Vertebrates

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Phylogeny Noun

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[fy-loj-uh-nee]

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Phylogeny

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The study of the evolutionary history and relationships among groups of organisms, which are often depicted in branching diagrams.

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Example: This diagram shows how different vertebrate groups are related through evolution, with branches indicating common ancestors and new traits like 'four limbs' appearing over time.

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Bilateral Symmetry Noun

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

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Bilateral Symmetry

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A body plan in which an organism can be divided into two mirror-image halves along a single central axis.

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Example: This image shows that an animal has bilateral symmetry when it can be divided by a central line into two identical, mirror-image halves.

Front

Cephalization Noun

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[sef-uh-luh-zey-shuhn]

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Cephalization

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An evolutionary trend involving the concentration of sensory organs and nervous tissue at the anterior, or head, end of an animal.

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Example: This diagram shows a planarian, an early animal with cephalization, where the brain and sensory organs like eyes are concentrated at the head end.

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Ectoderm Noun

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[ek-tuh-durm]

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Ectoderm

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The outermost of the three primary germ layers in an embryo, which develops into the skin and nervous system.

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Example: This diagram shows how an early vertebrate embryo develops, forming three layers of cells. The ectoderm is the outermost layer, shown in blue.

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Mesoderm Noun

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[mez-uh-durm]

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Mesoderm

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The middle primary germ layer of an embryo that gives rise to the coelom, muscles, skeleton, and circulatory system.

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Example: This diagram shows the mesoderm as the middle of three primary germ layers in a developing vertebrate embryo, located between the outer ectoderm and inner endoderm.

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Endoderm Noun

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[en-doh-durm]

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Endoderm

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The innermost primary germ layer of an embryo that develops into the lining of the digestive and respiratory tracts.

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Example: This diagram shows how a vertebrate embryo develops, forming three essential cell layers. The endoderm is the innermost layer, shown in purple, which will later form internal organs.

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Coelom Noun

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[see-luhm]

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Coelom

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A fluid-filled body cavity that is completely lined with tissue derived from the mesoderm and separates the gut from the body wall.

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Example: This cross-section diagram shows the coelom, which is the main body cavity in vertebrates, completely surrounded by the middle tissue layer called the mesoderm.

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Chordate Noun

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[kor-deyt]

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Chordate

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An animal belonging to the phylum Chordata, possessing a notochord and a dorsal nerve cord at some stage of its life.

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Example: This diagram shows the basic body plan of a chordate, highlighting the four key features all chordates share: a notochord, a dorsal hollow nerve cord, pharyngeal gill slits, and a post-anal tail.

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Notochord Noun

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[noh-tuh-kord]

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Notochord

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A flexible, rod-shaped cartilaginous structure that provides skeletal support in all chordate embryos and some adult chordates.

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Example: This diagram shows the notochord, a flexible rod, and its position in a chordate's body, located between the nerve cord and digestive system.

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Vertebrate Noun

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[vur-tuh-brit]

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Vertebrate

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A chordate animal with a backbone or spinal column composed of individual segments called vertebrae that protect the spinal cord.

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Example: This image shows examples of the five main classes of vertebrates: mammals, fish, reptiles, birds, and amphibians, which are all animals with a backbone.