Study Guide for Cells and Traits Test This is a picture of active transport. A group of organs that work together to perform a complex task is an organ system. Inflammation is one of the body’s defenses against disease. The nervous system controls all other organ systems in the body. Individual nucleotides of DNA contain the following combinations of substances: a phosphate, a sugar, and a nitrogen base. A spider’s ability to spin a web is an inherited trait. Deafness is not an adaptation. Growth of the human body results from cell division. Diffusion is the process that spreads substances through a gas or liquid. A hybrid is an organism that has two different genes for the same trait. Leaves, roots, and flowers are all examples of a plant’s organs. An acquired trait is one an organism develops after it is born. A contagious disease is one that can be spread easily form one person to another. Humans have 46 chromosomes in each body cell. A sugar that plants produce through photosynthesis is glucose. An adaptation helps an organism survive in its environment. The control center of the cell is the nucleus. Phagocytes surround and consume harmful organisms that invade the body. The circulatory system carries oxygen to the body. Each type of organism has a specific number of chromosomes. The process through which traits are passed from parents to offspring is called heredity. Each trait of an organism is determined by a short segment of DNA called the gene. The practice of breeding plants and animals for desirable traits is known as selective breeding.