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Questions and Answers
__________ are members of the phylum Echinodermata.
__________ are members of the phylum Echinodermata.
Sea stars, brittle stars, sea urchins, sand dollars, sea cucumbers, and their relatives
All echinoderms are __________.
All echinoderms are __________.
marine
They are the only animals that have a __________.
They are the only animals that have a __________.
water-vascular system
The water-vascular system consists of __________.
The water-vascular system consists of __________.
Echinoderms also have an endoskeleton that is embedded in the __________ portion of the skin.
Echinoderms also have an endoskeleton that is embedded in the __________ portion of the skin.
The pieces of the endoskeleton are referred to as ossicles and are made of __________.
The pieces of the endoskeleton are referred to as ossicles and are made of __________.
__________ of various species differ in shape and may or may not be fused together.
__________ of various species differ in shape and may or may not be fused together.
If the ossicles are not fused they often form a lattice network bound together by __________.
If the ossicles are not fused they often form a lattice network bound together by __________.
However the __________ of sea cucumbers are very small and scattered.
However the __________ of sea cucumbers are very small and scattered.
Ossicles that fit together compactly and that are fused are often referred to as __________.
Ossicles that fit together compactly and that are fused are often referred to as __________.
Species with __________ have a rigid skeleton.
Species with __________ have a rigid skeleton.
Spines extend from some of the __________ of most species of echinoderms.
Spines extend from some of the __________ of most species of echinoderms.
Adults are benthic and depending on the species are __________ symmetrical.
Adults are benthic and depending on the species are __________ symmetrical.
Concerning the nervous system they lack a brain, nerves extend out from one or more __________.
Concerning the nervous system they lack a brain, nerves extend out from one or more __________.
The peritoneum is ciliated and __________ flows as a result of ciliary action.
The peritoneum is ciliated and __________ flows as a result of ciliary action.
Respiratory gases and nutrients are transported mainly by __________ and to a lesser extent by the __________.
Respiratory gases and nutrients are transported mainly by __________ and to a lesser extent by the __________.
Most species are __________ and __________ fertilization occurs.
Most species are __________ and __________ fertilization occurs.
The __________ of the gastrula stage of echinoderms, hemichordates and chordates becomes the anus.
The __________ of the gastrula stage of echinoderms, hemichordates and chordates becomes the anus.
In contrast, the blastopore of members of the phyla studied previously (phylum Mollusca) becomes the __________ if they have a __________.
In contrast, the blastopore of members of the phyla studied previously (phylum Mollusca) becomes the __________ if they have a __________.
The larvae are __________ and are usually __________.
The larvae are __________ and are usually __________.
Members of each class produce one or more kinds of __________ larvae.
Members of each class produce one or more kinds of __________ larvae.
They have arms that are not sharply set off from the __________.
They have arms that are not sharply set off from the __________.
There is an __________ on each arm.
There is an __________ on each arm.
They have spines; __________ belong to this class.
They have spines; __________ belong to this class.
A __________ larvae develops that later becomes a __________ larvae.
A __________ larvae develops that later becomes a __________ larvae.
They have arms that are sharply set off from the __________.
They have arms that are sharply set off from the __________.
They do not have __________.
They do not have __________.
They have spines. __________ belong to this class.
They have spines. __________ belong to this class.
They typically have an __________ larva stage.
They typically have an __________ larva stage.
They do not have __________.
They do not have __________.
The endoskeleton consists of __________ and is rigid.
The endoskeleton consists of __________ and is rigid.
They have spines; each spine has a __________ at its base that fits over a tubercle on a plate and is moved by __________ at its base.
They have spines; each spine has a __________ at its base that fits over a tubercle on a plate and is moved by __________ at its base.
Since a __________ joint is present their spines are highly maneuverable.
Since a __________ joint is present their spines are highly maneuverable.
__________ belong to this class.
__________ belong to this class.
They have an __________ larva stage.
They have an __________ larva stage.
They do not have __________. They do not have __________.
They do not have __________. They do not have __________.
__________ belong to this class.
__________ belong to this class.
Sea cucumbers; They have an __________ larva that later becomes a __________ larva.
