AP 10th Class Biology 5th Lesson Questions and Answers Life Processes

AP State Board new syllabus AP Board Solutions Class 10 Biology 5th Lesson Life Processes Questions and Answers.

10th Class Biology 5th Lesson Life Processes Questions and Answers

10th Class Biology 5th Lesson Questions and Answers (Exercise)

Question 1.
The kidneys in human beings are a part of the system for
a) nutrition
b) respiration
c) excretion
d) transportation
Answer:
c) excretion

Question 2.
The xylem in plants is responsible for
a) transport of water
b) transport of food
c) transport of amino acids
d) transport of oxygen
Answer:
a) transport of water

Question 3.
The autotrophic mode of nutrition requires
a) carbon dioxide and water
b) chlorophyll
c) sunlight
d) all of the above
Answer:
d) all of the above

Question 4.
The breakdown of pyruvate to give carbon dioxide, water and energy takes place in
a) cytoplasm
b) mitochondria
c) chloroplast
d) nucleus
Answer:
b) mitochondria

Question 5.
How are fats digested in our bodies? Where does this process take piace?
Answer:

• Fats are present in the form of large globules in the small intestine.
• The small intestine gets the secretions in the form of bile juice and pancreatic juice respectively from the liver and the pancreas.
• The bile salts from the liver break down the large fat globules into smaller globules so that the pancreatic enzymes can easily act on them.
• This is referred to as emulsification of fats. It takes place in the small intestine.

Question 6.
What is the role of saliva in the digestion of food ?
Answer:
1. Saliva contains a digestive enzyme called salivary amylase, which breaks down starch into sugar.
2. Saliva has many functions in the digestion process as follows: It is used to lubricate the mouth. It helps to swallow the food.

Question 7.
What are the necessary conditions for autotrophic nutrition and what are its byproducts ?
Answer:

• Autotrophic nutrition takes place through the process of photosynthesis.
• Carbon dioxide, water, chlorophyll pigment and sunlight/are the necessary conditions required for autotrophic nutrition.
• Carbohydrates (food) and O₂ are the by-products of photosynthesis.
• The process of photosynthesis is commonly written as:
  6 CO₂+6 H₂O → C₆H₁₂O₆+6O₂

Question 8.
What are the differences between aerobic and anaerobic respiration? Name some organisms that use the anaerobic mode of respiration.
Answer:

Aerobic Respiration	Anaerobic Respiration
1. Aerobic respiration requires molecular oxygen.	1. Anaerobic respiration does not require molecular oxygen.
2. Aerobic respiration occurs in cyto­plasm and mitochondria.	2. Anaerobic respiration occurs in cytoplasm only.
3. The end products are CO2 and H2O.	3. The end products are CO2 and C2H5OH.
4. Large amount of energy is liberated during aerobic respiration.	4. Small amount of energy is liberated during anaerobic respiration.
5. In aerobic respiration, the respiratory materials are completely oxidized.	5. In anaerobic respiration, the respira­tory materials are incompletely oxidized.
6. During aerobic respiration, 38 ATP	6. During anaerobic respiration, only 2
moleules arfe generated.	ATP molecules are generated.
7. Reaction : C6H12O6+ 6O2 → 6CO2 + 6H2O + 680 K.Cal	7. Reaction : C6H12O6 → 2C2H5OH + 2CO2 + 56 K.Cal

Question 9.
How are the alveoli designed to maximize the exchange of gasses ?
Answer:

• Within the lungs, the passage divides into smaller and smaller tubes which finally terminate in balloon-like structures which are called alveoli.
• The alveoli provide a surface where the exchange of gasses can take place.
• The walls of the alveoli contain an extensive network of blood-vessels.
• When we breathe in, we lift our ribs and flatten our diaphragm, and the chest cavity becomes larger as a result. Because of this, air is sucked into the lungs and fills the expanded alveoli.
• The blood brings carbon dioxide from the rest of the body for release into the alveoli, and the oxygen in the alveolar air is taken up by blood in the alveolar blood vessels to be transported to all the cells in the body.

