Question 1

Question 1(h)Choose the ODD one out from the following terms given and name the CATEGORY to which the others belong: [5]Example: Nose, Tongue, Arm, EyeAnswer: Odd Term – Arm, Category – Sense organs(i) Detergents, X-rays, sewage, oil spills(ii) Lumen, muscular tissue, connective tissue, pericardium(iii) Dendrites, Medullary Sheath, Axon, Spinal cord(iv) Centrosome, Cell wall, Cell membrane, Large vacuoles(v) Prostate gland, Cowper's gland, seminal vesicle, seminiferous tubules.Answer(i) Odd term: X-rays    Category: Others are the pollutants of water.(ii) Odd term: Lumen     Category: Others are connective tissues.(iii) Odd term: Spinal cord      Category: Others are parts of nerve cell(neuron).(iv) Odd term: Centrosome      Category: Others are parts of the plant cell.(v) Odd term: Seminiferous tubules     Category: Others are accessory glands of male reproductive system.

Accepted Answer

Odd Term – Arm, Category – Sense organs
(i) Detergents, X-rays, sewage, oil spills
(ii) Lumen, muscular tissue, connective tissue, pericardium
(iii) Dendrites, Medullary Sheath, Axon, Spinal cord
(iv) Centrosome, Cell wall, Cell membrane, Large vacuoles
(v) Prostate gland, Cowper's gland, seminal vesicle, seminiferous tubules.
Answer
(i) Odd term: X-rays
Category: Others are the pollutants of water.
(ii) Odd term: Lumen
Category: Others are connective tissues.
(iii) Odd term: Spinal cord
Category: Others are parts of nerve cell(neuron).
(iv) Odd term: Centrosome
Category: Others are parts of the plant cell.
(v) Odd term: Seminiferous tubules
Category: Others are accessory glands of male reproductive system.

Question 2

Question 2(a)The diagram given below represents a stage during cell division. Study the same and answer the questions that follow: [5](i) Identify whether it is a plant cell or an animal cell. Give a reason in support of your answer.(ii) Name the stage depicted in the diagram. What is the unique feature observed in this stage?(iii) Name the type of cell division that occurs during:Replacement of old leaves by new ones.Formation of gametes.(iv) What is the stage that comes before the stage shown in the diagram?(v) Draw a neat, labelled diagram of the stage mentioned in (iv) above keeping the chromosome number constant.

Accepted Answer

(i) It is an animal cell as centrioles are present. (It can be a plant cell also as it is double layered which means cell wall is present. Moreover, astral rays are also absent).(ii) Metaphase. The unique feature is that chromosomes are in the equatorial plane.(iii) The respective cell divisions are mentioned below:MitosisMeiosis(iv) Prophase.(v) Labelled diagram of Prophase is shown below:

Question 3

Question 2(b)Mention the exact location of the following: [5](i) Epididymis(ii) Lacrimal gland(iii) Malleus(iv) Hydathodes(v) Pulmonary semilunar valve

Accepted Answer

(i) On top of the testis(ii) Upper sideward portion of the orbit of the eye.(iii) In the middle ear attached to tympanum and incus(iv) Margins of leaves(v) In the right ventricle and at the base of pulmonary artery.

Question 4

Question 3(a)Given below are diagrams showing the different stages in the process of fertilisation of an egg in the human female reproductive tract.Study the diagrams and answer the questions: [5](i) Arrange the letters given below each diagram in a logical sequence to show the correct order in the process of fertilisation.(ii) Where does fertilisation normally take place? What is 'Implantation' that follows fertilisation?(iii) Mention the chromosome number of the egg and zygote in humans.(iv) Explain the term 'Gestation'. How long does Gestation last in humans?(v) Draw a neat, labelled diagram of a mature human sperm.

Accepted Answer

(i) DCBA (It can also be CBAD as there is not a clear difference between egg cell and zygote)(ii) Fertilization usually takes place in fallopian tube (oviduct) that links an ovary to the uterus. The process of fixing of the blastocyst to the wall of the uterus/endometrium is termed implantation.(iii) Chromosome number of the egg is 23 and zygote is 46 / 23 pairs.(iv) The period of full term development of the embryo in the uterus. This period lasts for 280 days. It is the period between implantation and birth of baby.(v) Labelled diagram of a mature human sperm is shown below:

Question 5

Question 3(b)A potted plant with variegated leaves was taken in order to prove a factor necessary for photosynthesis. The potted plant was kept in the dark for 24 hours and then placed in bright sunlight for a few hours. Observe the diagrams and answer the questions. [5](i) What aspect of photosynthesis is being tested in the above diagram?(ii) Represent the process of photosynthesis in the form of a balanced equation.(iii) Why was the plant kept in the dark before beginning the experiment?(iv) What will be the result of the starch test performed on leaf 'A' shown in the diagram? Give an example of a plant with variegated leaves.(v) Draw a neat labelled diagram of a chloroplast.

