Olympiad Test: Transport And Excretion -2 - Class 7 MCQ

The droplets of water arranged at the edges of leaves or flower in the morning is due to water transpired from stomata and lenticels. 

Plants store waste materials in vacuoles and old leaves.
- Vacuoles: Vacuoles are membrane-bound structures found in plant cells. They serve various functions, including the storage of waste materials. Plant cells use vacuoles to store toxins, metabolic byproducts, and other waste substances. The vacuoles act as a repository for these waste materials, keeping them separate from the rest of the cell and preventing them from causing harm.
- Old Leaves: When plants shed their leaves, they often contain waste materials that are no longer needed by the plant. These waste materials can include metabolic byproducts, excess nutrients, and other substances that are no longer useful. Plants store these waste materials in old leaves before shedding them. This allows the plant to recycle some of the nutrients and resources stored in the leaves before they are discarded.
- Both: Therefore, the correct answer is (c) - plants store waste materials in vacuoles and old leaves.
- None of the above: The option (d) - none of the above is incorrect because plants do store waste materials in vacuoles and old leaves.

Answer:
The correct answer is C: blood is pumped from the right ventricle into the lungs.
When the muscles of the heart contract, it goes through a series of events called the cardiac cycle. During this cycle, the heart contracts and relaxes to pump blood throughout the body. Here is a detailed explanation of what happens when the muscles of the heart contract:
1. Contraction of the atria: The muscles of the atria, the upper chambers of the heart, contract first. This contraction pushes the blood into the ventricles.
2. Contraction of the ventricles: After the atria contract, the muscles of the ventricles, the lower chambers of the heart, contract. This contraction is responsible for pumping the blood out of the heart.
3. Closure of the atrioventricular valves: As the ventricles contract, the atrioventricular valves, which separate the atria from the ventricles, close. This prevents the backflow of blood into the atria.
4. Opening of the semilunar valves: Simultaneously, the contraction of the ventricles causes the semilunar valves, which separate the ventricles from the blood vessels, to open. This allows the blood to be pumped out of the heart.
5. Blood flow to the lungs: When the ventricles contract, the right ventricle pumps deoxygenated blood into the pulmonary artery. The pulmonary artery carries the blood to the lungs, where it picks up oxygen and gets rid of carbon dioxide.
Therefore, when the muscles of the heart contract, blood is pumped from the right ventricle into the lungs (Option C).

When the muscles of the heart relax, blood is pumped into the right auricle from all over the body and blood flows from lungs into the left auricle. This process occurs during the diastole phase of the cardiac cycle, which is the relaxation of the heart muscles. During this phase, the heart chambers fill with blood in preparation for the next contraction.
Here is a detailed explanation of the process:
1. Relaxation of the heart muscles:
- The diastole phase begins when the heart muscles relax.
- This relaxation allows the heart chambers to expand and fill with blood.
2. Blood flow into the right auricle:
- As the heart muscles relax, blood that has been circulated throughout the body returns to the heart.
- This deoxygenated blood enters the right atrium or auricle through the superior and inferior vena cava, which are large veins that bring blood back to the heart from the body.
- The right auricle fills with this deoxygenated blood.
3. Blood flow into the left auricle:
- Simultaneously, oxygenated blood from the lungs flows into the left atrium or auricle.
- This oxygenated blood enters the left auricle through the pulmonary veins, which carry blood from the lungs to the heart.
- The left auricle fills with this oxygenated blood.
4. Overall blood circulation:
- After the auricles are filled with blood, the next phase of the cardiac cycle begins, which is the contraction of the heart muscles (systole).
- During systole, the blood is pumped out of the heart chambers.
- From the right auricle, blood is pumped into the right ventricle and then to the lungs for oxygenation.
- From the left auricle, blood is pumped into the left ventricle and then to the rest of the body to supply oxygen and nutrients.
Therefore, the correct answer is option C: both (a) and (b).

Answer:
Blood from the left ventricle is pumped to all parts of the body. This process occurs through the systemic circulation, which delivers oxygenated blood to the organs and tissues and removes waste products.
Explanation:
The circulatory system consists of the heart, blood vessels, and blood. The heart has four chambers - two atria (left and right) and two ventricles (left and right). The left ventricle is responsible for pumping oxygenated blood to the rest of the body.
Here is a detailed explanation of how blood from the left ventricle is pumped to all parts of the body:
1. Left Ventricle Contraction: The left ventricle contracts, creating pressure that forces the blood out of the heart.
2. Aortic Valve Opens: As the left ventricle contracts, the aortic valve opens, allowing blood to flow into the aorta, which is the largest artery in the body.
3. Aorta: The aorta carries the oxygenated blood from the left ventricle to all parts of the body. It branches out into various arteries that supply blood to different organs and tissues.
4. Arteries: The arteries further divide into smaller branches called arterioles, which then lead to capillaries.
5. Capillaries: Capillaries are tiny, thin-walled blood vessels that allow for the exchange of oxygen, nutrients, and waste products between the blood and the surrounding tissues.
6. Systemic Circulation: The oxygenated blood is delivered to all the organs and tissues of the body through the extensive network of capillaries. At the same time, waste products, such as carbon dioxide, are picked up by the blood to be transported back to the heart and lungs for elimination.
7. Veins: The deoxygenated blood, now carrying waste products, returns to the heart through veins. The veins from the body merge into the superior and inferior vena cava, which then empty the blood into the right atrium of the heart.
8. Pulmonary Circulation: The deoxygenated blood is then pumped from the right atrium to the right ventricle and then to the lungs for oxygenation. This process is known as pulmonary circulation.
In summary, blood from the left ventricle is pumped to all parts of the body through the systemic circulation, ensuring the delivery of oxygen and nutrients and the removal of waste products.

