Madhyamik Class 10 Life Science Solved Paper 2013

Madhyamik Class 10 Life Science Solved Paper 2013

Life Science

Time – Three Hours and Fifteen Minutes

(First fifteen minutes for reading the question paper only)

Full Marks – 90

(For Regular and Sightless Regular Candidates)

Full Marks – 100

(For External and sightless External Candidates)

[Group A to C are common for both Regular and External Candidates. Group D is meant only for External Candidates]

Sightless Candidates will answer the alternative question as per the directive in Group C.

Figures in the margin indicate full marks for each question Special credits will be given for answers which are brief and to the point.

Marks will be deducted for spelling mistakes, untidiness and bad handwriting.

Group – A

[Candidates will have to answer question Nos. 1,2,3 and 4]

1. Complete the sentences choosing the correct answer (any five) : [1×5=5]

Question 1.1

The part of the human eye that functions as refraction media is

1. Cornea
2. Retina
3. Vitreous humour
4. Choroid

Answer

cornea

Explanation:

The part of the human eye that functions as the refraction media is the cornea. The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber.

Question 1.2

Which of the following endocrine gland secretes TSH?

1. Thyroid
2. Testes
3. Adrena
4. Pituitary

Answer

Pituitary

Explanation:

The endocrine gland that secretes thyroid-stimulating hormone (TSH) is the pituitary gland.

Question 1.3

In a DNA molecule, the complementary base pair of guanine is

1. Adenine
2. Cytosine
3. Thymine
4. Uracil

Answer

Cytosin

Explanation:

In a DNA molecule, the complementary base pair of guanine is cytosine. DNA consists of two strands that are held together by hydrogen bonds between complementary base pairs.

Question 1.4

The plant with distinct alternation of generations is

1. Moss (Pogonatum)
2. Mango tree
3. China-rose plant
4. Pine tree

Answer

moss (Pogonatum)

Explanation:

The plant with distinct alternation of generations is the moss (Pogonatum). Mosses are non-vascular plants that exhibit a life cycle with alternation of generations, involving two distinct multicellular stages: the gametophyte and the sporophyte.

Question 1.5

The flippers of whales and the wings of birds are

1. Analogous organ
2. Vestigial organ
3. Homologous organ
4. Replaced organ

Answer

Homologous organs

Explanation:

The flippers of whales and the wings of birds are homologous organs. Homologous organs are those that have a similar underlying structure and origin but may have different functions.

Question 1.6

The vision of the pigeon is very sharp due to the presence of

1. Rhodopsin
2. Iodopsin
3. Pecten
4. Pepsin

Answer

Iodopsin

Explanation:

The vision of the pigeon is very sharp due to the presence of iodopsin. Iodopsin is a photosensitive pigment that is found in the cone cells of the retina

Question 1.7

A disease against which a newborn baby is immunised in the National Immunisation Programme is

1. Polio
2. Typhoid
3. AIDS
4. Hepatitis

Answer

Polio

Explanation:

A newborn baby is immunized against polio in the National Immunisation Programme.

Question 2

Answer in one sentence (any ten) : [1×10=10]

1. Name one excretory substance secreted from the sweat gland of the skin.
2. Name one excretory substance produced by the plant, which helps in protein digestion.
3. Write the name of the short processes of a nerve cell.
4. Name the hormone which helps in the production of sperm.
5. Write the full chemical name of an artificial plant hormone.
6. In which type of cell division does ‘spindle formation’ not occur?
7. What is the name of the process in which offspring is directly formed from unfertilized eggs?
8. What type and in what number of sex chromosomes are found in normal men?
9. Give an example of a living fossil in a plant kingdom.
10. Name a vertebrate having ventricles with incomplete separating walls.
11. Why are the stomata present on the upper surface of the lotus leaf?
12. Name a disinfectant produced from the plant.
13. Which disease caused by protozoa can be prevented by the use of a sanitary latrine?

