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
atomSmallest 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
moleculeTwo 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
cellSmallest unit that can liveand reproduce on its ownor as part of a multicellularorganism. It has an outermembrane, DNA, andother components
Fig. 1-1d, p.2
tissueOrganized 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
organTwo 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 systemOrgans 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 organismIndividual made of different types of cellsCells of most organisms, including this Red Sea parrotfish, are organized as tissues, organs, and organ systems
Fig. 1-1h, p.3
populationGroup of single-celled or multicelled individuals of the same species occupying a specified areaThis is a fish population in the Red Sea
Fig. 1-1i, p.3
communityAll populations of all speciesoccupying a specified areaThis is part of a coral reefin the Gulf of Aqaba at thenorthern end of the Red Sea
Fig. 1-1j, p.3
ecosystemA community that is interacting with its physical environmentIt has inputs and outputs of energy and materialsReef ecosystems flourish in warm, clear seawater throughout the Middle East
Fig. 1-1k, p.3
the biosphereAll regions of the Earth’s waters, crust, and atmosphere that holdorganismsEarth 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
ProducersMake their own food
ConsumersObtain energy by eating other organisms
DecomposersBreak down remains and wastes
Energy input, from sun
NutrientCycling
Producersplants, and other
self-feeding organisms
Consumersanimals, 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
EubacteriaArchaebacteria
Eukaryotes
Protistans Plants Fungi Animals
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