does not match the question.

Key Takeaway Points

1️⃣ Dominant vs Recessive Traits

2️⃣ Recessive traits require two recessive alleles

For the dog to have attached ears, the genotype must be:

ff

3️⃣ Dominant traits only require one dominant allele

For short hair, either genotype works:

• SS
• Ss

4️⃣ Multiple traits are solved separately

When solving genetics problems:

1. Identify genotype for each trait separately
2. Combine the results

TEAS Exam Memory Trick

Remember:

Recessive trait = double letters

Examples:

This question relates to how the autonomic nervous system regulates heart rate.

The heart rate is controlled by two major branches of the autonomic nervous system:

1. Role of the Sympathetic Nervous System

The sympathetic nervous system is responsible for the fight-or-flight response.

When sympathetic nerve activity increases:

• The heart beats faster
• The force of contraction increases
• More blood is pumped to muscles and organs

This occurs because sympathetic nerves release norepinephrine, which stimulates the sinoatrial (SA) node, the heart's natural pacemaker.

This causes:

• Faster electrical impulses
• Faster heartbeats

2. The SA Node (Pacemaker of the Heart)

The sinoatrial (SA) node located in the right atrium controls the heart's rhythm.

It generates electrical impulses that travel through the heart, causing contraction.

When sympathetic stimulation increases, the SA node fires more frequently, leading to a faster heart rate.

3. Examples of Increased Sympathetic Output

Situations that increase sympathetic nerve activity include:

• Exercise
• Stress
• Fear
• Low blood pressure
• Shock
• Emergency situations

In these cases, the body increases heart rate to deliver more oxygen and nutrients to tissues.

Why the Other Options Are Incorrect

Increased blood volume

Increased blood volume typically activates baroreceptors, which can actually trigger reflex mechanisms that slow heart rate in order to maintain blood pressure balance.

Decreased pacemaker stimulus

If the pacemaker stimulus decreases, the SA node fires less frequently, resulting in a slower heart rate.

Decreased sympathetic nerve output

If sympathetic stimulation decreases, the heart rate will slow down, not speed up.

Key Takeaway Points

The sympathetic nervous system increases heart rate

This is part of the fight-or-flight response.

The parasympathetic nervous system slows heart rate

The vagus nerve releases acetylcholine to reduce heart rate.

The SA node controls heart rhythm

The sinoatrial node is the heart's natural pacemaker.

Norepinephrine increases heart activity

Sympathetic nerves release norepinephrine, which increases:

• heart rate
• contractility
• conduction speed

TEAS Exam Memory Trick

Think:

Sympathetic = Speed up

Parasympathetic = Pause

This helps remember that sympathetic stimulation increases heart rate.

CARDIAC CONDUCTION SYSTEM

This question tests your understanding of the scientific method, specifically why experiments are repeated.

In science, a single experiment is not enough to prove a conclusion. Scientists repeat experiments to ensure that the results are accurate, reliable, and reproducible.

The main purpose of repeating an experiment is to confirm that the results are valid and not due to random chance, error, or unusual conditions.

Therefore, the best answer is:

To verify the validity of the original findings

Why Repeating Experiments Is Important

1. Confirms results are reliable

When an experiment is repeated and produces the same results, scientists gain confidence that the findings are reliable.

If repeated experiments produce different results, the original conclusion may be incorrect or incomplete.

2. Reduces the effect of experimental errors

Experiments can be affected by many types of errors such as:

• measurement errors
• equipment malfunction
• environmental changes
• human mistakes

Repeating the experiment helps ensure that the results were not caused by accidental error.

3. Ensures results are reproducible

One of the most important principles of science is reproducibility.

Reproducibility means:

Other scientists can perform the same experiment and obtain the same results.

If results cannot be reproduced, the findings may not be scientifically valid.

Why the Other Options Are Incorrect

To expand upon the original investigation

Expanding an investigation may happen later, but it is not the main reason experiments are repeated.

