Describe an ecosystem and identify the different trophic levels.

Each trait of a plant is determined a. an allele b. one gene c. a pair of genes d. one dominant gene

Which statement describes an endocrine function rather than an exocrine function? a. salivary glands release saliva into the mouth. b. sweat glands release sweat onto the skin c. the pineal gland releases melatonin into the blood. d. esophageal glands release mucus into the esophagus.

Natural selection changes allele frequencies because some survive and reproduce more successfully than others.