Selina Concise Solutions for ICSE Class 7 Biology Chapter 5 Excretion in Humans

Synopsis -

• The substances which should be excreted are :
  1. urea, uric acid
  2. Bile pigments
  3. water
  4. extra salts such as sodium
  5. chloride extra vitamins.
• The vitamins passed out into urine if in excess are vitamin B and C.
• The kidneys are situated towards the back of the abdomen at the level of last two ribs.
• Right kidney is located at slightly lower level than the left kidney.
• The ureters run from the kidney to the urinary bladder and urethra runs from urinaiy bladder to the exterior.
• Accessory excretory organs are
  1. skin
  2. lung
  3. liver
• The main function of the skin is to cool the body.
• Liver converts highly toxic ammonia produced in the body to less toxic urea.
• Liver eliminates cholesterol, bile pigments, extra vitamins, and many durgs.
• The amount of urine produced by the glomerular filtrate after reabsorption per day is 1.2 litre.

(Review Questions)

MULTIPLE CHOICE QUESTIONS :

1. Put a tick mark (✓) against the most appropriate alternative in the following statements :

(i) The kidneys are made up of tiny tubular units called :
(a) glomerulus
(b) nephrons
(c) capillaries
(d) neurons
Answer: (b) nephrons
Nephrons are the fundamental functional units that filter waste products and excess substances from the blood to form urine. Each kidney contains approximately one million of these microscopic tubes working constantly to maintain body health.
Teacher's Tip: Think of "Nephrons" as "Net-phrons" because they act like tiny nets catching waste from your blood.
Exam Tip: Do not confuse nephrons with neurons; remember that "nephro" refers to kidneys and "neuro" refers to the brain.

(ii) In human beings, urea is produced in :
(a) liver
(b) kidney
(c) spleen
(d) urinary bladder
Answer: (a) liver
The liver performs the ornithine cycle to convert toxic ammonia, a byproduct of protein metabolism, into the much less harmful substance called urea. Once produced, this urea is released into the bloodstream to be filtered out later by the kidneys.
Teacher's Tip: Imagine the liver as a factory that packages dangerous chemicals into safer containers (urea) for shipping.
Exam Tip: If the question asks where urea is produced, always choose liver; if it asks where urea is filtered, choose kidney.

(iii) Besides water, the urine mainly contains :
(a) urea
(b) nitric acid
(c) glucose
(d) bile pigments
Answer: (a) urea
Urine is composed of about 95% water and 5% waste solutes, with urea being the primary nitrogenous waste product in humans. Other components include salts, uric acid, and creatinine in much smaller concentrations.
Teacher's Tip: "Urine" and "Urea" both start with the same letters, making it easy to remember they go together.
Exam Tip: Mentioning that glucose should not be found in the urine of a healthy person can help show extra knowledge.

(iv) Filtration of excretory wastes from the blood occurs in:
(a) collecting tubule
(b) ureter
(c) urinary bladder
(d) nephrons
Answer: (d) nephrons
Filtration happens specifically in the Malpighian body of the nephron, where high pressure forces liquid waste out of the blood capillaries. This process ensures that nutrients stay in the blood while toxins are sent toward the bladder.
Teacher's Tip: Nephrons are the "active" parts of the kidney where all the real cleaning work happens.
Exam Tip: Always specify that filtration occurs in the nephron, even though the whole organ is the kidney.

Short Answer Questions

1. Fill in the blanks :

1. Nitrogenous wastes in the urine are in the form of urea and uric acid.
Answer: uric acid
These nitrogen-based compounds are created when the body breaks down proteins and nucleic acids. Removing them is essential because they can become toxic if they build up in the bloodstream.
Teacher's Tip: Think of nitrogenous wastes as the "leftover scraps" from the food your cells "eat."
Exam Tip: Be sure to mention both urea and uric acid as the two main nitrogenous wastes in humans.

2. The unit of human kidney is called nephron.
Answer: nephron
The nephron is described as the structural and functional unit because it is the smallest part of the kidney that can perform filtration. There are millions of these units packed into the outer and inner regions of each kidney.
Teacher's Tip: Just like a house is made of individual bricks, a kidney is made of individual nephrons.
Exam Tip: Use the term "uriniferous tubule" as a synonym for nephron to impress the examiner.

3. Evaporation of sweat from skin surface has cooling effect.
Answer: cooling
Sweating is a form of excretion that also helps in thermoregulation, which is the control of body temperature. As sweat turns into vapor on the skin, it absorbs heat from the body, leaving the skin feeling cooler.
Teacher's Tip: This is why you feel a chill when you stand in front of a fan while you are sweaty.
Exam Tip: Use the term "latent heat" if you want to explain why evaporation causes cooling.

2. Define the following:

(i) Excretion:
Answer: During different metabolic activities taking place in our body, the body produces many substances of which some are useful and some are useless. The process of removal of useless and harmful metabolic waste substances is called excretion.
Excretion is a vital life process that maintains the internal balance by getting rid of chemical leftovers. It prevents the accumulation of toxins that could otherwise damage cells and organs.
Teacher's Tip: Excretion is like taking out the trash from your house so it stays clean and safe.
Exam Tip: Always use the word "metabolic" when defining excretion to distinguish it from the removal of undigested food.

