Question 1

In animal cells, diffusion is only effective

Accepted Answer

Diffusion is a slow process and is only effective over short distances, such as less than one or two millimetres, due to the time it takes for molecules to move across these distances.

Question 2

Which of the following statements about open circulatory systems is true?

Accepted Answer

E

Question 3

In an animal with an open circulatory system

Accepted Answer

In animals with an open circulatory system, the circulating fluid (hemolymph) mixes freely with the interstitial fluid, allowing direct exchange of nutrients and waste products between cells and the circulating fluid.

Question 4

Which groups of vertebrates have a completely divided double-circuit circulatory system?

Accepted Answer

Only birds and mammals have a completely divided double-circuit circulatory system, which allows for complete separation of oxygenated and deoxygenated blood, optimizing oxygen delivery to the body.

Question 5

In vertebrate animals, functional separation of deoxygenated and oxygenated blood

Accepted Answer

The functional separation of deoxygenated and oxygenated blood enhances the efficiency of gas exchange by ensuring that oxygen-rich blood is delivered to the body tissues and oxygen-poor blood is sent to the lungs or gills for reoxygenation. This separation is a key feature of the circulatory systems of many vertebrates, particularly those with a double circulatory system, such as mammals and birds, allowing for more efficient oxygen delivery and carbon dioxide removal.

Question 6

In primitive vertebrates the sixth aortic arch carried blood from the ventral aorta through the gills to the dorsal aorta. In reptiles, birds and mammals, the derivative of this vessel carries

Accepted Answer

The answer of In primitive vertebrates the sixth aortic arch...

Question 7

In the heart of a fish, a one-way valve prevents the back flow of blood from the

Accepted Answer

The one-way valve between the conus arteriosus and the ventricle ensures that blood flows in a single direction, from the ventricle into the conus arteriosus, without allowing it to flow back into the ventricle.

Question 8

Circulation in amphibians has which of the following features?

Accepted Answer

Amphibians have a three-chambered heart (two atria and one ventricle), which allows for partial separation of oxygenated and deoxygenated blood, a characteristic of their circulatory system.

Question 9

In the conus arteriosus of the frog, mixing of deoxygenated and oxygenated blood is minimised by

Accepted Answer

The conus arteriosus of the frog has a spiral fold that minimizes the mixing of deoxygenated and oxygenated blood, ensuring more efficient circulation.

Question 10

The pattern of circulation in a submerged crocodile is most like the pattern of circulation in a

Accepted Answer

The pattern of circulation in a submerged crocodile is most like that in a human fetus because both have a specialized circulatory system that allows for efficient gas exchange and nutrient delivery in environments where direct breathing is not possible. In the case of the human fetus, this system includes structures like the ductus arteriosus and foramen ovale, which bypass the lungs, directing blood flow from the placenta throughout the body. Similarly, crocodiles have a unique cardiovascular mechanism that allows them to shunt blood away from the lungs while submerged, optimizing oxygen usage.

Question 11

In the mammalian heartbeat

Accepted Answer

In the mammalian heart, the heartbeat cycle is initiated by the sinoatrial node (not the sinus venosus, which is a term more relevant to the hearts of fish and embryonic hearts), located in the right atrium, not the left atrium or the wall of the left atrium. The atria contract first, followed by the ventricles, meaning they do not contract at the same time. However, the two ventricles do contract simultaneously to efficiently pump blood to the lungs and the rest of the body.

Question 12

In mammalian hearts, the wall of the left ventricle is thicker than that of the right ventricle because

Accepted Answer

The left ventricle pumps blood through the systemic circulation, which requires more force to overcome the higher resistance and pressure in the systemic arteries compared to the pulmonary circulation handled by the right ventricle.

Question 13

In diastole

Accepted Answer

During diastole, the heart relaxes after contraction, allowing the ventricles to fill with blood from the atria, which occurs passively. This means the mitral and tricuspid valves are open, not closed, to allow blood flow from the atria to the ventricles, contradicting options A, C, and E.

Question 14

A recording of the electrical activity of a patient's heart shows that the atria are contracting regularly and normally, but every few beats the ventricles fail to contract. Which of the following is probably not functioning properly?

Accepted Answer

The atrioventricular node is responsible for transmitting the electrical signal from the atria to the ventricles. If the atria contract normally but the ventricles fail to contract every few beats, it suggests a problem with the AV node's ability to conduct signals consistently.

Question 15

The veins of vertebrates

Accepted Answer

Veins are blood vessels that carry blood towards the heart, which is their primary function. Unlike arteries, which carry blood away from the heart and often contain oxygenated blood, veins mostly carry deoxygenated blood from the tissues back to the heart, except for the pulmonary and umbilical veins. Veins also have lower blood pressure compared to arteries and have thinner walls with less elasticity, relying on skeletal muscle contractions and valves to help move blood back to the heart.

Question 16

Refer to the following diagram showing the relative composition of the walls (endothelium, elastin fibres, smooth muscle, collagen fibres) of four different types of vessels in the vertebrate circulatory system.
 Diagram 1 is most likely

Accepted Answer

The answer of Refer to the following diagram showing the...

Question 17

Refer to the following diagram showing the relative composition of the walls (endothelium, elastin fibres, smooth muscle, collagen fibres) of four different types of vessels in the vertebrate circulatory system.
 Diagram 3 is most likely

Accepted Answer

The answer of Refer to the following diagram showing the...

Question 18

Countercurrent heat exchange

Accepted Answer

Countercurrent heat exchange is a mechanism that helps to conserve body heat by transferring heat from arteries to veins as they pass each other, typically in extremities, to minimize heat loss to the environment. This is especially important in animals living in cold environments.

Question 19

In embryonic birds, how many circulatory loops to the placenta are there?

Accepted Answer

The answer of In embryonic birds, how many circulatory loops...

Question 20

Which blood vessels carry the largest volume of blood?

Accepted Answer

Veins carry the largest volume of blood in the body, acting as a storage system and returning deoxygenated blood back to the heart. They can hold up to 70% of the body's total blood volume at any given time, which is more than any other type of blood vessel.

Quiz 24: Circulation