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The amount of oxygen dissolved in water is very low, as compared to amount of oxygen in air. Thus, terrestrial organism has to make less efforts to obtain oxygen than an aquatic organism to obtain oxygen for respiration.

Terrestrial animals can breathe the oxygen in the atmosphere, but animals that live in water need to use the oxygen dissolved in water. This oxygen is absorbed by different organs in different animals. All these organs have a structure that increase the surface area which is in contact with the oxygen-rich atmosphere.

Nutrients: The substances like carbohydrates, proteins, lipids, vitamins, minerals etc. which are components of the food are called nutrients.

• There is severe population explosion in India. It has almost reached to 121 crores.
• This results into unemployment, decreasing per capita income and increasing loan, stress on natural resources, etc.
• Only by controlling population, the quality of life can be restored.
• Therefore, Indians should follow family planning for controlling the population.

1. Fibres are indigestible substance.

2. They are thrown out along with other useless and undigested matter.

3. This aids in egestion. Some fibres also help in digestion of other substances.

4. Green leafy vegetables, fruits, cereals, etc. are considered as important in diet as they supply nutritious fibres.

5. Thus, fibres are considered as one of the important nutrients.

(a) (i) Herbivores – Those animals which eat only plants are called herbivores. Example: Goat and cow. 

(ii) Carnivores – Those animals which eat only other animals as food are called carnivores. Example: Tiger and Lion. 

(iii) Omnivores – Those animals which eat both plants and animals are called omnivores. Example: Human Being and dog.

(b)

(c) The five steps involved in the process of nutrition in animals are

(i) Ingestion

(ii) Digestion

(iii) Absorption

(iv) Assimilation

(v) Egestion.

i. The figure indicates the menstrual cycle in human female.

ii. The ovary and uterus are primarily involved in this process. But the pituitary gland also controls this cycle.

iii. Following hormones regulate this menstrual cycle. Pituitary hormones: Follicle Stimulating Hormone (FSH) and Luteinizing Hormone (LH).

Ovarian hormones: Estrogen and progesterone.

iv. The menstrual cycle shows repetitive changes every 28 to 30 days.

v. A menstruating woman is not at all with impure body. It is a natural process in which the endometrium of the uterus is sloughed off and repaired.

She should get enough rest and nutrition during this period. It is painful period in which there is a possibility of infections. Therefore, she should take ! hygienic care and rest till the bleeding persists. But blind faith and superstition to keep her away from others should not be followed.

i. Fruits, vegetables, whole grains and legumes give rich amount of dietary fibre.

ii. Fibres help to relieve constipation and help in maintaining a healthy weight and lowering risk of diabetes, heart disease and some types of cancer.

iii. Are fibres digested in the body?

iv. Fibres pass through stomach, small intestine and colon.

v. Roughage is the fibre content of the food which consists of plant matter which cannot be digested by the human enzymes, hence form undigested bulk matter in the faeces.

i. Krebs cycle

ii. Haemoglobin

iii. 9 Kcal

iv. Gluconeogenesis

v. Metaphase

vi. Cytokinesis.

i. Through the process of reproduction, living species continue their existence.

ii. Fission, budding and parthenogenesis are the asexual methods of reproduction in Kingdom Animalia.

iii. Regeneration is the repair process than a reproductive process. It is not done with the intention of producing offspring, but is for healing or repairing the lost part.

iv. Plants reproduce by asexual as well as sexual methods. Asexual reproduction is by fragmentation, vegetative propagation, budding, spore formation, while by formation of gametes, sexual reproduction is done.

v. Cloning is the modern method of reproduction by which production of young one can be aimed at.

i. The co-enzymes NADH₂ and FADH₂ are shown in the above diagram.

ii. The chemical reaction that takes place in the mitochondria is called Electronic Transport Chain reaction. The molecules of H₂O, carbon dioxide and energy in the form of ATP are produced in this reaction.

The food stuffs are digested and converted into soluble nutrients. These nutrients are carried by blood to every cell of the body. The oxygen inhaled at the time of respiration is also carried to every cell. In the body cells, this oxygen carries out oxidation of nutrients and thus energy is produced. The energy helps the body to carry out all its functions. The nutrients help in the growth and development of the body.

True 

Bile, an alkaline fluid, is secreted by the liver, stored in gall bladder and released into the small intestine where it breaks down lipids into fatty acids, helps in absorption of fat soluble vitamins and neutralization of gastric acid.

