Echinodermata

Due to their spiny skin, it is named as (Greek "echinos" meaning "spiny" and echinoderms. This name is derived from Greek where "echinos" means "spiny'' and''dermos” means skin. This phylum is a collection of some 7,000 living species described here. Echinodermata are exclusively marine species. Echinoderms are all examples of marine stars, sea cucumbers, sea urchins, sand dollars, and brittle stars.

• An adult echinoderm body is radially symmetrical. 

• Echinoderm larva is bilaterally symmetrical 

• An echinoderm normally has 5 parts which make them pentamerous

• The mouth is surrounded by a central disk leading to grooves with podia. These grooves are called ambulacral grooves. 

• An echinoderm's endoskeleton is composed of individual parts, called ossicles. The ossicles are protected with skin or epidermis. 

• The ossicles form a rigid shell known as a test in some echinoderms, such as sand dollars and sea urchins. 

• In Sea cucumbers, these ossicles may also fuse to form various structures, such as the brittle spines of the sea urchin.

• The water vascular system is a primary part of echinoderm Biology. 

• The system consists of a series of fluid-bearing tubes that attach all over the organism in a ring-like structure. The system attaches to the podia and can be used to fill it with fluid that extends the podium and stiffens it.

• A few echinoderms are sessile filter feeders while others are actively hunting their prey. Though some filter feeder 's food is direct to their mouth

• Echinodermata circulatory system and nervous system is a basic system that circulates around its body. Their hemal system is environmentally open and allows for the exchange of gas through a series of channels throughout the body.

Classification of Echinodermata

The phylum echinoderms are classified into five classes: They are-

• Asteroidea (sea stars)

• Ophiuroidea (brittle stars)

• Echinoidea (sea urchins and sand dollars)

• Crinoidea (sea lilies or feather stars)

• Holothuroidea (sea cucumbers).

In this article, Echinodermata classes are discussed below in detail

Asteroidea: 

• Over all 1,800 species are well known

• Come in a large variety of shapes, colors, and sizes

• The key characteristic is it includes thick arms that extend from a central disk where organs penetrate into the arms.

• They use their tube feet for gripping surfaces and to grasp prey

• They have two stomachs, one of which can protrude into or on prey through their mouths and secrete digestive juices even before ingestion;

• Prey is liquified to make the digestion process easier.

Ophiuroidea:

• They have long, thin arms that are sharply demarcated from the central disk 

• They have the strongest tendency toward 5-segment radial (pentaradial) symmetry

• They are scavengers or detritivores

• Regrowth or regeneration of lost arms and disk is seen

Echinoidea:

• They do not have arms.

• Tube feet that are present are extruded through pores of a continuous internal shell called a test.

• They have roughly spherical bodies, with five equally-sized parts radiating out from their central axes.

• They are oval in shape.

• The body is slightly domed on the upper surface of, but the underside is flat.

 Crinoidea:

• These species are suspension feeders.

• They exist in shallow water and in depths as far as 6,000 meters.

• The crinoids are characterized by a mouth surrounded by feeding arms on the top surface.

• It consists of U-shaped gut and their anus is located next to the mouth

• They have more than five arms.

Holothuroidea:

• They are extended in the oral-aboral axis and have five rows of tube feet.

• It has bilateral symmetry.

• reduced to isolated microscopic ossicles joined by connective tissue.

Echinodermata Examples

Unlike other phyla invertebrate which contains hundreds or thousands of different animal types, Echinodermata contains only five different animal classes:

Starfish, or sea stars: These are the classic echinoderms that can come in a range of colors and textures and have five arms of varying thickness.

Brittle stars: These are also called serpent stars. It looks like typical starfish except that their legs are much skinnier and more fragile (thus the 'brittle' in their name), and they have more prominent spines than the sea stars.

Echinoid (sand dollars, sea urchins, and heart urchins): Echinoids contain no arm-like appendages. At the top, they are rounded and flat on the bottom and have spines of varying length. Sea urchins having longer spines and sand dollars and heart urchins having shorter spines.

Sea cucumbers: They have long, cucumber-like bodies with bumps on the surface.

Sea lilies: These are the most ancient echinoderms. They are lone sessile, immobile, organisms in the phylum. They have at least ten appendages that extend from their body's main stalk, which they use to feed on detritus or organic matter floating through the ocean.