Question 10.
What would be the consequences of a deficiency of hemoglobin in our bodies?
Answer:

• Hemoglobin is a respiratory pigment that plays an important role in transporting oxygen from the lungs to different parts of the body.
• Due to the presence of hemoglobin, blood appears red in colour.
• The deficiency of hemoglobin makes an individual anemia which means fewer red blood cells.
• The deficiency of hemoglobin will decrease the oxygen-carrying capacity of the blood.
• A decrease in hemoglobin in blood will lead to slow functioning of body parts and weakness due to the less supply of oxygen, this condition is called anemia.

Question 11.
Describe double circulation of blood in human beings. Why is it necessary ?
Answer:
The circulatory system is responsible for transporting blood, nutrients, oxygen, and waste products throughout the body. In mammals, including humans, the circulatory system is divided into two circuits: pulmonary circulation and systemic circulation.

Pulmonary Circulation :

• Deoxygenated blood from the body flows into the right atrium of the heart.
• The right atrium contracts, sending the blood into the right ventricle.
• Right ventricle then pumps the deoxygenated blood to the lungs through the pulmonary arteries.
• In the lungs, carbon dioxide is exchanged for oxygen, and the blood becomes oxygenated.
• The oxygenated blood returns to the heart via the pulmonary veins, entering the left atrium.

Systemic Circulation :

• The left atrium contracts, sending oxygenated blood into the left ventricle.
• The left ventricle then pumps the oxygenated blood into the aorta, which carries it to the rest of the body.
• Throughout the body, oxygen and nutrients are delivered to cells, and waste products are picked up.
• Deoxygenated blood returns to the heart through the superior and inferior vena cava, entering the right atrium and starting the cycle again.

The term “double circulation” emphasizes that blood passes through the heart twice in one complete circuit of the body. This type of double circulation is necessary in human beings to separate oxygenated and deoxygenated blood as this enhances the efficiency of cellular respiration in humans and consequently helps in maintaining a constant body temperature.

Question 12.
What are the differences between the transport of materials in xylem and phloem?
Answer:

Xylem	Phloem
1) It transports water and minerals.	1) It transports organic nutrients.
2) The movement is generally unidirectional.	2) The movement is multidirectional.
3) It is not influenced by metabolic inhibitors.	3) Phloem transport is inhibited by metabolic inhibitors.
4) It is carried out by xylem vessels and tracheids.	4) Takes place in sieve tubes with the help of adjacent companion cells.
5) Major operating forces are diffu­sion and transpiration pull.	5) Energy (ATP) is required for translocation.

Question 13.
Compare the functioning of alveoli in the lungs and nephrons in the kidneys with respect to their structure and functioning.
Answer:

Alveoli	Nephron
1) They are tiny balloon-like structures present inside the lungs.	1) They are tubular structure present inside the kidney.
2) The walls of alveoli are very thin.	2) Each nephron has two components – Bowman’s capsule and tubules.
3) Alveoli are surrounded by the exten­sive network of blood capillaries.	3) Blood capillaries from two paths – glomerulus and peritubular capillaries.
4) Alveoli are the sites of gaseous exchange, oxygen and carbon dioxide are exchanged between the blood of capillaries and the gases.	4) Nephrons regulate the concentration of water and salts by filtering the blood, reabsorbing what is needed and excreting the non-required as urine.

10th Class NS 5th Lesson Questions and Answers (InText)

Page No.6

Question 1.
Why is diffusion insufficient to meet the oxygen requirements of multicellular organisms like humans?
Answer:

• In multicellular organisms like humans all the body cells are not in direct contact with the surrounding environment.
• Therefore every cell of the body will not get oxygen as per need by the process of diffusion from the environment. Therefore diffusion is insufficient to meet the oxygen requirements of multicellular organisms.

Question 2.
What criteria do we use to decide whether something is alive ?
Answer:

• The key factors for determining whether something is alive are : breathing, respiration, transportation, and excretion.
• A few other elements, such as growth and mobility in living beings, are also crucial.
•  A living organism can also have movements, which are not visible to the naked eye.

Question 3.
What are outside raw materials used for by an organism ?
Answer:

• All living organisms require outside raw materials to survive and sustain themselves.
• Animals take in food, oxygen, and water as outside raw materials.
• Plants take in carbon dioxide, water, and sunlight as outside raw materials.
• Oxygen is used in breaking down the food particles for all organisms.

Question 4.
What processes would you consider essential for maintaining life?
Answer:
All the living organisms perform life maintaining processes called life processes. It includes various mechanisms essential for the survival of organisms. There are 7 essential life processes such as reproduction, nutrition, movement, growth, excretion, respiration, and responsiveness to stimuli.