False 

Xylem transports water and minerals in plants from roots up to the stem to the leaves. Thus, xylem only moves solution in upward direction only.

The amount of water reabsorbed depends on the quantity of excess water in the body and on the quantity of dissolved waste to be excreted.

It depends on the amount of :

(i) Excess water is present in the body.

(ii) Dissolved waste is to be excreted from the body

Filtration: Nitrogenous waste such as urea or uric acid are removed from the blood (capillaries).

Reabsorption: Glucose, amino acids, salts and a major amount of water are selectively reabsorbed.

Kidney → Ureters→Urinary bladder → Urethra

Glucose, amino acids, salts, and a major amount of water.

Detailed Answer:

The pathway of urine starting from the organ of its formation is :

Kidney → Ureters → Urinary bladder → Ureihra.

The four substances reabsorbed from the initial filtrate are-

(i) Amino acid (ii) glucose (iii) salts (iv) major amount of water.

• The efficiency of kidneys can be adversely affected by injury, infection or decreased blood supply. 
• If this happens, excess of toxic substances accumulates in the body and it can lead to death. 
• If kidneys fail, nitrogenous wastes are separated from the blood with the help of a man-made machine. 
• The process of separating the nitrogenous waste from the blood with the help of this machine is called dialysis.
•  About 500 ml of blood is sent at one time through this machine. Purified blood is reinfused into the body of the patient.

1. The process of separating the nitrogenous waste from the blood with the help of a manmade machine is called dialysis.

2. An immediate and involuntary response given to a stimulus from the environment is called a reflex action.

3. Proper co-ordination between various systems of an organism helps to maintain a state of equilibrium called homeostasis.

4. Movement or growth of any part of the plant in response to an external stimulus is called tropism.

The kidney is dysfunctional in the patient; nitrogenous wastes will not be excreted out from his body. As a result, salts and urea will get accumulated in the blood. The dialysis fluid is meant for filtering the blood, so it contains no nitrogenous wastes. As compared to blood, urea and salts should be at a lower concentration in the dialysis fluid.

The second stage of urine formation, tubular re-absorption, is called selective re-absorption because some substances such as glucose, amino acids, urea, salts and excess water are selectively reabsorbed back into the blood as urine is being filtered along the tubes. All components of plasma are not re-absorbed but only a few of them, hence, selective re-absorption.

Different organisms use varied strategies for excretion. Many unicellular organisms remove the wastes by simple diffusion from the body surface into the surrounding water. Multi cellular organisms use specialised organs to perform the same function. In human beings Nitrogenous waste products are removed by the nephrons in kidneys.

In a nephron, ultra-filtration occurs in the renal corpuscle (glomerulus + Bowman’s capsule). Glomerular filtration of blood is also known as ultra-filtration. It is a non-selective process and filtration is so fine that every component of plasma (water, glucose, amino acids, urea, etc) except proteins pass into the Bowman’s capsule. The epithelium of renal corpuscle has tiny filtration slits (also called slit pores) that help in ultra-filtration. This process ensures that only waste products and excess water are removed from the body and it also helps to concentrate the urine.

Peripheral nerves are of two types:

(a) Cranial nerves:

• Nerves originating from the brain are called cranial nerves. 
• They are associated with various parts in the head. 
• There are 12 pairs of cranial nerves.

(b) Spinal nerves:

• Nerves originating from the spinal cord are called spinal nerves. 
• They are associated with arms, legs, skin and some other parts of the body.
• There are 31 pairs of spinal nerves.

Haemodialysis serves as a substitute for kidney. It works on the principle of diffusion. The nitrogenous wastes (urea), creatinine and potassium ions diffuse out into the dialyzing fluid across the semi-permeable membranes along the concentration gradient (from high concentration to low concentration). It corrects electrolyte imbalance and removes waste from the body.

Accessory pigment – Carotene/Xanthophyll Essential pigment – Chlorophyll.

• Excretion is a simpler process in plants. There is no special organ or system for excretion in plants. 
• Gases are given out by diffusion. 
• Most of the waste substances of plants are stored in vacuoles of leaf-cells and in flowers, fruits and the bark of the stem. 
• After some time these parts fall off. 
• Some other waste materials are stored in old and worn out xylem in the form of resin and gum. 
• Some waste materials are also given out through roots in the surrounding soil.

