38 Inheriting Stripes-Mid

Inheriting Stripes FOCUS Question How do animals develop stripes?

So Many Stripes Many animals have a striped body. Zebras have bold black-and-white stripes, and tigers have bands of black and orange. Some fish, insects, and reptiles flash blue, green, red, and yellow stripes. Ring-tailed lemurs, raccoons, and some birds have striped parts, too. Even your pet cat may have stripes.

Why Stripes? Stripes look like simple decorations, but they help an animal in important ways. Stripes may make it hard for a predator to single out one zebra in a large group. They also help tigers blend in with the shadows of trees or tall grass. In both cases stripes help to camouflage (CA-muh-flahj) the animal. Stripes help other animals stand out. Coral snakes have colored stripes that warn animals about their venomous bite. Skunks also have bold stripes as an alert to other animals. So how do animals develop stripes? Do You Know? Stripes may also help protect zebras from flies that bite. Scientists think the flies cannot see the stripes, so they don't land on zebras.

Traits A trait is a physical feature or behavior. An animal's color is a trait. Height is a trait. Being able to run fast is another trait. Stripes are also a trait. Living things get many of their traits from their parents. They inherit the traits. One trait that animals inherit is color. The colors of an animal's fur, scales, or other body covering come from pigments. A pigment is any chemical that gives off a color. Pigments usually make dark colors, but they can also create bright colors. Science in Your World Most mammals have a pigment called melanin. This chemical can create many colors, from black to brown to red. The pigment in a zebra's stripes is the same pigment as in human skin.

Pigments are made inside the cells of an animal's skin. Cells are the tiny parts that make up all living things. The pigments add color to the animal's fur, feathers, or scales. Some skin cells make a lot of pigment, which produces dark areas. Other skin cells make less pigment, which produces light areas. Some skin cells make no pigment at all. These areas are white. The amount of pigment an animal has is a trait that it inherits from its parents. An animal with dark fur will likely have babies with dark fur. In some animals like zebras, the pigment-making cells all line up together. They form stripes The cells in the dark stripes make a lot of pigment. The cells in the light stripes do not.

How Stripes Form A baby zebra inherits a striped pattern from its parents. The pattern forms as the baby zebra grows inside its mother. But each zebra is not an exact copy of its parents. Every zebra's stripes vary a little, as human fingerprints do. How do some cells make pigment and other cells don't? How do the cells line up and form stripes? How can a pattern be inherited but also be different? Scientists are still trying to answer these questions. Read on to find out how they think it works.