Madhyamik Class 10 Life Science Solved Paper 2017

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)

For Regular candidates, the questions for Group ‘A’, ’B’, ‘C’, and ‘D’ will have to be answered.

Special Instruction for Sightless Candidates

In Group ‘D’ instead of Question No. 4.1, 4.1 (A) will also have to be answered in addition to Group ‘A’, ‘B’, ‘C’ and D.

Instructions regarding the number of questions to be attempted have been indicated at the beginning of each group.

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

1. Multiple choice question.

Question 1.1

Some flowers are open after sunrise and close after sunset. This is –

Photonasty
Seismonasty
Chemonasty
Thermonasty

Solution

(a) Photonasty

Explanation

Photonasty is a nastic movement that is associated with changes in light intensity.

Question 1.2

A person affected with Diabetes Mellitus is unable to secrete which of the following hormones in adequate quantity-

Adrenaline
Insulin
Thyroxine
Testosterone

Solution

(b) Insulin

Explanation

A person affected with Diabetes Mellitus cannot secrete insulin in adequate quantity. Insulin is a hormone produced by the pancreas that helps the body use glucose for energy.

Question 1.3

The part of the human brain associated with controlling body temperature is

Thalamus
Cerebellum
Hypothalamus
Medulla

Solution

Explanation

The part of the human brain associated with controlling body temperature is the hypothalamus.

Question 1.4

You have observed the separation of two sister chromatids at one stage of mitotic cell division the stage is

Prophase
Telophase
Anaphase
Metaphase

Solution

Explanation:

The stage of mitosis where the separation of two sister chromatids occurs is anaphase.

Question 1.5

Which of the following pairs is correct

Budding-Yeast
Fragmentation
Sphere-formation-amoeba
Regeneration-Dryopteris

Solution

(a) Budding-Yeast

Explanation:

The correct pair is Budding-Yeast. Budding is a type of asexual reproduction in which a small bud grows off of the parent cell.

Question 1.6

Which phase of human development is associated with the maturity of reproductive organs and reproductive gland –

Childhood
Adolescence
Late Adulthood
Infancy

Solution

(b) Adolescence

Explanation:

The phase of human development associated with the maturity of reproductive organs and reproductive glands is adolescence.

Question 1.7

Which of the following traits in pea plant is recessive –

Wrinkled seed
Yellow-coloured seed
Purple-coloured flower
Axial flower

Solution

(a) Wrinkled seed

Explanation:

The recessive trait in pea plant is a wrinkled seed. The dominant trait is a round seed. The other options are all dominant traits.

Question 1.8

How many types of gametes are formed by pea plants having genotype YyRr?

Solution

(b) 4

Explanation:

The possible types of gametes are: YR, Yr, yR, and yr.

Question 1.9

The probability of haemophilic girl children born to a haemophilia carrier mother and normal father is –

75%
50%
100%
0%

Solution

(b) 0 %

Explanation:

The probability of having a hemophilic girl from a carrier mother (XX) and a normal father (XY) is 0. A girl needs two X chromosomes, but the father can only pass on a normal X. Therefore, it’s impossible for a hemophilic girl to be born in this case.

Question 1.10

The gas which was absent in the environment during the origin of life is –

Hydrogen
Oxygen
Methane
Ammonia

Solution

(b) Oxygen

Explanation:

The gas which was absent in the environment during the origin of life is oxygen.

Question 1.11

The feature of analogues organ is –

Differences in origin and function are also different
Different in origin but function are same
Indicates divergent evolution
Identical in origin and structure

Solution

(b) Different in origin but function are same

Explanation:

Analogous organs are organs that have different origins but perform the same function.

Question 1.12

Which of the following absorbs the gas of the swim bladder in bony fishes –

Red gland
Anterior chamber
Gastric gland
Retia mirabilia

Solution

(a) red gland

Explanation:

The gas in the swim bladder of bony fishes is absorbed by a structure called the red gland.

Question 1.13

Which of the following phase of the nitrogen cycle Pseudomonas is associated with-

Nitrogen fixation
Nitrification
Denitrification
Ammonification

Solution

Explanation:

Pseudomonas is associated with the phase of the nitrogen cycle known as denitrification.

