A group of organs that all work and function together.

Explanation:

Two or more organs work together to form an organ system. Various types of organ systems include the skeletal system, the circulatory system, the muscular system, the digestive system, the endocrine system, and the respiratory system.

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Organ systems

An organ system is a group of organs that work together to do a job. Key human organ systems: The circulatory system includes the heart, veins and arteries. Its function is to transport substances in the blood, around the body.

•there must be variation for the particular trait within a population.

•the variation must be inheritable (that is, it must be capable of being passed on from the parents to their offspring).

•individuals with one version of the trait must produce more offspring than those with a different version of the trait.good

explanation:

the answer is d.) homologous; have mammary glands