Time : 1 Hour 30 Minute

STD 10 Science Total Marks : 50

Biology Unit test.

SECTION A

* Select and write one most appropriate option out of the four options given for each of the [8]
questions

1. The diagram shows a vertical section through the heart.

What are the functions of the numbered blood vessels?
Carri Carri Carrie Carri
es es s es
bloo bloo blood blood
d to d to from from
body lung lungs body
s
(a) 1 2 3 4
(b) 1 3 4 2
(c) 2 4 3 1
(d) 3 1 4 2

(A) (a) (B) (b) (C) (c) (D) (d)

Ans. :
d. (d)
Explanation:
a. Pulmonary artery.
b. Vena cava.
c. Aorta.
d. Pulmonary vein.
2. Which of the following statements are true?
i. Sudden action in response to something in the environment is called reflex action.
ii. Sensory neurons carry electrical signals from spinal cord to muscles in a reflex
action.
iii. Motor neurons carry signals from receptors to spinal cord in a reflex action.
iv. The pathway of transmitting signals from a receptor to a muscle is a reflex action.

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 (A) (i) and (ii). (B) (i) and (iii). (C) (i) and (iv). (D) (i), (ii) and (iii).

Ans. :
c. (i) and (iv).
Explanation:
Statements (i) and (iv) are correct, while statements (ii) and (iii) are not. Sensory
neurons carry signals from the receptors to the brain or the spinal cord, while motor
neurons carry signals from the brain or the spinal cord to the effector organs like
muscles and glands.
3. In a synapse, chemical signal is transmitted from:
(A) Axon to cell body (B) Cell body to axon (C) Dendrite end of (D) Axon end of one
of the same neuron. end of the same one neuron to axon neuron to dendrite
neuron. end of adjacent end of adjacent
neuron. neuron.

Ans. :
d. Axon end of one neuron to dendrite end of adjacent neuron.
Explanation:
In a synapse, a chemical signal is transmitted from the axon end of one neuron to
the dendrite end of the adjacent neuron.
4. The factors responsible for the rapid spreading of bread mould on slices of bread are:
i. Presence of large number of spores in air.
ii. Presence of large number of thread-like branched hyphae.
iii. Presence of moisture and nutrients.
iv. Formation of round shaped sporangia.
(A) (i) and (iii). (B) (ii) and (iv). (C) (i) and (ii). (D) (iii) and (iv).

Ans. :
a. (i) and (iii).
Explanation:
The factors responsible for the rapid spreading of bread mould on slices of bread are
the presence of a large number spores in air and the presence of moisture
and nutrients in bread that act as food for the fungi.
5. A student while observing an embryo of a pea seed in the laboratory listed various parts
of the embryo as given below: Testa, Tegmen, Radicle, Plumule, Micropyle, Cotyledon.
On examining the list the teacher remarked that only three parts are correct. Select
three correct parts from the above list:
(A) Testa, Radicle, (B) Tegmen, Radicle, (C) Cotyledon, (D) Radicle,
Cotyledon. Micropyle. Plumule, Testa. Cotyledon, Plumule.

Ans. :
D. Radicle, Cotyledon, Plumule.
Explanation:
A dicot embryo consists of radicle, plumule and a pair of cotyledons. Testa, tegmen and

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 micropyle are the parts of the seed coat.

6. Height of a plant is regulated by :

(A) DNA which is directly influenced by growth hormone.
(B) Genes which regulate the proteins directly.
(C) Growth hormones under the influence of the enzymes coded by a gene.
(D) Growth hormones directly under the influence a gene.

Ans. : (C) Growth hormones under the influence of the enzymes coded by a gene.
7. Heterozygous purple-flowered plant was crossed with homozygous recessive white-
flowered plant.The observed phenotype is:
(A) All purple (B) All white (C) 50% purple, 50% (D) 75%
white

Ans. :
c. 50% purple, 50% white
Explanation:
Heterozygous Purple flower - Pp
Gametes: P and p
Recessive white flower: pp
Gametes: p
Fusion thus yields: Pp (Purple) and pp (white)
The ratio is 1:1
8. In the given food chain, suppose the amount of energy at fourth trophic level is 5kJ, what
will be the energy available at the producer level?
Grass → Grasshopper → Frog → Snake → Hawk
(A) 5kJ. (B) 50kJ. (C) 500kJ. (D) 5000kJ.