(ii) Excretory organs :
Answer: During different metabolic activities taking place in our body, the body produces many substances of which some are useful and some are useless. If retained in the body the unwanted substances may become poisonous and cause much harm and in severe cases, even death. The organs which remove these unwanted and toxic substances from the body are called excretory organs.
While the kidneys are the primary organs, others like the lungs and skin also help remove carbon dioxide and sweat. Together, these organs form a system that keeps the blood purified.
Teacher's Tip: Think of these organs as the "cleanup crew" of your body's biological factory.
Exam Tip: List kidneys, lungs, and skin as examples whenever you define excretory organs for a complete answer.

(iii) Dialysis :
Answer: The artificial process which cleans and filters the blood in a person where one or both the kidney may stop working properly is called dialysis.
Dialysis uses a specialized machine to act as an external kidney when the natural ones fail to filter waste. It is a life-saving treatment for patients with chronic kidney disease or failure.
Teacher's Tip: Dialysis is like a "backup filter" for the body when the main filters break down.
Exam Tip: Remember that dialysis is a temporary or regular treatment and not a permanent cure like a transplant.

(iv) Nephron:
Answer: Inside the kidney, there are millions of microscopic tubes called renal tubules or nephrons. It is the structural and functional unit of kidney.
Each nephron consists of a filter called the glomerulus and a long tubule that reabsorbs water and nutrients. The waste left behind after this process becomes urine.
Teacher's Tip: Nephrons are the "micro-machines" that do the heavy lifting of blood purification.
Exam Tip: Clearly state that the nephron is both "structural" and "functional" to secure full marks.

3. Write True (T) or False (F) for the following statements in the spaces provided. Rewrite the false statements in correct form.

1. Removal of solid undigested food is excretion
Answer: False
Correct: Removal of solid undigested food is egestion.
Egestion involves getting rid of food that the body could not digest, whereas excretion involves chemical wastes from cells. They are two different processes involving different organ systems.
Teacher's Tip: Egestion starts with "E" for "Exit" of food that never actually entered the body's cells.
Exam Tip: When rewriting, make sure to change only the key term "excretion" to "egestion" for clarity.

2. Medulla of kidney passes urine into urinary bladder.
Answer: False
Correct: Medulla of kidney passes urine into funnel-like pelvis.
The pelvis is a central collecting area that acts like a funnel to direct urine into the ureter. From the ureter, the urine then travels down to the bladder.
Teacher's Tip: The pelvis is like the "waiting room" where urine gathers before leaving the kidney.
Exam Tip: Remember the sequence: Medulla -> Pelvis -> Ureter -> Bladder.

3. Excess sugar in blood is a symption ofdiabetes.
Answer: True
Diabetes occurs when the body cannot properly regulate blood glucose levels. High sugar levels often lead to the presence of glucose in the urine, which is a key diagnostic sign.
Teacher's Tip: Think of sugar as "fuel" - if there is too much in the blood, the body tries to "dump" it into the urine.
Exam Tip: If asked why sugar appears in urine, explain that the kidneys cannot reabsorb the excess amount.

4. Urine is devoid of blood cells.
Answer: True
In a healthy urinary system, blood cells are too large to pass through the filtration membrane of the nephron. If blood cells are found in urine, it usually indicates an injury or infection in the system.
Teacher's Tip: The kidney filter is like a sieve with tiny holes that let water through but stop large "beads" like blood cells.
Exam Tip: The presence of blood in urine is called hematuria, a term you can use to show deeper understanding.

4. Name the blood vessel that brings blood to the kidneys.
Answer: Renal Artery
The renal artery carries oxygenated blood filled with metabolic wastes directly from the heart to the kidneys. Once inside, the blood is distributed to the nephrons for cleaning.
Teacher's Tip: Remember "Artery" starts with "A" for "Away" from the heart and "At" the kidney.
Exam Tip: Always use the specific name "Renal Artery" rather than just saying "artery."

5. Where in the urinary system do the following processes take place ?
Answer:
1. Urine formation: kidneys.
2. Transport of urine away from kidney: urethra.
3. Temporary storage of urine : urinary bladder.
The kidneys act as the processing center, while the bladder serves as a reservoir. The urethra is the final exit tube that allows the body to release stored urine.
Teacher's Tip: Think of the kidneys as the "factory," the bladder as the "warehouse," and the urethra as the "delivery ramp."
Exam Tip: Pay close attention to the difference between "ureter" (transport to bladder) and "urethra" (transport out of body).

