Animals, Invertebrates, Cnidarians, Mollusks

Science

An animal that does not have a cavity separating its gut from its body wall

Acoelomate

An animal that does not have a cavity separating its gut from its body wall. Acoelomate. An acoelomate is an organism that lacks a fluid-filled body cavity.

Body plan composed of two halves which are mirror images of each other

Bilateral symmetry

Body plan composed of two halves which are mirror images of each other. Bilateral symmetry. In Science, bilateral symmetry means that an organism's left and right sides are identical mirror images.

A hollow ball of cells of an animal embryo, it develops into a gastrula

Blastula

A hollow ball of cells of an animal embryo, it develops into a gastrula. Blastula. The blastula is an early stage in embryonic development where cells form a spherical layer surrounding a fluid-filled cavity.

The concentration of sensory organs and nerve tissue at an animal’s front end or ‘head’

Cephalization

The concentration of sensory organs and nerve tissue at an animals front end or head. Cephalization is when animals have most of their important sensory parts at their head.

A circulation system in which blood flows within a network of vessels

Closed circulatory system

A circulation system in which blood flows within a network of vessels. Closed circulatory system. A closed circulatory system is where blood is contained within vessels, allowing efficient nutrient and oxygen transport throughout the body.

A stinging cell of a cnidarian

Cnidocyte

A stinging cell of a cnidarian. Cnidocyte. A cnidocyte is a specialized cell found in jellyfish and similar animals that is used to capture prey and defend against predators.

The fluid-filled main body cavity, lined with mesoderm, it contains the internal organs

Coelom

The fluid-filled main body cavity, lined with mesoderm, it contains the internal organs. Coelom. The coelom is a hollow space within the body that houses and protects internal organs, allowing them to move independently from the body wall.

An animal whose anus is formed from the blastopore, before its mouth develops

Deuterostome

An animal whose anus is formed from the blastopore, before its mouth develops. Deuterostome. Deuterostomes are animals, like humans, where the anus forms before the mouth during early development.

Outer germ layer in most animals, it develops from the outer surface of the gastrula

Ectoderm

Outer germ layer in most animals, it develops from the outer surface of the gastrula. Ectoderm. Ectoderm is the layer of cells in an embryo that forms structures like the skin and nervous system.

Inner germ layer in most animals, it develops from the inner surface of the gastrula

Endoderm

Inner germ layer in most animals, it develops from the inner surface of the gastrula. Endoderm. The endoderm is the innermost layer of cells in an embryo that develops into the lining of the digestive and respiratory systems.

An internal skeleton, it is made of bone and/or cartilage

Endoskeleton

An internal skeleton, it is made of bone andor cartilage. Endoskeleton. An endoskeleton is a support structure located inside the body of an animal.

The hard outer covering that protects some animals, like spiders

Exoskeleton

The hard outer covering that protects some animals, like spiders, is called an exoskeleton. An exoskeleton is a rigid external shell that supports and protects the bodies of certain animals, like insects and crustaceans.

The union of sperm and eggs outside the female’s body

External fertilization

The union of sperm and eggs outside the females body. External fertilization. It is when sperm and eggs come together outside the female's body to create new life.

An organism that eats by straining food particles from water

Filter feeder

An organism that eats by straining food particles from water. Filter feeder. A filter feeder is an animal that feeds by passing water through a part of its body to capture tiny food particles.

A mass of nerve cells

Ganglion

A mass of nerve cells. Ganglion. A ganglion is a cluster of nerve cells found in the peripheral nervous system that helps transmit signals in the body.

The large cavity where digestion occurs in cnidarians

Gastrovascular cavity

The large cavity where digestion occurs in cnidarians gastrovascular cavity. The gastrovascular cavity is a central body chamber that helps with both digestion and circulation in simple animals like jellyfish and corals.

Embryo development stage with two or three cell layers, it follows the blastula stage

Gastrula

Embryo development stage with two or three cell layers, it follows the blastula stage. Gastrula. The gastrula is an early stage in embryonic development where the embryo starts forming distinct layers that will become different tissues and organs.

The breathing organ of aquatic animals

Gill

The breathing organ of aquatic animals. Gill. A gill is a structure in fish and some amphibians that allows them to extract oxygen from water.

Muscular digestive structure that grinds down food, found in birds and earthworms

Gizzard

Muscular digestive structure that grinds down food, found in birds and earthworms. Gizzard It's a part of the digestive system that uses muscles to help break down food mechanically.

An animal that can produce both eggs and sperm

Hermaphrodite

An animal that can produce both eggs and sperm. Hermaphrodite. In simple terms, a hermaphrodite is an organism that has both male and female reproductive organs and can produce both eggs and sperm.