Ans. :
d. 5000kJ.
Explanation: Energy level available at a particular trophic level is 10 times the
energy level at the next trophic level. Hence, third trophic level has 50kJ, 2nd has
500kJ and 1st has 5000kJ.

* Question consist of two statements - Assertion (A) and Reason (R). Answer these [2]
questions by selecting the appropriate option given below:
A. Both A and R are true, and R is the correct explanation of A.
B. Both A and R are true, and R is not the correct explanation of A.

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C. A is true but R is false.
D. A is false but R is true

9. For two statements are given- one labelled Assertion (A) and the other labelled Reason
(R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as
given below:
a. Both A and R are true and R is correct explanation of the assertion.
b. Both A and R are true but R is not the correct explanation of the assertion.
c. A is true but R is false.
d. A is false but R is true.
Assertion: The movement of water and dissolved salts in xylem is always upwards.
Reason: The upward movement of water is due to low pressure created by transpiration.
Ans. :
a. Both A and R are true and R is correct explanation of the assertion.
Explanation:
The plants take in water (containing dissolved minerals) from the soil through their
roots. This water, called xylem sap is carried by the xylem vessels to all the parts of
the plant. The xylem vessels of the root of the plant are connected to the xylem
vessels of its stem. So, the water (containing dissolved minerals) enters from the root
xylem vessels into stem xylem vessels. The xylem vessels of the stem branch into the
leaves of plants. So, the water and minerals carried by the xylem vessels in the stem
reach the leaves through branched xylem vessels. Since the cells of the leaf are
losing water by transpiration, so water from the xylem vessels in the leaf will travel to
the cells by osmosis to make up this loss of water. Thus, water is constantly being
taken away from the top of the xylem vessels in the leaves thus reduces the effective
pressure at the top of the xylem vessels. The pressure at the top of the xylem vessels
(in the leaves) is lowered whereas the pressure at bottom of the xylem vessels
remains high. Due to this water flows up the xylem vessels.
10. For two statements are given- one labelled Assertion (A) and the other labelled Reason
(R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as
given below:
a. Both A and R are true and R is correct explanation of the assertion.
b. Both A and R are true but R is not the correct explanation of the assertion.
c. A is true but R is false.
d. A is false but R is true.
Assertion: A geneticist crossed two plants and got 50% tall and 50% dwarf progenies.
Reason: This cross follows Mendelian law as one of the parent plant might be
heterozygous.
Ans. :
b. Both A and R are true but R is not the correct explanation of the assertion.
Explanation:
The given cross can be illustrated as follows:

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 SECTION B

* Answer the following question. : [ 2 marks each ] [10]

11. When a person breathes in air, the air enters into his body through an organ Ahaving two
holes B in it. The air then passes through pharynx and larynx and enters into a tube C.
The tube C divides into two smaller tubes D at its lower end. The two smaller tubes are
attached to two respiratory organs E. Each smaller tube divides inside the organs E to
form a large number of still smaller tubes called F. The smallest tubes F have air-sacs G at
their ends in which gaseous exchange takes place in the body of the person. What are A,
B, C, D, E, F and G?

Ans. : Here, A, B, C, D, E, F and G refer to the nose, nostrils, trachea, bronchi, lungs,
bronchioles and alveoli, respectively.
12. a. Name one gustatory receptor and one olfactory receptor present in human
beings.
b. Write a and b in the given flow chart of neuron through which information travels
as an electrical impulse.

Ans. :
a. Gustatory receptors are located on the tongue. They help to detect taste.
The olfactory receptors are located in the nose. They help to detect smell.
b.

13. List four advantages of vegetative propagation.

Ans. : Four advantages of vegetative propagation:

1. Plants grown by vegetative propagation grow much faster than those grown from
seeds.
2. A large number of plants can be produced by the method of vegetative
propagation.
3. The plants grown by vegetative propagation usually need attention in their early
years than the plants grown from seeds.
4. Seedless plants can also grown from seeds.
14. ‘‘The chromosomal number of the sexually producing parents and their offspring is the
same.’’ Justify this statement.

