Receptors are molecules and structures that detect stimuli. Organisms connect with one another by a one-way flow of energy through them and a cycling of materials among them. Their interconnectedness affects the structure, size and composition of populations, communities, ecosystems and the biosphere. Producers trap, convert and use or store energy from the sun. Protista - An eukaryotic kingdom.
Mutations are the original source of variations in heritable traits.
This process helps explain evolution. A hypothesis is an educated guess about possible answers to questions, or solutions to problems. It is used as a guideline to develop tests. It is open to revision and has not been disproved. An atom is the smallest particle that retains the properties of an element.