-Major function of the kidneys is to remove waste products and excess fluid from the body. These waste products and excess fluid are removed through the urine. The production of urine involves highly complex steps of excretion and re-absorption.

-Blood carries oxygen and other important nutrients that all body organs need to stay healthy and to work properly. Our heart is a muscle, and its job is to pump blood throughout your circulatory system.

-our lungs are part of the respiratory system, a group of organs and tissues that work together to help us breathe. The respiratory system's main job is to move fresh air into our body while removing waste gases.

-The stomach is a hollow organ, or "container," that holds food while it is being mixed with stomach enzymes. These enzymes continue the process of breaking down food into a usable form. Cells in the lining of the stomach secrete a strong acid and powerful enzymes that are responsible for the breakdown process.

Explanation:
The increase in sugar level inside a potato during a potato experiment is due to the movement of water from outside to inside the potato. This process is called osmosis. Osmosis is the movement of water molecules from an area of lower solute concentration to an area of higher solute concentration through a semi-permeable membrane.
Here is a detailed explanation of how osmosis causes the increase in sugar level inside the potato:
- Osmosis: Osmosis is the process by which water molecules move from an area of lower solute concentration to an area of higher solute concentration through a semi-permeable membrane. In this case, the solute refers to the sugar molecules.
- Semi-permeable membrane: The potato's cell membrane acts as a semi-permeable membrane. It allows the passage of water molecules but restricts the movement of larger solute molecules such as sugar.
- Sugar solution: The potato is placed in a sugar solution. The sugar solution has a higher solute concentration compared to the potato cells.
- Concentration gradient: There is a concentration gradient between the sugar solution and the potato cells. The sugar molecules are more concentrated in the sugar solution compared to the potato cells.
- Osmotic pressure: Due to the higher solute concentration in the sugar solution, there is an osmotic pressure created. This osmotic pressure drives the movement of water molecules from outside to inside the potato cells.
- Osmosis in potato cells: As water moves into the potato cells through osmosis, it causes an increase in the overall water content inside the cells. This increase in water content leads to an increase in the sugar level inside the potato.
In conclusion, the sugar level inside a potato increases during a potato experiment due to the movement of water from outside to inside the potato cells through osmosis.

Osmosis is the flow of water molecules from the region of higher water pressure to lower water pressure through a semipermeable membrane is called osmosis.

Animals that excrete ammonia in gaseous form
- Aquatic animals are known to excrete ammonia in gaseous form. Ammonia is a toxic waste product that is produced by the metabolism of proteins and nucleic acids in the body. It needs to be eliminated from the body to prevent accumulation and harm to the animal.
- Ammonia is highly soluble in water, and aquatic animals have evolved to excrete it directly into the surrounding water through their gills or other specialized excretory structures.
- Fish, in particular, excrete ammonia as their primary nitrogenous waste product. They constantly produce ammonia as a byproduct of protein metabolism, and it is quickly eliminated through their gills. This is why fish tanks and aquariums need to be regularly maintained and their water changed to prevent ammonia buildup, which can be harmful to the fish.
- Other aquatic animals, such as crustaceans and amphibians, also excrete ammonia in gaseous form, although the mechanisms may differ slightly.
- Land animals, on the other hand, typically convert ammonia into less toxic forms such as urea or uric acid, which can be excreted in a more concentrated form. This allows them to conserve water and adapt to the drier environments of land.
- Desert animals, aerial animals, and other land-dwelling creatures may excrete urea or uric acid as their primary nitrogenous waste product, rather than ammonia.
- It is important to note that while ammonia is toxic, it is an efficient and energy-saving way for aquatic animals to excrete waste in water environments. However, the conversion of ammonia to less toxic forms in land animals allows for better water conservation and adaptation to their specific habitats.

Human heart represents:
- The human heart represents double circulation, which refers to the circulation of blood through two different pathways in the body.
- These two pathways are pulmonary circulation and systemic circulation.
- Pulmonary circulation is the circulation of blood between the heart and the lungs. It carries deoxygenated blood from the heart to the lungs to pick up oxygen and release carbon dioxide.
- Systemic circulation is the circulation of blood between the heart and the rest of the body. It carries oxygenated blood from the heart to all the organs and tissues in the body, delivering oxygen and nutrients while removing waste products.
- The heart plays a crucial role in maintaining this double circulation by pumping blood through both the pulmonary and systemic circuits.
- The heart consists of four chambers: two atria and two ventricles. The atria receive blood, and the ventricles pump blood out of the heart.
- The atria receive deoxygenated blood from the body and oxygenated blood from the lungs, while the ventricles pump deoxygenated blood to the lungs and oxygenated blood to the body.
- The heart's muscular walls contract and relax rhythmically, allowing for the continuous flow of blood and maintaining double circulation.
- This double circulation is essential for the efficient exchange of gases and nutrients throughout the body, ensuring the proper functioning of organs and tissues.