sludge is the organic waste which settles at the bottom of the first sedimentation tank

Scum is the organic waste which contains waste less denser than water like grease oil etc

Water is removed from the top and is stored in a tank. The treated water has low level of organic material and suspended matter. It is discharged into a sea, a river or into the ground. Sometimes it is disinfected through chemicals like Chlorine and ozone and then distributed to towns.

Biogas is also called as gobar gas. This gas primarily consists of carbon dioxide and methane. It is a renewable energy source. Biogas is produced due to the decomposition of organic matter. This process occurs through anaerobic digestion. When plant or animal waste is broken down by bacteria in the absence of oxygen they release gases such as carbon dioxide and methane.

Uses of Biogas

i) It is commonly used in ruler area as cooking gas.

ii) It can be used for the production of electricity.

Cocoons are collected and kept under the sun, or boiled, or exposed to steam. This helps in separating out the silk fibres. The process by which silk thread is separated from the cocoon is called reeling the silk. The boiling of cocoon leads to formation of vapours that can pollute the environment and also cause respiratory problems. It is for this reason that sericulture is not  considered as an eco-friendly practice.

The workers of sericulture industry often develop asthma ,chronic bronchitis and difficulty in breathing due the liberation of allergy causatives during the development of silkworm. The allergens from the silk worm excrete, silkworm cocoon, scales and the cuticles of the abdomen and wings of the silk moth are the main causative agents of the asthma and other respiratory problems. 

Sericulture is a process of rearing silk worms for silk production. Healthy moths are selected to lay eggs as the eggs hatch once in a year. These eggs are washed and stored. Larvae that hatch from the eggs are spread on wooden trays, fed with chopped mulberry leaves and allowed to grow. After 20 – 35 days, twigs are placed on the trays, on which the worms start spinning their cocoons. This may take about 3 – 7 days. Once the cocoons are completely built, they are put in hot water, for reeling, in which the worms are killed and the filaments of silk are drawn from the cocoons.. Filaments from several cocoons are wounded on a reel, which are then dyed and woven into a silk fabric.

Sorter job in wool industry is a risky job because it makes the worker the victim of serious and highly fatal bacterial disease called ANTHRAX which affects the blood system of the body.

In the process of wool manufacturing, once the skin of the sheep is removed along with thin layer of skin, it must be processed to second stage called sorting in which skin which of good quality must be identified by the worker through sense of touch. As the skin of the animal may have many contaminants including dirt, bacteria etc it may lead to fatal blood infection.

Sheep shearing is always done after winter because in summer season the day is hot so the sheep can surive without there fur and before winter come there fur comes again.And if there fur is taken out in winter they will die.For that the sheep don't die the sheep keepers take out there fur in winter.And again share its fur in summer season.

1. Take a cupful of water in a beaker and add a few drops of dilute sulphuric acid.
2. Heat the water.
3. When it starts boiling, add copper sulphate powder slowly while stirring continuously.
4. Continue adding copper sulphate powder till no more powder can be dissolved.
5. Filter the solution.
6. Allow it to cool. Do not disturb the solution when it is cooling.
7. Crystals of copper sulphate will be seen at the bottom of the beaker.

 Extracellular digestion is a process which is carried out of the cell, where the food is broken down into simple substances by specific molecules known as enzymes.
Extracellular digestion takes place in fungi and other decomposers.
Fungi with the help of enzymes or chemicals break down the food they live on and then absorb the nutrients.

An amylase or ptyalin present in saliva, that catalyzes the hydrolysis of starch into maltose and dextrin. An enzyme found in the saliva of humans and herbivorous animals that helps in the pre digestion of starches. Ptyalin is a type of amylase. Pepsin, rennin and lipase are absent in saliva.

Digestion in Amoeba is intracellular, as it takes place within the cell.

Tentacles is the food processing structure present in hydra.

Pangolin or Manis are commonly called scaly anteaters. They have a protective covering of sales on their bodies which are basically made up of keratin. They are nocturnal animals and mainly feed on ants and termites. They have long protrusible tongues that help them to catch ants and termites The presence of sticky saliva on their tongues also enhance their ability to catch their prey.