Question 1.14

One endangered species of the Eastern Himalayas biodiversity hotspot is –

Lion-tailed macaque
Orangutan
Red panda
Nilgiri thar

Solution

Explanation:

The red panda is a small, furry mammal that is native to the Eastern Himalayas and the Eastern Himalayas biodiversity hotspot. It is listed as Endangered on the IUCN Red List due to habitat loss, poaching, and competition from other animals.

Question 1.15

The diseases associated with air pollution are –

Diarrhoea, Typhoid, Hepahepatitis,
Hepahepatitis, Bronchitis, Deafness
Bronchitis, Asthma, Lung cancer
Lung cancer, Polio, Malaria

Solution

Group – B

2. Answer the following question (alternatives are to be noted).

Fill in the blanks:

Question 2.1 – 2.6

The process of necessary adjustment of the lens’s focal length in human eyes is called ____.
Adenine is a __ type of nitrogenous base.
__ is a disease created by sex-linked genes.
The earliest ancestor in the evolution of horses is ___.
An inflammable greenhouse gas produced from the paddy field is __.
____ is a biosphere reserve located in West Bengal.

Solution

The process of necessary adjustment of the focal length of the lens in human eyes is called accommodation.
Adenine is a purinic type of nitrogenous base.
Hemophilia is a disease created by sex-linked genes.
The earliest ancestor in the evolution of horses is Hyracotherium.
An inflammable greenhouse gas produced from the paddy field is methane.
Sundarbans is a biosphere reserve located in West Bengal.

Decide whether the following statements are true or false (any five)

Question 2.7

Gibberellin hormone prevents immature shedding of the leaf of plants.

Solution

True

Reasons: Gibberellins are plant hormones that promote cell division and elongation. They can also prevent the abscission of leaves, which is the natural process of leaf shedding.

Question 2.8

Ovum is only produced as a result of mitosis.

Solution

False.

Reasons: The ovum, or egg cell, is produced by meiosis, not mitosis. Meiosis is a type of cell division that reduces the number of chromosomes in half.

Question 2.9

Self–pollination can be exercised in pea plant flowers according to the need.

Solution

True.

Reasons: Pea plant flowers have both male and female reproductive organs. This means that they can self-pollinate, which is the process of pollen from the same flower fertilizing the egg cell.

Question 2.10

The fundamental tenet of the evolutionary theory of Darwin is the process of natural selection.

Solution

True.

Reasons: Charles Darwin’s theory of evolution by natural selection is based on the idea that individuals with traits that make them better suited to their environment are more likely to survive and reproduce.

Question 2.11

A degradable pollutant is responsible for biomagnification.

Solution

False.

Reasons: Biomagnification is the process by which pollutants become more concentrated as they move up the food chain.

Question 2.12

Flagella is the locomotory organ of Paramecium.

Solution

False.

Reasons: Flagella is not the locomotory organ of Paramecium. Paramecium is a single-celled organism belonging to a group of ciliates. It moves using numerous hair-like structures called cilia.

Match the right column with the left column: (Any five)

Column–A	Column–B
2.13) Blind Spot	a) Pollution of groundwater
2.14) Cytokinesis	b) The point of connection of the retina and optic nerve
2.15) 44A+XY	c) Homologous organs
2.16) Wings of bats and birds	d) Formation of cell plates
2.17) Arsenic	e) Pollen grain
2.18) Transfer to stigma	f) Sound pollution
	g) Chromosomal attachments of human male

Solution

2.13. – (b), 2.14. – (d), 2.15. – (g), 2.16. – (c), 2.17. – (a), 2.18. – (e)

Answer in a single word or in a single sentence (any six) :

Question 2.19

Choose the odd one and write it: TSH, ACTH, GTH, CSF

Solution

CSF

Explanation: TSH (Thyroid-stimulating hormone), ACTH (Adrenocorticotropic hormone), and GTH (Gonadotropin hormone) are all hormones produced by the pituitary gland.

Question 2.20

Write one function of the myelin sheath.

Solution

Myelin sheath increases the rate of transmission of nerve impulses.

Question 2.21

A pair of related terms is given below. On the basis of the relationship in the first pair write the suitable word in the gap of the second pair.