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 Ans. : The first step in sexual reproduction is gamete formation. In this step, the number of
chromosomes gets halved. Thus, each gamete receives half the number of chromosomes
to that of somatic cells. During fertilisation, the fusion of male and female gametes takes
place, which results in the number of chromosomes in the zygote to be equal to that of
somatic cells. Thus, the chromosomal number of the sexually producing parents and their
offspring is the same.
15. Give reason to justify the following:
a. The existence of decomposers is essential in a biosphere.
b. Flow of energy in a food chain is unidirectional.
Ans. :
a. Existence of decomposer is essential because they convert the complex substance
into simple this ensure that the material taken out from environment is again get
into it for further use.
b. Flow of energy is unidirectional becoz the energy that get transfer from plant to
herbivores cannot get into plant again

SECTION C

* Answer short answer questions. [3 Mark each] [12]

16. Draw a labelled diagram of stomata. List two functions of stomata.

Ans. : Two functions of stomata:

1. It facilitates the exchange of gases between plant and its surroundings. It is through
stomata that plant release oxygen and take up carbon dioxide.
2. It helps the plant to get rid of excess water through transpiration. The stomata also
close down to prevent loss of water. Thus, it regulates the water content in plant
cells.
Diagram of stomata:

17. Why is chemical communication better than electrical impulses as a means of

communication between cells in a multi-cellular organism?
Ans. :

Electrical impulses have limited access to only those cells that are connected by
nervous tissue/ neurons, whereas chemical signals can reach each and every cell
of the body.
Cells need time to reset in order to create repeated/ new electrical impulses
whereas no such time is required for chemical communication.
18. List four methods of contraception used by humans.
Justify the following statement: ‘‘The use of contraceptive methods has a direct effect on
the health and prosperity of a family.’

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 Ans. : Following are the four methods of contraception used by humans:
i. Natural method: It involves avoiding the chances of meeting of the sperm and
the ovum. In this method, the sexual act is avoided from day 10th to day 17th of the
menstrual cycle because during this period, ovulation is expected; therefore, the
chances of fertilisation are very high.
ii. Barrier method: In this method, fertilisation of the ovum and sperm is prevented
with the help of barriers. Barriers are available for both males and females.
Condoms, which are made of thin rubber, are used to cover the penis in males and
the vagina in females.
iii. Oral contraceptives: In this method, tablets or drugs are taken orally. These
contain small doses of hormones that prevent the release of eggs, thus preventing
fertilisation.
iv. Implants and surgical methods: Contraceptive devices such as the loop or
copper-T are placed in the uterus to prevent pregnancy. Some surgical methods
can also be used to block the gamete transfer. In vasectomy, the vas deferens is
blocked to prevent the transfer of sperms. Similarly, in tubectomy, the fallopian
tubes of the female can be blocked so that the egg does not reach the uterus.
Effects of contraception on the health and prosperity of a family:

It helps in preventing unwanted pregnancies.

It prevents the chances of frequent pregnancies, which otherwise affect the health
of females.
It helps in family planning by controlling the number of children in a family, thus
reducing the chances of poverty.
It also reduces the chances of transmission of sexually transmitted diseases such as
AIDS.
In this way, birth control methods play an important role in the health and prosperity
of a family.
19. If we cross pure-bred tall (dominant) pea plant with pure-bred dwarf (recessive) pea plant
will get pea plants of F1 generation. If we now self-cross the pea plant of F1 generation,
then we obtain pea plants of F2 generation.
i. What do the plants of F1 generation look like?
ii. State the ratio of tall plants to dwarf plants in F2 generation.
iii. State the type of plants not found F1 in generation but appeared in F2 generation,
mentioning the reason for the same.
Ans. :
i. All the plants of F2 generation are tall.
ii. The ratio of tall to dwarf plants in the F2 generation is 3:1
iii. The dwarf plants are not found in the F1 generation but appear in the F2
generation.
The trait for dwarfness is recessive. Thus, t does not express itself in the
heterozygous condition that is when the Dominant T allele is present (tallness).
 In F1 generation the plants produced are all heterozygous tall. Thus the Dwarf allele
(t) does not express itself. However in the F2 generation due to independent
assortment the plant acquire homozygous condition and thus the dwarf allele
expresses itself.

