Biology test #1

Species

Unique type of organism. Of sexual reproducers, often defined as one or more groups of individuals that can potentially interbreed, produce fertile offspring, and do not interbreed with other groups. Designated by genus name and specific epithet.

**Biology**

The scientific study of life

Atom

Smallest unit of matter. Consists of varying numbers of protons, neutrons, and electrons.

Molecule

Two or more atoms joined by chemical bonds.

Cell

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Smallest unit of life. All start out life with a plasma membrane, cytosol, and DNA.

Tissue

In multicelled organisms, collection of specialized cells organized in a way that allows them to perform a collective function.

Organ

In multicelled organisms, a structure that consists of tissues engaged in a collective task.

Organ System

In multicelled organisms, a set of interacting organs and tissues that carry out one or more body functions.

Organism

Individual that consists of one or more cells

Population

A group of organisms of the same species who live in a specific location and breed with one another more often than they breed with members of other populations.

Community

All populations of all species in a defined area

Ecosystem

A community interacting with its environment

Biosphere

All regions of Earth where organisms live

Nutrient

A substance that an organism must acquire from the environment to support growth and survival

Producer

Autotroph. Organism that makes its own food using energy and nonbiological raw materials from the environment.

Photosynthesis

Metabolic pathway by which most autotrophs use light energy to make sugars from carbon dioxide and water.

Consumer

Heterotroph. Organism that acquires carbon by feeding on the tissues, wastes, or remains of other organisms; most also acquire energy the same way.

Homeostasis

Process in which cells and multicelled organisms keeps their internal conditions within tolerable ranges by sensing and responding appropriately to change.

DNA

Deoxyribonucleic acid. Double-stranded nucleic acid that consists of deoxyribose-containing nucleotides. Carries hereditary information.

Growth

Increases in the number, size, and volume of cells.

Reproduction

Processes by which organisms produce offspring. *See* sexual reproduction, asexual reproduction.

Development

In multicelled species, the process by which the first cell of a new individual gives rise to an adult.

Inheritance

Transmission of DNA to offspring.

Bacteria

Singular, bacterium. The largest, most diverse and well-known group of prokaryotes (organisms that lack a nucleus); branched off from the lineage leading to archaea and eukaryotes early in the history of life.

archaea

Singular, archaeon. Group of prokary-otes that are more closely related to eukaryotes than to bacteria.

prokaryotes

Informal name for single-celled organisms with no nucleus (bacteria and archaea).

eukaryotes

Organisms whose cells characteristically have a nucleus (protists, fungi, plants, and animals).

Protist

General term for eukaryote that is not a fungus, plant, or animal.

Fungi

Plural, fungi. Single-celled or multicelled eukaryotic consumer that breaks down material outside itself, then absorbs nutrients released from the breakdown.

Plants

A multicelled eukaryotic producer; most are photosynthetic and live on land. Develops from an embryo that forms on the parent and is nourished by it.

Animals

A multicelled eukaryotic consumer that is made up of unwalled cells and develops through a series of stages. Most ingest food, reproduce sexually, and can move from place to place.

Genus

Plural, genera. A group of species that share a unique set of traits. First part of a species name.

Taxonomy

Practice of naming, describing, and classifying species.

Traits

An inherited characteristic of an organism or species.

taxon

Plural, taxa. A rank in the classification of life; consists of a group of organisms that share a unique set of traits. E.g., domain, kingdom, phylum, class, order, family, genus, species.

Critical Thinking

The act of evaluating information before accepting it.

science

Systematic study of the observable world.

hypothesis

Testable explanation for a natural phenomenon.

prediction

Statement, based on a hypothesis, about a condition that should reasonably occur if the hypothesis is correct.

experiment

**Procedure designed to evaluate a prediction; typically yields data.**

data

Factual information collected from experiments or observations of the natural world.

variable

In an experiment, a characteristic or event that differs among individuals or over time.

model

Analogous system in an experiment; tested in place of another subject.

experimental group

In an experiment, a group of individuals who have a certain characteristic or receive a certain treatment. Tested side by side with a control group.

control group

In an experiment, a group of individuals identical to an experimental group except for the variable under investigation.

scientific method

Making hypotheses, evaluating predictions that flow from them, and forming conclusions based on the resulting data.

Sampling error

Difference between results obtained from a subset, and results obtained from the whole.

Probability

Out of all possible outcomes of an event, the chance that a particular outcome will occur.

statistically significant

Refers to a result that is statistically very unlikely to have occurred by chance alone.

scientific theory

A hypothesis that stands after many years of systematic testing, is consistent with existing evidence, and is useful for making predictions about a wide range of phenomena.

law of nature

Generalization describing a consistent natural phenomenon that has an incomplete scientific explanation.

pseudoscience

Claims, arguments, or methods that are presented as science, but do not follow scientific principles.

plasma membrane

Membrane that encloses a cell and separates it from the external environment.

cytosol

Jellylike mixture of water and solutes enclosed by a cell’s plasma membrane.

Organelles

Structure that carries out a specialized function inside a cell; e.g., a nucleus, mitochondrion, or ribosome.