Long Answer Questions

Question 1: Define excretion. Write the four organs of human urinary system in their correct sequence.
Answer:
The process of elimination of unwanted and toxic products from the body is called excretion.
The four organs of the urinary system from above to downward are:
1. kidneys
2. ureter .
3. urinary bladder
4. urethera.
Excretion is necessary to keep the internal environment of the body clean and functional. The sequence of organs ensures that waste is filtered, transported, stored, and finally eliminated in a controlled manner.
Teacher's Tip: Memorize the sequence using the acronym "K-U-B-U" (Kidney, Ureter, Bladder, Urethra).
Exam Tip: Drawing a small flow chart of these organs can help you visualize the correct sequence and avoid mistakes.

Question 2: Why is excretion necessary in living beings ?
Answer:
The excretion is necessary because the toxic products if allowed to be retained in the body act as poison and cause great harm to the body. If they exceed the threshold, they may even cause death.
Accumulated waste like urea and ammonia can change the pH of the blood and interfere with organ functions. Regular excretion ensures that the body maintains a stable internal state known as homeostasis.
Teacher's Tip: Without excretion, your body would become like a trash can that is never emptied.
Exam Tip: Mention "homeostasis" or "internal balance" to explain the deeper biological necessity of excretion.

Question 3: What is meant by osmoregulation ?
Answer:
The process of maintaining accurate concentration of water and salts in the body is called osmoregulation. This is done by the kidneys.
Kidneys adjust the amount of water reabsorbed into the blood based on how much you drink and sweat. This ensures that your cells don't swell up or shrivel away due to salt imbalances.
Teacher's Tip: Think of osmoregulation as a "thermostat" but for water and salt instead of temperature.
Exam Tip: Note that "osmoregulation" and "excretion" are two distinct but related functions performed by the kidneys.

Question 4: Describe the structure of kidney with the help of a labelled diagram.
Answer:
Section through the kidney to show different regions The kidneys is composed of:
1. an outer darker area called Cortex
2. an inner lighter area called Medulla.
The microscopic structure of kidney is formed of millions of tubules called renal tubules or nephrons.
(The diagram shows labels: MEDULLA (pyramids), CORTEX, PAPILLA OF MEDULLA, RENAL ARTERY, RENAL VEIN, PELVIS, CAPSULE, URETER.)
The cortex contains the filtering parts of the nephrons, while the medulla contains the collecting ducts that form pyramid shapes. The pelvis acts as a central basin that collects urine and funnels it into the ureter.
Teacher's Tip: Remember "C" for Cortex is the "Cover" (outer) and "M" for Medulla is the "Middle" (inner).
Exam Tip: When drawing the diagram, use sharp pencils and ensure all labels are on one side for a neater look.

Question 5: What are the two ways by which a person can get relief in case of kidney failure ?
Answer:
The two ways by which a person can get relief in case of kidney failure are:
1. Dialysis: this is a method in which an artificial machine cleans and filters the blood.
2. The patient can undergo kidney transplant.
Dialysis must be performed regularly, often several times a week, to keep the blood clean. A transplant is a more permanent solution where a healthy kidney from a donor is surgically placed into the patient's body.
Teacher's Tip: Dialysis is like renting a filter, while a transplant is like buying a brand-new one.
Exam Tip: Clearly distinguish between the artificial machine (dialysis) and the surgical replacement (transplant).

Question 6: Draw a diagram of human excretory system and label the following parts : Kidney, ureter, urinary bladder and urethra.
Answer:
(The diagram illustrates the bean-shaped kidneys, the long thin ureters connecting to the sac-like urinary bladder, and the final exit tube called the urethra.)
The kidneys filter the blood, and the resulting urine travels through the ureters. The bladder stores the urine until it is excreted through the urethra.
Teacher's Tip: Draw the kidneys like large beans and the ureters like long spaghetti strands.
Exam Tip: Label the left and right kidneys correctly; remember that in a diagram, the "right" kidney is on the viewer's left.

Question 7: How are kidney stones formed ?
Answer:
Kidney stones are formed when crystal forming substances such as calcium oxalate, calcium phosphate and uric acid are more than the fluid in the urine. When these chemicals start sticking together, they from crystals, commonly called kidney stones. They may be formed and cause severe plain.
These stones can range in size from a grain of sand to a golf ball and can block the flow of urine. Staying hydrated is the best way to prevent these substances from concentrating and forming crystals.
Teacher's Tip: Think of it like adding too much sugar to a small cup of tea; eventually, the sugar just sits at the bottom as crystals.
Exam Tip: Mentioning that "dehydration" is a major cause will show that you understand why the fluid levels matter.

Question 8: What are the symptoms of an urinary tract infection ?
Answer:
Common symptoms include a strong and frequent urge to urinate, and a painful and burning sensation while urinating.
An infection can occur in any part of the system, including the kidneys, ureters, or bladder. It is often caused by bacteria entering the system through the urethra.
Teacher's Tip: "UTI" stands for Urinary Tract Infection, and the main "red flag" is pain during urination.
Exam Tip: Listing "cloudy or strong-smelling urine" as an additional symptom can help provide a more complete answer.