Repeating an experiment focuses on confirming the original results, not expanding the scope.

To attempt to disprove the hypothesis

Scientists do test hypotheses critically, but repeating an experiment is primarily done to verify the results, not specifically to disprove the hypothesis.

To manipulate the independent variable

Manipulating the independent variable is something that occurs during the experiment itself, not the reason for repeating the experiment.

Key Takeaway Points

Repeating experiments increases reliability

If an experiment is repeated multiple times and produces the same result, the findings are considered more trustworthy.

Science requires reproducibility

Scientific results must be repeatable by other scientists.

This ensures the findings are valid and objective.

Replication strengthens conclusions

Replication means performing the same experiment again to confirm the results.

More replication = stronger scientific evidence.

One experiment is never enough

In science, conclusions are supported by multiple trials and repeated experiments.

This helps eliminate random error or coincidence.

TEAS Exam Memory Trick

Think of the phrase:

“Repeat to Verify.”

Experiments are repeated to verify results and confirm that findings are valid and reliable.

The original hypothesis says that parasitic worm infestation is damaging to the host. Then the new finding adds an important detail: worm infestation can relieve the effects of certain autoimmune disorders.

That means the hypothesis should not be thrown out completely, but it should be revised to include this newly discovered benefit in some situations.

Choice B is best because it directly matches the new evidence:

• the worms can relieve effects
• relieving effects means they can reduce severity
• this applies to certain autoimmune disorders, not all disorders

Why the other choices are not correct:

A. Lack of worm infestations is the cause of some autoimmune disorders.
This goes too far. The question only says worm infestation can relieve the effects of some autoimmune disorders. It does not say that not having worms causes those disorders.

C. Worm infestations exacerbate the body's immune reactions.
“Exacerbate” means make worse. But the new finding says worm infestation can relieve effects, so this is the opposite of what the evidence supports.

D. Worm infestation prevents the body from immune malfunction.
This is too absolute. The question says worm infestation can relieve the effects of certain autoimmune disorders. It does not say worm infestation completely prevents immune malfunction.

Key Reasoning

When a hypothesis is modified based on new findings, the best answer usually:

• keeps as much of the original idea as possible
• adds only what the new evidence supports
• avoids extreme words like cause, prevents, or always, unless the evidence clearly proves them

Here, the evidence supports a limited revision:
worm infestation may be harmful in general, but it may also reduce the severity of some autoimmune conditions.

Takeaway Points

• A hypothesis should be revised, not automatically discarded, when new evidence appears.
• The best revision is the one that matches the evidence exactly.
• Be careful with extreme answer choices that go beyond the information given.
• In science questions, wording matters:
  • relieve effects = reduce severity
  • not necessarily cause, prevent, or cure

This question is about gas behavior, phase changes, and pressure in a sealed container.

To understand it, we need to understand sublimation and gas pressure.

1. What is Dry Ice?

Dry ice is the solid form of carbon dioxide (CO₂).

Unlike most substances, dry ice does not melt into a liquid under normal atmospheric conditions. Instead, it undergoes sublimation.

Sublimation

Sublimation is the process where a substance changes directly from:

Solid → Gas

without passing through the liquid phase.

Example:

Dry ice (solid CO₂) → CO₂ gas

2. What Happens During Sublimation in a Sealed Container?

When dry ice sublimates:

• Solid CO₂ becomes CO₂ gas molecules
• The number of gas particles increases
• Gas particles spread out and occupy more space

Because the container is sealed, the gas cannot escape.

This leads to:

• More gas molecules moving freely
• More collisions with the container walls

These collisions cause pressure.

3. Why Pressure Increases

Pressure in a container is caused by gas molecules hitting the container walls.

When dry ice sublimates:

1️⃣ More CO₂ molecules enter the gas phase
2️⃣ Gas particles spread out and occupy more volume
3️⃣ The particles collide with the container walls more frequently

More collisions = higher pressure.

Why the Other Options Are Incorrect

Gas CO₂ molecules move faster when CO₂ is a solid.