Page No.16

Question 5.
What are the differences between autotrophic nutrition and heterotrophic nutrition?
Answer:

Autotrophic Nutrition	Heterotrophic Nutrition
1) Food is synthesised from simple inorganic raw material such as CO2 and water.	1) Food is obtained directly or indirectly from autotrophs. This food is broken down with the help of enzymes.
2) Presence of green pigment (chlorophyll) is necessary.	2) No pigment is required in this type of nutrition.
3) Food is generally prepared during day time.	3) Intake of food takes place at any time.
4) All green plants and some bacteria have this type of nutrition.	4) All animals and fungi have this type of nutrition.

Question 6.
Where do plant’ get each of the raw materials required for photosynthesis ?
Answer:
Three raw materials are required by plants for the process of photosynthesis.

• Carbon Dioxide : It is obtained by plants from the earth’s atmosphere.
• Water: It is absorbed by plants from the soil.
• Sunlight : Without sunlight photosynthesis would not be possible
• Chlorophyll : Its present in the leaves of plants.

Question 7.
What is the role of the acid in our stomach ?
Answer:

• The acid in our stomach is called hydrochloric acid ( HCl ). The hydrochloric acid in the gastric juice breaks down the food and the digestive enzymes split up the proteins.
• The acidic gastric juice also kills bacteria.
• The mucus covers the stomach wall with a protective coating.
• Acid makes the medium in the stomach acidic so as to facilitate the action of pepsin.

Question 8.
What is the function of digestive enzymes ?
Answer:
1. Digestive enzymes are chemical substances that help with the breakdown of food.
2. It works by breaking down large macromolecules such as protein, fat and carbohydrates into their smaller building blocks so that they can be absorbed by the body.
3. So, that the nutrients contained within the food can be absorbed.

The 3 main enzymes are :

• Proteases and peptidases enzymes which break protein down into amino acids.
• Lipase enzymes which break fat down into fatty acids.
• Amylase enzymes which break carbohydrates such as starches and sugar into simple sugars and glucose.

Question 9.
How is the small intestine designed to absorb digested food ?
Answer:

• The small intestine is the most important part of the alimentary canal for digestion and absorption of food.
• It has three regions : a U-shaped duodenum, a long coiled middle portion jejunum and highly coiled ileum.
• The innermost layer lining the lumen of the alimentary canal is the mucosa. This layer forms irregular folds (rugae) in the stomach and small finger-like foldings called villi in the small intestine.
• These modifications increase the surface area for more absorption. Villi are supplied with a network of capillaries and a large lymph vessel called the lacteal.
• It transports lipid molecules. The wall of the intestine is surrounded by the blood vessels which assimilate the food molecules to the different parts of the body.

Page No.24

Question 10.
What advantage over an aquatic organism does a terrestrial organism have with regard to obtaining oxygen for respiration?
Answer:

• Terrestrial organisms take up oxygen from the atmosphere whereas aquatic animals obtain oxygen dissolved in water.
• Air contains about 21% oxygen while water has 1% oxygen in dissolved state. A terrestrial organism is able to get several times more oxygen than an aquatic animal.
• Air contains more O₂ as compared to water. Since the content of O₂ in the air is high.
• So, terrestrial animals do not have to breathe faster to get more oxygen.

Question 11.
What are the different ways in which glucose is oxidised to provide energy in various organisms?
Answer:
Breaking down glucose involves two processes. In the first step, it is broken into three carbon molecules called pyruvate. The pyruvate is further broken down into energy in following different ways in various organisms.

• Aerobic respiration : In this case, pyruvate is broken down into water and carbondioxide along with release of energy. It commonly occurs in mitochondria of cells.
• Anaerobic respiration : In aerobic respiration breakdown of pyruvate takes place in presence of oxygen to give rise 3 molecules of carbon dioxide and water and pyruvate is converted into ethanol and carbon dioxide.

Question 12.
How is oxygen and carbon dioxide transported in human beings?
Answer:
Respiration: It is the process through which energy is released inside the body by taking in oxygen and removing carbon dioxide.

