Madhyamik Class 10 Life Science Solved Paper 2015

Madhyamik Class 10 Life Science Solved Paper 2015

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]

1.1. Myelin Sheath is observed on

1. the axon of all neurones
2. the dendron of some neurones
3. the axon and dendron of all neurones
4. the axon of some neurones.

Answer

the axon of all neurons

Explanation

The myelin sheath is observed on the axon of all neurons. It is a fatty layer that insulates the axon and helps to speed up the transmission of nerve impulses.

1.2. Insulin hormone secreting gland is

1. Adrenal
2. Pituitary
3. Thyroid
4. Pancreas

Answer

Pancreas

Explanation

The gland that secretes the insulin hormone is the pancreas. The pancreas is a large gland that is located behind the stomach.

1.3. The Phase of mitosis in which the nuclear membrane reappears is

1. Prophase
2. Metaphase
3. Anaphase
4. Telophase

Answer

Telophase

Explanation

The nuclear membrane reappears during telophase.

During telophase, the chromosomes uncoil and return to their chromatin form. The nuclear envelope reforms around the chromatin, and the nucleolus reappears. The spindle fibers disappear, and the cell begins to divide.

1.4. A plant which performs vegetative reproduction with the help of Sub-aerial stem is

1. Potato
2. Water hyacinth
3. Ginger
4. Onion

Answer

Ginger

Explanation

Ginger is a plant that reproduces vegetatively by means of its rhizomes, which are thick, underground stems. The rhizomes are divided into segments, each of which can be planted to produce a new plant.

1.5. The organ in the human body which considered a vestigial organ is

1. Stomach
2. Colon
3. Appendix
4. Rectum

Answer

appendix

Explanation

A vestigial organ is an organ that has no apparent function in a particular organism, but may have had a function in its ancestors.

1.6. The Organ absent in Pigeons to aid in flight is

1. Left ovary
2. Gall bladder
3. Lung
4. Right kidney

Answer

right kidney

Explanation

Pigeons have a single kidney located on the left side of their body. This is because the right kidney would interfere with the flight muscles on the right side of the body.

1.7. The disease which is caused by viral infection is

1. Influenza
2. Cholera
3. Malaria
4. Tuberculosis

Answer

Influenza

Explanation

Influenza, commonly known as the flu, is a contagious respiratory illness caused by influenza viruses that infect the nose, throat, and sometimes the lungs.

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

1. Which substance present in the latex of papaya helps in the digestion of protein?
2. An organ in the human body, where urea is synthesized, is ________. (Fill in the blank and write the complete sentence)
3. What is Meninges?
4. One of the sites of the formation of the Gibberellin hormone is _______.  (Fill in the blank and write the complete sentence)
5. Which hormone is related to the pounding of the heart when scared?
6. Mention one significance of meiosis cell division.
7. How many pairs of contrasting characters in pea plants were selected by Mendel for his experiments on heredity?
8. What kind of reproduction the spore is the unit of?
9. Write the name of an organ of an animal which is homologous to bird’s wings.
10. Mention one important change in the evolution of the horse.
11. Due to the presence of _____ in the eye of the Pigeon, the vision becomes very sharp. (Fill in the blank and write the complete sentence)
12. Name one fungus that infects human lungs.
13. Why is the skin wiped with spirit (alcohol) before pushing an injection?

Answer

1. Papain helps in the digestion of protein in the latex of papaya.
2. Liver
3. Meninges
4. Apical meristem is one of the sites of the formation of the Gibberellin hormone.
5. Adrenaline is the hormone related to the pounding of the heart when scared.
6. Meiosis cell division is significant in producing gametes.
7. Seven pairs of contrasting characters in pea plants were selected by Mendel for his experiments on heredity.
8. Asexual reproduction is the unit of spore.
9. The flippers of a whale are homologous to a bird’s wings.
10. An increase in size is one important change in the evolution of horses.
11. Papillae
12. Aspergillosis is one fungus that infects human lungs.
13. To prevent infection the skin is wiped with spirit (alcohol) before pushing an injection.

