Fish, like all other complex life forms, need oxygen to survive. They get theirs in the form of oxygen gas dissolved in the water.
Warm water will have less oxygen compared to cold water. Depleted oxygen levels are the most common cause of fish kills.

Cockroach blood is not red because they do not use hemoglobin to carry oxygen. In fact their bloodstream is not used to carry oxygen either. They use a system of pipes called tracheae to bring the oxygen and remove carbon dioxide from their tissues. The blood does not contain haemoglobin, as unlike in chordates, the respiratory system and the circulatory system are completely unconnected.

Fe + CuSO₄ → FeSO₄ (iron sulphate) + Cu(copper)

The small intestine is a hollow, muscular tube about 20 feet long that comprises the longest part of your digestive system. Your small intestine connects your stomach above it to your large intestine (or colon) below it. Your small intestine has three parts.

• The duodenum is a short section at the top of the small intestine that takes semi-digested food from your stomach and digests it further, using bile from your gallbladder and liver and enzymes from the pancreas.
• The jejunum is the middle portion of the small intestine. It uses wave-like contractions to push the food through to the lower part of your small intestine. As the food moves through the jejunum it continues being digested and takes on a more fluid state.
• The ileum is the longest part of the small intestine and the part from which most nutrients and liquid are absorbed from food, before the remainder of the food is deposited into the large intestine.

• Alternative Arrangement of Sewage Disposal: In such places where sewage treatment plants are not accessible, alternative methods for sewage disposal are used. To improve sanitation, low cost onsite sewage disposal systems are being encouraged. For example - septic tanks, chemical toilets, composting pits. A septic tank is a highly efficient underground waste water treatment system. It is less expensive than other sewer systems and uses natural processes to treat the waste water. Some organizations offer hygienic on-site human waste disposal technology in which the toilets do not require scavenging. Excreta from the toilet seats flow through covered drains into a biogas plant and biogas is produced.

Water cycle is the cyclic movement of water from the atmosphere to the earth and back to the atmosphere through various processes.  This constant, never ending circulation of water in nature is known as the water cycle.
The process includes:
Evaporation: Water in seas, rivers, lakes, ponds or streams evaporates because of the heat of the sun.
Transpiration: Plants give out a large amount of water through their leaves
Condensation: Water vapor rises up and condenses on dust particles to form cloud.
Precipitation: Water stored in clouds reaches the ground in the form of rain, hail or snow.

A body suspended by a thread or wire which twists first in one direction and then in the reverse direction, in the horizontal plane is called a torsional pendulum.The first torsion pendulum was developed by Robert Leslie in 1793.
The period of oscillation of torsion pendulum is given as,
T = 2π√I/C
Where   I = moment of inertia of the suspended body; C = couple/unit twist 

The biosphere,  is the layer of the planet Earth where life exists. This layer ranges from heights of up to ten kilometres above sea level, used by some birds in flight, to depths of the ocean such as the Puerto Rico trench, at more than 8 kilometres deep.
The biosphere includes the lithosphere, hydrosphere and atmosphere. The biosphere includes all living organisms, and also dead organic matter.

• Lithosphere which includes the soil and rocks.
• Hydrosphere which includes all the water.
• Atmosphere which includes all the gases.

The biosphere is the place where life exists on planet Earth.

• Lithosphere which includes the soil and rocks.
• Hydrosphere which includes all the water.
• Atmosphere which includes all the gases.

The biosphere includes the lithosphere, hydrosphere and atmosphere. The biosphere includes all living organisms, and also dead organic matter.

Rainwater, oceans, rivers, lakes, streams, ponds and springs are natural sources of water. Dams, wells, tube wells, hand-pumps, canals, etc, are man-made sources of water.

Rain Water: Rain water collects on the earth in the form of surface water and underground water.

Surface Water: Water present on the surface of the earth in the form of oceans, rivers, lakes, ponds and streams is called surface water. The water in rivers and lakes comes from rain and melting of snow on mountains. Rivers flow into the sea.

Underground Water: Some of the rainwater seeps through the soil on to the non-porous rocks below. This is underground water. Sometimes due to high pressure, this water sprouts out in the form of springs. It can be obtained by digging wells, sinking tube wells, etc.

A colloid is a heterogeneous mixture whose particles are not as small as solution but they are so small that cannot be seen by naked eye. When a beam of light is passed through a colloid then the path of the light becomes visible. For example milk, smoke etc. A colloid is a heterogeneous mixture. Colloids are big enough to scatter a beam of light passing through it and make its path visible.

Magnification is the process of enlarging the apparent size, not physical size, of something. 

Mineral acids :- 1) They are produced synthetically in labatories . 2) They are highly corrosive in nature than organic acids. 3) They are used in most chemical reactions . 4) They have a high pH value. Ex:- Hydrochloric acid, sulfuris acid, hydrofluoric acid, nitric acid.

Organic acids :- 1) They are produced naturally in organisms. 2) It's very less corrosive and can barely cause any damage. 3) They aren't used in much chemical reactions as they are weak acids. 4) Their pH value is comparatively low to that of the mineral acids. Ex:- Malic acid, citric acid, oxolic acid, tartaric acid.

An exchange of oxygen and carbon dioxide takes place in the alveoli, small structures within the lungs. The carbon dioxide, a waste gas, is exhaled and the cycle begins again with the next breath.
Adults normally take 12 to 20 breaths per minute. Strenuous exercise drives the breath rate up to an average of 45 breaths per minute.

Trees maintain water cycle. They absorb water from the soil and bring water back to soil as rain. Thus forests prevent floods.

Fish gulps water through mouth and forces it between the gills. The oxygen in it gets diffused into the blood circulating in gills and carbon dioxide in the bloodstream diffuses into the water which is carried out through a gap between fish’s body and the gill cover.