Nitrogen is an essential element used in the synthesis of proteins and other compounds. It is taken up in the form of inorganic nitrates (or nitrites) or as organic compounds prepared by bacteria from atmospheric nitrogen.

Some of the methods employed by plants to get rid of excretory products are :

(i) Gaseous wastes (CO2 water \rapour, O₂) are removed through'stomata' in leaves and 'entities' in stems and released into the air.

(ii) Plants get rid of excess water by transpiration.

(iii) Some waste products are stored as resins and gums.

(a) Thevarious methods used by the plants to get rid of their waste products are 

(i) the plants get rid of gaseous waste products through stomata in leaves and lenticels in stems. 

(ii) They get rid of solid and liquid waste by shedding off leaves, peeling of bark and falling of fruits. 

(iii) Secreting gums and resins. 

(iv) Plants excrete some waste substances into the soil around them. 

(b) Excretion in amoeba: In amoeba, the waste material carbon dioxide is removed by diffusion through the cell membrane, but nitrogenous waste and excess water are removed by contractile vacuole.

(a) Atria

(b) Ventricles

(c) Capillaries

(d)(i) Right side

(ii) Left side

The answer is (d) Pisces only

• This is because of single circulation where deoxygenated blood from all part of the body is pumped into heart. 
• From heart it is pumped to gills where it gets oxygenated and gets transferred to all parts of the body. 
• Hence it proves pisces will not receive oxygenated blood.

(a) Atria 

(b) Ventricles 

(c) Capillaries 

(d) 

(i) Right side 

(ii) Left side

High blood pressure is called hypertension. It is caused by the constriction of very small arteries which results in increased resistance to blood flow. Very high blood pressure can lead to rupture of artery and internal bleeding.

Amoeba engulfs the food particles with the help of finger like projections called pseudopodia.

a) Photosynthesis

b) Autotrophs 

c) Chloroplasts 

d) Guard cells 

e) Heterotrophs 

f) Pepsin

The first enzyme to mix with food in the digestive tract is amylase. It is secreted by the salivary gland and it acts on starch present in the food and breaks it down into smaller carbohydrate molecules.

The answer is (c) Amylase

• Amylase is secreted in mouth and acts on the starch to convert into simpler molecules. 
• Hence Amylase is the first enzyme to mix with food in the digestive tract

Common features between all the respiratory organs are:
(i) All the respiratory organs have large surface areas to get enough oxygen.
(ii) All the respiratory organs are thin-walled for easy diffusion of gases and substances.
(iii) All the respiratory organs (like skin, lungs. gills) have a rich supply of blood for transporting respiratory gases.
The mechanism of gaseous exchange between tissues and blood is as follows:
(i) The blood reaching the tissues has higher concentration of oxygen than in the cells so it gets diffused into the cells.
(ii) The carbon dioxide, which is formed in the cells, gets accumulated in higher concentration as compared in the blood, so it easily diffuses into the blood'
(iii) The blood with CO₂, takes this gas to the lungs, from where it is expelled out during exhalation.
 

The common features of all respiratory organs ? skin, gills and lungs are: 

(i) All the respiratory organs have a large surface area to get enough oxygen.

(ii) All the respiratory organs have thin walls for easy diffusion and exchange of respiratory gases

(iii) All the respiratory organs like skin, gills and lungs have a rich blood supply for transporting respiratory gases.

The main components of blood are: 

(i) Plasma: It carries all the dissolved substances such as proteins, digested food, common salt etc from one part to another part of the body. 

(ii) Red blood corpuscles (RBC): It carries oxygen from the lungs to all the cells of the body. 

(iii) White blood corpuscles (WBC): It fights infection and protects us from diseases. 

(iv) Platelets: It helps in the coagulation of blood in a cut or wound.

Urea is the main nitrogenous waste in human blood. It is removed from the body in the form of urine through the kidneys.

Peristaltic movement.

Human circulatory system is a system which is responsible for the transport of materials inside the body. The various organs of the circulatory system in humans are: heart, arteries, veins and capillaries.

• Small intestine has specialized structures that facilitate absorption of digested food. 
• Small intestine has number of folds that increase the area of absorption. 
• Small intestine also has fingerlike projection called microvilli which are richly supplied by blood vessels.

Amoeba has no fixed place for egestion. The undigested food gets collected inside amoeba, then its cell membrane suddenly ruptures and the undigested food is thrown out of the body of amoeba.

it is a Paramecium.

(i) Small Intestine.

(ii) Large Intestine.