Transportation of oxygen :

• In our body, 97 % of the total oxygen is transported via the red blood cells and the rest 3% is transported by being dissolved in the plasma.
• Hemoglobin binds with oxygen and transports it to various cells of the body.
• After binding with oxygen, the hemoglobin forms a compound called oxyhemoglobin.
• This oxygen mixed blood is then transported to all cells of the body.
• When the blood gives away all the oxygen to the cells, it picks up the carbon dioxide from them and transports it back to the heart.

Transportation of carbon dioxide :

• Carbon dioxide is primarily transported in the dissolved form because hemoglobin has very less affinity towards carbon dioxide.
• In the dissolved form, carbon dioxide is given to the alveoli of the lungs, and oxygen is taken.
• Hemoglobin carries 20-25% of carbon dioxide as carbamino-hemoglobin.
• 70% of the carbon dioxide is transported in the form of bicarbonate ions and the rest 7% is in the dissolved state through plasma.
• The binding of carbon dioxide or oxygen with hemoglobin is due to their partial pressure.

Question 13.
How are the lungs designed in human beings to maximize the area for exchange of gages ?
Answer:

• Each lungs has a highly branched respiratory tract called respiratory tree.
• A primary bronchus divides into secondary bronchi, secondary into segmental bronchi, segmental bronchus into bronchioles which divides into terminal bronchioles, respiratory bronchioles, alveolar sacs and alveoli.
• Alveoli are small rounded pouches which are extremely thin walled and possess a network of capillaries over their surface.
• They function as respiratory surfaces. The total area of all the alveoli is more than 80m²
• It is several times more than the surface of the whole human body.
• Thus, the human lungs are designed to maximize the area of exchange of gasses.

Page No.32

Question 14.
What are the components of the transport system in human beings? What are the functions of these components ?
Answer:
The human circulatory system transports necessary nutrients and minerals throughout the body while also transporting metabolic waste products away from the body.
Components of the transport system : Heart, Blood, Blood vessels.

Heart : Two upper chambers, the left, and right atria, and two inferior chambers, the left, and right ventricles, make up the heart.
The human heart’s primary role is to circulate blood throughout the body.
Oxygenated blood is pumped to the body by the left side of the heart (left atrium and left ventricle).
Deoxygenated blood is pumped to the lungs via the right side of the heart (right atrium and right ventricle).

Blood : Blood comprises blood plasma and formed elements.
Transportation of oxygen, carbon dioxide, nutrients, hormones, heat, and wastes.

Blood vessels :

• Arteries – carries oxygenated blood away from the heart to the capillaries.
• Veins – returns deoxygenated blood from the capillaries to the heart.
• Capillaries – These facilitate the exchange of materials with the tissues.

Question 15.
Why is it necessary to separate oxygenated and deoxygenated blood in mammals and birds ?
Answer:

• Separation of oxygenated and deoxygenated blood allows a highly efficient supply of oxygen to the body.
• This is useful in animals that have high energy needs, such as birds and mammals, which constantly use energy to maintain their body temperature.
• In animals that do not use energy for this purpose, the body temperature depends on the temperature in the environment.
• Such animals, like amphibians or many reptiles have three-chambered hearts, and tolerate some mixing of the oxygenated and deoxygenated blood.

Question 16.
What are the components of the transport system in highly organised plants ?
Answer:
Xylem and phloem are the 2 main components of the plant’s transport system :

• Xylem helps in the upward transport of water.
• Whereas phloem helps in the transport of food from the leaves to other plant parts.

Question 17.
How are water and minerals transported in plants ?
Answer:
Transport of water in plants :

• Xylem is water transport tissue in plants.
• In xylem tissue, vessels and tracheids of the roots, stems and leaves are interconnected to form a continuous system of water-conducting channels reaching all parts of the plant.
• At the roots, cells in contact with the soil actively take up ions.
• This creates a difference in the concentration of these ions between the root and the soil.
• Water, therefore moves into the root from the soil to eliminate this difference.
• This means that there is steady movement of water into the root xylem, creating a column of water that is steadily pushed upwards.

Question 18.
How is food transported in plants ?
Answer:

• Food that is prepared by photosynthesis transport in plants through the phloem.
• This transport of soluble products of photosynthesis is called translocation and it occurs in the part of the vascular tissue known as phloem.
• Besides the products of photosynthesis, the phloem transports amino acids and other substances.
• These substances are especially delivered to the storage organs of roots, fruits and seeds and to growing organs.
• The translocation of food and other substances takes place in the sieve tubes with the help of adjacent companion cells both in upward and downward directions.