Accepted Answer

(i) Chlorophyll is necessary for photosynthesis.(ii) Balanced chemical equation representing the process of photosynthesis is given below:6CO2+12H2O  ⟶chlorophylllight energy  C6H12O6+6H2O+6O2↑6CO_2 + 12H_2O \space \space \overset{	ext{light energy}}{\underset{	ext{chlorophyll}}{\longrightarrow}} \space \space C_6H_{12}O_6 + 6H_2O + 6O_2 \uparrow6CO2​+12H2​O  chlorophyll⟶​light energy​  C6​H12​O6​+6H2​O+6O2​↑(iii) The plant was kept in the dark to ensure that the leaves are free from starch.(iv) After the starch test on leaf A, the green part of the leaf turns blue black and the pale yellow part will turn brown with iodine solution.Example of plant with variegated leaves — Coleus, Geranium and Croton.(v) Labelled diagram of a chloroplast is shown below:

Question 6

Question 4(a)The diagram given below shows the internal structure of a spinal cord depicting a phenomenon. Study the diagram and answer the questions: [5](i) Name the phenomenon that is depicted in the diagram. Define the phenomenon.(ii) Give the technical term for the point of contact between the two nerve cells.(iii) Name the parts numbered 1, 2 and 3.(iv) How does the arrangement of neurons in the spinal cord differ from that of the brain?(v) Mention two ways by which the spinal cord is protected in our body.

Accepted Answer

(i) The phenomenon that is depicted here is the reflex action which is involuntary action and instant movement in response to stimuli.(ii) Synapse(iii) The parts numbered 1, 2 and 3 are:1 → Sensory nerve2 → Motor nerve3 → Grey matter/Central canal(iv) In the brain, Gray matter is present on the outside and white matter on the inner side. In Spinal cord, white matter is present on the outside and Gray matter on the inner side.(v) Two ways by which the spinal cord is protected in our body are:The spinal cord is protected by 26 bones called vertebral columns.CSF or cerebrospinal fluid also protects the spinal cord.

Question 7

Question 4(b)Give appropriate biological or technical terms for the following: [5](i) Process of maintaining water and salt balance in the blood.(ii) Hormones which regulate the secretion of other endocrine glands.(iii) Movement of molecules of a substance from their higher concentration to lower concentration when they are in direct contact.(iv) The condition in which a pair of chromosomes carry similar alleles of a particular character.(v) The complex consisting of a DNA strand and a core of histones.(vi) The onset of menstruation in a young girl.(vii) Squeezing out of white blood cells from the capillaries into the surrounding tissues.(viii) The fluid which surrounds the foetus.(ix) The relaxation phase of the heart.(x) The difference between the birth rate and the death rate.

Accepted Answer

(i) Osmoregulation(ii) Tropic hormones(iii) Diffusion(iv) Homozygous chromosomes(v) Nucleosome(vi) Menarche(vii) Diapedesis(viii) Amniotic fluid(ix) Diastole(x) Growth rate of population

Question 8

Question 5(a)The diagram given below is that of a structure present in a human kidney. Study the same and answer the questions that follow: [5](i) Name the structure represented in the diagram.(ii) What is the liquid entering part '1' called? Name two substances present in this liquid that are reabsorbed in the tubule.(iii) What is the fluid that comes to part '2' called? Name the main nitrogenous waste in it.(iv) Mention the three main steps involved in the formation of the fluid mentioned in (iii) above.(v) Name the substance which may be present in the fluid in part '2' if a person suffers from Diabetes mellitus.

Accepted Answer

(i) The structure represented in the diagram is that of Nephron.(ii) The liquid entering part 1 is called Glomerular filtrate which is formed by the ultrafiltration of blood through glomerulus. The two substances present in this liquid are — Glucose and Water.(iii) The fluid that comes to part 2 is called urine. The main nitrogenous waste in urine is Urea.(iv) The three main steps involved in the formation of urine are:UltrafiltrationSelective reabsorptionTubular secretion.(v) If a person suffers from diabetes mellitus Glucose will be present in the urine.

Question 9

Question 6(a)Given below is a diagram of a human blood smear. Study the diagram and answer the questions that follow: [5](i) Name the components numbered '1' to '4'.(ii) Mention two structural differences between the parts '1' and '2'.(iii) Name the soluble protein found in part '4' which forms insoluble threads during clotting of blood.(iv) What is the average lifespan of the component numbered '1'?(v) Component numbered '1' do not have certain organelles but are very efficient in their function. Explain.

