Properties of Life

Biology

The science that studies life.

Virology

A branch of biology that studies viruses.

Why are viruses not considered living?

They are not made of cells and lack some characteristics of living entities (they must hijack a living cell to reproduce).

Properties of Life (8 characteristics)

Order, sensitivity/response to stimuli, reproduction, adaptation, growth and development, regulation/homeostasis, energy processing, and evolution.

Positive response vs. Negative response

Movement toward a stimulus is considered positive; movement away from a stimulus is considered negative.

Chemotaxis

Movement of bacteria toward or away from chemicals.

Phototaxis

Movement of bacteria toward or away from light.

Adaptation

A "fit" to the environment; a consequence of evolution by natural selection.

Homeostasis

The relatively stable internal environment required to maintain life.

Thermoregulation

A process where organisms regulate their body temperature.

Mutations

Random changes in hereditary material over time that drive diversity and evolution.

Atom

The smallest and most fundamental unit of matter that retains the physical and chemical properties of an element.

Element

Pure chemical substances composed of identical atoms that cannot be broken down into simpler substances by ordinary chemical means.

Molecule

A chemical structure consisting of at least two atoms held together by a chemical bond.

Compound

Molecules that contain two or more different elements chemically bonded together.

Macromolecules

Large molecules typically formed by combining smaller units called monomers (e.g., DNA).

Organelles

Specialized sub-cellular structures that each perform a specific function for the cell.

Cell

The smallest structural, functional, and biological unit of living organisms.

Prokaryotes

Single-celled organisms that lack membrane-bound organelles and a nucleus.

Eukaryotes

Organisms whose cells have membrane-bound organelles and a nucleus.

Tissue

A group of similar cells carrying out the same function.

Organ

An organized structure composed of two or more tissue types that work together to perform a specific function.

Organ System

A collection of organs that work toward a common purpose.

Organism

An individual living entity.

Population

A group of individuals of the same species living in the same area at the same time.

Community

Groups of interacting populations (all the different species) living in the same area.

Ecosystem

All the living and non-living (abiotic) things in a particular area.

Biosphere

The collection of all ecosystems on Earth; represents the zones of life.