3. Attempt any six questions : [2×6=12]

3.1. Mention the source and one economic importance of resin.

Answer

• Source: Resin is produced by plants.
• Economic importance: Resin is used to make varnish, adhesives, ink, and perfume.

3.2.What is inborn reflex action ? Give an example.

Answer

An inborn reflex action is an automatic, involuntary response to a stimulus. It is not learned and is present at birth. An example of an inborn reflex action is the knee jerk reflex. When the patellar tendon is tapped, the lower leg will extend automatically.

3.3.From which gland TSH is secreted ? Write down its one main function.

Answer

TSH is secreted from the pituitary gland. Its main function is to stimulate the thyroid gland to produce thyroid hormones.

3.4. What are the sex chromosomes in the male and female human body ?

Answer

Humans have 23 pairs of chromosomes, for a total of 46. The first 22 pairs, called autosomes, look the same in both males and females. The 23rd pair, the sex chromosomes, differ between males and females.

• Females have two copies of the X chromosome (XX).
• Males have one X chromosome and one Y chromosome (XY).

3.5.What do you mean by parthenogenesis ? Give an example of it.

Answer

Parthenogenesis is a type of reproduction in which an offspring develops from an unfertilized egg cell.

An example of parthenogenesis is the queen honey bee. The queen honey bee can lay both fertilized and unfertilized eggs. The fertilized eggs develop into male drones, while the unfertilized eggs develop into female worker bees.

3.6. From which observations Darwin arrived at the conclusion – “Struggle for Existence”?

Answer

• Overpopulation: Darwin observed that all organisms produce more offspring than can survive. For example, a single female rabbit can produce up to 40 offspring in a year. This means that there is a lot of competition for resources, such as food and mates.
• Competition: Darwin observed that organisms compete for resources, such as food, water, and mates. For example, two male lions may fight for the right to mate with a female lion. This competition can lead to the death of one of the lions.

3.7. Discuss one adaptive importance each of lateral line sense organ and swim bladder in rohu fish. Mention two structural characteristics of ‘virus’.

Answer

The adaptive importance of lateral line sense organ and swim bladder in rohu fish:

Lateral line sense organ

• Helps the fish to detect movement and vibrations in the water, which can be used to find food, avoid predators, and navigate.

Swim bladder

• Helps the fish to maintain its buoyancy, which allows it to swim easily and conserve energy.

Here are two structural characteristics of a virus:

• Nucleic acid: Viruses contain either DNA or RNA, but not both. The nucleic acid is the genetic material of the virus and is responsible for carrying the virus’s instructions for replication.
• Capsid: The capsid is a protein coat that protects the virus’s nucleic acid. The capsid is made up of many individual protein subunits that are arranged in a specific way.

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

4.1. Write one function each of Glomerulus, Proximal Convoluted Tubule and Henle’s loop of a nephron. 

Answer

The functions of the glomerulus, proximal convoluted tubule, and Henle’s loop of a nephron:

• Glomerulus: The glomerulus is a tuft of capillaries that filters blood and produces glomerular filtrate.
• Proximal convoluted tubule: The proximal convoluted tubule is the first part of the nephron and is responsible for reabsorbing water, nutrients, and electrolytes from the glomerular filtrate.
• Henle’s loop: Henle’s loop is a U-shaped tube that is located in the medulla of the kidney and is responsible for concentrating the urine.

4.2. Mention one function of each of Cerebrum, Cerebellum and Medulla Oblongata in human brain.

Answer

The functions of the cerebrum, cerebellum, and medulla oblongata:

• Cerebrum: The cerebrum is the largest part of the brain and is responsible for higher-order functions such as thinking, planning, and decision-making. It also controls voluntary movement and sensation.
• Cerebellum: The cerebellum is located at the back of the brain and is responsible for coordinating movement, balance, and posture. It also plays a role in learning and memory.
• Medulla oblongata: The medulla oblongata is located at the base of the brain and is responsible for controlling involuntary functions such as breathing, heart rate, and blood pressure. It also plays a role in arousal and sleep.

