Life’s Underlying Unity Life’s organization extends from the molecular level to the biosphere Shared features at the molecular level are the basis of life’s unity

Levels of Organization Cell Multicelled organism Population Community Ecosystem Biosphere

Fig. 1-1a, p.2 atom Smallest unit of an element that still retains the element’s properties. Electrons, protons, and neutrons are its building blocks. This hydrogen atom’s electron zips around a proton in a spherical volume of space

Fig. 1-1b, p.2 molecule Two or more joined atoms of the same or different elements. The “molecules of life” are complex carbohydrates, lipids, proteins, DNA, and RNA. In today’s world only living cells make them

Fig. 1-1c, p.2 cell Smallest unit that can live and reproduce on its own or as part of a multicellular organism. It has an outer membrane, DNA, and other components

Fig. 1-1d, p.2 tissue Organized cells and substances that interact in a specialized activity. Many cells (white) made this bone tissue from their own secretions

Fig. 1-1e, p.2 organ Two or more tissues interacting in some task. A parrotfish eye, for example, is a sensory organ used in vision

Fig. 1-1f, p.2 organ system Organs interacting physically, chemically, or both in some task Parrotfish skin is an organ system with tissue layers, organs such as glands, and other parts

Fig. 1-1g, p.3 multicelled organism Individual made of different types of cells Cells of most organisms, including this Red Sea parrotfish, are organized as tissues, organs, and organ systems

Fig. 1-1h, p.3 population Group of single-celled or multicelled individuals of the same species occupying a specified area This is a fish population in the Red Sea

Fig. 1-1i, p.3 community All populations of all species occupying a specified area This is part of a coral reef in the Gulf of Aqaba at the northern end of the Red Sea

Fig. 1-1j, p.3 ecosystem A community that is interacting with its physical environment It has inputs and outputs of energy and materials Reef ecosystems flourish in warm, clear seawater throughout the Middle East

Fig. 1-1k, p.3 the biosphere All regions of the Earth’s waters, crust, and atmosphere that hold organisms Earth is a rare planet; without its abundance of free-flowing water, there would be no life

Nothing Lives without Energy Energy = capacity to do work Metabolism = processes by which cells acquire and use energy for maintenance, growth, and reproduction

Interdependencies among Organisms Producers Make their own food Consumers Obtain energy by eating other organisms Decomposers Break down remains and wastes

Energy input, from sun Nutrient Cycling Producers plants, and other self-feeding organisms Consumers animals, most fungi, many protists, many bacteria Energy output (mainly metabolic heat) Fig. 1-3, p.5

Homeostasis Organisms maintain certain conditions in their internal environment A defining feature of life

Mutation: Source of Variation Mutation = change in structure of DNA Basis for variation in heritable traits May be harmful, neutral, or beneficial

Evolution Heritable change in a line of descent over time Changes in populations result in diversity

Classification Systems Organisms are grouped into three domains: Eubacteria (Bacteria) Archaebacteria (Archaea) Eukaryotes (Eukarya)

Origin of life Eubacteria Archaebacteria Eukaryotes ProtistansPlantsFungiAnimals Major Groups

Unity of Life All organisms –Consist of one or more cells –Have the capacity to reproduce based on instructions in DNA –Engage in metabolism –Sense and respond to the environment