Molecules in solids move very little.
Gas molecules move much faster than solid molecules, not the other way around.

CO₂ molecules combine to form larger molecules in the gas phase.

CO₂ molecules do not combine during sublimation.
They remain individual CO₂ molecules.

CO₂ particles exert less force on the container walls as a gas.

Gas particles actually exert more force because they move freely and collide with the container walls more frequently.

Key Takeaway Points

1️⃣ Sublimation

Sublimation is the change from:

Solid → Gas

Example: Dry ice → CO₂ gas

2️⃣ Gas pressure

Gas pressure is caused by collisions of gas particles with container walls.

More particles = more collisions = higher pressure

3️⃣ Gas occupies more space than solids

Gas molecules are farther apart and move freely, allowing them to expand and fill available space.

4️⃣ Sealed containers trap gas

When gas is produced in a sealed container, pressure increases because the gas cannot escape.

TEAS Exam Memory Trick

Remember this rule:

More gas particles = More collisions = Higher pressure

The correct answer is A. Divide by 1,000.

The question asks how to convert from grams per cubic meter (g/m³) to kilograms per cubic meter (kg/m³).

The key conversion is:

1 kilogram = 1,000 grams

So when converting from grams to kilograms, you divide by 1,000.

Why this works

A kilogram is a larger unit than a gram. Whenever you convert from a smaller unit to a larger unit, the numerical value becomes smaller.

For example:

• 1,000 g = 1 kg
• 500 g = 0.5 kg
• 2,500 g = 2.5 kg

The per cubic meter (m³) part does not change, because the volume unit stays the same. Only the mass unit changes.

So:

g/m³ ÷ 1,000 = kg/m³

Example

Suppose the solubility is:

3,500 g/m³

To convert to kg/m³:

3,500 ÷ 1,000 = 3.5 kg/m³

So:

3,500 g/m³ = 3.5 kg/m³

Why the Other Choices Are Incorrect

B. Multiple by 10

This is incorrect. There is no grams-to-kilograms conversion factor of 10.

C. Multiply by 1,000

This would be used if converting from kilograms to grams, not from grams to kilograms.

D. Divide by 10

This is incorrect because grams and kilograms differ by a factor of 1,000, not 10.

Key Concept

Metric conversions depend on the relationship between units.

For mass:

• 1,000 milligrams = 1 gram
• 1,000 grams = 1 kilogram

A quick way to think about it:

• going from g → kg, divide by 1,000
• going from kg → g, multiply by 1,000

Since the denominator m³ stays the same, only the mass unit changes.

Take Away Points

• 1 kilogram = 1,000 grams
• To convert g/m³ to kg/m³, divide by 1,000
• The m³ unit stays the same during this conversion
• Converting from a smaller unit to a larger unit makes the number smaller
• Watch for metric conversion traps using 10 instead of 1,000

The correct answer is A because amino acids are the building blocks of proteins, and proteins are essential for growth, tissue repair, enzyme production, muscle development, and overall body function.

In preterm infants, growth is especially important because they are still developing rapidly and may need extra nutritional support. When supplemental amino acids are given intravenously, they can be delivered directly into the bloodstream and then used by the body to synthesize proteins. Those proteins help build and repair tissues, which directly supports growth.

Why amino acids matter for growth

Amino acids are small molecules that link together to form proteins. Proteins are needed to build:

• muscle tissue
• skin
• organs
• blood proteins
• enzymes
• hormones involved in growth and development

Because growth depends heavily on making new body tissues, providing extra amino acids gives the body the raw materials it needs to make those tissues.

Why “direct mechanism” matters

The question asks for the direct mechanism by which amino acids promote growth. The most direct role of amino acids is protein synthesis.

Although amino acids can sometimes be converted into other molecules through metabolism, their primary and most immediate growth-related function is to be assembled into proteins.