Answer

1. Urea is secreted from the sweat gland of the skin.
2. Uric acid is produced by the plant, which helps in protein digestion.
3. Dendrites are the short processes of a nerve cell.
4. Testosterone is the hormone which helps in the production of sperm.
5. Auxin is the full chemical name of an artificial plant hormone.
6. Mitosis is the type of cell division in which spindle formation does not occur.
7. Parthenogenesis is the process in which offspring is directly formed from unfertilized eggs.
8. Normal men have XY sex chromosomes.
9. Ginkgo biloba is an example of a living fossil in a plant kingdom.
10. Amphibians have ventricles with incomplete separating walls.
11. The stomata are present on the upper surface of the lotus leaf to absorb carbon dioxide for photosynthesis.
12. Chlorine is a disinfectant produced from the plant.
13. Dysentery is a disease caused by protozoa that can be prevented by the use of a sanitary latrine.

Question 3

Attempt any six questions : [2×6=12]

1. Name one reabsorbed and one secretory substance of the renal tubule.
2. On which other hormones does the secretion of hormones from the testes and ovaries depend?
3. Why does a perforation in the eardrum hamper hearing ?
4. Write any two differences between DNA and RNA.
5. What do you understand by ‘pure’ and ‘hybrid’ in heredity? State with example.
6. How do the structural changes of the heart of Amphibia and Mammalia support the evolution ?
7. Mention one adaptive feature of each of the leaf blades and thalamus of the lotus plant.
8. Mention the name of the micro-organism living in the root nodule of the leguminous plant and state its beneficial role.

Answer

1. Reabsorbed substance: water; Secretory substance: urea
2. Gonadotropin-releasing hormone (GnRH) from the hypothalamus
3. Perforation in the eardrum hampers hearing because it disrupts the transmission of sound waves to the inner ear.
4. DNA is a double-stranded molecule, while RNA is single-stranded. DNA is found in the nucleus of the cell, while RNA is found in the cytoplasm.
5. Pure: an organism that has two identical alleles for a trait. Hybrid: an organism that has two different alleles for a trait. Example: pure-bred dog vs. cross-bred dog.
6. The structural changes of the heart of Amphibia and Mammalia support the evolution because they show how the heart has changed over time to become more efficient at pumping blood.
7. Leaf blades: have a waxy coating that helps to reduce water loss. Thalamus: has a spongy structure that helps to trap air and keep the plant cool.
8. Rhizobium bacteria live in the root nodules of leguminous plants and fix nitrogen from the air, which the plant can then use to make proteins.

4. Attempt any ten questions : [3×10=30]

Question 4.1

“All waste materials are not excretory products”. — Explain. [3]

Answer

1. Waste materials can be stored in the body. For example, the liver stores excess glucose as glycogen, and the muscles store excess glucose as glycogen or fat. These stored materials are not excreted until they are needed by the body.
2. Waste materials can be recycled. For example, the kidneys recycle water and other substances from the urine.
3. Waste materials can be used by other organisms. For example, dead organisms are decomposed by bacteria and other decomposers, which release nutrients back into the environment that can be used by other organisms.

Question 4.2

Mention the types of the reflex action of the following with reasons:

1. secretion of saliva at the sight of delicious food.
2. sucking of breast milk by the baby.
3. learn to ride bi-cycle. [1+1+1]

Answer

• Secretion of saliva at the sight of delicious food: This is an unconditioned reflex. Unconditioned reflexes are innate, meaning they are not learned. They are triggered by a stimulus, in this case the sight of delicious food, and they produce a specific response, in this case the secretion of saliva.
• Sucking of breast milk by the baby: This is also an unconditioned reflex. It is triggered by the baby’s hunger and it produces the response of sucking.
• Learning to ride a bicycle: This is a conditioned reflex. Conditioned reflexes are learned. They are triggered by a stimulus, in this case, the sight of a bicycle, and they produce a specific response, in this case the ability to ride a bicycle.