Sea cucumbers; They have an __________ larva that later becomes a __________ larva.
They have __________, there is an __________ on each arm.
They have __________, there is an __________ on each arm.
They do not have __________.
They do not have __________.
__________ belong to this class.
__________ belong to this class.
Two categories of them are __________.
Two categories of them are __________.
They have __________ larva stage.
They have __________ larva stage.
In some species the doliolaria is preceded by an __________.
In some species the doliolaria is preceded by an __________.
These animals are __________ shaped.
These animals are __________ shaped.
Their bodies consist of arms attached to a __________.
Their bodies consist of arms attached to a __________.
Most species have __________ arms.
Most species have __________ arms.
Their __________ increase in width from the apex to the base.
Their __________ increase in width from the apex to the base.
Many tube feet extend from an __________ on the underside of each arm.
Many tube feet extend from an __________ on the underside of each arm.
__________ of these animals function for locomotion and for handling food.
__________ of these animals function for locomotion and for handling food.
Tube feet and other components of the water-vascular system are as follows: __________.
Tube feet and other components of the water-vascular system are as follows: __________.
The __________ is located on the aboral surface of the central disc.
The __________ is located on the aboral surface of the central disc.
The surface of the madreporite has __________ on it.
The surface of the madreporite has __________ on it.
Many pores are present at the bottom of each __________.
Many pores are present at the bottom of each __________.
Water passes in and out of it through the __________.
Water passes in and out of it through the __________.
This allows for adjustments to be made to changes in __________ that result from depth differences due to tidal fluctuations.
This allows for adjustments to be made to changes in __________ that result from depth differences due to tidal fluctuations.
Canals of the water vascular system are lined with __________ epidermis.
Canals of the water vascular system are lined with __________ epidermis.
Little pouches called __________ are attached to the ring canal.
Little pouches called __________ are attached to the ring canal.
Tiedemann's bodies produce phagocytic cells called __________ which remove bacteria and other foreign matter from incoming water.
Tiedemann's bodies produce phagocytic cells called __________ which remove bacteria and other foreign matter from incoming water.
Some water and coelomocytes pass through Tiedemann's bodies into the __________.
Some water and coelomocytes pass through Tiedemann's bodies into the __________.
Little sacs called __________ are also attached to the ring canal of some species. They function for fluid storage.
Little sacs called __________ are also attached to the ring canal of some species. They function for fluid storage.
Concerning locomotion, longitudinal muscles on one side of tube foot contract, which cause it to bend in that direction; then as the __________ contracts, a valve in the lateral canal closes and water is forced into the tube foot which elongates.
Concerning locomotion, longitudinal muscles on one side of tube foot contract, which cause it to bend in that direction; then as the __________ contracts, a valve in the lateral canal closes and water is forced into the tube foot which elongates.
Contraction of __________ muscles in the tube foot forces water back into the ampulla and tube foot shortens. This process is continually repeated.
Contraction of __________ muscles in the tube foot forces water back into the ampulla and tube foot shortens. This process is continually repeated.
All of the __________ move in the same direction but not in unison.
All of the __________ move in the same direction but not in unison.
As many tube feet shorten the animal is slowly pulled __________.
As many tube feet shorten the animal is slowly pulled __________.
The tube feet of most species have a __________ at the distal end.
The tube feet of most species have a __________ at the distal end.
When a __________ comes in contact with hard substrate such as a rock, the sucker adheres; when on mud or sand the tube feet function as legs (no suction).
When a __________ comes in contact with hard substrate such as a rock, the sucker adheres; when on mud or sand the tube feet function as legs (no suction).
__________ cells are scattered in the epidermis.
__________ cells are scattered in the epidermis.
An __________ is located at the tip of each arm.
An __________ is located at the tip of each arm.
Most species feed on __________.
Most species feed on __________.
Some feed mainly on __________; when doing so a sea star humps over its prey, attaches its tube feet to the valves, and pulls.
Some feed mainly on __________; when doing so a sea star humps over its prey, attaches its tube feet to the valves, and pulls.