SECTION D

* Long answer questions [5 Mark each] [10]

20. a. Mention any two components of blood.

b. Trace the movement of oxygenated blood in the body.
c. Write the function of valves present in between atria and ventricles.
d. Write one structural difference between the composition of artery and veins.
Ans. :
a. Components of blood: Plasma and blood cells (corpuscles)
b. Movement of oxygenated blood in the body:

c. Valves present in between atria and ventricles help to restrict the backflow of the
blood from the ventricle to the atrium when the ventricle contracts.
d. Differences between artery and vein:
Artery Vein
1. It has thick elastic muscular It has thin, non-elastic walls.
walls.
2. It does not contain valves. It contains valves to prevent the backflow of
blood.
3. Blood flows under high Blood flows under low pressure.
pressure.

21. a. Draw a sectional view of human female reproductive system and label the part
where:
i. Eggs develop.
ii. Fertilisation take place.
iii. Fertilised egg gets implanted.
b. Describe, in brief, the changes the uterus undergoes:
i. To receive the zygote.
ii. If zygote is not formed.
Ans. :
a.
 Parts where:
i. Eggs develop–Ovary.
ii. Fertilisation take place–Fallopian tubes.
iii. Fertilised egg gets implanted–Uterus.
b.
i. The inner uterus lining (endometrium) becomes thick and soft with lots of
blood capillaries before of a fertilised egg (zygote). The uterus has to keep
this zygote for further development and supply it with food, oxygen, etc.
ii. If the egg is not fertilised, then the uterus lining break down along with its
bloods vessels in the form of vaginal bleeding called menstrual flow.

SECTION E

* case - based/data -based questions [8]

22. Nastic movements in plants are not directional movements. They are not dependent on the
stimulus and are growth independent. For example, the leaves of a touch me not plant
(Mimosa pudica), fold up immediately when touched. These kinds of changes occur due to
the changes in the amount of water in the leaves. Depending on the quantity, they either
swell up or shrink. Plant hormones or phytohormones are responsible for the control and
coordination of plants. There are different types of hormones, which affect the growth of a
plant. Phytohormones are chemical compounds which are released by stimulated cells. These
hormones are diffused around the plant cells. They have a role in the cell division, cell
enlargement, cell differentiation, fruit growth, falling of leaves, ripening of fruits, ageing of
plants etc.
(i) Name the phenomenon called for the movement in growth of plants.
(ii) What do you mean by nastic movement?
(iii) What are the different types of harmonies of plants?
or
(iv) The plant harmone help in the cell growth at the shoot tips by elongating the cells and
help in the growth process is :
Ans. : (i) Growth-dependent movements are called the Tropic Movements (towards or away
from a stimulus).
(ii) Non-growth dependent movements called the nastic Movements (independent of stimulus).
(iii) The different types of phytohormones are :
(a) Auxins
(b) Gibberellins
(c) Cytokinins
(d) Abscisic acid
 or
(iv) Auxins
23. Read the following and answer any three questions from (i) to (iv).
In human, the allele for brown eyes (B) is dominant over that for blue eyes (b). A brown
eyed woman marries a blue eyed man, and they have six children. Four of the children
are brown eyed and two of them are blue eyed.
i. What is the genotype of blue eyed offspring?

ii. What is the woman's genotype?

iii. a) The ovum, produced by the mother carries the gene regarding eye colour?
b) What is the gene carried by of the man's spenn regarding the eye colour?

OR

iv. The ratio of brown eyed children to blue eyed children in this family is 2 : I, which
deviates from typical phenotypic ratios for monohybrid inheritance. What might
be the reason?

Ans. :
i. (c) bb
ii. (b) Bb
Explanation:
According to the given passage some children show recessive trait, i.e., homozygous.
So, the woman must be heterozygous.
iii. (c) B or b
Explanation:
Human ova are haploid, hence they only contain one copy of each gene. Since the
woman has a Bb genotype her ova would contain either B orb allele.
iv. (d) The actual ratio differs from the expected ratio because the sample size is too
small.
Explanation:
According to the given passage, within a single family, the sample size of offspring in
each generation is very small. Hence, the actual phenotypic and genotypic ratios
often deviate from expected ratios. It is only when sample sizes of offspring is large
that actual ratios approach theoretical or expected ratios more closely.
v. (c) b only
Explanation:
Human sperm is haploid, hence they only contain one copy of each gene. Since the
man has a bb genotype, his sperm would contain allele b only.
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