4.3. Mention one structural feature of each of Sclera, Choroid and Retina in a human eyeball.

Answer

One structural feature of each of Sclera, Choroid and Retina in a human eyeball:

• Sclera: White, tough outer layer that protects the eye.
• Choroid: Middle layer of the eye that contains blood vessels that supply oxygen and nutrients to the retina.
• Retina: Light-sensitive layer at the back of the eye that converts light into electrical signals that are sent to the brain.

4.4. Mention two differences between exocrine and endocrine glands. Give an example of a mixed gland in human body.

Answer

An example of a mixed gland in the human body is Pancreas

4.5. Mention three roles of Auxin hormone in the growth of plants.

Answer

The three roles of Auxin hormone in the growth of plants:

• Cell elongation: Auxin promotes cell elongation by stimulating the production of enzymes that break down cell walls. This allows the cells to grow longer and wider.
• Apical dominance: Auxin promotes apical dominance, which is the growth of the main stem at the expense of side branches. This is important for the plant to grow tall and reach sunlight.
• Tropism: Auxin is involved in tropisms, which are plant movements in response to environmental stimuli such as light and gravity.

4.6. What is cell cycle ? Name any two stages of Interphase.

Answer

The cell cycle is the process by which a cell grows and divides to produce two identical daughter cells. The cell cycle has two main phases: interphase and mitosis.

• Interphase is the longest phase of the cell cycle. During interphase, the cell grows and DNA is replicated.
• Mitosis is the phase of the cell cycle in which the cell divides to produce two identical daughter cells.

Two stages of interphase are:

• G1 phase (first gap): The cell grows and carries out biochemical functions, such as protein synthesis.
• S phase (synthesis): DNA is duplicated into two sister chromatids.

4.7. What is cytokinesis? Mention two differences in between  cytokinesis of plant and animal cell.

Answer

Cytokinesis is the division of the cytoplasm of a cell into two daughter cells. It is the final stage of mitosis.

Here are two differences between cytokinesis in plant and animal cells:

• Plant cells form a cell plate, which is a new cell wall that divides the cytoplasm. Animal cells form a cleavage furrow, which is a groove that pinches the cytoplasm in half.
• Plant cells have a cell wall, which provides support and prevents the cell from collapsing. Animal cells do not have a cell wall, so they rely on the cytoskeleton to provide support.

4.8. What is ‘Alternation Of Generation“? Name two plant groups where alternation of generation is seen distinctly.

Answer

Alternation of generations is a type of life cycle in which a plant alternates between two multicellular phases: a haploid gametophyte and a diploid sporophyte. The gametophyte is the sexual phase, and the sporophyte is the asexual phase.

Two plant groups where alternation of generations is seen distinctly are mosses and ferns. In mosses, the gametophyte is the dominant phase, and the sporophyte is a small, attached structure. In ferns, the sporophyte is the dominant phase, and the gametophyte is a small, free-living structure.

4.9. Write down Mendel’s Law of Segregation. Mention one difference in between phenotype and genotype.

Answer

Mendel’s Law of Segregation states that during gamete formation, the two copies of each gene segregate (separate) from each other so that each gamete receives only one allele for each gene.

The difference between phenotype and genotype is that phenotype is the physical appearance of an organism, while genotype is the genetic makeup of an organism.

4.10.Write name of three ancestors of modern horse.

Answer

The three ancestors of modern horses:

• Hyracotherium, also known as the “dawn horse”, was a small, four-toed creature that lived about 55 million years ago.
• Mesohippus, which lived about 40 million years ago, had three toes on each foot and was about the size of a modern fox.
• Merychippus, which lived about 30 million years ago, had three toes on each foot and was about the size of a modern pony.

