A terrestrial organism can obtain oxygen directly from the air and has a slow breathing rate, whereas an aquatic organism has to obtain oxygen dissolved in water and so, it has a high breathing rate. The amount of oxygen dissolved in water is fairly low as compared to the amount of oxygen present in the air. So, aquatic organisms have high breathing rate. Therefore, terrestrial organisms have much easier access to oxygen and have an advantage over aquatic organisns.

Hydrochloric acid (HCI) is the acid secreted inside the stomach and plays the following roles
(i) It makes medium inside the stomach acidic, which is necessary for the activation of enzyme called pepsin. It converts inactive pepsin into active pepsin.
(ii) It also kills any bacteria, entering the stomach along with the food.

Organisms that feed on dead plants and animals are called decomposers, e.g. bacteria, fungi, etc. They breakdown the complex organic compounds present in the dead remains into simpler substances and obtain nutrition from them. These substances are released into the soil and the atmosphere.
Thus, they play the following roles
(i) They help in recycling of materials, replenishment of the soil's nutrients, etc.
(ii) They clean our surroundings by decomposing dead organisms and organic wastes.

The different methods of contraception are:
(i) Barrier Methods The device such as condoms are used as physical barriers, which prevents sperms from meeting the egg
(ii) Hormonal Methods These contain hormonal preparations in the form of 'pills' which prevent the release of ovum.
(iii) Chemical Methods The vaginal pills contain the chemicals called spermicides which kill the sperms.
(iv) Surgical Methods In males, a small portion of sperm duct is cut by surgical method. The cut end is tied properly to prevent the sperms from coming out. In females, a small part of the Fallopian tube/oviduct is cut and tied to prevent the egg from entering the oviduct.

Differences between pollination and fertilisation are

Some diabetes patients are given injections of insulin to fulfil the requirement of insulin in their body. Insulin is a hormone produced by the pancreas and helps in regulating blood sugar levels in our body. If sugar level increases in the blood, due to lack of insulin, it leads to many harmful effects.

The smell reaches the neurons of olfactory receptor of nose. It causes the generation of nerve impulses that reach the olfactory lobes of the forebrain to produce the sensation of smell.

(i) Rings of cartilage They ensure that air passage does not collapse.
(ii) Alveoli They increase the surface area for exchange of gases in lungs.
(iii) Haemoglobin It is a respiratory pigment present in RBCs which takes up the oxygen from the air in lungs and carries it to the tissues.
(iv) Lining of mucus These along with fine hairs are present in nostrils which help to filter the air entering through nostrils.

Photosynthesis is a process by which green plants, having chlorophyll, synthesise the simple sugar (glucose) from the simple raw materials, water and carbon dioxide using the energy of sunlight. Oxygen is released in this process.
\(\underset{\begin{array}{c} \text { Carbon } \\ \text { dioxide } \end{array}}{6 \mathrm{CO}_2}+\underset{\text { Water }}{12 \mathrm{H}_2 \mathrm{O}} \xrightarrow[\text { Chlorophyll }]{\text { Sunlight }} \underset{\text { Glucose }}{\mathrm{C}_6 \mathrm{H}_{12} \mathrm{O}_6}+6 \mathrm{H}_2 \mathrm{O}+\underset{\text { Oxygen }}{6 \mathrm{O}_2} \uparrow\)
The photosynthesis takes place in the following three steps
(i) Absorption of light energy by chlorophyll.
(ii) Conversion of light energy into chemical energy and splitting of water molecules into hydrogen and oxygen.
(iii) Reduction of carbon dioxide by hydrogen to form carbohydrate like glucose by utilising the chemical energy.
The steps do not need to take place one after the other immediately. For example, desert plants take up carbon dioxide at night and prepare intermediate which is acted upon by the energy absorbed by the chlorophyll during the day.

RRYY                     \(\times\)         rryy              Parents
(Round yellow)                  (Wrinkled green)
RrYy                       \(\times\)       RrYy             F₁-generation
(Round yellow)                   (Round yellow)
(i) In F₁ - generation the combination of characters is
Round yellow = 9, Round green = 3
Wrinkled yellow = 3, Wrinkled green = 1
Thus, the genotypic ratio is 9 : 3 : 3 : 1
(ii) In F₁ - generation, the production of all round yellow seeds explains that the round shape and yellow colour of the seeds were dominant traits over the wrinkled shape and green colour of the seeds which segregated during F₂ - generation.

(i) Dendrites These are the protoplasmic, branched finger-like projections of the cell body, which receive and transmit impulses.
(ii) Axon These are long, fibre-like cytoplasmic process. They conduct impulses away from the cell body. The axon may be covered by a protective sheath called myelin sheath.

In accordance with 10% law of energy transfer in food chain, only 10% of energy available at one trophic level is transferred to the next trophic level. So, A will represent more energy transfer as compared to C and E and B will be represent more energy transfer as compared to D.

A male germ cell which forms gametes carries one X and one Y-chromosome, while a female germ cell carries two X-chromosomes.
Therefore, sex of the child depends upon what happens during fertilisation.
(i) If a sperm carrying X-chromosome fertilises the egg then, the child born will be a female (XX).
(ii) If a sperm carrying Y-chromosome fertilises the egg then, the child born will be a male (XY).
Thus, the sperm (the male gamete) determines the sex of the child.
 