Prophase: Disappearance of nuclear membrane and nucleolus:: ___: Reappearance of nuclear membrane and nucleolus.

Solution

Telophase

Question 2.22

Give an example of a variation inherited in man along with the generation.

Solution

Attached ear/ Common tongue.

Question 2.23

Which type of chromosome in humans carries the gene responsible for the disease thalassemia?

Solution

The gene responsible for thalassemia is carried on an autosome.

Question 2.24

Mention one morphological adaption of the cactus to prevent transpiration.

Solution

One key morphological adaptation of a cactus to prevent transpiration is its spines, which are modified leaves.

Question 2.25

Among the following four terms one includes the other three, Find out that term and write it:

Embryo, meristematic tissue, Seed, Cryopreservation.

Solution

Cryopreservation is a method used to preserve biological materials like embryos, meristematic tissue, and seeds at very low temperatures, typically in liquid nitrogen.

Question 2.26

Write the name of the cause of the latest concern regarding the environment of Sundarbans.

Solution

Global warming or pollution is the cause of the latest concern regarding the environment of Sundarbans.

Group – C

3. Answer any 12 questions in 2-3 sentences out of 17 questions given below:

Question 3.1

Write two differences between tropic movement and nastic movement.

Solution

Tropic Movements	Nastic Movements
The movement bears relation to the direction of the stimulus.	The movement bears relation to the intensity of the stimulus.
Growth-dependent	Growth-independent

Question 3.2

Write two roles of GTH in the secretion of hormones from the reproductive glands in the human body.

Solution

GTH (Gonadotropin) plays two important roles in the secretion of hormones from the reproductive glands in the human body:

Stimulation: GTH stimulates the production and secretion of hormones from the reproductive glands, such as the ovaries in females and the testes in males.
Feedback Regulation: GTH also provides feedback regulation to maintain hormonal balance.

Question 3.3

Categorize the following actions as natural or inherited reflex actions.

The willingness of infants to breast-feeding, Cycling, Sneezing, and Catching ball by wicket-keeper with swiftness

Solution

Action	Natural Reflex Action	Inherited Reflex Action
The willingness of infants to breast-feeding	Natural	Inherited
Cycling	Natural	–
Sneezing	Natural	–
Catching the ball by the wicket keeper with swiftness	–	Inherited

Question 3.4

Write the parts of the central nervous system and peripheral nervous system.

Solution

Central Nervous System (CNS):

Brain
Spinal cord

Peripheral Nervous System (PNS):

Cranial nerves
Spinal nerves
Ganglia

Question 3.5

Write two importance of the cell cycle.

Solution

The two importance of the cell cycle:

Growth and development: The cell cycle allows for the growth and development of organisms by allowing cells to divide and create new cells.
Repair and maintenance: The cell cycle also allows for the repair and maintenance of organisms by allowing cells to divide and replace damaged or dead cells.

Question 3.6

Distinguish between DNA and RNA based on the following features: Pyrimidine base 5-C sugar

Solution

Feature	DNA	RNA
Pyrimidine base	Thymine (T)	Uracil (U)
5-C sugar	Deoxyribose	Ribose

Question 3.7

Which agents perform the function of pollination in the following plants? Paddy Hydrilla Shimul Mango.

Solution

Plant	Pollination Agent
Paddy	Wind
Hydrilla	Water
Shimul	Insects
Mango	Birds

Question 3.8

State with an example of how the dominant trait is expressed in the experiment of hybridization.

Solution

In the experiment of hybridization dominant trait is expressed in F₁ generation and the recessive trait is suppressed. Example – In the cross between pure Black Male (B.B.) and pure white female (bb), all the guinea pig in F₁ generation are phenotypically black because blackness is the dominant character. In F₁ generation black and white both types of guineapigs are produced.

Question 3.9

What would be the ratio of phenotype and genotype of F2 generation in a monohybrid experiment in case of incomplete dominance?

Solution

In incomplete dominance, the phenotypic ratio of the F2 generation is 1:2:1, the same as the genotypic ratio.

Question 3.10

Show with the help of a cross, how colour blindness is inherited.