Why the Other Choices Are Incorrect

B. The supplemental amino acids are used to make carbohydrates.

This is not the best answer. Some amino acids can eventually be converted into glucose through metabolic pathways, but that is not their main direct role in promoting growth. Growth is more directly supported by protein formation.

C. The supplemental amino acids are used to make lipids.

Amino acids are not primarily used to make lipids. Lipids are mainly built from fatty acids and glycerol. While metabolism is interconnected, this is not the direct growth-promoting mechanism being tested here.

D. The supplemental amino acids are used to make nucleic acids.

Nucleic acids such as DNA and RNA are built from nucleotides, not amino acids. Amino acids are specifically the monomers of proteins.

Core Biology Concept

This question tests your understanding of biological macromolecules and their building blocks:

• Proteins are made of amino acids
• Carbohydrates are made of monosaccharides
• Lipids are made from fatty acids and glycerol
• Nucleic acids are made of nucleotides

Since amino acids specifically build proteins, and proteins are crucial for body growth, A is the correct answer.

Clinical Connection

In preterm infants, intravenous nutrition may be used because they may not be able to get enough nutrients by mouth or through normal feeding. Amino acid supplementation helps ensure they have the materials needed for:

• tissue growth
• organ development
• healing
• production of essential proteins in the body

That is why amino acids are strongly associated with supporting growth in newborn care.

Take Away Points

• Amino acids are the building blocks of proteins.
• Proteins are essential for growth and tissue repair.
• The most direct way amino acids promote growth is through protein synthesis.
• Amino acids are not the basic building blocks of carbohydrates, lipids, or nucleic acids.
• For TEAS questions, match each macromolecule with its correct monomer.

The movement of carbon dioxide (CO₂) from the blood into the alveoli of the lungs occurs primarily through diffusion, which is a type of passive transport.

1. What Happens During Gas Exchange in the Lungs?

Gas exchange occurs in tiny air sacs in the lungs called alveoli. These alveoli are surrounded by a network of capillaries that carry blood.

During respiration:

• Oxygen (O₂) moves from the alveoli → blood
• Carbon dioxide (CO₂) moves from the blood → alveoli

This exchange happens across a very thin membrane called the respiratory membrane.

2. What Is Diffusion?

Diffusion is the movement of molecules from an area of higher concentration to an area of lower concentration.

No energy (ATP) is required.

In the lungs:

Because CO₂ concentration is higher in the blood, it naturally diffuses into the alveoli, where it is then exhaled from the body.

This process is called diffusion down a concentration gradient.

3. Why Diffusion Is Efficient in the Alveoli

Several features make diffusion very efficient:

• Thin alveolar walls (one cell thick)
• Large surface area of alveoli
• Moist surface
• Extensive capillary network

These features allow gases to move quickly and efficiently between blood and air.

Why the Other Options Are Incorrect

Active transport using energy

Active transport requires ATP and moves substances against their concentration gradient.

Gas exchange in the lungs does not require energy and occurs naturally through diffusion.

Conversion to carbon monoxide

Carbon dioxide is not converted into carbon monoxide during respiration.

Carbon monoxide is a toxic gas that binds strongly to hemoglobin.

Passive transport using carrier proteins

Carrier proteins are used in facilitated diffusion for substances like glucose or ions.

CO₂ is a small, nonpolar gas molecule that diffuses directly across membranes without needing carrier proteins.

Key Takeaway Points

1️⃣ Gas exchange occurs in the alveoli

Alveoli are the primary site of gas exchange in the lungs.

2️⃣ Diffusion drives gas movement

Both oxygen and carbon dioxide move through diffusion.

3️⃣ Diffusion moves substances from high → low concentration

No energy is required.

4️⃣ CO₂ transport in blood

Carbon dioxide travels in the blood in three forms:

When blood reaches the lungs, CO₂ is released and diffuses into the alveoli.

TEAS Exam Memory Trick

Remember this rule:

Gas exchange = Diffusion

If a TEAS question asks how oxygen or carbon dioxide moves in the lungs, the answer is usually:

➡ Diffusion down a concentration gradient