Invertebrates: Anatomy of a Hydra, Earthworm, and Sea Star (Starfish)

These flashcards cover key vocabulary related to the anatomy and classification of invertebrates, based on the provided lecture notes.

Invertebrates

Animals without a backbone, including species like Hydra, earthworms, and sea stars.

Bilateral Symmetry

A body plan in which the animal can be divided into two equal halves by a single plane, usually through the anterior and posterior ends.

Radial Symmetry

A body plan that can be divided into multiple equal parts around a central axis, typical in organisms like jellyfish.

Coelom

A fluid-filled body cavity completely lined with mesoderm tissue, found in coelomate animals like earthworms.

Diploblastic

Organisms that have two germ layers, the ectoderm and endoderm, such as those in the phylum Cnidaria.

Triploblastic

Organisms that have three germ layers: ectoderm, endoderm, and mesoderm, characteristic of more complex animals.

Gastrovascular Cavity

A central cavity in certain animals that serves both digestive and circulatory purposes, like in hydras.

Nematocyst

A specialized stinging cell found in cnidarians used for capturing prey and defense.

Ectoderm

The outermost germ layer in embryonic development, which gives rise to the skin and nervous system.

Endoderm

The innermost germ layer that develops into the lining of the digestive tract.

Mesoderm

The middle germ layer that gives rise to muscles, bones, and the circulatory system.

Protostome

A developmental pathway in which the blastopore becomes the mouth, characteristic of including annelids.

Deuterostome

A developmental pathway in which the blastopore becomes the anus, and the mouth forms second.

Metamerism

A condition in which the body is divided into a linear series of segments, seen in annelids.

Hydrostatic Skeleton

A structure found in soft-bodied animals that uses fluid pressure to maintain shape and facilitate movement.

Amoeboid Movement

A form of locomotion seen in Hydras, where they move by changing the shape of their body, particularly the basal disc.

Hermaphroditic

Organisms that have both male and female reproductive organs, such as earthworms.

Cephalization

The concentration of sensory and neural structures at one end of the organism, typically the head.

Invertebrates

Animals without a backbone, including species like Hydra, earthworms, and sea stars.

Bilateral Symmetry

A body plan in which the animal can be divided into two equal halves by a single plane, usually through the anterior and posterior ends.

Radial Symmetry

A body plan that can be divided into multiple equal parts around a central axis, typical in organisms like jellyfish.

Coelom

A fluid-filled body cavity completely lined with mesoderm tissue, found in coelomate animals like earthworms.

Diploblastic

Organisms that have two germ layers, the ectoderm and endoderm, such as those in the phylum Cnidaria.

Triploblastic

Organisms that have three germ layers: ectoderm, endoderm, and mesoderm, characteristic of more complex animals.

Gastrovascular Cavity

A central cavity in certain animals that serves both digestive and circulatory purposes, like in hydras.

Nematocyst

A specialized stinging cell found in cnidarians used for capturing prey and defense.

Ectoderm

The outermost germ layer in embryonic development, which gives rise to the skin and nervous system.

Endoderm

The innermost germ layer that develops into the lining of the digestive tract.

Mesoderm

The middle germ layer that gives rise to muscles, bones, and the circulatory system.

Protostome

A developmental pathway in which the blastopore becomes the mouth, characteristic of including annelids.

Deuterostome

A developmental pathway in which the blastopore becomes the anus, and the mouth forms second.

Metamerism

A condition in which the body is divided into a linear series of segments, seen in annelids.

Hydrostatic Skeleton

A structure found in soft-bodied animals that uses fluid pressure to maintain shape and facilitate movement.

Amoeboid Movement

A form of locomotion seen in Hydras, where they move by changing the shape of their body, particularly the basal disc.

Hermaphroditic

Organisms that have both male and female reproductive organs, such as earthworms.

Cephalization

The concentration of sensory and neural structures at one end of the organism, typically the head.

Acoelomate

An animal without a body cavity between the digestive tract and outer body wall, such as flatworms.

Pseudocoelomate

An animal with a body cavity that is not completely lined by mesoderm, such as roundworms.

Asymmetry

Lacking any form of symmetry, typical of sponges.

Blastula

An early stage of embryonic development consisting of a hollow ball of cells.

Gastrulation

The process of cell and tissue movements in which the blastula is transformed into a gastrula containing the primary germ layers.

Exoskeleton

A rigid external covering for the body in some invertebrate animals, providing support and protection, such as in arthropods.

Sessile

An organism that is fixed in one place; immobile.

Filter Feeder

An animal that feeds by passing water over a specialized filtering structure.