The conventional water treatment:
i) Pre-screening
ii) Aeration
iii) Sludge Management and Water Reuse.
(i) Pre-screening: Screening of waste water to remove soil and solid particulates.
(ii) Aeration: Screened wastewater is pumped to an aeration tank. Microbial contaminants are removed by the biological degradation that occurs in the presence of air.
(iii) Sedimentation process: The solid particles in suspension form are allowed to settle under the effect of gravity. The particles that settle out from the suspension is known as sludge.
(iv) Sludge removal: The sludge generated by the degradation process is transferred periodically from the tank for safe disposal.
(v) Disinfection: Chlorination and Ultra Violet (UV) radiation of treated water to remove any microorganism contamination.
(vi) Water recycling: The water will then be supplied for domestic or industrial purposes.

(i) Obesity is the state in which there is an accumulation of excess body fat with an abnormal increase in body weight.
(ii) Obesity occurs if intake of calories is more than the expenditure of energy.
(iii) Overweight and obesity are conditions where the body weight is greater than the mean standard weight for age and height of an individual.
(iv) Body Mass Index (BMI) is an estimate of body fat and health risk. BMI = Weight (kg) / Height (m)²
Causes and risk factors :
(i) Obesity is due to genetic factors, physical inactivity, eating habits (overeating) and endocrine factors.
(ii) Obesity is a positive risk factor in development of hypertension, diabetes, gall bladder disease, coronary heart disease, and arthritis.
Prevention and Control of Obesity :
(i) Diet Management: Low calorie, normal protein, vitamins and mineral, restricted carbohydrate and fat, high fiber diet can prevent overweight.
(ii) Physical exercise: A low calorie diet accompanied by moderate exercise will be effective in causing weight loss. Meditation, yoga and physical activity can also reduce stress related to overeating.

Genetically Modified Organisms:
(i) Genetic modification refers to the alteration or manipulation of genes in the organisms using rDNA techniques in order to produce the desired characteristics.
(ii) The DNA fragment inserted is called transgene. Plants or animals expressing a modified endogenous gene or a foreign gene are also known as transgenic organisms.
Advantages:
(i) The transgenic plants are much stable, with improved nutritional quality, resistant to diseases and tolerant to various environment conditions.
(ii) Similarly transgenic animals are used to produce proteins of medicinal importance at low cost and improve livestock quality. eg Golden Rice is a genetically modified Rice which can produce Beta carotene.

'Scratch' is a software used to create animations, cartoons and games easily. Scratch, on the other hand, is a Visual Programming Language. It was developed in the Massachusetts Institute of Technology (MIT) Media Lab to make programming easier and more fun to learn.
Scratch Environment Editor:
(i) The Scratch editor has three main parts: They are Stage, Sprite and Script editor.
(ii) Stage: Stage is the background appearing when we open the scratch window. The background will most often be white. You can change the background colour as you like.
(iii) Sprite: The characters on the background of a Scratch window are known as Sprite. Usually a cat appears as a sprite when the Scratch window is opened. The software provides facilities to make alternations in sprite.
(iv) Script editor / Costume editor: Where you edit your programs or your sprite's pictures.
The script editor has three main parts :
(a) Script area: Where you build scripts.
(b) Block menu: Where you choose the category of blocks (programming statements) to use.
(c) Block palette: Where you choose the block to use.

(i) Arachaeopteryx.
(ii) It had wings with feathers like a bird.
(iii) It had conical teeth like a reptile.

(i) The term mutation was introduced by Hugo De Vries in 1901 when he observed phenotypic changes in the evening Primrose plant, Oenothera lamarckiana.
(ii) Mutation is an inheritable sudden change in the genetic material (DNA) of an organism.
(iii) Mutations are classified into two main types, namely chromosomal mutation and gene mutation. Chromosomal mutation: The sudden change in the structure or number of chromosomes is called chromosomal mutation. This may result in
Changes in the structure of chromosomes:
Structural changes in the chromosomes usually occurs due to errors in cell division. Changes in the number and arrangement of genes takes place as a result of deletion, duplication, inversion and translocation in chromosomes. Changes in the number of chromosomes: They involve addition or deletion in the number of chromosomes present in a cell. This is called ploidy. There are 2 types of ploidy:
Euploidy in plants and animals:
(a) Euploidy: It is the condition in which the individual bears more than the usual number of diploid (2n) chromosomes. If an individual has three haploid sets of chromosomes, the condition is called triploidy (3n). If it has four haploid sets of chromosomes. It is called Tetraploidy. Tetraploid plants are advantageous as they often result in increased fruit and flower size.
(b) Aneuploidy: It is the loss or gain of one or more chromosomes in a set. It is of 3 types:
(i) Monosomy (2n-1),
(ii) Trisomy (2n+1)
(iii) Nullisomy (2n-2). In man, Down's syndrome is one of the commonly known aneuploid condition.
Gene or point mutation:
(i) Gene mutation is the changes occurring in nucleotide sequence of a gene.
(ii) It involves substitution, deletion, insertion or inversion of a single or more than one nitrogenous base.
(iii) Gene alteration results in abnormal protein formation in an organism.

A small family is a happy family. If there are one or two children in a family, the parents can afford to give them good education, food, personal care and other facilities required for them to grow into healthy and happy individuals. Thus it is important for parents to plan a small family which will also build a healthy nation.