1.1 Characteristics of Life

Chemical Level

The simplest level of organization in life, involving atoms and molecules.

Atoms

Fundamental units of matter, such as carbon, hydrogen, oxygen, and nitrogen.

Molecules

Two or more atoms joined together, examples include water (H2O) and glucose (C6H12O6).

Cellular Level

The level of organization that includes organelles and cells as the basic unit of structure and function in living organisms.

Tissues

Groups of similar cells that work together to perform a specific function.

Organ Level

Structures made up of two or more types of tissues that work together to perform complex functions.

Organ System Level

Groups of organs that cooperate to perform major functions of the body.

Organismal Level

A complete living being, composed of one or more organ systems working together to maintain life.

Population

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

Community

All the different populations of species living and interacting in a particular area.

Ecosystem

Consists of all living organisms in an area and the non-living physical components interacting as a functional unit.

Biosphere

The sum of all the ecosystems on Earth; the parts of Earth where life exists.

Metabolism

All of the chemical reactions that occur in a cell to maintain life.

Producers

Photosynthetic organisms that convert light energy into chemical energy.

Consumers

Organisms that obtain energy by feeding on others; includes herbivores, carnivores, and omnivores.

Decomposers

Organisms that break down dead organic matter and return essential nutrients to the ecosystem.

Homeostasis

Maintenance of normal internal conditions in a cell or organism by means of self-regulating mechanisms.

Adaptations

Species' modifications that make them more suitable to their environment.

Mutation

Change in the nucleotide structure of an organism's DNA, which can lead to variations in traits.

Behavior

Observable, coordinated responses of organisms to environmental stimuli.

Natural Selection

The process by which individuals with favorable traits are more likely to survive and reproduce.