Additional Questions

CHECK YOUR PROGRESS

1 State if the following statements are true or false. Correct the statemenet if it is false.

1. The organs that help our body to get rid of waste are called respiratory organs.
Answer: False. The organs that help our body to get rid of waste are called excretory organs.
Respiratory organs are primarily for gas exchange, specifically taking in oxygen and removing carbon dioxide. While carbon dioxide is a waste, the entire system for waste removal is called the excretory system.
Teacher's Tip: Remember "Respiratory" is for breathing and "Excretory" is for exiting waste.
Exam Tip: Always provide the corrected statement in full to show you understand exactly why the original was wrong.

2. Each kidney contains millions of microscopic filtering units called ureters.
Answer: False. Each kidney contains millions of microscopic filtering units called nephrons.
Ureters are large tubes that carry urine away from the kidney; they do not filter blood. Nephrons are the actual microscopic structures where filtration takes place inside the kidney tissue.
Teacher's Tip: Remember "Nephrons" are inside the kidney and "Ureters" are the tubes outside the kidney.
Exam Tip: Watch out for similar-sounding words like ureter and urethra which are often used to trick students.

3. The Bowman’s capsule and glomerulus together form the Malpighian body.
Answer: True
This structure is located at the start of the nephron and is responsible for the first stage of blood filtration. The glomerulus provides the blood pressure, and the Bowman’s capsule catches the filtrate.
Teacher's Tip: Imagine the glomerulus as a ball of yarn and the Bowman’s capsule as a cup holding it.
Exam Tip: Note that the Malpighian body is also known as the renal corpuscle.

4. Liver produces bile pigments from the haemoglobin of broken RBCs.
Answer: True
When old red blood cells are broken down, the iron is recycled, and the remaining part of the hemoglobin is turned into bile pigments like bilirubin. These pigments are eventually excreted through the digestive system.
Teacher's Tip: Think of the liver as a recycling center that processes old blood cells into digestive juices.
Exam Tip: Remember that bile pigments are what give feces their characteristic color.

EXERCISES

A.Tick the most appropriate answer.

1. The process of removing waste from the body is called
a. respiration
b. excretion
c. inspiration
d. expiration
Answer: b. excretion
Excretion is the fundamental biological process that clears metabolic toxins from the system. It involves the coordinated action of kidneys, lungs, and skin.
Teacher's Tip: Think of "Ex" in Excretion as "Exit" for waste.
Exam Tip: Be careful not to confuse excretion with egestion, which is the removal of undigested food.

2. The opening of the urinary bladder is called
a. nephron
b. uriniferous tubule
c. urethra
d. nephridia ‘
Answer: c. urethra
The urethra is the duct that allows urine to leave the bladder and exit the body. In males, it also serves a reproductive function, while in females it is purely for urination.
Teacher's Tip: Urethra has "a" at the end, and it is the "last" part of the system.
Exam Tip: Remember the sequence is bladder then urethra.

3. A network of capillaries present in the Bowman’s capsule is called
a. Malphigian body
b. glomerulus
c. Uriniferous tubule
d. ureter
Answer: b. glomerulus
The glomerulus is a tight knot of capillaries where high blood pressure pushes waste out into the capsule. It acts like a high-pressure sieve for the blood.
Teacher's Tip: Glomerulus sounds like "Glow" - imagine a glowing ball of blood vessels.
Exam Tip: If the question asks for the "network" specifically, choose glomerulus; if it asks for the "whole structure," choose Malpighian body.

4. The blood vessel that supplies impure blood to a kidney is the
a. renal artery
b. renal vein
c. portal artery
d. portal vein
Answer: a. renal artery
The renal artery brings oxygenated but waste-heavy blood to the kidney to be filtered. After the cleaning process, the purified blood leaves through the renal vein.
Teacher's Tip: "Artery" starts with "A," which stands for blood that "Arrives" at the kidney for cleaning.
Exam Tip: Don't let the word "impure" confuse you; arteries carry oxygenated blood, but in this case, that blood still contains metabolic waste.

5. The Bowman’s capsule and glomerulus together form the
a. urinary body
b. Malpighian tubule
c. Malpighian body
d. urinary tubule
Answer: c. Malpighian body
The Malpighian body is the very first part of the nephron located in the renal cortex. It is the site where the initial stage of filtration takes place.
Teacher's Tip: It's named after the scientist Marcello Malpighi who first studied these structures.
Exam Tip: Make sure to distinguish "Malpighian body" in humans from "Malpighian tubules" which are found in insects.

6. Quinine is used in the treatment of
a. filaria
b. dengue
c. malaria
d. paralysis
Answer: c. malaria
Quinine is a natural plant byproduct originally derived from the bark of the cinchona tree. While it is a "waste product" for the plant, it has been used for centuries as a medicine for humans.
Teacher's Tip: "Quinine" and "Malaria" both have an "ia" or "ine" sound that can help you link them.
Exam Tip: This question shows that plant waste products can often be very useful in human medicine.

