Characteristics of Life

Front

Organism Noun

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[or-guh-niz-uhm]

Back

Organism

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An individual living being, such as an animal, plant, or single-celled life form, that exhibits all characteristics of life.

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Example: This diagram shows how an organism is the highest level of biological organization, built from organ systems, organs, tissues, cells, and molecules.

Front

Cell Noun

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[sel]

Back

Cell

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The basic and smallest structural and functional unit of all known organisms, which is considered the fundamental unit of life.

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Example: This diagram shows a basic animal cell, labeling key parts like the nucleus, cytoplasm, and cell membrane, which are the fundamental components of life.

Front

Unicellular Adjective

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[yoo-ni-sel-yuh-ler]

Back

Unicellular

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Describing an organism that is composed of only one single cell, which carries out all essential life functions.

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Example: This image shows a single, complete organism, an amoeba, which performs all life functions within one cell, defining it as unicellular.

Front

Multicellular Adjective

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[muhl-tee-sel-yuh-ler]

Back

Multicellular

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Describing an organism that is composed of more than one cell, with different cells specialized for various functions.

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Example: This diagram shows that a large structure, like a muscle, is made up of many smaller, individual muscle cells working together, which is the definition of multicellular.

Front

Tissue Noun

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[tish-oo]

Back

Tissue

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A group of similar cells from the same origin that work together to perform a specific function in a multicellular organism.

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Example: This diagram shows how many similar cardiac muscle cells group together to form cardiac tissue, which then makes up an organ like the heart.

Front

Organ Noun

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[or-guhn]

Back

Organ

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A structure composed of different types of tissues that work together to perform one or more specific, complex functions.

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Example: This diagram shows the heart, an organ made of different tissues that work together to pump blood throughout the body, a key characteristic of life.

Front

Organ System Noun

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[or-guhn sis-tuhm]

Back

Organ System

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A group of organs that work together to perform major functions or meet the physiological needs of the organism.

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Example: This diagram shows the nervous system, an example of an organ system, where organs like the brain, spinal cord, and eyes work together to process signals and control the body.

Front

Stimulus Noun

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[stim-yuh-luhs]

Back

Stimulus

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A detectable change in the internal or external environment that causes a response or reaction in a living organism.

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Example: Touching a sharp cactus spine is an external stimulus that causes a living organism to react, in this case, by feeling pain and pulling away.

Front

Reproduction Noun

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[ree-pruh-duhk-shuhn]

Back

Reproduction

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The biological process by which new individual organisms, known as offspring, are produced from their parent or parents.

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Example: This diagram shows asexual reproduction. When a planarian worm is cut, each piece regenerates its missing parts, creating new, complete organisms from the original one.

Front

Sexual Reproduction Noun

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[sek-shoo-uhl ree-pruh-duhk-shuhn]

Back

Sexual Reproduction

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A type of reproduction involving two parents, combining their genetic material to produce a new, genetically unique organism.

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Example: Sexual reproduction involves two key steps: meiosis, which creates haploid cells with half the chromosomes, and fertilization, where two haploid cells combine to form a new diploid organism.