All questions of Transport in Plants for Grade 9 Exam

Plants lose gallons of water every day through the process of transpiration, the evaporation of water from plants primarily through pores in their leaves. Up to 99% of the water absorbed by roots is lost via transpiration through plant leaves.

- Root hairs are tiny, hair-like extensions of root cells.
- They significantly increase the surface area of the roots.
- This larger surface area allows for more efficient absorption of water and essential nutrients from the soil.
- While xylem transports water throughout the plant and stomata regulate gas exchange, root hairs are specifically designed for the initial uptake of water.
- Therefore, root hairs are crucial for a plant's hydration and overall health.

Main Excretory Product in Humans
The primary excretory product in human beings is urea, which plays a crucial role in the body's waste elimination process. Here's a detailed explanation:
What is Urea?
- Urea is a nitrogenous compound formed in the liver from ammonia, a toxic byproduct of protein metabolism.
- It is less toxic than ammonia, making it safer for the body to transport and excrete.
Why Urea Over Other Excretory Products?
- Ammonia: Highly toxic and requires large amounts of water for excretion. This is why aquatic animals excrete ammonia directly.
- Uric Acid: Less toxic and conserves water, but it is not the primary excretory product in humans. It is more common in reptiles and birds.
- Creatinine: A breakdown product of creatine phosphate in muscle, but it is not the main waste product the body needs to eliminate.
Formation of Urea
- Urea is produced through the urea cycle in the liver, where ammonia combines with carbon dioxide.
- The kidneys filter urea from the blood, and it is excreted in urine.
Importance of Urea in Excretion
- Urea helps to regulate the body’s nitrogen balance.
- Its excretion is crucial for removing excess nitrogen from the body, maintaining homeostasis.
Conclusion
In summary, urea is the main excretory product in humans due to its less toxic nature and efficient removal from the body through urine. Understanding urea's role helps clarify why it is preferred over other nitrogenous waste products.

B

Hydra

Hydra is an animal that does not possess a circulatory system. Unlike other animals, Hydra lacks a well-developed circulatory system to transport nutrients, oxygen, and waste products throughout its body. Instead, Hydra relies on a simple diffusion process to exchange gases and nutrients with its surroundings.

Structure of Hydra

Hydra is a small, freshwater animal that belongs to the phylum Cnidaria. It has a tubular body with a mouth surrounded by tentacles at one end and a basal disc at the other end for attachment. The body of Hydra consists of two cell layers: an outer epidermis and an inner gastrodermis, separated by a jelly-like substance called mesoglea.

Diffusion in Hydra

As Hydra lacks a circulatory system, it relies on diffusion to transport substances throughout its body. Diffusion is the process by which particles move from an area of higher concentration to an area of lower concentration. In Hydra, this process occurs directly between the cells of its body and the surrounding water.

Gas Exchange in Hydra

Hydra obtains oxygen from the water through diffusion. Oxygen molecules present in the surrounding water passively diffuse into the body of Hydra, where they are taken up by the cells for respiration. Similarly, carbon dioxide, a waste product of cellular respiration, diffuses out of the body of Hydra into the surrounding water.

Nutrient Transport in Hydra

Hydra obtains nutrients through its mouth, which is connected to a simple digestive cavity. Once food is ingested, it is broken down and absorbed by the cells lining the digestive cavity. Nutrients, such as sugars and amino acids, then diffuse from these cells into the surrounding tissues for utilization.

Waste Removal in Hydra

Waste products, such as ammonia and urea, are also eliminated through diffusion in Hydra. These waste products are produced as a result of cellular metabolism and diffuse out of the cells into the surrounding water.

Simplified System

While Hydra's method of nutrient and waste exchange through diffusion is effective for its small size and simple body structure, it is not suitable for larger and more complex organisms. Animals with a more advanced circulatory system, like frogs, earthworms, and cockroaches, have specialized structures such as blood vessels, hearts, and respiratory organs to facilitate efficient transport of substances throughout their bodies.

In conclusion, Hydra is an animal that does not possess a circulatory system. It relies on diffusion for gas exchange, nutrient transport, and waste removal.

