Category: Biology Second Paper

A fish has two lateral lines running from tip to tail on either side of its body. It is called sensory side line because it contains sensory cells. It works as a chemoreceptor or chemical receiver.

Ruhi fish looks long, squishy and mace-shaped. Such structure is called streamlined. It is silvery white in color. They are over three feet tall and can weigh 20-25 kg. The body of roe fish consists of three parts. Head, body and tail
1. Head: The part from the tip of the body to the neck is called the head. The surface of the head is convex, smooth and free from scales. A semi-circular mouth hole is located just below the head. The mouth is surrounded by fleshy lips. On either side of the mouth opening are thread-like sensory maxillary barbels. There are two eyes on either side of the head. There is no pallava in the eyes. There is one nostril in front of the eyes. Each side has a large movable kanko. Beneath the kanko are four comb-like gills. At the free end of the conch there is a thin bronchiostigmal membrane.
2. Body: The part from the back of the fin to the anus is called the body. It is the largest part of the body. On either side of the body there are two lateral lines from tip to tail. It is called sensory side line because it contains sensory cells. It contains numerous lateral line organs or neuromasts. The body of ray fish has even and odd fins. These are a pair of pectoral fins, a pair of pelvic fins, a large dorsal fin and an anal fin. The stem is covered with thin cycloid scales. There are three tiny pores on the base of the body. Anus, genitals and rectal pores. Dr. Siddiq Publications
3. Tail: The end of the body from the anus is called the tail. At the tip of the tail is a homocircular caudal fin. It is divided into two parts. Super-symmetric and Semi-symmetric. The tail has 6 fins. Tail fin is the only moving part of fish.

A large amount of cotton is found in lakes, rivers, haor-baor, canal-bil, ponds etc. in Bangladesh, India and Myanmar. They live in the middle layer of water. Roe fish does not survive below 14 degrees Celsius. The best temperature for its growth is 30-32 degrees Celsius.
Ruhi fish are omnivores. Caterpillars feed on zooplankton and Angulipona feed on phytoplankton. Adult fish feed on algae and soft plants. The food of commercially cultivated cotton fish is rice bran, wheat husk, mustard husk, other supplementary food etc.

1. The body is long, the abdomen is round.
2. The head is large and blunt.
3. The pore is semi-oval and transversely situated.
4. Eyes and ears wide.
5. A pair of slender and slender maxillary barbels is present on the body.
6. It has a pair of pectoral fins, a pair of pelvic fins, a dorsal fin and a digital fin.
7. Caudal fin is homocircular in nature.

Cold-blooded aquatic vertebrates that swim with fins and breathe with gills are called fish. Rui is a carp fish. Small and light carp are called minor carp (bata, ghania) and large and heavy carp are called major carp (rui, katla, mrigel). Under normal conditions, roe fish fry are 35–45 cm (1–1.5 ft) long and weigh 700–800 g. But the fish of Halda river weigh 2-2.5 kg in a year. Therefore, the price of hatching fish or hatching eggs of Halda river is 60-65 thousand taka per kg. Dr. Siddiq Publications

(i) Food processing: Amylase is used to make corn syrup from starch. Protease enzymes are used to reduce the protein content of biscuit dough. Cellulase is needed to process coffee. Catalase enzyme is used in the bakery industry to make sugar from starch.
(ii) Baby food: Trypsin is used to make baby food easier to digest.
(iii) In paper industry: Amylase is used in paper sizing and coating. Xylanase is used to reduce the amount of bleaching when decolorizing paper. Cellulase is needed to smooth the paper and reduce the water content of the paper. Ligninase enzyme is used to remove lignin from paper.
(iv) In Alcohol Industry: Amylase, Gluconase and Protease are used in the preparation of raw materials for alcohol. α amylase and β amylase are used in beer and wine making. Protease enzymes are used to remove turbidity in beer.
(v) In dairy industry: Rennin is used to make cheese from milk protein. In France, lipase is used to ripen sheep’s milk blue cheese. Lactase enzyme is required to make glucose and galactose from lactose.
(vi) In photography industry: Protease is used to clear gelatin from film.
(vii) In rubber industry: Catalase enzyme is required during manufacture of rubber from latex.
(viii) Biological detergents: Protease is used to remove protein stains from fabrics. Amylase is used to remove starch stains from clothes and dishes. Cellulase is used as a biological conditioner for fabrics. Lipase enzyme is used to remove oil and grease stains from fabrics.
(ix) In biofuel industry: Cellulase is used to produce ethanol in fermentation process.
(x) Ice cream making: Soft and malleable ice cream is made using lactase enzyme.
(xi) Candy making: Candy is made using invertase enzyme.
The use of enzymes in various research works including molecular biology is increasing day by day. Metabolism and life cannot exist without enzymes. So it can be said that the systemic activity of enzymes is life.

Enzymes like pepsin, trypsin, chymotrypsin, aminotrypsin, peptidase etc. digest protein food to produce amino acids. Enzymes like tyalin, amylase, maltase, isomaltase, lactase etc. digest carbohydrates and convert them into glucose. Enzymes like lipase, phospholipase, lecithinase, cholesterol esterase, monoglyceridase etc. digest lipids to produce fatty acids and glycerol.

Fruit juice is a popular food these days. Enzymes are used to make juice from fruits like mango, grape, apple, orange, pineapple etc. Cellulase and pectinase enzymes are used to clarify fruit juices.

Today environmental protection has become a global movement. Enzyme technology has made it possible to save the environment. Biosensors are made using enzymes. These biosensors determine the amount of various pollutants present in the environment.

In 1929, Alexander Fleming first produced the antibiotic Penicillin from Penicillium notatum, which saved the lives of many patients. It works against bacterial activity. It revolutionized medicine.