When the valves separate, the sea star everts its __________ through its mouth and wraps it around the soft parts of the bivalve.
When the valves separate, the sea star everts its __________ through its mouth and wraps it around the soft parts of the bivalve.
Digestive enzymes are released and the soft parts of the prey are converted into a __________, then the sea star pulls in its stomach.
Digestive enzymes are released and the soft parts of the prey are converted into a __________, then the sea star pulls in its stomach.
Digestion continues within the __________.
Digestion continues within the __________.
There is one pair of __________ per arm.
There is one pair of __________ per arm.
The body wall consists of __________.
The body wall consists of __________.
Respiration and excretion occur through __________ and to a lesser extent through the tube feet.
Respiration and excretion occur through __________ and to a lesser extent through the tube feet.
Papulae are __________ of the body wall, where they are present the peritoneum extends outward between the ossicles and is almost in contact with the epidermis. The dermis here is very thin and muscle tissue is absent.
Papulae are __________ of the body wall, where they are present the peritoneum extends outward between the ossicles and is almost in contact with the epidermis. The dermis here is very thin and muscle tissue is absent.
Oxygen diffuses in and carbon dioxide diffuses out through the __________.
Oxygen diffuses in and carbon dioxide diffuses out through the __________.
Also __________ and other soluble metabolic waste diffuse out through them (papulae).
Also __________ and other soluble metabolic waste diffuse out through them (papulae).
Amoeboid cells called __________ engulf particulate waste and either exit the body through the papulae or the tube feet.
Amoeboid cells called __________ engulf particulate waste and either exit the body through the papulae or the tube feet.
These animals have minute pincer-like structures called __________ that keep the body surface free of debris and small animals that settle there so that respiration and excretion are not hindered.
These animals have minute pincer-like structures called __________ that keep the body surface free of debris and small animals that settle there so that respiration and excretion are not hindered.
Each pedicellaria consists of a __________ and __________.
Each pedicellaria consists of a __________ and __________.
The stalk portion can extend, retract, and bend; when the jaws are touched on the outside they snap __________, when touched on the inside they snap __________.
The stalk portion can extend, retract, and bend; when the jaws are touched on the outside they snap __________, when touched on the inside they snap __________.
They also snap shut in response to __________ stimuli.
They also snap shut in response to __________ stimuli.
The pedicellariae pinch and cut or break up __________ which are then moved off the body surface as cilia of epidermal cells beat.
The pedicellariae pinch and cut or break up __________ which are then moved off the body surface as cilia of epidermal cells beat.
Two __________ are located in each arm. They are large and filled with gametes; otherwise, they are quite small.
Two __________ are located in each arm. They are large and filled with gametes; otherwise, they are quite small.
Sea stars __________ missing parts and can also undergo autotomy.
Sea stars __________ missing parts and can also undergo autotomy.
__________ refers to the deliberate breaking off of an injured part of the body by the organism itself; for these animals, it refers to casting off an arm.
__________ refers to the deliberate breaking off of an injured part of the body by the organism itself; for these animals, it refers to casting off an arm.
Many species can regenerate a complete sea star from a detached arm that contains about __________ of the central disc.
Many species can regenerate a complete sea star from a detached arm that contains about __________ of the central disc.
In the past, mops were dragged through oyster beds and the starfish that were collected were chopped up with a hatchet or knife and thrown back into the water; instead of destroying them, this had the __________ effect.
In the past, mops were dragged through oyster beds and the starfish that were collected were chopped up with a hatchet or knife and thrown back into the water; instead of destroying them, this had the __________ effect.
These animals are __________ shaped.
These animals are __________ shaped.
Their bodies consist of arms attached to a __________.
Their bodies consist of arms attached to a __________.
All organs of their digestive and reproductive system are located within the __________.
All organs of their digestive and reproductive system are located within the __________.
Their arms are slender and fragile. Most species have __________ arms.
Their arms are slender and fragile. Most species have __________ arms.
Each arm contains a column of __________ that are connected by muscles.
Each arm contains a column of __________ that are connected by muscles.