Question 4.3

Write the names of two parts connecting two cerebral hemispheres and two hemispheres of the cerebellum respectively. Write two functions each of the cerebrum and cerebellum. [(½+½)+2]

Answer

1. Cerebral hemispheres: The corpus callosum is a thick band of nerve fibres that connects the two cerebral hemispheres.
2. Cerebellum: The pons is a smaller bundle of nerve fibres that connects the two hemispheres of the cerebellum.

Here are two functions each of the cerebrum and cerebellum:

• Cerebrum:
  • Thinking and reasoning
  • Planning and decision-making
  • Voluntary movement
• Cerebellum:
  • Balance
  • Coordination

Question 4.4

Point out two differences, with examples, between the ‘Exocrine gland’ and the ‘Endocrine gland’. [3]

Answer

Question 4.5

Why the edible salt should be iodised? Where testosterone is produced? [2+1]

Answer

1. Iodine is a mineral that is essential for human health. It is needed for the production of thyroid hormones, which regulate metabolism, growth, and development. Iodine deficiency can cause a number of health problems, including goitre, hypothyroidism, and intellectual disabilities. Iodized salt is salt that has been added to iodine. It is a safe and effective way to ensure that people get enough iodine in their diet.
2. Testosterone is a male sex hormone that is produced in the testicles.

Question 4.6

Write two differences between cytokinesis in plant and animal cells. What is the important feature of the ‘S’ phase of the cell cycle? [2+1]

Answer

• The S phase (synthesis phase): During the S phase, the cell’s DNA is replicated. This means that each chromosome is duplicated so that each daughter cell will have a complete set of chromosomes.

Question 4.7

Mention the components of your chromosomes. What do you understand by ‘gene’ ? [2+1]

Answer

The components of chromosomes:

• DNA: DNA is the genetic material that makes up chromosomes. It is made up of four nucleotides: adenine (A), thymine (T), guanine (G), and cytosine (C).
• Histones: Histones are proteins that bind to DNA and help to organize it into chromosomes.
• Non-histone proteins: Non-histone proteins are other proteins that interact with DNA and play a role in gene regulation.

A gene is a unit of heredity that is passed from parents to offspring. Genes are made up of DNA and they code for specific proteins. Proteins are the building blocks of life and they play a role in all aspects of cell function.

Question 4.8

What type of experiment did Mendel perform to propound the law of independent assortment? Explain the law. (details of the experiment are not required). [1+2]

Answer

Gregor Mendel performed a series of experiments on pea plants to study inheritance. He crossed pea plants with different traits, such as flower colour and seed shape. He found that the traits were passed down to the offspring in predictable patterns.

Mendel’s law of independent assortment states that genes for different traits are inherited independently of each other. This means that the probability of an offspring inheriting a particular trait is not affected by the other traits that it inherits.

For example, if a pea plant has yellow flowers and round seeds, the offspring of that plant will have a 25% chance of having yellow flowers and round seeds, a 25% chance of having yellow flowers and wrinkled seeds, a 25% chance of having white flowers and round seeds, and a 25% chance of having white flowers and wrinkled seeds.

Question 4.9

Write three differences between vegetative and asexual reproduction in plants. [1+1+1]

Answer

Question 4.10

Who is the propounder of ‘Inheritance of acquired characters’ ? Write briefly your opinion regarding the acceptability of the law, with reasons. [1+2]

Answer

1. Jean-Baptiste Lamarck is the propounder of the ‘Inheritance of acquired characters’.
2. The law is not acceptable because there is no scientific evidence to support it. Changes acquired during an organism’s lifetime are not passed on to its offspring.