The mouth parts of Lepidoptera mainly consist of the sucking kind; this part is known as the proboscis or 'haustellum'. The proboscis consists of two tubes held together by hooks and separable for cleaning. The proboscis contains muscles for operating.

The steps are as follows:-

1) Ingestion: The process of taking food into the body is called ingestion.
2) Digestion: the process in which the food containing large, insoluble molecules is broken down into small, water soluble molecules is called digestion.
3) Absorption: The process in which the digested food passes through the intestinal wall into blood stream is called absorption.
4) Assimilation: The process in which the absorbed food is taken in by the body cells and used for energy, growth and repair is called assimilation.
5) Egestion: The process in which the undigested food is removed from the body is called egestion.

Ruminants are referred to the plant-eating mammals including sheep, goat, deer cattle, buffaloes, bison, giraffes, yaks, etc. These cud-chewing mammals have four chambers of stomachs used for their digestion.

Carbohydrates, proteins, fats, vitamins and minerals are essential components of food, these components are called nutrients.

Mode of nutrition

1. Autotrophs or Autotrophic: - Plants that have chlorophyll trap the energy from the sun and prepare their own food. Such nutrition wherein the food is prepared by the organisms itself is called autotrophic nutrition. The organisms capable of preparing their own food are called autotrophs. All green plants are Autotrophs (Auto means self and trophos means nourishment). They prepare their own food by a process called photosynthesis.
2. Heterotrophs or heterophobic: - Heterotrophic organisms are those who obtain food from other organisms. Since these organisms depend on other organisms for their food, they are called consumers. All animals and non-green plants like fungi come under this category.Organisms that follow the heterotrophic mode of nutrition are called heterotrophs.

Farmers grow fruits and vegetables crops inside large green house because it protects it from high blowing wind, and rodents also green house protects the plant from the climatic conditions of outside and it can have its own suitable temperature for the growth of plants.

Farmers get advantages of the following things:

(i) They have control over their climatic conditions (Temperature, humidity etc.)

(ii)  Free from pests, rodents and also from birds and animals so they have increased producibility.

 pH scale use to measure pH of solution.

pH Value and Nature of a Solution

• If [H+] > 10-7, pH is less than 7 and the solution is acidic.
• If [H+] = 10-7, pH is 7 and the solution is neutral.
• If [H+] < 10-7, pH is more than 7 and the solution is basic.

demonstrate that chlorophyll is essential for photosynthesis.

Requirements : A potted plant with variegated leaves - for example, Croton or money plant (variegated leaves are partly green and partly white), rice paper, pencil, white paper sheath, beaker, test tube, 70% alcohol, KL solution, water bath.

Method : Keep the potted plant with variegated leaves in dark for three days so that the leaves become free from starch. Then place the plant in bright sun light for about 6 hours. Take a variegated leaf of the potted plant kept in bright sunlight. Trace the outline of leaves and its variegated parts on the tracing paper (the variegated leaves show pale yellow spots in green leaves. These areas indicate the absence of chlorophyll). Dip the leaf in boiling water for a few minute. Now boil the leaf in 70% alcohol till it decolorizes. Now dip the leaf in boiled water to make the leaf soft. Take out the leaf and stain with iodine (KL) solution. Observe the change in colour.

Observation : The blue colour appears only in those parts of leaf which were green in colour. The blue colour will not appear in variegated parts. This shows that starch formation takes place only in green (chlorophyll containing) parts of the leaf. Thus, the chlorophyll is essential for photosynthesis.

Nutrition is of two types namely, autotrophic and heterotrophic mode of nutrition. Plants exhibit autotrophic mode of nutrition. They prepare their own food by the process of photosynthesis.

There are two modes of nutrition:

• Autotrophic – Plants exhibit autotrophic nutrition and are called as a primary producer. Plants synthesis their food by using light, carbon dioxide and water.
• Heterotrophic – Both animals and human beings are called heterotrophs, as they depend on plants for their food.