Accepted Answer

(i) Components numbered '1' to '4' are:1 → RBC / Erythrocytes2 → WBC / Leucocytes3 → Platelets / Thrombocytes4 → Plasma(ii) Two structural differences between the parts '1' (RBC) and '2' (WBC) are:RBCWBCBiconcave disc likeIrregular, AmoeboidNucleus absentNucleus present(iii) The soluble protein found in part '4' is Fibrinogen.(iv) The average lifespan of the component numbered '1' (i.e., RBC) is 120 days.(v) The component numbered 1 i.e., Red Blood Corpuscles (RBCs) do not have mitochondria or ribosomes and nucleus; they are denucleated. The main function of RBCs is the transport of oxygen to the cells of the body, hence they do not have mitochondria making them more efficient. They lack a nucleus which enables them to squeeze through and move easily through narrow vessels like capillaries.

Question 10

Question 6(b)Give biological explanations for the following: [5](i) Education is very important for population control.(ii) The placenta is an important structure for the development of a foetus.(iii) All the food chains begin with green plants.(iv) Plants growing in fertilized soil are often found to wilt if the soil is not adequately watered.(v) We should not put sharp objects into our ears.

Accepted Answer

(i) If people are literate they will understand the benefits of having a small family, the superstitious and traditional beliefs that a son is essential can be overcome through education, they will be able to realize the importance of spacing and limiting the number of children in the family. They will be more aware and adopt family planning measures.(ii) The placenta serves as an interface between the mother and the developing foetus, it is through the placenta that the foetus receives its nutrition, and sends out the nitrogenous wastes, exchange of respiratory gases is enabled because of the placenta.(iii) Green plants are capable of Photosynthesis and Photosynthesis is ultimately the source of energy and food for all living beings. Through Photosynthesis, green plants utilise sunlight as the source of energy to synthesise food. They are the primary producers as they have the maximum amount of energy which is transmitted to higher trophic level in the food chain. For these reasons, all the food chains begin with green plants.(iv) Fertilisers lead to the soil becoming hypertonic leading to exosmosis taking place and the cells losing their water content, as a result the cells become flaccid and the plant wilts.(v) Sharp objects can damage eardrum / tympanum leading to deafness.

Question 11

Question 7(a)The diagram below represents a process in plants. The set up was placed in bright sunlight. Answer the following questions: [5](i) Name the physiological process depicted in the diagram. Why was oil added to the water?(ii) When placed in bright sunlight for four hours, what do you observe with regard to the initial and final weight of the plant? Give a suitable reason for your answer.(iii) What happens to the level of water when this setup is placed in:Humid conditions?Windy conditions?(iv) Mention any three adaptations found in plants to overcome the process mentioned in (i).(v) Explain the term 'Guttation'

Accepted Answer

(i) Transpiration process is depicted in the diagram. Oil was added to the water in order to prevent the loss of water by evaporation.(ii) When placed in bright sunlight for four hours, the final weight of the plant will be lesser than the initial weight because some water will be lost from the aerial parts of the plant by transpiration.(iii) The the level of water is affected as below:Humid conditions — Slight or no drop in water level.Windy conditions — Drop in level of water in the jar as rate of transpiration increases.(iv) Three adaptations found in plants to overcome transpiration are:Sunken stomataNarrow leavesReduced exposed surface by rolling or folding of leaves.(v) Loss of water in the form of droplets from the margins (hydathodes) of leaves is called guttation.

Question 12

Question 7(b)A pea plant which is homozygous for Green pods which are inflated [GGII] is crossed with a homozygous plant for yellow pods which are constricted [ggii]. Answer the following questions: [5](i) Give the phenotype and genotype of the F1 generation. Which type of pollination has occurred to produce F1 generation?(ii) Write the phenotypic ratio of the F2 generation.(iii) Write the possible combinations of the gametes that can be obtained if two F1 hybrid plants are crossed.(iv) State Mendel's law of 'Segregation of Gametes'.(v) What is the scientific name of the plant which Mendel used for his experiments on inheritance?

Accepted Answer

(i) Phenotype: All plants with green coloured pods and with inflated pod shape; Genotype: All plants with GgIi.Cross pollination has occurred to produce F1 generation.(ii) 9 : 3 : 3 : 1(iii) GI, Gi, gI, gi(iv) Mendel's law of 'Segregation of Gametes' states that the two members of a pair of factors separate during the formation of gametes. They do not blend but segregate or separate into different gametes. The gametes combine together by random fusion at the time of zygote formation.(v) Pisum Sativum.

Solved 2018 Question Paper ICSE Class 10 Biology

Section I 40 Marks

Section Ii 40 Marks