Question 4.11

Write one role for each of the myotome muscles, lateral line sense organ and swim bladder in fish. [1+1+1]

Answer

• Myotome muscles: The myotome muscles are responsible for swimming in fish. They are a series of muscles that run along the sides of the fish and contract and relax to move the fish’s body through the water.
• Lateral line sense organ: The lateral line sense organ is a system of sensory organs that detects movement and vibration in the water. It is located along the sides of the fish and is used to help them navigate, avoid predators, and find food.
• Swim bladder: The swim bladder is a gas-filled sac that helps fish maintain their buoyancy. It is located in the body cavity of the fish and is filled with gas that is produced by the fish’s kidneys. The swim bladder helps fish stay afloat and to control their depth in the water.

Question 4.12

Name the vectors of malaria and filariasis and mention two measures to control these vectors. [(½+½)+2]

Answer

Question 4.13

Which blood-transmitted disease damages the liver? Write two preventive measures for this disease. [1+2]

Answer

There are many blood-transmitted diseases that can damage the liver, including hepatitis B, hepatitis C, and HIV.

These diseases can be prevented by:

1. Getting vaccinated: There are vaccines available for hepatitis B and hepatitis C. These vaccines can help to protect you from getting these diseases.
2. Practising safe sex: This includes using condoms and getting tested for HIV regularly.

Group – B

(Answer any five questions from Question No. 5 to Question No. 11)

Question 5

Write four nitrogenous excretory products of humans. Write whether the filtered liquid collected in Bowman’s capsule of human nephron can be called urine. Give reasons in support of your answer. [2+3=5]

Answer

• Urea: Urea is the main nitrogenous waste product in humans. It is formed in the liver from ammonia, which is a toxic waste product. Urea is then transported to the kidneys, where it is excreted in the urine.
• Uric acid: Uric acid is another nitrogenous waste product. It is formed when the body breaks down purines, which are found in certain foods, such as meat, poultry, and fish. Uric acid is also excreted in the urine.
• Creatinine: Creatinine is a waste product that is formed when muscles break down creatine phosphate. Creatine phosphate is a form of energy that is stored in muscles. Creatinine is excreted in the urine.
• Ammonia: Ammonia is a toxic waste product that is produced by the liver. Ammonia is converted to urea in the liver before it is excreted in the urine.

The filtered liquid collected in Bowman’s capsule of the human nephron is not urine. Urine is the final product of urine formation, which occurs in the collecting duct of the nephron. The filtered liquid collected in Bowman’s capsule is called glomerular filtrate. The glomerular filtrate is similar to blood plasma, but it does not contain blood cells or proteins.

The glomerular filtrate is further processed in the nephron, and water, salts, and other substances are reabsorbed into the blood. The remaining substances, including urea, uric acid, creatinine, and ammonia, are excreted in the urine.

Question 6

Mention one structural and one functional difference between sensory and motor neurones. Which chemical matter transmits nerve impulses from one neurone to another? Mention the location and function of the ‘Organ of Corti’. [2+1+2=5]

Answer

• Structural difference: Sensory neurons have a single long axon that carries signals to the central nervous system (CNS), while motor neurons have multiple dendrites that receive signals from the CNS and a single axon that carries signals to an effector organ.
• Functional difference: Sensory neurons transmit information from the environment to the CNS, while motor neurons transmit commands from the CNS to effector organs.
• The chemical matter that transmits nerve impulses: The chemical matter that transmits nerve impulses from one neuron to another is called a neurotransmitter. There are many different types of neurotransmitters, and each one has a different effect on the neuron it is acting on.
• Location and function of the Organ of Corti: The Organ of Corti is a structure located in the inner ear. It is responsible for converting sound waves into electrical signals that are sent to the brain. The Organ of Corti contains hair cells that are sensitive to sound waves. When sound waves enter the ear, they cause the hair cells to move. This movement generates an electrical signal that is sent to the brain. The brain interprets this signal as sound.

