Appetizer
One of the most fascinating aspects of life on earth is the millions of different living things, called organisms. Living organisms are animals, birds, insects, bacteria and plants. There are 4,500 different species of mammals, 10,000 bird species, 1 million insect species and about 350,000 plant species. And we still haven’t found them all! Scientists discover 7 to 10,000 new insect species every year. Differences in all these organisms represent their diversity.
Living organisms are animals, birds, insects, bacteria and plants. We can tell the difference between one organism and another by its characteristics, for example, its color, its shape, its size. Often organisms have similar characteristics. The more they have in common, the more likely they are to be related.
An organism's characteristics are determined by the information in its cells, the individual compartments that make up the organism. That information is organized into single units, called genes. The genes are the recipes that make up a master cookbook and are used to create the entire meal: appetizer, main dish and a dessert. Genes contain the information for proteins. We get protein from the foods we eat, like cheese, meat and beans. For example, when we eat beans, our bodies break down the proteins and use them to make things our bodies need. You can think of all of an organism's genes as a cookbook of recipes. For humans and certain bacteria and plants like rice, the information in all the recipes has been determined. There are 20,000 to 25,000 genes that specify a protein in a human cell. Surprisingly plants have slightly more genes than humans, around 35,000 to 50,000.
In plants these gene-recipes are responsible for the proteins that determine the characteristics of the plant. Traits for animals include smooth or scaly skin, gills or lungs, fins or legs. For plants, they include fuzz on a peach, sweet taste of a strawberry, tearful smell of an onion, and color of an apple.
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