How to Approach Echinodermata Studies?

• Maintain an optimistic approach 

Always thinking that you won’t be able to succeed will never bring success. Living in a fear that oh, you’ll fail again, will surely bring failure only. This is due to the fact that we usually do things that we think about. For example, if we’re planning to sleep then we’ll surely sleep; similarly, if we keep thinking that we won’t be able to do a particular task then our mind will be set up in such a way only that it will keep pushing us towards procrastination instead of hard work. Hence, it is important for you to be positive while studying and get rid of negativity to avoid procrastination and study with a relaxed mind.

• Make sure to start early

Studying just a few days before the exam might not be a good option at all. Firstly, you’ll be feeling tense after seeing so much pending syllabus and secondly, it won’t be possible to complete the whole syllabus in such a short span of time. Studying early has several benefits. As you’re studying regularly, it builds up your confidence and motivates you to work even more. If you’re done with your syllabus you can have a look at extra questions too, it may help! This can only be possible if you’ve decided to study from the start, otherwise even completing your syllabus might feel like a burden.

• Create summaries of your study sessions

Making notes and summaries while studying is essential so that the next time when you study, you'll have short notes to revise. It’s not possible to go through the whole syllabus again and hence, for easy and effective revision, summaries of every topic should be created to save time and to memorise everything. Hence, students shall always make it a point to take notes and make summaries of every lesson. 

• Set specific goals for yourself

Hard work without a goal is of no use. If you don’t know why and what you are working for then there’s no point in working. Therefore, it is important to create a goal. It is one of the most important things because of which an effective plan can be formed. Create a goal that you think is possible for you to complete, and try to work as hard as possible for the same. Having specific goals for each subject not only helps in getting good marks but helps in acquiring a good knowledge of the subject too. 

• Organize your study material before you attend a class or sit to study 

Before you start your study session, keep your stationery ready with you. Otherwise, you may feel distracted during your study time if anything is left. Keep everything you need by your side so that you can remain focused at your studying spot. Whether it is the notes or some extra textbooks, make sure that everything is around you so that you don't have to get up frequently. 

• Create your study materials

Creating study materials keeps students interested in the subject and they feel happier while studying instead of running away from it. Making organisers, quizzes etc helps in remembering things easily and for a long time. 

• Use Technology

Today we all have our smartphones with us that provide every bit of information required. It’s so simple to get 1000 words on any topic. So why not utilise this device as much as possible. Technology has advanced today and there are a number of other devices available in the market that can be used for both work and entertainment. Try not to just complete your syllabus but also to work on your skills too and acquire extra information about the subject as well. 

• Take advantage of all the available resources

Almost every student goes to study at coaching centres. A number of centres provide notes and assignments which are so helpful for revision and practice. Take the best advantage of these resources and try to practice as much as possible! Ask as many doubts as you have without hesitation. You have full right to do so. You can ask questions related to and out of your syllabus too, there are many specialists and experienced professors at the centres.

• Eat Healthily 

Eating a balanced diet is crucial. Eating less would make you feel weak and eating too much would make you feel sleepy and drowsy. It’s important to eat in a balance so that you can study well without feeling either weak or tired. 

• Take short breaks and rest 

Putting so much pressure on your mind will not be of any advantage. Trying to mug up all the things would not be a smart decision. Instead, try to learn and understand the concepts and take a rest at regular intervals. Do not pressurise your mind with so much work. Taking a break is important for a healthy mind. Resting regularly helps your brain to perform and complete the task with better results.

Key Points

• Echinoderms exist in aquatic environments only; they are widely divergent, with more than 7,000 recognized species in the phylum.

• Echinoderms have pentaradial symmetry and a calcareous endoskeleton and may have pigment cells and give them a wide variety of colors and toxin-possessing cells.

• Echinoderms have a water vascular system consisting of a central canal ring that extends along each arm, through which water circulates for exchange and nutrition of gasses.

• The Echinodermata nervous system is very simple. It consists of a concentrated nerve ring and five radial nerves running outwards along the arms; no structure resembles a brain.

• In echinoderms, there are two sexes, each releasing their eggs and sperm into the water; here, the sperm will fertilize the eggs.

• Through regeneration echinoderms can reproduce asexually