(i) Digestive enzymes - Foods need to be broken into their small or simpler molecules so that they can be absorbed into the bloodstream. However, the physical breakdown of food is not enough. Enzymes are hence needed for the chemical breakdown of food and speeding up the digestive process. The products of digestion should be smaller enough to be absorbed.
(ii) Hydrochloric acid helps to kill the germs which might have entered into the system through food. It creates acidic medium for the pepsin to act on food to break down proteins.
 (iii) Villi are finger-like projections in the small intestine. They help to increase the surface area for absorption of the digested food. Villi are richly supplied with blood vessel which help to absorb digested food from the bloodstream.

The different constituents of blood are plasma (the fluid part of the bloo(d) and blood corpuscles consisting of RBCs, WBCs, and platelets)
WBCs are known as the soldiers of the body because they fight against the pathogenes that invade our body, thus preventing the occurence of diseases.

(i) The blood vessel C (pulmonary artery) has got deoxygenated blood, while the blood vessel F (pulmonary vein) has got oxygenated blood.
(ii) The blood vessel D (aorta) receives oxygen rich blood from the left ventricle and circulates it to different parts of the body.
(iii) Interventricular septum separates part A (right ventricle) and part B (left ventricle).
(iv) Reptile and amphibian circulatory systems are both closed and entail double circulation, in which veins carry blood towards the heart and arteries carry it away from the heart. While reptiles have either a three or four-chambered heart, all amphibians have a three-chambered heart with two atria and one ventricle.

(i) 1. Waxy cuticle
2. Upper epidermis
3. Chloroplast
4. Guard cell
5. Stomatal pore

The pituitary gland secretes a number of hormones that regulate various functions of the body. It also controls the functioning of the other endocrine glands. Hence, called the master gland.
Location Pituitary gland is located just below the hypothalamus at the base of brain.
Pituitary gland secretes the following hormones, i.e.
(i) Growth hormnone regulates the growth and development of bones and muscles.
(ii) Tropic hormone regulates the secretion from other endocrine glands.

Food chain: The flow of food from sun to autotrophs, from autotrophs to herbivores and from herbivores to carnivores is called food chain. A food chain can have two levels or five to six levels also.
Food web: When an organism is eaten by two or more other kinds of organisms, instead of straight chain an interlinked chain is formed, is termed as food web.

Smaller the food chain, the energy available for the next level of consumer in such a chain is more. As the loss of energy at each step takes place and very little energy is left after four trophic levels.
The green plants in terrestrial ecosystem capture about 1% of the sun's energy and convert it into food energy. When green plants are eaten by primary consumers-a great deal of energy is lost for the life processes and only 10% of the energy is available for the next level of consumers.

(a) A - Stigma
B - Pollen tube
C - Ovary
D - Female germ cell / Egg cell
(b) Pollination - Transfer of pollen grains from anther to the stigma of a flower.
Significance of pollination - Process of pollination leads to fertilization as it brings the male and female gametes together for fusion.
(c) After a pollen falls on a suitable stigma, the pollen tube grows out of the pollen grain and travels through the style to reach the ovule in the ovary. Here the male germ cell (carried by the pollen tube) fuses with the female germ cell to form a zygote.
(i) Ovule (ii) Ovary

(a) A - Stigma B - Pollen tube C - Ovary D - Ovule (ovum)
(b) The transfer of pollen grains from anther (male sexual part) of a flower to the stigma part of the pistil (female sexual part) is known as pollination. Signification of pollination. It may be the cause of variation in a species of a plant.
(c) Fertilisation in flower. A pollen grain contains two male gametes. When a pollen grain falls on the stigma of the carpel, it grows a pollen tube downwards into the
style. One of the male gametes reaches the ovary through pollen tube and fuses with female gamete present in the ovule. This fertilisation of the two germ cells forms a zygote. The zygote is capable of growing into a new plant. The other male gamete fuses with two polar nuclei to form endosperm nucleus. This fusion is called triple fusion. The zygote grows into an embryo and an endosperm nucleus grows into endosperm (the food storage tissue of seed).
(i) All the eggs in the ovule present in the ovary of a flower gets fertilised by male gametes from pollen grains and grow to become seeds.
(ii) The ovary of flower develops and becomes fruit.

(a) No new organisms are formed in complex multicellular organisms like regrowing a lost limb, such as the tail of a lizard. In some organisms like planaria and hydra it is a mode of reproduction.
(b) Complex organisms' body is organized in different types of tissues, organs and organ system. Only specialised cells, capable of proliferating may participate in regeneration and fragmentation. Most of the cells cannot divide to reproduce therefore they have specialized organs and cells for reproduction as they have for other life processes .
(c) Specialised cells called regenerative cells which can make large number of new cells.
(d) Planaria and Hydra.
 

(a) Vitamin D
(b) The exposure to sunlight helps in the formation of vitamin D by our body.
(c) Fast food has more of sugar and carbohydrates that leads to obesity and diabetes at very young age.
(d) Bent legs.

(a) Yes it was
(b) The lower surface of leaf
(c) (i) 38.5
(d) (iii) C

(c) If assertion is true and reason is false.

(a) If both assertion and reason are true and the reason is correct explanation of assertion.

(a) If both assertion and reason are true and the reason is correct explanation of assertion.

(b) If both assertion and reason are true but reason is not a correct explanation of assertion.