4.11. Name three adaptive features for flight in Pigeon.

Answer

The three adaptive features for flight in pigeons:

• Broad, pointed wings: Pigeons have broad, pointed wings that help them to generate lift and thrust.
• Strong breast muscles: Pigeons have strong breast muscles that allow them to flap their wings powerfully.
• Streamlined body: Pigeons have a streamlined body that helps them to reduce drag.

4.12. Write down the modes of transmission of Influenza vims, HIV and Polio vims.

Answer

The modes of transmission of influenza, HIV, and polio viruses:

• Influenza virus can be transmitted through respiratory droplets produced when an infected person coughs or sneezes. These droplets can land in the mouths or noses of people who are nearby or possibly be inhaled into the lungs.
• HIV is transmitted through contact with blood, semen, vaginal fluids, and breast milk. It can also be transmitted from mother to child during pregnancy, childbirth, or breastfeeding.
• Polio virus can be transmitted through contact with the feces of an infected person. It can also be transmitted through contaminated food or water.

4.13.Mention one beneficial role each of Saccharomyces (Yeast), Penicillium and Rhizobium.

Answer

One beneficial role each of Saccharomyces (Yeast), Penicillium and Rhizobium:

• Saccharomyces (Yeast) is used in the production of bread, beer, wine, and other fermented foods and beverages. It is also used in the production of biofuels.
• Penicillium is a fungus that produces the antibiotic penicillin. Penicillin is used to treat a variety of bacterial infections, including pneumonia, meningitis, and syphilis.
• Rhizobium is a bacteria that forms a symbiotic relationship with legume plants. Rhizobium bacteria live in the roots of legume plants and fix nitrogen from the air. This nitrogen is then used by the legume plant for growth and development.

Group – B

(Answer any five questions)

5. Mention one economic importance each of Quinine, Reserpine and Morphin. What are the means of removal of excretory products in silk cotton (simul) and guava? [(1×3)+2]

Answer

One economic importance each of quinine, reserpine and morphine:

• Quinine is used to treat malaria.
• Reserpine is used to treat high blood pressure and anxiety.
• Morphine is used to relieve pain.

Silk cotton (simul) and guava trees excrete their waste products through their leaves, stems and roots. The leaves of these trees have small pores called stomata, which allow water vapor and carbon dioxide to pass in and out of the leaf. The stems of these trees also have stomata, but they are not as numerous as the stomata on the leaves. The roots of these trees excrete waste products into the soil.

6. Write down one structural and one functional difference between the Afferent and Efferent Nerve. What is synapse and what is its function? Mention one function of the spinal cord. [2+2+1]

Answer

One beneficial role each of Saccharomyces (Yeast), Penicillium and Rhizobium:

• Saccharomyces (Yeast) is used in the production of bread, beer, wine, and other fermented foods and beverages. It is also used in the production of biofuels.
• Penicillium is a fungus that produces the antibiotic penicillin. Penicillin is used to treat a variety of bacterial infections, including pneumonia, meningitis, and syphilis.
• Rhizobium is a bacteria that forms a symbiotic relationship with legume plants. Rhizobium bacteria live in the roots of legume plants and fix nitrogen from the air. This nitrogen is then used by the legume plant for growth and development.

7. Write down the names of sites of secretion and one function each of Testosterone and Oestrogen. Mention one function of GTH. [2+2+1]

Answer

8. What is Amitosis? What events take place during the Prophase and Telophase stages of mitosis? [1+(2+2)]

Answer

Amitosis is a type of cell division that does not involve the formation of spindle fibres or the separation of chromosomes.

Events take place during the Prophase and Telophase stages of mitosis:

• Prophase is the first stage of mitosis. During prophase, the chromosomes condense and become visible. The nuclear envelope breaks down and the spindle fibres form. The centrosomes move to opposite poles of the cell.
• Telophase is the final stage of mitosis. During telophase, the chromosomes decondensed and return to their original state. The nuclear envelope reforms and the spindle fibres disappear. The cell divides into two identical daughter cells.

