Biology: The Unity and Diversity of Life - Chapter 1

Cell

Smallest unit that still displays the properties of life; it has the capacity to survive and reproduce on its own. Composed of an outer membrane, DNA, and other components.

Species

Of sexually reproducing species, one or more natural populations of individuals that successfully interbreed and are isolated reproductively from other such groups. By a cladistic definition, one or more natural populations of individuals with at least one unique trait derived a common ancestor that occurs in no other groups.

Emergent Properties

With respect to life's levels of organization, a new property that emerges through interactions of entities at lower levels, none of which displays the property; e.g., living cells that emerge from "lifeless" molecules.

Energy

A capacity to do work.

Producer

An autotrophic organism, one that synthesizes its own food from simple inorganic compounds in its environment with energy captured from the sun or from oxidizing inorganic substances.

Consumer

Type of heterotroph that feeds on the tissues of other organisms as its source of carbon and energy.

Receptor (sensory)

Sensory cell or a specialized ending of one that detects a particular kind of stimulus.

Homeostasis

State in which physical and chemical aspects of internal environment are being maintained within ranges that are tolerable for cell activities.

DNA

Deoxyribonucleic acid. Double-stranded nucleic acid twisted into a helical shape; it's base sequence encodes the primary hereditary information for all living organisms and many viruses.

Genus

A grouping of species more closely related to one another in morphology, ecology, and history than to others at the same taxonomic level. Plural genera.

Bacteria

Domain of prokaryotic species; the first kinds of cells that formed after life originated. Collectively, bacteria are the most metabolically diverse organisms. Most kinds are chemoheterotrophs, organisms that obtain energy from the oxidation of organic compounds.

Archaea

Eon extending from the time that life originated, 3.8 billion years ago, to 2.5 billion years ago.

Protist

Informal name for all structurally simple eukaryotes, which are now being classified as monophyletic groups.

Monophyletic groups are sets of species that share a derived trait, a novel feature that evolved in one species and is present only in its descendants; all of the evolutionary branchings from a single stem.

Fungi

Type of eukaryotic heterotroph that obtains nutrients by extracellular digestion and absorption; fungi are notable for being prolific spore producers and decomposers.

Plants

A multicelled photoautotroph, most with well-developed roots and shoots (e.g., stems, leaves), as well as photosynthetic cells that include starch grains as well as chlorophylls a and b, and polysaccharides such as cellulose, pectin, and lignin in cell walls. The primary producers on land.

Animal

Any multicelled heterotroph that ingests other organisms or their tissues, develops through a series of embryonic stages, and is motile during part or all of the life cycle. Most species have epithelial tissues and extracellular matrixes.

Mutation

Heritable change in DNA's molecular structure. Original source of new alleles and life's diversity.

Natural Selection

Microevolutionary process; the outcome of differences in survival and reproduction among individuals of a population that differ in the details of their heritable traits.

Evolution

Genetic change in a line of descent by microevolutionary events (gene mutation, natural selection, genetic drift, and gene flow); basis of large-scale patterns, rates, and trends in the history of life.

Hypothesis

An explanation of a phenomenon, one that has the potential to be proven false by experimental tests.

Prediction

A statement, based on a hypothesis, about what you expect to observe in nature, the "if-then process."

Test

Any standardized or innovative means by which a prediction based on a hypothesis might be disproved; often requires designing and conducting experiments, making observations, or developing models.

Model

Theoretical explanation of any object or event that has not been or cannot be directly observed.

Experiment

A test that simplifies observation in nature or the laboratory by manipulating and controlling conditions under which observations are made.

Scientific Theory

A time-tested, widely accepted intellectual framework used to interpret a broad range of observations and data about some aspect of nature. Tested rigorously but is still open to tests, revision, and tentative acceptance or rejection.

Variable

Of experimental tests, a specific aspect of an object or event of interest that may differ over time and among individuals. A single variable is directly manipulated in a experimental group.

Control Group

In experimental tests, a group used as a standard for comparison against one or more experimental groups.

Experimental Group

A group of objects or individuals that display or are exposed to the variable under investigation. Test results for this group are compared against the results for a control group.

Mimicry

A case of one species (the mimic) closely resembling another (its model) in form, behavior, or both.

Nature

The external world in its entirety.

Atom

The smallest unit of an element that still retains the element's properties. Elements are fundamental forms of matter. Electrons, protons, and neutrons are the building blocks of atoms.

Molecule

Two or more covalently bonded atoms of the same or different elements. "Molecules of life" are complex carbohydrates, lipids, proteins, DNA, and RNA. Only living cells now make them.

Tissue

Of multicelled organisms, a group of cells and matrixes interacting in the performance of one or more tasks.

Organ

Body structure with definite form and function made of more than one tissue.

Organ System

A set of organs that are interacting chemically, physically, or both in a common task.

Multicelled Organism

Organism that consists of many cells that, at the least, have formed layers; most have differentiated cells that have formed true tissues, organs, and organ systems.

Population

All single-celled or multicelled individuals of the same species living in a specified area.

Community

All populations of all species in a habitat.

Ecosystem

Array of organisms, together with their environment, interacting by a flow of energy and cycling of materials.

Biosphere

All regions of Earth's waters, crust, and atmosphere in which organisms live.

Stimulus (Stimuli)

A specific form of energy that activates a sensory receptor able to detect it; e.g., pressure.

Reproduction

Any asexual or sexual process by which a parent cell or organism produces offspring.

Eukaryotic Cell

Type of cell that starts life with a nucleus and other membrane-bound organelles.

Prokaryotic Cell

A single-celled organism, often walled, that does not have the organelles characteristic of eukaryotic cells. Only bacteria and archaeans are prokaryotic.