7. Plants maintain the concentration of sap inside their body with
a. respiration
b. transpiration
c. osmosis
d. absorption
Answer: b. transpiration
Transpiration is the loss of water vapor from the leaves, which creates a pull that moves water and minerals upward. It also helps the plant get rid of excess water, similar to how humans sweat.
Teacher's Tip: Think of transpiration as a straw sucking up water from the roots to the leaves.
Exam Tip: Transpiration also helps in cooling the plant, similar to evaporation of sweat in humans.

8. Transpiration is affected by
a. light and temperature
b. humidity and wind
c. wind and temperature
d. all of these .
Answer: d. all of these .
The rate of transpiration changes based on the environment; for example, hot and windy days speed it up. High humidity, on the other hand, slows it down because the air is already full of moisture.
Teacher's Tip: Think about how clothes dry on a clothesline; they dry faster when it's sunny, windy, and warm.
Exam Tip: When "all of these" is an option, double-check if at least two other options are correct before choosing it.

B. Fill in the blanks.

1. Kidneys are a pair of reddish-brown, bean-shaped structures that lie on the either side of the backbone.
Answer: Kidneys
These organs are located in the upper abdominal area against the back muscles. Their shape is very similar to kidney beans, which is where the beans got their name.
Teacher's Tip: Just touch your lower back; that is roughly where your kidneys are located inside.
Exam Tip: Describe the shape and color (reddish-brown, bean-shaped) for a more complete answer.

2. Urine contains urea, ammonia and uric acid as nitrogenous waste.
Answer: urea, ammonia
Ammonia is the most toxic of these and is quickly converted by the liver into urea. Small amounts of uric acid are also present, produced from the breakdown of nucleic acids.
Teacher's Tip: Remember the "Three A's and U's" - Ammonia, Urea, and Uric acid.
Exam Tip: List urea first as it is the most abundant nitrogenous waste in human urine.

3. Ureter carries urine from the kidney to the urinary bladder.
Answer: Ureter
There are two ureters, one for each kidney, and they use muscle contractions called peristalsis to move urine downward. This ensures urine flows into the bladder even if you are lying down.
Teacher's Tip: Ureter has two "e's," just like you have two ureters.
Exam Tip: Don't confuse the spelling of Ureter with Urethra; remember Ureter connects the kidney to the bladder.

4. Malpighian body consists of Bowman’s capsule and glomerulus.
Answer: glomerulus
The glomerulus provides the blood to be filtered, and the Bowman’s capsule is the funnel that catches the filtrate. This partnership is what makes blood purification possible.
Teacher's Tip: It's like a coffee filter (glomerulus) and the coffee pot (Bowman’s capsule).
Exam Tip: Spelling "Malpighian" correctly is important, so practice writing it a few times.

5. Liver produces bile pigments from the haemoglobin of broken RBCs.
Answer: Liver
The liver acts as a large chemical processing plant for the entire body. By breaking down old blood cells, it creates bile, which helps digest fats while also acting as a way to excrete waste pigments.
Teacher's Tip: The liver is the body's "Master Chemist."
Exam Tip: Mention that this process helps the body get rid of old Red Blood Cells (RBCs).

6. Resins are present in the stem of pine tree that make the pinewood strong and durable.
Answer: Resins
Resins are sticky substances produced by many plants as a defense mechanism against insects and rot. For the plant, they are waste, but for humans, they are used to make varnishes and glues.
Teacher's Tip: Think of pine resin as the "thick, sticky sap" that smells like a pine forest.
Exam Tip: Resins are a great example of how plant waste can actually serve a protective purpose for the plant.

7. Morphine is found in the seeds of poppy plants.
Answer: Morphine
Morphine is a powerful chemical found in the opium poppy that has medicinal properties for pain relief. It is an example of a secondary metabolite, which is a type of chemical "waste" that plants produce.
Teacher's Tip: "Morphine" sounds a bit like "Poppy" if you think of the "o" and "p" sounds.
Exam Tip: Note that while it is useful as medicine, it is technically a metabolic byproduct for the poppy plant.

8. When air is humid, the rate of transpiration is low.
Answer: low
Humidity means there is already a lot of water vapor in the air, so it's harder for the plant to release more. This is similar to how you don't feel as cool when you sweat on a humid day because the sweat won't evaporate.
Teacher's Tip: High moisture in the air "clogs" the exit for the plant's water vapor.
Exam Tip: Remember that humidity is the only factor that has an "inverse" relationship with transpiration (more humidity = less transpiration).

C. Differentiate between

1. ureter and urethra.
Answer:
Ureter
1. It is a tube that leads out from each kidney.
2. These tubes carry urine from the kidneys of the urinary bladder.
3. There are two ureters.
Urethra
1. It is a canal like opening at the bottom of the urinary bladder.
2. This opening excretes urine out of the body.
3. There is only one urethra.
The ureters are the transport system between internal organs, while the urethra is the exit out of the entire body. The ureters work in a pair, whereas the urethra is a single tube.
Teacher's Tip: Ureter (longer word) is the longer tube; Urethra (shorter word) is the shorter tube.
Exam Tip: Use a table format for "differentiate between" questions to make your answers easy for the examiner to read.