The __________ are internal to the outer plates that are within the dermis.
The __________ are internal to the outer plates that are within the dermis.
Their arms are very flexible; locomotion is by __________. There are two main methods.
Their arms are very flexible; locomotion is by __________. There are two main methods.
The ends of the arms coil around rocks, seaweeds, or other objects and __________ the animal forwards; because of the snake-like movement of the arms when doing this, these animals are sometimes called serpent stars.
The ends of the arms coil around rocks, seaweeds, or other objects and __________ the animal forwards; because of the snake-like movement of the arms when doing this, these animals are sometimes called serpent stars.
The central disc is held above the substrate by three of the arms and the other two arms are moved forwards in pairs and function as __________.
The central disc is held above the substrate by three of the arms and the other two arms are moved forwards in pairs and function as __________.
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Study Notes
Echinoderms Overview
- Echinoderms belong to the phylum Echinodermata, encompassing sea stars, brittle stars, sea urchins, sand dollars, sea cucumbers, and related species.
- All echinoderms are marine organisms.
Unique Features of Echinoderms
- Possess a unique water-vascular system, exclusive to echinoderms, which facilitates movement and feeding.
- The water-vascular system comprises a madreporite, canals, ampullae, and tube feet.
Skeletal Structure
- Echinoderms have an endoskeleton embedded in the dermis, made of calcium carbonate ossicles.
- Ossicles vary in shape, may or may not be fused, and are supported by connective tissue when not fused.
- Fused ossicles create a rigid skeletal form in some species.
Symmetry and Nervous System
- Adults display radial, biradial, or bilateral symmetry, depending on the species.
- Lacking a brain, their nervous system consists of nerve rings from which nerves extend.
Respiratory and Circulatory Functions
- Coelomic fluid, driven by ciliary action, aids in respiration and nutrient transport.
- Oxygen and nutrients primarily move through coelomic fluid, with some assistance from blood.
Reproductive Traits
- Most echinoderms are dioecious, with external fertilization being common.
- The blastopore during embryonic development becomes the anus in echinoderms.
Larval Characteristics
- Echinoderm larvae exhibit bilateral symmetry and are typically planktonic.
- Larvae types include ciliated forms specific to each class.
Class-Specific Characteristics
Asteroidea (Sea Stars)
- Characterized by arms that merge with a central disc.
- Possess ambulacral grooves and tube feet used for locomotion and feeding.
- Exhibit bipinnaria and brachiolaria larval stages.
Ophiuroidea (Brittle Stars)
- Arms sharply distinct from the central disc; lack ambulacral grooves.
- Have brittle and flexible arms, utilizing locomotion methods like coiling around objects for movement.
- Their larval stage typically includes ophiopluteus.
Echinoidea (Sea Urchins, Sand Dollars)
- Lack arms; their endoskeleton consists of fused plates.
- Spines are highly maneuverable, facilitated by ball and socket joints.
- Have an echinopluteus larval stage.
Holothuroidea (Sea Cucumbers)
- Lack arms and spines; have elongated bodies.
- Display auricularia and doliolaria larval stages during development.
Crinoidea (Crinoids)
- Possess arms and ambulacral grooves but lack spines.
- Include two main types: sea lilies and feather stars.
- Larvae often undergo both doliolaria and auricularia stages.
Feeding and Digestion in Sea Stars
- Primarily consume slow-moving prey, including bivalve mollusks, by eviscerating them with their stomachs.
- Digestive enzymes dissolve prey into a thick broth, continuing digestion in the stomach and pyloric ceca.
Respiration and Excretion in Sea Stars
- Respiration occurs through papulae and tube feet; ammonia diffuses out alongside carbon dioxide.
- Pedicellariae function to keep the body surface clean of debris.
Regeneration and Autotomy
- Sea stars can regenerate arms and undergo autotomy to escape predators, allowing for the potential recovery of full star from a detached arm containing part of the disc.
Conclusion
- Echinoderms exhibit a variety of specialized structures and functions adapted to their marine environments, making them a diverse and fascinating group within the animal kingdom.
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