9. What is Vegetative Reproduction? Give two examples of Natural Vegetative Reproduction in plants. Mention two importance of Vegetative Reproduction. [1+(2+2)]

Answer

Vegetative reproduction is a type of asexual reproduction in plants where new plants are produced from parts of the parent plant. This can happen naturally or artificially.

Two examples of natural vegetative reproduction in plants are:

• Stolons: These are horizontal stems that grow along the ground and root at the nodes. New plants are produced from the roots.
• Rhizomes: These are underground stems that grow horizontally and store food. New plants are produced from the rhizomes.

Two importance of vegetative reproduction are:

• It is a quick and easy way to produce new plants.
• It can be used to propagate plants that are difficult to grow from seeds.

10. Explain the ‘Law of Use and Disuse’ and ‘Inheritance of Acquired Character as proposed by Lamarck. What is the variation? [(2+2)+1]

Answer

The two laws proposed by Jean-Baptiste Lamarck:

• Law of Use and Disuse: This law states that organisms that use a particular body part or organ more often will develop that body part or organ more strongly, while organisms that do not use a particular body part or organ as often will develop it less strongly. For example, if a giraffe stretches its neck to reach higher leaves, its neck will become longer over time.
• Inheritance of Acquired Characters: This law states that acquired characteristics, such as a longer neck in a giraffe, can be passed on to offspring. This means that the offspring of a giraffe with a long neck will also have a long neck.

Variation is the difference in physical characteristics between individuals of the same species. Variation is caused by a combination of factors, including genes, environment, and random chance.

11. Mention the adaptive significance of the following organs : [1×5]

1. Breathing roots of Sundri
2. Gill of Rohu fish
3. Petiole of Lotus
4. Leaf of Cactus
5. Tail Fin of Rohu fish.

Answer

1. Breathing roots of Sundri: Allow oxygen uptake in waterlogged environments.
2. Gill of Rohu fish: Facilitates oxygen extraction from water for respiration.
3. Petiole of Lotus: Supports leaf adaptation to aquatic environments.
4. Leaf of Cactus: Minimizes water loss through reduced surface area and thick cuticle.
5. Tail Fin of Rohu fish: Enables precise manoeuvrability and propulsion in water.

Group – C

(Answer any one question)

12. Draw a scientific diagram of an ideal neurone of the human body, and label the following parts in the diagram: [5+3]

1. Nodes of Ranvier
2. Axon
3. Schwann Cell

13. Draw neat and scientific diagrams of each of ‘Second Phase’ and ‘Third Phase’ of Karyokinesis of Mitosis in an animal cell and label the following parts: [(2½ + 2½) +(2½ +2½)]

1. Continuous Fibre
2. Centromere
3. Chromosomal Fibre

[For Sightless Candidates Only]

(Diagram not required)

Answer any one question

12(A). Define neurone. Name the two types of processes of an ideal human neurone and write their respective structures in brief. What are the functions of these two types of processes respectively? [1+1+4+2]

Answer

A neuron is a nerve cell that carries information to and from the brain. Neurons are the basic building blocks of the nervous system.

13(A). Discuss the characteristics and significance of the ‘Second Phase’ and ‘Third Phases’ of Karyokinesis of Mitosis in an animal cell. [4+4]

Answer

During mitosis, the process of cell division, the nucleus of a cell goes through a series of stages called karyokinesis. Karyokinesis is divided into several phases, including the second phase and the third phase. Let’s discuss their characteristics and significance in an animal cell:

Second Phase of Karyokinesis:

• Also known as metaphase, it follows the first phase (prophase) and precedes the third phase (anaphase) of karyokinesis.
• During metaphase, the replicated chromosomes align along the cell’s equator, forming a single plane called the metaphase plate.
• The centromeres of the chromosomes attach to spindle fibres, which extend from opposite ends of the cell.
• The chromosomes become fully condensed and visible under a microscope.

Significance:

• • The metaphase stage ensures the proper alignment of chromosomes, allowing for their even distribution to daughter cells.
  • It serves as a checkpoint to ensure accurate segregation of chromosomes during cell division.
  • The precise alignment of chromosomes in metaphase ensures the equal distribution of genetic material to daughter cells, promoting genomic stability.