2. bowman’s capsule and glomerulus.
Answer:
Bowman’s capsule
1. Each nephron of kidney consists of a cup-shaped structure at one end called the Bowman’s capsule.
Glomerulus
1. Glomerulus is a network of blood capillaries present inside the Bowman’s capsule.
The Bowman's capsule acts as a receiving cup that collects the fluid squeezed out of the blood. The glomerulus is the actual cluster of blood vessels that provides the pressure for filtration.
Teacher's Tip: Think of the glomerulus as the "sprinkler" and the Bowman's capsule as the "bucket" catching the water.
Exam Tip: Mention that these two parts together form the Malpighian body for a more detailed answer.

3. tannins and resins
Answer:
Tannins
1. These are group of complex compounds found in the bark and leaves.
2. Its presence in tea leaves makes tea taste bitter.
Resins
1. These are the secretions of many plants like coniferous trees.
2. It is used in the production of varnishes and adhesives and perfumes and incense.
Tannins are often dissolved in the plant's fluids and help protect the plant from being eaten by being bitter. Resins are thicker and sticky, used to seal wounds in the plant's bark.
Teacher's Tip: Tannins make tea "Tingy" (bitter); Resins make pine trees "Runny" (sticky).
Exam Tip: For plant waste products, giving a common example (like tea for tannins) helps illustrate the point well.

4.excretion and transpiration
Answer:
Excretion
1. It is the process of removing or getting rid of waste matter from the body.
2. Excretion rate is independent of time of the day.
3. All living beings have special organs called excretory organs to get red of their harmful wastes.
4. It occurs both in plants and animals.
Transpiration
1. It is the process of losing excess water from aerial plant parts in the form of water vapour.
2. Rate of transpiration is more during the day.
3. Plants lose water through stomata and lenticels.
4. It occurs only in plants.
Excretion is a general term for getting rid of all chemical wastes, while transpiration is specifically about water loss in plants. While excretion happens constantly, transpiration is heavily influenced by sunlight and heat.
Teacher's Tip: Excretion is "general cleaning"; Transpiration is "water evaporation."
Exam Tip: Be sure to mention that transpiration happens "only in plants" as a key difference.

D. Find the odd one out. Give reasons for your choice.

1. ureter, kidney, urinary bladder, lung, urethra
Answer: lung, because all others are organs of excretory system and it is a respiratory organ.
While the lung does help remove carbon dioxide waste, it is primarily categorized as part of the respiratory system. The other organs listed are the primary components of the urinary system specifically.
Teacher's Tip: Group the organs by their "main job" to find the odd one.
Exam Tip: Always provide the "reason" part clearly, as that is usually worth half the marks.

2. skin, heart, lung, liver, kidney
Answer: Heart because it helps to pump blood in our body and the rests help in excretion.
The heart is the central organ of the circulatory system and doesn't remove waste from the body itself. The others all have a specific role in filtering or eliminating waste products.
Teacher's Tip: The "Heart" is a pump, while the others are "Filters" or "Exits."
Exam Tip: Make sure to identify which system the "odd one" belongs to (circulatory system in this case).

3. tannin, urine, latex, resin
Answer: urine, because it is excretory product of animals and rests are excretory products of plants.
Tannin, latex, and resin are all secondary metabolites produced by plants during their metabolic processes. Urine is the liquid waste produced by mammals and other animals.
Teacher's Tip: Look at the "source" of the waste (Plant vs. Animal).
Exam Tip: Categorizing the items into "plant products" and "animal products" is the key to this question.

E. Answer the following in short.

1. What is excretion ?
Answer: The process of removing waste, formed as a result of chemical reactions in the body is called excretion.
Chemical reactions, or metabolism, produce byproducts that can be harmful if they stay in the blood. Excretion is the way our body maintains a healthy internal environment by clearing these out.
Teacher's Tip: "Excretion" means "Exit of Waste."
Exam Tip: Include the phrase "formed as a result of chemical reactions" to make your definition scientifically accurate.

2. What are the main organs involved in the human excretory system ?
Answer: The main organs involved in the human excretory system are a pair of bean shaped kidneys, ureters from each kidney, urinaiy bladder, urethra.
Each organ has a specific role: kidneys filter, ureters transport, bladder stores, and urethra eliminates. Together, they work as a pipeline to keep the body's blood clean.
Teacher's Tip: Remember the system is like a "filter-and-flush" mechanism.
Exam Tip: Mentioning that there are "a pair" of kidneys and "a pair" of ureters adds important detail.

3. What is urethra ?
Answer: Urethra is a canal like opening at the bottom of the urinary bladder through which urine is passed out from the body.
It is the final tube in the urinary tract and is controlled by a sphincter muscle. This muscle allows us to voluntarily control when we decide to urinate.
Teacher's Tip: Urethra is the "Exit Canal."
Exam Tip: Don't spell it as "ureter"; the 'h' in urethra helps you remember it's the last part.