Question 7

Write briefly the name, origin and function of a female and a male sex hormone of human. [1+1+(1½+1½)=5]

Answer

Female sex hormone: Estrogen

• Origin: Ovaries
• Function: Regulates the menstrual cycle, development of female sex characteristics, and reproduction

Male sex hormone: Testosterone

• Origin: Testes
• Function: Regulates the development of male sex characteristics, sperm production, and sex drive

Question 8

Give an example of an organism which divides by amitosis. Mention two differences between the mitosis of plant and animal cells. What are the different phases of a cell cycle? [1+2+2=5]

Answer

1. Example of an organism which divides by amitosis: Bacteria.
2. Two differences between the mitosis of plant and animal cells:
   1. Plant cells have a cell wall, while animal cells do not.
   2. Plant cells have chloroplasts, while animal cells do not.
3. Different phases of a cell cycle:
   • Interphase
   • Prophase
   • Metaphase
   • Anaphase
   • Telophase

Question 9

What are the differences between anisogamy and oogamy? What do you mean by dominant and recessive characters? Explain with an example when does the recessive character express? [1+2+2=5]

Answer

Anisogamy is a type of sexual reproduction in which the gametes are not of equal size. The smaller gametes are called sperm, and the larger gametes are called eggs. Oogamy is a type of sexual reproduction in which the gametes are of unequal size and function. The larger gamete, the egg, is non-motile and is fertilized by the smaller, motile sperm.

Dominant and recessive characters are terms used to describe the expression of genes. A dominant character is one that is expressed even if only one copy of the gene is present. A recessive character is only expressed if both copies of the gene are recessive.

For example, the gene for eye colour is dominant. If a person has one copy of the gene for brown eyes and one copy of the gene for blue eyes, they will have brown eyes. The brown eye colour is dominant over the blue eye colour.

The recessive character will only be expressed if both copies of the gene are recessive. For example, the gene for albinism is recessive. If a person has one copy of the gene for albinism and one copy of the gene for normal pigmentation, they will have normal pigmentation. Normal pigmentation is dominant over albinism.

Question 10

What is the variation? How do variations help in the origin of species in evolution? [2+3=5]

Answer

Variation refers to the differences that exist within a population or among individuals of a species. These variations can be observed in traits such as physical characteristics, behaviour, or genetic makeup.

Variations play a crucial role in the origin of species through evolution. Here’s how:

1. Variation provides the raw material: Variations introduce new genetic traits into a population. This genetic diversity is essential for natural selection to act upon, as it allows for the possibility of advantageous traits that can increase an organism’s chances of survival and reproduction.
2. Natural selection: Variations provide the basis for natural selection to occur. Organisms with beneficial variations that are well-suited to their environment have a higher chance of survival and reproductive success. Over time, these advantageous traits become more common in the population, leading to the formation of new species.

Question 11

Mention the adaptive significance of the following: [1×5=5]

1. Scale of fish
2. Aerenchyma tissue of lotus
3. Air-sacs of pigeon
4. Pneumatophore of Sundri
5. Leaf spine of cactus

Answer

Group – C

(Answer any one question)

Question 12

Draw a diagram of a typical nephron of a human and label the following parts :

1. Bowman’s capsule;   
2. Proximal convoluted tubule;   
3. Distal convoluted tubule;  
4. Henle’s loop;   
5. Glomerulus and Collecting tubule.  [5+3=8]

Answer

Question 13

Draw diagrams of metaphase and cytokinesis of mitosis in an animal cell.  

Label chromatid; metaphase plate; spindle fibres and centriole in the first diagram. Label a daughter nucleus and middle furrow in the second diagram. [5+3=8]

Answer

Coming Soon

[For Sightless Candidates Only]

(Answer any one question)

(Diagram not required)

Question 12(A)

Write in brief the structure of a typical human nephron. What are the functions of malphigian corpuscle and proximal convoluted tubule ? [6+2=8]

Answer

Structure of a typical human nephron:

• Malpighian corpuscle: This is the filtering unit of the nephron. It consists of a glomerulus, which is a tuft of capillaries, and Bowman’s capsule, which is a cup-shaped structure that surrounds the glomerulus.
• Proximal convoluted tubule: This is the first part of the nephron tubule. It is located in the cortex of the kidney. The proximal convoluted tubule reabsorbs most of the water, glucose, and amino acids from the filtrate.