Page No.36

Question 19.
Describe the structure and functioning of nephrons.
Answer:
Structure of nephron :

• Nephron is the basic filtration unit in the kidney.
• It consists of a tubule which is connected with a collecting duct at one end and a cup shaped structure at the other end, called Bowman’s capsule.
• Every Bowman’s capsule contains a cluster of capillaries called glomerulus within the cup-shaped structure.
• The blood enters into glomerulus through the afferent arteriole of renal artery and leaves it through the different arteriole.

Basic functions of Nephrons :
i. Filtration: Filtration of the blood takes place in Bowman’s capsule in the capillaries of the glomerulus. Then this filtrate passes into the tubular part of the nephron. The filtrate contains glucose, amino acids urea and uric acid and a large amount of water.

ii. Reabsorption: The filtrate flows along the tubule and useful substances such as glucose, amino acids, salts and some water are reabsorbed into the blood by the capillaries surrounding the nephron tubule.

iii. Urine formation : The filtrate which remains after the reabsorption is called the urine, which is collected from nephron by the collecting duct to carry it to the urinary bladder and then to the urethra.

Question 20.
What are the methods used by plants to get rid of excretory products?
Answer:

• Plants use completely different strategies for excretion than those of animals.
• Oxygen itself can be thought of as a waste product generated during photosynthesis.
• They can get rid of excess water by transpiration.
• For other wastes, plants use the fact that many of their tissues consist of dead cells, and that they can even lose some parts such as leaves.
• Many plant waste products are stored in cellular vacuoles.
• Waste products may be stored in leaves that fall off.
• Other waste products are stored as resins and gums, especially in old xylem.
• Plants also excrete some waste substances into the soil around them.

Question 21.
How is the amount of urine produced regulated ?
Answer:

• The amount of urine produced depends on the amount of excess water and dissolved wastes present in the body.
• Some other factors such as the habitat of an organism and hormones such as Antidiuretic hormone (ADH) also regulate the amount of urine produced.
• The amount of water re-absorbed depends on how much excess water there is in the body, and on how much of dissolved waste there is to be excreted.

AP Board Solutions Class 10 Biology Chapter 5 Questions and Answers (Lab Activities)

Activity – 5.1

• Take a potted plant with variegated leaves – for example, money plant or crotons.
• Keep the plant in a dark room for three days so that all the starch gets used up.
• Now keep the plant in sunlight for about six hours.
• Pluck a leaf from the plant. Mark the green areas in it and trace them on a sheet of paper.
• Dip the leaf in boiling water for a few minutes.
• After this, immerse it in a beaker containing alcohol.
• Carefully place the above beaker in a water-bath and heat till the alcohol begins to boil.

Question 1.
What happens to the color of the leaf? What is the color of the solution?
Answer:
The leaf loss its green color and become pale, the solution become green, because the chlorophyll dissolve in alcohol.

• Now dip the leaf in a dilute solution of iodine for a few minutes.
• Take out the leaf and rinse off the iodine solution.
• Observe the color of the leaf and compare this with the tracing of the leaf done in the beginning.

Question 2.
What can you conclude about the presence of starch in various areas of the leaf ?
Answer:
The leaf where it has green color before boiling, turns into bluish black, which indicate the presence of starch, it means photosynthesis is done in the greenish area. So we confirm that chlorophyll is necessary for photosynthesis.

Activity – 5.2

• Take two healthy potted plants which are nearly the same size.
• Keep them in a dark room for three days.
• Now place each plant on separate glass plates. Place a watch-glass containing potassium hydroxide by the side of one of the plants. The potassium hydroxide is used to absorb carbon dioxide.
• Cover both plants with separate bell-jars as shown in adjacent figure.
• Use vaseline to seal the bottom of the jars to the glass plates so that the set-up is airtight.
• Keep the plants in sunlight for about two hours.
• Pluck a leaf from each plant and check for the presence of starch as in the above activity.

Question 1.
Do both the leaves show the presence of the same amount of starch ?
Answer:
No, the plant leaf that does not have KOH near shows a high amount of starch.

Question 2.
What can you conclude from this activity ?
Answer:
We conclude that CO₂ is necessary for photosynthesis.

