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