Biology Revisited :: essays research papers

Concepts and Methods in BiologyBiology RevisitedA. What is life?1. Experience and education refine our questions and our answers.2. Consider the meaning of "alive."3. This book is biology revisited. It will provide:a. Deeper understanding.b. A more organized level of understanding.B. To biologists, life reflects its ancient molecular origins and its degree of organization. Life is:1. A way of capturing and using energy and materials.2. A way of sensing and responding to specific changes in the environment.3. A capacity to reproduce, grow, and develop.4. Capable of evolving.I. DNA, Energy, and LifeA. Nothing Lives Without DNAl. Living and nonliving matter are composed of the same particles, operating according to laws governing energy.a. Deoxyribonucleic acid, or DNA, is the special molecule that sets the living world apart from the nonliving.b. DNA carries the hereditary instructions for assembly of proteins.2. Each organism is part of a reproductive continuum that extends back through countless generations.a. Each organism arises through reproduction in which DNA instructions are transmitted from parents to offspring.b. DNA also guides development of a fertilized egg into a multicelled organism.B. Nothing Lives Without Energy1. Energy, the capacity to do work, is transferred throughout the universe.2. Metabolism refers to the cell’s capacity to extract and convert energy from its surroundings and use energy to maintain itself, grow, and reproduce.a. Plants acquire energy from sunlight and transfer some of the energy into ATP.b. Underlying the assembling and tearing down of biological structures are energy transfers.3. Organisms can sense changes in the environment and make controlled responses to them.a. Receptors detect specific information about the environment.b. Special cells receive stimuli and make appropriate responses.c. Homeostasis is the maintenance of a tolerable internal environment.II. Energy and Life’s OrganizationA. Levels of Biological Organization1. The cell, composed of "biological molecules," is the basic unit of life.4. Multicelled organisms have increasingly complex levels of organization that result in tissues >>> organs >>> organ systems >>> organisms >>> populations >>> communities >>> ecosystems >>> biosphere. B. Interdependencies Among Organisms1. Energy flows from the sun.a. Plants (producers) trap this energy by photosynthesis.b. Animals (consumers) feed on the stored energy in plants, using aerobic respiration.c. Bacteria and fungi (decomposers) break down the biological molecules of other organisms in order to recycle raw materials.2. All organisms are part of webs that depend on one another for energy and raw materials.III. If So Much Unity, Why So Many Species?A. All organisms are made of the same materials and function according to the same laws of energy.