The fluid-filled cavity that aids movement in animals like earthworms

Hydrostatic skeleton

The fluid-filled cavity that aids movement in animals like earthworms hydrostatic skeleton. A hydrostatic skeleton is a structure in some soft-bodied animals where a fluid-filled cavity is used to support the body and help with movement.

The union of sperm and eggs inside the female’s body

Internal fertilization

The union of sperm and eggs inside the females body. Internal fertilization. This process occurs when sperm fertilizes an egg within the body of an organism.

Invertebrate explained in an easy to understand way.

An umbrella-shaped free-swimming organism, like a jellyfish or hydra

Medusa

An umbrella-shaped free-swimming organism, like a jellyfish or hydra. Medusa. In simple terms, medusa is the life stage of some sea creatures, like jellyfish, where they are free-swimming and umbrella-shaped.

The cell layer between the ectoderm and endoderm, it develops into the circulatory, reproductive and excretory systems

Mesoderm

The cell layer between the ectoderm and endoderm, it develops into the circulatory, reproductive, and excretory systems. Mesoderm is the middle layer of an embryo that forms muscles, bones, and other internal organs.

A capsule with a coiled threadlike tube that cnidarians use to poison or capture prey

Nematocyst

A capsule with a coiled threadlike tube that cnidarians use to poison or capture prey. Nematocyst is a tiny, stinging structure used by jellyfish and other cnidarians to catch food.

The excretory organ that removes waste from an annelid’s body

Nephridium

The excretory organ that removes waste from an annelids body is called nephridium. A nephridium is an organ in some animals, like earthworms, that helps remove waste from their bodies.

A cnidarian’s nervous system, made of a network of nerve cells spread through its body

Nerve net

A cnidarians nervous system, made of a network of nerve cells spread through its body. Nerve net. A nerve net is a simple system with interconnected nerve cells that allow cnidarians to respond to their environment without a central brain.

A system in which blood moves through open spaces as well as vessels

Open circulatory system

A system in which blood moves through open spaces as well as vessels. Open circulatory system. In an open circulatory system, blood does not always stay inside vessels but can flow freely through body spaces.

A tube-shaped organism usually attached to a surface, it is a life stage of a cnidarian

Polyp

A tube-shaped organism usually attached to a surface, it is a life stage of a cnidarian. Polyp. A polyp is a simple organism, like a small sea anemone, found commonly in coral reefs.

A section of a tapeworm that contains reproductive organs, flame cells and nerves

Proglottid

A section of a tapeworm that contains reproductive organs, flame cells and nerves. Proglottid. In simple terms, a proglottid is a segment of a tapeworm that contains its reproductive structures.

An animal whose mouth develops from the blastopore before the anus is formed

Protostome

An animal whose mouth develops from the blastopore before the anus is formed. Protostome. In protostomes, the mouth forms first during early embryonic development.

The fluid-filled cavity between the mesoderm and endoderm

Pseudocoelom

The fluid-filled cavity between the mesoderm and endoderm. Pseudocoelom. A pseudocoelom is a body cavity in some organisms that is not fully lined with mesoderm, unlike a true coelom.

Body parts arranged in a circle around a central point

Radial symmetry

Body parts arranged in a circle around a central point. Radial symmetry. Radial symmetry is when an organism's body parts are organized around a central axis, like spokes on a wheel, often seen in starfish or jellyfish.

A tonguelike organ with teeth in mollusks like snails

Radula

A tonguelike organ with teeth in mollusks like snails. Radula. The radula is a specialized feeding organ that acts like a rasp, helping mollusks scrape food particles off surfaces.

The knob-shaped head of a tapeworm, it may have suckers or hooks

Scolex

The knob-shaped head of a tapeworm, it may have suckers or hooks. Scolex. The scolex is the part of a tapeworm that attaches to the host's intestines.

Describes an organism that is unable to move from a location

Sessile

Describes an organism that is unable to move from a location. Sessile. In science, sessile refers to organisms, like barnacles, that are fixed in one place and do not move around.

A hollow tube that mollusks use for sucking in and expelling water

Siphon

A hollow tube that mollusks use for sucking in and expelling water. Siphon. In science, a siphon is a tube used to move liquid from one level to a lower one using gravity.

The balanced distribution of duplicate body parts within an organism

Symmetry

The balanced distribution of duplicate body parts within an organism. Symmetry. Symmetry in science is when parts of an object or organism mirror each other in size, shape, and position.

Vertebrate explained in an easy to understand way.