What do cnidarians and flatworms have in common

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Press ESC to cancel. Skip to content Home Articles Which of the following characteristics is shared by both cnidarians and flatworms which of the following characteristics is shared by both cnidarians and flatworms? Ben Davis March 23, Which of the following characteristics is shared by both cnidarians and flatworms which of the following characteristics is shared by both cnidarians and flatworms?

Which characteristic is shared by both cnidarians and Ctenophores? Animals without a circulatory system have limited abilities to deliver oxygen and nutrients to their body cells because of the way that molecules behave. As molecules spread through water, they become less concentrated as they move away from their source.

This is known as diffusion. But cnidarians have no problem with diffusion because most cells of their bag-shaped bodies are in direct contact with the water, making the exchange of oxygen and nutrients easy Fig. Flatworms, bag-shaped but flattened, also get oxygen and nutrients to their body cells easily because all their cells are close to either their outer surface or their digestive cavity Fig.

As animals become larger and more complex, diffusion is often no longer an option, and then we begin to see the development of circulatory and respiratory systems.

Species in the phylum Nematoda from the Greek root word nema meaning thread are better known as the roundworms Fig. There are about 25, species of nematodes formally described by scientists. Nematodes are found in almost every habitat on Earth. One species was first discovered living inside felt beer coasters in German alehouses.

Studies of farmlands have found as many as 10, nematodes in cubic centimeters cm 3 of soil. Nematodes are similarly abundant in marine and freshwater sediments where they serve as important predators, decomposers, and prey for other species like crabs and snails.

Like flatworms, roundworm species adopt either a free-living or a parasitic lifestyle. Parasitic nematodes Fig. Many nematodes that are parasitic on plants can devastate crops. Some nematodes are cryptobiotic and have demonstrated a remarkable ability to remain dormant for decades until environmental conditions become favorable. Like the flatworms, nematodes are bilaterally symmetrical. They take their name from their round body cross-sectional shape. Unlike the flatworms in which food and waste enter and exit from the same opening, nematodes have a complete digestive system.

An animal with a complete digestive system has a mouth at one end, a long tube with specialized parts in the middle, and an anus at the other end.

With a complete digestive system an animal can eat while its previous meal digests. Parts of the digestive system can specialize to do different jobs, digesting food in stages Fig. As the food moves along, it is broken into molecules and absorbed by the cells lining the tube. Muscles surrounding the tube contract, squeezing the food and pushing it along in a process called peristalsis. Indigestible wastes pass out through the anus.

Unlike flatworms, nematodes are slender, and they are covered by a protective cuticle. A cuticle is a waxy covering secreted by the epidermis, or outermost cellular tissue. Because of this covering, gas exchange cannot occur directly across the skin as in flatworms.

Rather, gas exchange and waste excretion in nematodes occurs by diffusion across the wall of the gut. Although nematodes do have a space in the body between the digestive tract and the body wall, it is not lined with tissue and is not considered to be a true coelom. Thus, nematodes are sometimes referred to as pseudocoelomates Fig. Most worms have two bands of muscles: longitudinal muscles that run the length of the body and circular muscles that form circular bands around the body.

Unlike other worms that have two bands of muscles, nematodes only have longitudinal muscles. This explains their characteristic thrashing movement, as they can move only by contracting the long muscles on either side of their body and wriggling forward.

The nervous system of nematodes consists of a set of nerves that run the length of the body and connect to anterior ganglia. Free-living nematodes are capable of sensing light with ocelli, and most nematodes have fairly complex chemosensory abilities. Most nematodes are not hermaphrodites , with both sexes in one individual, but are known as dioecious —having individuals of separate sexes.

Their chemosensory abilities are very helpful, as they rely on pheromones to locate potential mates. The worms in the phylum Annelida from the Latin root word annelus meaning ring typically have complex segmented bodies Fig. The body of an annelid is divided into repeating sections called segments with many internal organs repeated in each segment. Earthworms class Oligochaeta are familiar terrestrial members of this phylum and leeches class Hirudinea are well-known parasitic members of the phylum, most commonly found in freshwater.

They occur mostly in marine and brackish water habitats. Polychaete from the Greek root words poly meaning many and chaeta meaning bristle annelid worms are so named because most of their segments have bristles called chatae or setae. The free-moving not sessile polychaetes have muscular flaps called parapodia from the Greek para meaning near and podia meaning feet on their sides, and the setae on these parapodia dig into the sand for locomotion.

Fireworms are a type of polychaete that have earned their name from stinging bristles on each parapodium Fig. These bristles can penetrate human skin, causing irritation, pain and swelling, similar to the irritation caused by exposure to fiberglass. Tubeworms are sessile polychaetes that live in tubes that they build by secreting the tube material.

The tubes, attached to rocks or embedded in sand or mud, may be leathery, calcareous, or sand-covered depending on the worm species Fig.

Tubeworms feed by extending tentacles from the tube. Bits of food move along grooves in the tentacles to the mouth. Some tubeworms retract their tentacles when food lands on them. Tubeworms use their parapodia to create currents of water that flow through the tubes to aid in respiration and help clean the tubes.

By contrast, the free-living or mobile polychaete worms have a proboscis that can extend from their mouths to catch prey. This is a feeding organ that is often armed with small teeth or jaws on its tip. Oxford University scientists have discovered that an extremely rare gutless worm is related to sea anemones and jellyfish , rather than similar-looking animals, reports the journal Science.

The ancient flatworms were the first animals to develop a central nervous system and a head with a brain. The head had eyes—the first in the animal world.

Flatworms are hermaphroditic and capable of sexual and asexual reproduction. Their bodies have only a single opening, which serves as both a mouth and an anus. They are, as their name implies, flat. They have no circulatory system or body cavity coelom , but they do have an excretory and digestive system. Flatworms are hermaphroditic having both male and female sex organs and they typically reproduce both sexually and asexually.

The majority of sexual reproduction is through cross-fertilization where both individuals fertilize each other. The free-living species of flatworms are predators or scavengers. Parasitic forms feed on the tissues of their hosts. Most flatworms, such as the planarian shown in Figure 1, have a gastrovascular cavity rather than a complete digestive system. Like humans, flatworms are bilateral : Their body plans are symmetric.

The team's research proved that these flatworms represent the first creatures to split from a long-dead ancestor common to all bilateral animals. After years of infection, the parasite can damage the liver, intestine, lungs and bladder. Rarely, it can also cause seizures, paralysis or spinal cord inflammation. More than million people have this disease and more than million people are at risk of infection. The most commonly used medicine for tapeworms is praziquantel Biltricide.

These medications paralyze the tapeworms, which let go of the intestine, dissolve, and pass from your body with bowel movements. If worms are large, you may have cramping when they pass. Not only are they an invasive species that can cause real environmental damage , but they also are known to carry a parasite called rat lungworm that can cause a form of meningitis in humans.

Besides that, this flatworm produces toxic secretions that may trigger an allergic reaction in some people. Cestodes have no digestive tract; they absorb nutrients from the host across the body wall. Most other flatworms, however, have conspicuous digestive systems.

They both have two openings mouth and anus ; and they also have an esophagus, pharynx.