Activity – 5.3

• Take 1 mL starch solution (1%) in two test tubes (A and B).
• Add 1 mL saliva to test tube A and leave both test tubes undisturbed for 20-30 minutes.
• Now add a few drops of dilute iodine solution to the test tubes.

Question 1.
In which test tube do you observe a colour change?
Answer:
The test tube which does not have saliva change its colour , it means the starch is still remaining in the test tube.

Question 2.
What does this indicate about the presence or absence of starch in the two test tubes?
Answer:
The test tube which saliva is not added have starch, starch is absence in the test tube where saliva is added.

Question 3.
What does this tell us about the action of saliva on starch ?
Answer:
The saliva acts on starch and converted into sugars.

Activity – 5.4

• Take some freshly prepared lime water in a test tube.
• Blow air through this lime water.
• Note how long it takes for the lime water to turn milky.
• Use a syringe or pichkari to pass air through some fresh lime water taken in another test tube.
• Note how long it takes for this lime water to turn milky.

Question 1.
What does this tell us about the amount of carbon dioxide in the air that we breathe out?
Answer:
1. The lime water turns milkish white quickly, when we blow air, than the used a syringe.
2. It means exhaled air has more CO₂.

Activity – 5.5

• Take some fruit juice or sugar solution and add some yeast to this. Take this mixture in a test tube fitted with a one-holed cork.
• Fit the cork with a bent glass tube. Dip the free end of the glass tube into a test tube containing freshly prepared lime water.

Question 1.
What change is observed in the lime water and how long does it take for this change to occur?
Answer:
The lime water turns into milkish white in half an hour

Question 2.
What does this tell us about the products of fermentation?
Answer:
It tells us CO₂ is released in the fermentation process.

Activity – 5.6

Question 1.
Observe fish in an aquarium. They open and close their mouths and the gill-slits (or the operculum which covers the gill-slits) behind their eyes also open and close. Are the timings of the opening and closing of the mouth and gill-slits coordinated in some manner?
Answer:
Yes. Are the timings of the opening and closing of the mouth and gill-slits coordinated in some manner.

Question 2.
Count the number of times the fish opens and closes its mouth in a minute.
Answer:
12-18 times per minute, so the fish breathe rate is 12-18 breaths per minute.

Question 3.
Compare this to the number of times you breathe in and out in a minute.
Answer:
Fish breaths 12-18 per minute surprisingly in humans it’s also 12 to 18 breaths per minute.

Activity – 5.7

Question 1.
Visit a health center in your locality and find out what is the normal range of hemoglobin content in human beings.
Answer: 12 to 18 g/dl.

Question 2.
Is it the same for children and adults ?
Answer:
No, childrens range is less than adults.

Question 3.
Is there any difference in the hemoglobin levels for men and women?
Answer:
Yes, men has more Hb rate than the females.

• Adult Males 14 – 18
• Adult Women 12 – 16

Question 4.
Visit a veterinary clinic in your locality. Find out what is the normal range of hemoglobin content in an animal like the buffalo or cow.
Answer:
The normal range of hemoglobin content in cattle is 10.4-16.4 \mathrm{~g} / \mathrm{dl}.

Question 5.
Is this content different in calves, male and female animals ?
Answer:
Yes, calves and female have less hemoglobin than the males.
Compare the difference seen in male and female human beings and animals.
Answer:
A) Adult Males 14-18
B) Adult Women 12-16
C) Animals 11-17

Question 6.
How would the difference, if any, be explained?
Answer:
Menstruation is the key reason why hemoglobin levels are, on average, lower in females than in males. Menstruation leads to loss of iron, which in turn contributes to lowering the levels of hemoglobin in the blood.

Activity -5.8

• Take two small pots of approximately the same size and have the same amount of soil. One should have a plant in it. Place a stick of the same height as the plant in the other pot.
• Cover the soil in both pots with a plastic sheet so that moisture cannot escape by evaporation.
• Cover both sets, one with the plant and the other with the stick, with plastic sheets and place in bright sunlight for half an hour.

Question 1.
Do you observe any difference in the two cases ?
Answer:

• The pot which placed the stick does not have any changes.
• But in the pot that has a plant loses its weight lightly, because the plant loses the water through the transpiration which is absorbed from soil.