Hickman Integrated Principles of Zoology 19e Answer Key For Chapter Questions Chapter 1 1. Life is defined as the most recent common ancestor of Archaea, Bacteria and Eukaryota, and all descendants of that ancestral population.. 2. Living systems have a unique chemical organization. There is a complex combination of carbohydrates, lipids, proteins, and nucleic acids that does not occur in nonliving material. 3. The hierarchical organization of life recognizes a series of increasingly large and complex levels, each of which has emergent properties. Emergent properties are the result of combining components of previous levels to create new possibilities for functions and structures as those components work together. The hierarchy begins with cells and then continues to organisms, populations, and species. 4. Heredity describes the faithful transmission of traits from parent to offspring. Variation occurs when offspring differ from their parents and from other members of their population. Heredity and variation occur together in living populations. Heredity stabilizes traits that are necessary for survival, while variation provides the material for natural selection and evolutionary change. 5. Living forms acquire chemical-bond energy in macromolecules, and subsequently break the chemical bonds to recover energy for their own cellular metabolism. This energy eventually dissipates in a nonusable form that exemplifies the second law of thermodynamics. 6. Animals and fungi are heterotrophs, because they take in nutrients from other sources. Animals obtain nutrition by consuming plants, animals, or other organisms. Fungi obtain nutrients by absorbing them from their environment. Plants are autotrophs because they utilize energy from the sun to synthesize glucose from carbon