4. List five waste products of plants.
Answer: Tannins, resins, latex, gums, essential oils, caffeine, qiunine, morphine, etc.
Plants often store these wastes in their bark, leaves, or old fruit since they don't have a specialized urinary system. Many of these "wastes" are actually useful to humans for making medicines, rubber, and food.
Teacher's Tip: Think of products you see in the kitchen or workshop that come from plants (like tea or rubber).
Exam Tip: Listing more than the required "five" is a good way to ensure you get full marks if you misspell one.

5. Define transpiration in plants.
Answer: The process of losing excess water in the form of water vapour from a living plant is known as transpiration.
This mostly happens through tiny pores in the leaves called stomata. It helps the plant stay cool and also pulls more water up from the roots.
Teacher's Tip: Transpiration is like "plant breathing with water."
Exam Tip: Always specify that the water is lost "in the form of water vapour" and not liquid water.

F. Answer the following in detail.

Question 1: Draw a labelled diagram of the urinary system in human beings and describe each part.
Answer:
Human beings have urinary system to eliminate nitrogenous waste products. It consists of –
1. Kidneys – These are a pair of reddish-brown, bean-shaped structures that lie on either side of the backbone. They filter the impure blood and produce urine.
2. Ureters – A pair of ureters are tubes that lead out from each kidney. These tubes carry urine from the kidneys to the urinary bladder.
3. Urinary bladder – It is a pouch-like muscular structure in which urine is stored temporarily.
4. Urethra – It is a canal like opening at the bottom of the urinary bladder through which urine is passed out.
(The diagram illustrates the anatomical position of the kidneys connected by ureters to the bladder.)
The urinary system works like a complex plumbing system where kidneys are the filter stations and the bladder is the storage tank. This continuous process is essential for maintaining the body's pH and salt balance.
Teacher's Tip: When describing the system, start from the top (kidneys) and work your way down to the exit (urethra).
Exam Tip: Use bullet points or numbered lists for the descriptions to make them easier to read.

Question 2: Explain the structure of a nephron with the help of a diagram.
Answer:
The microscopic filtering unit of kidney is called nephron or uriniferous tubule. Each nephron consists of a cup-shaped structure at one end called Bowman’s capsule. Inside the cup is a network of blood capillaries called glomerulus. The Bowman’s capsule and the glomerulus together form the Malpighian body. The Bowman’s capsule extends into a long tubule. These tubules are surrounded by a network of renal capillaries. The urinary tubules of the nephrons in each kidney joins to form a common tube called ureter.
(The diagram labels include: GLOMERULUS, BOWMAN'S CAPSULE, URINARY TUBULE, RENAL ARTERY, RENAL VEIN, RENAL CAPILLARIES, COLLECTING DUCT.)
The nephron is where the blood is actually cleaned through three steps: filtration, reabsorption, and secretion. The long tubule is crucial because it allows the body to take back useful things like glucose and water before they are lost.
Teacher's Tip: Imagine the nephron tubule as a long "sorting conveyor belt" where the body picks out what it wants to keep.
Exam Tip: Highlight the "Malpighian body" as the primary site of filtration for a high-scoring answer.

Question 3: Describe the process of urine formation.
Answer:
The process of urine formation takes place in the following steps :
1. Glomerular Alteration – Blood containing waste material enters the kidneys through the renal artery. It then enters the glomerulus under high pressure. Water and small solutes are filtered in the Bowman’s capsule.
2. Tubular reabsorption – Filterate passes through the thin walls of the Bowman’s capsule into the urinary or renal tubule. As it passes through the tubule, water and many useful substances are reabsorbed by the renal blood capillaries.
3. Tubular secretion – The remaining liquid, along with wastes such as urea, uric acid, etc is called urine and is collected in the urinary bladder.
4. Excretion – Urine leaves the kidneys and passes into the urinary bladder through the ureters. When the urinary bladder is full, urine is passed out through the urethra.
Urine formation is essentially a process of "cleaning and reclaiming." It ensures that harmful toxins are removed while vital resources like water and sugar are not wasted.
Teacher's Tip: Remember the three steps: Filter (Glomerulus), Reabsorb (Tubule), and Collect (Bladder).
Exam Tip: Use the term "selective reabsorption" to describe how the body only takes back the "good" stuff.

Question 4: How do skin and lungs help in excretion ?
Answer:
1. Skin – excretes excess water, urea, salts and other metabolic wastes in the form of sweat. These waste products are carried by the blood from all body parts to sweat glands in the skin.
2. Lungs – Eliminate carbon dioxide produced as a result of respiration through the nose.
The skin uses sweat glands to dump excess salts and water, which also cools the body down. The lungs are responsible for removing gaseous waste, which is the byproduct of every cell breathing.
Teacher's Tip: Skin and lungs are like "secondary chimneys" that help the main "purifier" (kidneys).
Exam Tip: Always mention that skin excretes "sweat" and lungs excrete "carbon dioxide" specifically.