Solution

P – Normal male × Normal Female (but carrier)

Son-1 Normal – 1 Colour blind,

∴ 1 : 1, So 50% : 50%

Question 3.11

Write the name of reactants used and one origin compound formed in the experiment of Miller and Urey in connection with the chemical origin of life

Solution

Ammonia, Hydrogen and Methane were used in the experiment on the biochemical origin of life by Miller and Urey.

Question 3.12

Write four important features modified in the evolution of the horse.

Solution

The four important features modified in the evolution of the horse:

Size: Horses have evolved to be much larger than their early ancestors. The first horses, called Eohippus, were about the size of a fox. Modern horses can be up to 18 hands high (6 feet tall).
The number of toes: Early horses had four toes on each foot. Over time, the number of toes has decreased, and modern horses have only one toe on each foot.
Teeth: Early horses had teeth that were adapted for browsing on leaves. Modern horses have teeth that are adapted for grazing on grass.
Brain size: The brain size of horses has increased over time. This is thought to be due to the need for more complex cognitive abilities, such as navigation and social behaviour.

Question 3.13

How Sundari plant excretes the excess salt in its body?

Solution

Sundari plants excrete excess salt through specialized glands called salt glands. These glands are located on the underside of the leaves. The salt glands transport salt from the leaves to the stems, where it is excreted through pores. This process is known as transpiration-driven salt efflux.

Question 3.14

Write the names of two microorganisms participating in the process of biological nitrogen fixation.

Solution

Two microorganisms that participate in the process of biological nitrogen fixation:

Rhizobium
Azotobacter

Question 3.15

Mention two damages as a result of acid rain.

Solution

The two damages as a result of acid rain:

Damage to forests. Acid rain can damage trees by making it difficult for them to take up nutrients from the soil.
Damage to aquatic life. Acid rain can make lakes and streams more acidic, which can harm fish and other aquatic life.

Question 3.16

Give four examples of damages to biodiversity as a result of global warming.

Solution

Four examples of damage to biodiversity as a result of global warming:

Species extinction: As the Earth’s climate changes, many species will be unable to adapt and will go extinct.
Habitat loss: As the Earth’s climate changes, many habitats will be destroyed or degraded.
Invasive species: As the Earth’s climate changes, invasive species will become more common. These species are not native to the area and can outcompete native species for food and resources. This can lead to the decline or extinction of native species.
Disease: As the Earth’s climate changes, the range of conditions will expand.

Question 3.17

Write the major topics regarding biodiversity documented in the People’s Biodiversity Register (PBR).

Solution

The major topics regarding biodiversity documented in the People’s Biodiversity Register (PBR) include:

Landscape – Cultivated lands, aquatic bodies (rivers, ponds, ditches, canals), forests, wastelands, pastures, gardens, burial grounds, and cemeteries.
Life Scape – Crop plants, vegetables, fruits, wild plants, wild animals, domestic animals, birds, insects, micro-flora, and fauna.
People Scape – Traditional knowledge associated with biodiversity and its use.
Ecological History – Information on the ecological history of the area.
Endemic and Endangered Species – Documentation of local endemic and endangered species.

Group – D

4. Answer 6 questions or their alternative given below.

Question 4.1

Draw a neat diagram of the vertical section of the eyeball of the human eye and label the following parts:

Cornea
Lens
Vitreous humour
Retina

Or,

Draw a neat diagram of the metaphase of mitosis of a plant cell or an animal cell division and label the following parts:

Chromosome
Spindle fibre
Polar region
Centromere

Solution

The vertical section of the eyeball:

Metaphase of mitosis of an animal cell

Question 4.2

Explain the interrelationship among chromosomes and genes and distinguish between euchromatin and heterochromatin on the following two aspects. (a) Coiling (b) Activity

Or,

How micropropagation is done? States that happens in the following three phases of sexual reproduction of flowering plants:-

Production of gamete or reproductive cell
Fertilization
Formation of the embryo and new plant

Solution

Chromosomes and genes

Chromosomes are structures that contain genetic material. They are made up of DNA, which is tightly wrapped around proteins called histones. Genes are segments of DNA that code for specific proteins.

Euchromatin and heterochromatin

Euchromatin and heterochromatin are two types of chromatin, which is the material that makes up chromosomes. Euchromatin is less condensed than heterochromatin, and it is associated with active gene expression. Heterochromatin is more condensed than euchromatin, and it is associated with inactive gene expression.