Third Phase of Karyokinesis:

• Also known as anaphase, it follows metaphase and precedes the final phase (telophase) of karyokinesis.
• During anaphase, the centromeres of sister chromatids separate, resulting in the division of each replicated chromosome into two identical chromatids.
• The spindle fibres shorten and pull the separated chromatids towards opposite poles of the cell.

Significance:

• • Anaphase is a crucial phase as it ensures the accurate segregation of chromosomes.
  • It facilitates the separation of sister chromatids, ensuring that each daughter cell receives an identical set of chromosomes.
  • The proper segregation of chromosomes during anaphase is vital for the maintenance of genetic stability in daughter cells and the prevention of chromosomal abnormalities.

Group – D

[Only for External Candidates]

Answer any one question

14. (a) Describe the structure and function of Mitochondria.

(b) Point out three differences in between ‘Plant Cell’ and ‘Animal Cell’.

(c) Discuss the Characteristics and functions of ‘Skeletal Muscles’.  [4+3+3]

Answer

(a) Mitochondria:

Structure:

• Double-membraned organelles
• Outer membrane and inner membrane with folds called cristae
• Inner membrane encloses the mitochondrial matrix
• Matrix contains enzymes, DNA, and ribosomes

Function:

• Cellular respiration: Generates ATP, the cell’s primary energy source
• Metabolism: Converts nutrients and oxygen into ATP through chemical reactions
• Citric acid cycle and electron transport chain take place in mitochondria

(b) Differences between Plant Cells and Animal Cells:

1. Cell Wall: Plant cells have a rigid cell wall composed of cellulose, which provides structural support and protection for the cell. Animal cells do not have a cell wall.
2. Chloroplasts: Plant cells contain chloroplasts, specialized organelles that carry out photosynthesis and enable plants to produce their own food. Animal cells lack chloroplasts.
3. Vacuoles: Plant cells typically have one large central vacuole that stores water, ions, and nutrients. Animal cells may have smaller vacuoles, but they are not as prominent as in plant cells.

(c) Characteristics and Functions of Skeletal Muscles:

Characteristics:

1. Striated: Skeletal muscles have a striped or striated appearance due to the arrangement of protein filaments called actin and myosin.
2. Voluntary Control: Skeletal muscles are under conscious control, allowing individuals to initiate and control their movements.

Functions:

1. Body Movement: Skeletal muscles work together with bones and joints to produce voluntary movements such as walking, running, and lifting objects.
2. Posture and Stability: Skeletal muscles help maintain body posture and provide stability by holding the skeleton in proper alignment.

15. Write short notes on any four : [4×2½]

1. Nucleus 
2. Plastid
3. Cell wall 
4. Ribosome
5. Golgi Bodies

Answer

Nucleus

The nucleus is the control centre of the cell. It contains the cell’s DNA, which is the genetic material that determines the cell’s structure and function. The nucleus is surrounded by a nuclear envelope, which is a double membrane that protects the DNA from damage. The nucleus also contains the nucleolus, which is a small organelle that produces ribosomes.

Plastid

Plastids are organelles that are found in plant cells. They are responsible for photosynthesis, which is the process by which plants convert sunlight into food. Plastids come in different shapes and sizes, and they can perform different functions. For example, chloroplasts are plastids that are responsible for photosynthesis. Chromoplasts are plastids that store pigments, such as carotenoids and anthocyanins.

Cell wall

The cell wall is a rigid structure that surrounds the cell membrane. It is made up of cellulose, a type of carbohydrate. The cell wall provides support and protection for the cell. It also helps to keep the cell’s shape.

Ribosome

Ribosomes are small organelles that are found in the cytoplasm of the cell. They are responsible for protein synthesis. Ribosomes are made up of two subunits, a large subunit and a small subunit. The large subunit contains the enzymes that are needed for protein synthesis. The small subunit contains the RNA that is needed for protein synthesis.