| A | B |
|---|
| sexual reproduction | Reproduction that involves the joining of a male sex cell & a female sex cell. |
| sperm | A male sex cell. |
| egg | A female sex cell. |
| fertilization | The process by which a sperm & an egg unite to form a cell that will develop into a new individual. |
| zygote | A fertilized egg cell. |
| embryo | An early stage in the development of an organism. |
| fetus | A stage in the development of an organism that follows the embryo stage. |
| chromosomes | A threadlike structure in the nucleus of a cell; it carries the genes that determine the traits an offspring inherits from its parent or parents. |
| gene | One of the units that make up a chromosome; genes determine the traits an offspring inherits from its parents. |
| dominant gene | A gene that if inherited, will be expressed. |
| recessive gene | A trait that will be hidden if paired with a dominant trait. |
| infancy | This stage lasts from birth to about the age of 1. |
| childhood | This stage lasts from about age 1 to about age 12. |
| adolescence | This stage last from about age 12 to about age 18 or 20. |
| adulthood | This stage begins at the end of the teenage years and lasts the rest of a person's life. |
| puberty | A process of sexual development through which a person reaches reproductive maturity. |
| endocrine gland | An organ that releases chemical messengers into the bloodstream. |
| hormones | Chemical messengers that cause a response n tissues and organs in other parts of the body. |