Understanding the Red Color of Blood
Blood gets its distinctive red color primarily due to the presence of hemoglobin, a vital protein found in red blood cells. Let’s explore this in detail.
What is Hemoglobin?
- Hemoglobin is an iron-containing protein that plays a crucial role in transporting oxygen from the lungs to the rest of the body.
- It is composed of four subunits, each containing an iron atom that can bind to oxygen molecules.
Role of Iron in Hemoglobin
- The iron in hemoglobin is fundamental to its function. When oxygen binds to the iron, it changes the shape of the hemoglobin molecule, allowing it to carry more oxygen.
- While iron contributes to hemoglobin's ability to transport oxygen, it is not solely responsible for the red color.
Color Variations of Blood
- Oxygenated blood (blood rich in oxygen) appears bright red, while deoxygenated blood (blood returning to the heart) is a darker red.
- This color change occurs because of how hemoglobin absorbs and reflects light when it is in different states (bound to oxygen or not).
Conclusion
- Thus, hemoglobin, with its iron content, is the primary reason for blood's red color. It’s essential not only for color but also for the vital function of oxygen transport in the body.

Fishes and other aquatic animals remove waste chemicals from their bodies by excreting cell waste as ammonia, which can easily dissolve in water. This helps them to get rid of harmful substances and maintain a healthy internal environment.

Role of White Blood Cells (WBCs)
White blood cells (WBCs), or leukocytes, are a crucial component of the immune system. Their primary role is to protect the body against infections and diseases.
Key Functions of WBCs
- Defense Against Pathogens:
WBCs identify and eliminate pathogens such as bacteria, viruses, fungi, and parasites. They recognize these foreign invaders and initiate an immune response.
- Types of WBCs:
There are several types of WBCs, each with specific functions:
- Neutrophils: The most abundant WBCs that act quickly to engulf and destroy pathogens.
- Lymphocytes: Include B cells and T cells, which play critical roles in adaptive immunity, recognizing and remembering specific pathogens.
- Monocytes: These cells transform into macrophages and help clear out dead cells and debris, as well as engulf pathogens.
- Eosinophils and Basophils: Involved in allergic reactions and combating parasites.
Immune Response Activation
- Response Coordination:
WBCs communicate with each other and with other immune system components to coordinate the body’s response to infections.
- Inflammation:
Upon detecting an infection, WBCs release chemicals that trigger inflammation, increasing blood flow to the affected area, bringing more immune cells to fight the infection.
Conclusion
In summary, the correct answer is option 'B' because white blood cells are vital for fighting against germs and protecting the body from various diseases. Their ability to detect, respond, and eliminate pathogens makes them essential for maintaining health and preventing infections.

Immediate Consequence of No Platelets in the Blood:
Platelets play a crucial role in blood clotting, so if there were no platelets in the blood, the immediate consequence would be:

Uncontrollable Bleeding:
Without platelets, the blood would not be able to clot properly. Platelets are responsible for forming clots at the site of a wound, which helps to stop bleeding. In the absence of platelets, even a small cut or injury could lead to excessive bleeding that would be difficult to control. This could potentially be life-threatening, especially in cases of major injuries or surgeries.
In addition to their role in blood clotting, platelets also play a role in wound healing and tissue repair. Without platelets, the body's ability to repair damaged tissues would be compromised, further exacerbating the consequences of uncontrollable bleeding.
In conclusion, the immediate consequence of having no platelets in the blood would be uncontrollable bleeding, which could lead to severe health complications and even death.

Excretory System in Humans
The excretory system in humans is responsible for removing waste products from the body. It plays a crucial role in maintaining the body's internal environment by filtering and eliminating metabolic waste products.

Components of the Excretory System
- Kidneys: The kidneys are bean-shaped organs that filter waste products from the blood to form urine. They also help regulate blood pressure and electrolyte balance.
- Ureters: The ureters are tubes that carry urine from the kidneys to the bladder. They ensure the flow of urine from the kidneys to the bladder.
- Bladder: The bladder is a muscular organ that stores urine until it is ready to be excreted from the body. It expands as it fills up with urine.
- Urethra: The urethra is a tube that carries urine from the bladder to the outside of the body during urination. It also plays a role in the excretory process.

Function of the Excretory System
The excretory system performs the vital function of removing waste products such as urea, excess salts, and water from the body. It helps maintain the body's internal balance and prevents the accumulation of harmful substances.
Therefore, the statement that the excretory system in humans includes the kidneys, ureters, bladder, and urethra is True. These organs work together to eliminate waste products and maintain the body's overall health and function.