Question 5: Explain the process of transpiration. Describe some factors that effect it.
Answer:
Large quantities of water are absorbed by plants for photosynthesis and other processes. Excess of water is lost in the form of water vapour through the stomata and lenticels from the aerial parts of the plant by transpiration. It helps plants to maintain the concentration of sap inside the plant body. If plants do not remove excess water through transpiration, the dilute sap will prevent further absorption of water and minerals from the soil.
Factors affecting rate of transpiration are :
1. Sunlight – Rate of transpiration is more during the day as stomata are open. Stomata remain closed at night and thus no transpiration takes at night.
2. Temperature – Transpiration is more on hot days than on cold days.
3. Wind – Blowing wind removes water vapour faster from the leaves and hence transpiration rate increases.
4. Humidity – If the air is humid, rate of transpiration is low. In the rainy season, transpiration is less since humidity is more.
Transpiration creates a "pulling force" that draws water all the way from the roots to the highest leaves. It is also the main way plants regulate their internal temperature on hot days.
Teacher's Tip: Think of transpiration as a plant "breathing out water" through tiny mouth-like stomata.
Exam Tip: For humidity, use the word "inverse" - when humidity goes UP, transpiration goes DOWN.

Question 6: Write a short note on artificial kidneys.
Answer:
Artificial kidneys : Kidneys play an important role not only by filtering the blood and getting rid of waste products, but also by balancing salt levels in the body. controlling blood pressure, and stimulating the production of red blood cells. A person can lead a normal life with one kidney but when both of them stop functioning it could prove fatal if no treatment is provided. An artificial kidney or a dialyser is a machine used to filter the blood of a patient whose kidneys are damaged. This process is called dialysis.
(The diagram shows a Hemodialysis machine with "Blood flows to dialyser" and "Blood flows back to body" tubes.)
The machine works by pumping the patient's blood through a filter that uses a special fluid to pull out toxins. This technology allows people with kidney failure to survive for many years while waiting for a transplant.
Teacher's Tip: An artificial kidney is basically a "big filter machine" that sits outside your body.
Exam Tip: Mention that dialysis is necessary when "both" kidneys stop working to emphasize the seriousness of the condition.

G. Correct the sequence of the following steps to explain the process of urine formation.
1. Blood enters the glomerulus under high pressure.
2. The filtrate passes through the thin walls of the Bowman’s capsule into the renal tubule
3. As the filtrate it passes through the tubule, water and many useful substances are reabsorbed by the walls of the blood capillaries.
4. Water and small solutes are filtered in the Bowman’s capsule.
5. The remaining liquid, along with waste is called urine and is collected in the urinary bladder.
6. Blood containing waste material enters the kidneys through the renal artery.
Answer:
1. Blood containing waste material enters the kidneys through the renal artery.
2. Blood enters the glomerulus under high pressure.
3. Water and small solutes are filtered in the Bowman’s capsule.
4. The filtrate passes through the thin walls of the Bowman’s capsule into the renal tubule
5. As the filtrate it passes through the tubule, water and many useful substances are reabsorbed by the walls of the blood capillaries.
6. The remaining liquid, along with waste is called urine and is collected in the urinary bladder.
The correct sequence follows the physical path of the blood and waste through the anatomy of the nephron. It starts with entry, moves to high-pressure filtering, then to "sorting" (reabsorption), and finally to storage.
Teacher's Tip: Follow the flow: Artery -> Glomerulus -> Capsule -> Tubule -> Bladder.
Exam Tip: If you get stuck, draw a quick sketch of a nephron to help visualize which part the blood reaches first.

H. One of Harry’s organs is not functioning properly. There is extra fluid build up in his body causing swelling in his ankles and feet. What should Harry do? Tick the correct answer.

I. Which of Harry’s organs is not working properly ? (brain/heart/kidneys)
Answer: Kidneys
When kidneys fail, they can no longer remove excess water from the blood, leading to fluid retention. This fluid often settles in the lower parts of the body like ankles due to gravity, causing swelling called edema.
Teacher's Tip: Swollen ankles are a classic sign that the body's "water drainage system" is clogged.
Exam Tip: Mention that the swelling is caused by "fluid retention" to show your understanding of the pathology.

2. He should see a (nephrologist/cardiologist/neurologist)
Answer: nephrologist
A nephrologist is a doctor who specializes specifically in diseases and functions of the kidney. They are trained to manage conditions like kidney stones, infections, and kidney failure.
Teacher's Tip: Remember "Nephron" = "Nephrologist."
Exam Tip: Make sure you can identify the other doctors too: cardiologist for heart and neurologist for brain.

3. Harry most probably needs a (placemaker/dialysis/skin graft)
Answer: dialysis
Dialysis is the standard treatment to clear the excess fluid and toxins that Harry's kidneys are failing to remove. It will help reduce the swelling in his ankles by filtering his blood artificially.
Teacher's Tip: Dialysis "does the work" that Harry's kidneys can't do right now.
Exam Tip: If a patient has fluid buildup from kidney issues, dialysis is the most common immediate intervention.