Coiling

Euchromatin is more loosely coiled than heterochromatin. This makes it easier for transcription factors to access the DNA in euchromatin, and it allows for more active gene expression. Heterochromatin is more tightly coiled, which makes it more difficult for transcription factors to access the DNA. This leads to less active gene expression in heterochromatin.

Activity

Euchromatin is more active than heterochromatin. This is because euchromatin is more accessible to transcription factors, which are proteins that bind to DNA and regulate gene expression. Heterochromatin is less accessible to transcription factors, which is why it is less active.

Micropropagation is a technique for rapidly producing large numbers of plants from a single plant. It involves taking small pieces of plant tissue, such as leaves, stems, or roots, and growing them in a sterile environment on a nutrient-rich medium. The cells in the tissue culture multiply and differentiate into new plants.

The three phases of sexual reproduction in flowering plants are:

Production of gametes: In flowering plants, gametes are produced by the male and female reproductive organs, the stamen and pistil.
Fertilization: This process occurs when the pollen grain from the stamen lands on the stigma of the pistil. The pollen grain then germinates and grows a pollen tube, which delivers the sperm to the egg.
Formation of the embryo and new plant: After fertilization, the zygote (fertilized egg) divides repeatedly to form an embryo. The embryo develops into a seed, which contains the new plant. The seed then germinates and the new plant grows.

Question 4.3

With the help of a checkerboard show the types of offspring that might be produced in a cross between a hybrid black guineapig and a pure white guineapig. State the law of segregation as proposed by Mendel. [3+2=5]

Mention the symptoms of thalassemia disease. In many families, mothers are labelled as responsible for the birth of a daughter’s child. Demonstrate with the help of a cross, that these beliefs are not justified.

Solution

When a hybrid black guinea pig (Bb) is crossed with a pure white guinea pig (bb), the potential offspring can have two genotypes: Bb (black) and bb (white).

Using a Punnett square, we can represent the possible combinations:

	B	b
b	Bb	bb
b	Bb	bb

From the Punnett square, we can see that there is a 50% chance of producing offspring with the Bb genotype (black) and a 50% chance of producing offspring with the bb genotype (white).

State the law of segregation as proposed by Mendel: The law of segregation states that actors passed from one generation to another in an unaltered manner; they separate during gamete formation, reunite during fertilization and pass to the next generation.

Symptoms of thalassemia:

Fatigue and weakness
Pale or yellowish skin
Shortness of breath
Delayed growth and development

Regarding the belief that mothers are responsible for the birth of a daughter’s child, let’s consider a simple cross to demonstrate why this belief is not justified:

From this cross, we can observe that the father’s contribution of the Y chromosome determines the birth of a male child. Therefore, it is incorrect to solely blame or attribute the birth of a daughter’s child to the mother.

Question 4.4

Mentions two features of internal structures on the basis of which, the ‘flipper of whales’ and ‘wings of birds’ are considered as homologous organs. How a worker bee of a beehive communicates with other worker bees regarding the source and location of food?

Solution

The flipper of whales and the wings of birds are considered homologous organs due to their shared internal structures. Both have similar skeletal structures, including the humerus, ulna, radius, and carpals. Additionally, their muscle structures for controlling movement are also alike. These similarities suggest a common ancestry, despite their different functions in swimming and flying, respectively.

In a beehive, a worker bee communicates food source information to others through two main dances. The waggle dance conveys the direction and distance of the food source. The angle of the dance represents the direction relative to gravity, while the duration of the waggle indicates the distance. For food sources within 75 meters, the round dance is performed, signalling the availability of food without specifying the direction. Other worker bees interpret these dances and follow the communicated information to locate the food source.

Or, Show the major evolutionary events with the help of a flow chart.

Solution

Protovirus → Virus → Bacteria → Protozoa → Multicellular organism → Chlorophyllous organism → Plants

Question 4.5

What are the causes of Asthma? What are the roles of Joint Forest Management in the conservation of biodiversity?

Assess the causes of depletion of the biodiversity with proper examples.

