« previous next »
« previous next »
 

Did you know?

Sperm cells are so tiny that 400 to 500 million (400,000,000–500,000,000) of them fit onto 1 tsp.

Did you know?

Signs of depression include feeling sad most of the time for 2 weeks or longer; loss of interest in things normally enjoyed; lack of energy; sleep and appetite disturbances; weight changes; feelings of hopelessness, helplessness, or worthlessness; an inability to make decisions; and thoughts of death and suicide.

Did you know?

Essential fatty acids have been shown to be effective against ulcers, asthma, dental cavities, and skin disorders such as acne.

Did you know?

Symptoms of kidney problems include a loss of appetite, back pain (which may be sudden and intense), chills, abdominal pain, fluid retention, nausea, the urge to urinate, vomiting, and fever.

Did you know?

Thyroid conditions cause a higher risk of fibromyalgia and chronic fatigue syndrome.

Girl with young cat Girl with young cat
Mother giraffe and calves feeding. It is mostly the females that raise young, and they may gather in Mother giraffe and calves feeding. It is mostly the females that raise young, and they may gather in
School-age children are often independent and industrious, with a developing sense of self-confidenc School-age children are often independent and industrious, with a developing sense of self-confidenc
Parents around the world teach their children their religious beliefs and practices. This photo is ... Parents around the world teach their children their religious beliefs and practices. This photo is ...
Large families on U.S. farms used to be common. Children helped plant and harvest crops, take care ... Large families on U.S. farms used to be common. Children helped plant and harvest crops, take care ...
Examples of how the recessive gene for straight hair passes from parents to children Examples of how the recessive gene for straight hair passes from parents to children
Video: Semidiscontinuous DNA replication

For a complete list of videos, visit our video library