| A | B |
|---|
| phylogenetic tree | a tool used to represent the evolutionary relationships among various species that are believed to have a common ancestor |
| phototropism | a plant’s growth response toward or away from the stimulus of sunlight |
| polarity | the separation of charged regions of a molecule such as water |
| predation | when one organism, the predator, eats another, the prey |
| physiology | the study of how organs and their systems function |
| polypeptide | a chain of amino acids |
| primary producers | the first trophic level, plants |
| primary consumers | the second trophic level, herbivores |
| pioneer species | plants that can grow in newly created, barren, or altered environments |
| polysaccharide | complex carbohydrate consisting of two or more attached sugar molecules |
| population density | a measurement of the number of individuals of the same species living in a designated unit of space |
| population | a group of individuals of the same species living in the same area |
| plasmid | within a bacterial cell, the DNA in the form of a ring |
| pollution | the release of harmful substances into the air, soil, and water |
| point mutation | a change in a single nitrogenous base |
