Invertebrates

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Eukaryotic Adjective

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[yoo-kar-ee-ot-ik]

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Eukaryotic

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Describes an organism whose cells contain a distinct nucleus and other membrane-bound organelles, unlike prokaryotic cells.

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Example: This diagram shows the nucleus, the control center of a eukaryotic cell, which contains the cell's genetic material enclosed within a membrane.

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Heterotroph Noun

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[het-er-o-trof]

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Heterotroph

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An organism that cannot produce its own food and must obtain energy by consuming other living organisms.

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Example: This diagram shows a cow, an example of a heterotroph, eating grass. It illustrates the complex digestive system used to get energy from the plants it consumes.

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Phylum Noun

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[fy-lum]

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Phylum

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A principal taxonomic category in biological classification that ranks above the level of class and below kingdom.

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Example: This diagram shows that Phylum is a level of biological classification, more specific than Kingdom but more general than Class, used to group organisms.

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Radial Symmetry Noun

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[ray-dee-ul sim-i-tree]

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Radial Symmetry

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A body plan in which body parts are arranged around a central axis, similar to spokes on a wheel.

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Example: A starfish shows radial symmetry because its body parts are arranged equally around a central point, like the spokes of a wheel.

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Bilateral Symmetry Noun

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[by-lat-er-ul sim-i-tree]

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Bilateral Symmetry

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A body plan with two symmetrical halves, creating a distinct head (anterior) and tail (posterior) end.

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Example: This image shows a butterfly, an invertebrate, which can be divided by a central line into two identical, mirror-image halves, demonstrating bilateral symmetry.

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Exoskeleton Noun

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[ek-so-skel-i-tun]

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Exoskeleton

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A rigid external supporting structure or protective covering on the outside of an animal's body.

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Example: This image compares an insect's external view with a see-through view, showing the hard outer shell (exoskeleton) that protects its internal body parts.

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Ectothermic Adjective

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[ek-to-thur-mik]

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Ectothermic

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Describes an organism, often called cold-blooded, whose main source of body heat is the external environment.

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Example: An ectotherm's body temperature is regulated by its surroundings, gaining heat from the sun (radiation) and warm surfaces (conduction), and losing it through other processes.

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Chordata Noun

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[kor-dah-tuh]

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Chordata

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The phylum of animals that includes all vertebrates, characterized by having an internal skeleton and other specific features.

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Example: This diagram shows the key anatomical features that all chordates share, such as a notochord and a dorsal hollow nerve cord, using a simple invertebrate example.

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Sessile Adjective

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[ses-ahyl]

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Sessile

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Describes an organism that is non-motile and lives fixed in one place, such as a sponge or barnacle.

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Example: This diagram shows the life cycle of a barnacle, which is motile in its early stages but becomes sessile, or fixed in one place, as an adult.

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Hermaphrodite Noun

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[her-maf-ro-dyt]

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Hermaphrodite

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An organism that possesses reproductive organs normally associated with both the male and female sexes during its lifetime.

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Example: This diagram compares normal human male reproductive development with a specific intersex condition, showing differences in anatomical structures.