Solution

Asthma: During breathing, we inspire air from the environment. If air is polluted, polluted air enters into the respiratory system and serious damage to the lung and respiratory tracts occurs.Toxic materials (both gas and suspended particles) when enter the respiratory tract and lungs, and the cells of the living are damaged. Due to such damage, the diseases that may develop are asthma, bronchitis, lung cancer etc.
Joint Forest Management (JFM): JFM is a community-based approach to forest management that involves local people in the planning, implementation, and monitoring of forest activities. JFM has been shown to be effective in conserving biodiversity by providing local people with a stake in the forest and by promoting sustainable forest management practices.

Or,

Habitat loss and fragmentation: This is the most significant cause of biodiversity loss. When habitats are destroyed or fragmented, species are unable to find food, mates, or suitable places to live. For example, deforestation is a major cause of habitat loss for many species of plants and animals.
Overexploitation: This is the excessive use of a species’ resources. This can lead to the depletion of the population and even extinction. For example, overfishing has led to the decline of many fish populations.
Invasive species: These are species that are introduced to an ecosystem and then become established and spread. Invasive species can outcompete native species for resources, leading to the decline or extinction of native species. For example, the introduction of the brown tree snake to Guam has led to the extinction of many native bird species.
Climate change: Climate change is already having a significant impact on biodiversity. As the climate changes, species are being forced to move to new areas or adapt to the changing conditions. Some species will not be able to adapt and will go extinct. For example, rising sea levels are threatening the habitats of many coastal species.

Question 4.6

Propose two conservation measures that could be taken to increase the number of Indian one-horned rhinos. Make your opinion based on your experience of how the source of freshwater becomes polluted. [2+3=5]

Which conditions do you consider to declare one area out of two as a biodiversity hotspot? Give two examples of ex-situ conservation.

Solution

Part I.

Rhino and baby rhinos should be kept isolated in sanctuaries/ favourable environments.
Hunting and poaching should be strictly prohibited by enacting the law.

Part II.

Agricultural runoff containing pesticides, herbicides and fertilizers containing NO₃.
Domestic wastewater (sewage) mainly detergents containing phosphates. Sewage helps the overgrowth of algae. This makes the water unfit for bathing and drinking.

Or,

The two conditions that need to be met for an area to be considered a biodiversity hotspot:

It must have at least 1,500 vascular plant species as endemics.
It must have lost at least 70% of its original natural vegetation.

Here are two examples of ex-situ conservation:

Botanical gardens: Botanical gardens are places where plants are grown in a controlled environment. This allows for the conservation of plants that are threatened in their natural habitats.
Zoos: Zoos are places where animals are kept in captivity. This allows for the conservation of animals that are threatened in their natural habitats.

Group – E

[For External Candidate Only]

5. Answer any four questions : [1×4=4]

Question 5.1

Mention one feature of unstriated muscle.

Solution

One feature of unstriated muscle is that it is not attached to bones.

Question 5.2

Which cell organelle is referred to as the “kitchen of the cell”?

Solution

The mitochondria are referred to as the “kitchen of the cell”.

Question 5.3

In which type of cell, the nucleus is not well organized?

Solution

Anucleate cells do not have a nucleus. This type of cell is found in bacteria and some other single-celled organisms.

Question 5.4

Give an example of a flower pollinated by air.

Solution

Paddy.

Question 5.5

Write one important feature of life.

Solution

One important feature of life is the ability to reproduce.

6. Answer any three questions : [2×3=6]

Question 6.1

Write two features of epithelial tissue.

Solution

It is made up of tightly packed cells that form a continuous sheet.
It has no blood vessels, so it relies on diffusion to get nutrients and oxygen.

Question 6.2

Write two functions of collenchyma tissue.

Solution

Collenchyma tissue is a type of tissue that provides support and flexibility to plant organs. Two functions of collenchyma tissue are:

It helps to keep plant organs from collapsing.
It allows plant organs to bend without breaking.

Question 6.3

Write two differences between plant cells and animal cells.

Solution

Two differences between plant cells and animal cells are:

Plant cells have a cell wall, while animal cells do not.
Plant cells have chloroplasts, which allow them to make their own food through photosynthesis. Animal cells do not have chloroplasts.

Question 6.4

Give one example for each prokaryotic and eukaryotic cell.

Solution

Examples of prokaryotic and eukaryotic cells: