environmental contamination by humans

All life on Earth depends on water. Contamination of rivers, lakes, seas, and precipitation poses serious environmental problems. Human activity is threatening quality of water. The burning of fossil fuels releases air-polluting compounds and large amounts of carbon dioxid into the atmosphere. The chemical reactions of these compounds with water alter the delicate balance of conditions for life by affecting water pH. Acid precipitation has killed fish and damaged other forms of life in lakes and streams, and it also changes soil chemistry and has negatively affected some forests. Major product of fossil fuel combustion is carbon dioxide which stays in the atmosphere. Some carbon dioxide is taken up by plants for their photosynthesis and about 30% is absorbed by the oceans. An increase of carbon dioxide is expected to change ocean chemistry and harm marine life and ecosystems.

Anabolic steroids

Anabolic steroids are synthetic variants of the male hormone testosterone.As prescription drugs,they are used to treat general anemia and diseases that destroy body muscle. Some individuals abuse these drugs,with serious consequences. Overdosing may cause liver damage leading to cancer,or alter cholesterol levels and lead to high blood pressure,increasing the risk of cardiovascular problems.Use of these drugs can reduce sex drive,infertility and breast enlargement in men. Use in women has been linked to menstrual cycle disruption and development of masculine characteristics and in teens can cause stunting growth.

Down syndrome

People with Down syndrome usually have a life span shorter than normal.Down syndrom was named after John Longdon Down,who characterized the syndrome in 1866.What causes Down syndrome? Normal human has 23 chromosomes pairs.They are numbered from 1 to 23.
So all together normal human has 46 chromosomes.People with Down syndrome have instead of 46 chromosomes one more chromosome number 21,so instead two chromosomes 21they have three chromosome 21.This condition is called trisomy 21. Trisomy 21 is the most common chromosome number abnormality. People with Down syndrome exhibit varying mental retardation. However,some individuals with the syndrome live to midle age or beyond,and many are socially adept and able to hold jobs. A few women with Down syndrome have had children,though most people with the syndrom are sexually underdeveloped and sterile.

Health

Low-fat diet . Before beginning a low-fat diet, it is important to understand that some fats are essential for good health. Fat is necessary for storing energy and absorbing certain vitamins. A diet low in saturated fat and cholesterol will yield the best health benefit. Keeping track of how much fat is in our diet, we need to know read nutritional labels on the food we buy. Low-fat diet should include no more than 65 grams of fat each day. To loose weight ,it is necessary to exercise enough to burn more calories than the body consumes. Eating in smaller, more frequent portions is important. Simple changes like switching to skim milk ,avoiding fried foods,and substituting traditionally high-fat dairy products such as sour cream and cream cheese with fat free version or yogurt helps with low-fat diet. In low-fat diet many people mistakenly believe if they eat only foods labeled low or reduced fat that they are following a low-fat diet. In low-fat diet less than 30 % of a pearson's total caloric intake should come from fat. People attempt to eat a low fat-diet to lower total fat and cholesterol to reduce health risk such as heart disease and also to achieve weight loss.