The functions of the malpighian corpuscle and proximal convoluted tubule are to:

• Filter the blood: The malpighian corpuscle filters the blood to form the filtrate. The filtrate is a watery solution that contains all of the substances in the blood except for the blood cells, proteins, and large molecules.
• Reabsorb nutrients: The proximal convoluted tubule reabsorbs most of the water, glucose, and amino acids from the filtrate. This is important for maintaining the body’s fluid balance and for providing the body with nutrients.

Question 13 (A)

Describe in brief the metaphase and the cytokinesis of mitosis in an animal cell. [4+4=8]

Answer

Metaphase

• In metaphase, the chromosomes line up in the middle of the cell.
• This is done by the spindle fibres, which are microtubule structures that attach to the centromeres of the chromosomes.
• The centromeres are the regions where the two sister chromatids of each chromosome are joined together.

Cytokinesis

• Cytokinesis is the division of the cytoplasm to form two daughter cells.
• In animal cells, cytokinesis is accomplished by a ring of actin filaments that contract, pinching the cell in two.
• This ring of actin filaments is called the cleavage furrow.
• Once the cleavage furrow has been completed, two daughter cells are formed.
• Each daughter cell has a complete set of chromosomes and cytoplasm.

Group – D

[Only for External Candidates]

(Answer any one question)

Question 14

Distinguish between bacteria and bacteriophage. How is bacteriophage beneficial to us? Write briefly about the mode of transmission of three harmful viruses. [2+2+(3×2)=10]

Answer

Distinguish between bacteria (A) and bacteriophage (B)

Bacteriophages, or viruses that infect bacteria, can be used to treat bacterial infections. They are specific to their host bacteria, so they do not harm human cells. Bacteriophages are also relatively inexpensive to produce, and they can be used to treat infections that are resistant to antibiotics.

Here are three harmful viruses and their modes of transmission:

• HIV/AIDS: The Human Immunodeficiency Virus (HIV) is transmitted through contact with contaminated bodily fluids, such as blood, semen, vaginal fluids, and breast milk.
• Influenza: The Influenza virus is transmitted through contact with contaminated respiratory droplets, such as those produced when an infected person coughs or sneezes.
• Common cold: The Common cold virus is transmitted through contact with contaminated respiratory droplets, such as those produced when an infected person coughs or sneezes.

Question 15

What is reflex action? Mention the types with examples. What is the name of the structural and functional unit of the nervous system? Why is it so-called?  Describe briefly the structure of that unit. [2+3+1+1+3=10]

Answer

1. Reflex action: An involuntary, rapid, and automatic response to a stimulus.
2. Types of reflex actions:
   • Stretch reflex: A reflex that occurs when a muscle is stretched. The muscle contracts in response to the stretch, which helps to maintain its length.
   • Withdrawal reflex: A reflex that occurs when the skin is touched by something hot or painful. The body quickly withdraws the limb from the stimulus to avoid injury.
   • Pupillary reflex: A reflex that occurs when the amount of light in the environment changes. The pupils constrict in bright light and dilate in dim light.
   • Cardiac reflex: A reflex that occurs when the heart rate changes. The heart rate increases in response to exercise and decreases in response to rest.
3. Nerve cell: The structural and functional unit of the nervous system. It is made up of a cell body, dendrites, and an axon.
4. The nerve cell is called a neuron because it is shaped like a neuron, which is a Greek word for “thread.”
5. Brief description of the structure: The cell body contains the nucleus and other organelles. The dendrites are short, branching fibres that carry information to the cell body. The axon is a long, thin fibre that carries information away from the cell body.