Ribosomes

Organelle of protein synthesis. An intact ribosome has two subunits, each composed of rRNA and proteins.

cytoplasm

In a eukaryotic cell, collective term for everything between the cell’s plasma membrane and its nucleus. In a prokaryotic cell, everything enclosed by the plasma membrane.

surface-to-volume ratio

A relationship in which the volume of an object increases with the cube of the diameter, and the surface area increases with the square. Limits cell size.

cell theory

Theory that all organisms consist of one or more cells; the cell is the basic unit of life; all cells come from division of preexisting cells; and all cells pass hereditary material (DNA) to offspring.

fluid mosaic

Model of a cell membrane as a two-dimensional fluid of mixed composition.

adhesion proteins

Plasma membrane protein that helps cells stick together in animal tissues. Some types form adhering junctions and tight junctions.

receptor proteins

Membrane protein that triggers a change in cell activity in response to a stimulus such as a hormone binding to it.

transport proteins

Membrane protein that passively or actively helps specific ions or molecules move across the membrane.

cell wall

Rigid, permeable layer of extracellular matrix that surrounds the plasma membrane of some cells.

pili

Plural, pili. Protein filament that projects from the surface of some prokaryotic cells.

Flagella

Plural, flagella. Long, slender cellular structure used for movement.

biofilm

Community of microorganisms living within a shared mass of secreted slime.

nuclear envelope

A double membrane that constitutes the outer boundary of the nucleus. Nuclear pores in the membrane control the entry and exit of large molecules.

mitochondria

Double-membraned organelle that produces ATP by aerobic respiration in eukaryotes.

chloroplasts

Organelle of photosynthesis in the cells of plants and photosynthetic protists. Outer membranes enclose stroma and a highly folded thylakoid membrane.

Vesicles

Saclike organelle that stores, transports, or breaks down its contents.

lysosomes

Enzyme-filled vesicle that breaks down particles such as cellular debris.

Endoplasmic reticulum (ER)

Membrane-enclosed organelle that consists of a continuous system of sacs and tubes extending from the nuclear envelope. Rough ER makes and modifies proteins; smooth ER makes phospholipids, stores calcium, and has additional functions in some cells.

Golgi body

Organelle that modifies polypeptides and lipids, then sorts and packages the finished products into vesicles. Also called Golgi apparatus.

cytoskeleton

Network of protein filaments that support, organize, and move eukaryotic cells and their internal structures. *See* microtubule, microfila-ment, intermediate filament.

microtubules

Cytoskeletal element of eukaryotes that forms a dynamic scaffolding for many cellular processes involving movement. Hollow filament of tubulin subunits.

microfilaments

Cytoskeletal element of eukaryotes that reinforces cell membranes and functions in cell movement. Fiber of actin subunits.

Intermediate filaments

Stable cytoskeletal element that structurally supports cells and tissues of animals and some protists. Different types are assembled from different fibrous proteins.

Motor proteins

Type of energy-using protein that interacts with cytoskeletal elements to move the cell’s parts or the whole cell.

cilia

Singular, cilium. Short, hairlike motile structures that project from the plasma membrane of some eukaryotic cells.

pseudopods

A temporary protrusion from a eukaryotic cell that helps it move or engulf prey.

Extracellular matrix (ECM)

Complex mixture of substances secreted by a cell onto its surface; composition and function vary by cell type

cuticle

Secreted covering at a body surface.

Cell junctions

Molecular assembly that connects a cell to another cell or to extracellular matrix; e.g., tight junction, adhering junction, or gap junction (of animals).

autotrophs

Producer. Organism that makes its own food using energy from the environment and carbon from CO2.

Heterotrophs

Consumer. Organism that obtains carbon from organic compounds assembled by other organisms.

thylakoid membrane.

Inner membrane system of chloroplasts and cyanobacteria; site of light-dependent reactions of photosynthesis.

stroma

Cytosol-like fluid between the thylakoid membrane and the two outer membranes of a chlo-roplast.

stomata

Singular, stoma. Closable gaps formed by pairs of guard cells on aboveground plant surfaces. When open, they allow the plant to exchange gases with air. When closed, they limit water loss.

wavelength

Distance between the crests of two successive waves.

Pigments

Organic molecule that can absorb light of certain wavelengths. Wavelengths that are not absorbed impart a characteristic color.

**chlorophyll** ***a***

Main photosynthetic pigment in eukaryotes and cyanobacteria.

electron transfer phosphorylation

Process by which electron flow through electron transfer chains sets up a hydrogen ion gradient that drives ATP formation.

Calvin–Benson cycle

Cyclic carbon-fixing pathway that forms sugars from CO2; light-independent reactions of photosynthesis.

carbon fixation

Process in which carbon from an inorganic source such as carbon dioxide becomes incorporated (fixed) into an organic molecule.

rubisco

Carbon-fixing enzyme of the Calvin-Benson cycle.

Cellular respiration

Any of several pathways that break down organic molecules (typically glucose) to form ATP and include an electron transfer chain.

aerobic

Involving or requiring the presence of oxygen.

aerobic respiration

Oxygen-requiring cellular respiration. Includes glycolysis, the citric acid cycle, and electron transfer phosphorylation.

anaerobic

Occurring in (or requiring) the absence of oxygen.