How does Platyhelminthes differ from annelids?
Flatworms (phylum Platyhelminthes) are simple animals that are slightly more complex than a cnidarian. Roundworms (phylum Nematoda) have a slightly more complex body plan. Segmented worms (phylum Annelida) are the most complex animals with worm-like body plans. Worms are invertebrate animals with bilateral symmetry.
What is the main difference between roundworms and annelids?
Annelids are segmented worms whereas roundworms are not segmented. Further, annelids have a true coelom while roundworms have a pseudocoelom. This means annelids have a well-developed mesoderm while roundworms lack a mesoderm. These are the main features that distinguish annelids from roundworms.
What differentiates Polychaetes from other annelids?
Polychaetes differ from other annelids in having a well differentiated head with specialized sense organs and no clitellum. They have many setae, usually arranged in bundles on the parapodia. The head bears eyes, antennae, and sensory palps.
What type of digestion does annelids have?
Digestion. Since an annelid’s segments contain the same organs as all the others, there is little need for a very specialized digestion system. Instead, the digesting occurs through a long tube that extends from the mouth to the anus. It is held in the center of the worm as one continuous structure.
How are platyhelminthes more advanced than cnidarians?
Flatworms are more complex than cnidarians. Cnidarians have two layers of cells, the ectoderm and the endoderm; flatworms have a middle layer called the mesoderm between the other two layers (Fig. The cells of the ectoderm and endoderm are also more organized than similar cells of cnidarians.
Do annelids have a complete digestive system?
Annelids show the presence of a true coelom, derived from embryonic mesoderm and protostomy. Hence, they are the most advanced worms. A well-developed and complete digestive system is present in earthworms (oligochaetes) with a mouth, muscular pharynx, esophagus, crop, and gizzard being present.
What are two differences between annelids and nematodes?
The key difference between nematodes and annelids is that nematodes are roundworms which are not segmented while annelids are true segmented worms. The presence and absence of a true coelom is another difference between nematodes and annelids. Nematodes possess a pseudocoelom while annelids possess a true coelom.
What are the differences between nematodes and annelids?
Nematodes have an unsegmented body whereas annelids are metamerically segmented. Nematodes are pseudocoelomate, whereas annelids have a true coelom. Nematodes are dioecious, i.e. sexes are separate. Annelids are mostly hermaphrodites and free-living.
What is the difference between Metameres and Septa?
What is the difference between metameres and septa? External segments are called metameres and internally, septa, or dividing walls, are located between the segments. Annelids are worms with cylindrical bodies segmented both internally and externally, which includes earthworms.
What is the difference between leeches and polychaetes?
Polychaetes are the most diverse group of annelids and most live in the marine environment. They differ from earthworms and leeches in that they have appendages called parapodia and do not possess a clitellum. In size they range from 1 mm (0.04”) to 3 m (10′) but most are around 10 cm (4”).
Does annelids have complete digestive system?
Do camels have complete digestive systems?
Although camels ruminate they are not true ruminants, as they lack the four well-defined stomachs of the ruminants; the rumen, reticulum, omasum and abomasum.
Is the Onychophora part of the Annelida phylum?
Onychophora has many characters of Annelida, particularly its general body organisation. But it also exhibits many important features that take it closer to Arthropods. Hence this animal has been assigned to an independent status of phylum between Annelida and Arthropoda.
What kind of body does an Onychophora have?
Onychophora are worm-like body covered with thin, flexible, chitinous cuticle. 2. Onychophora are sluggish in nature. 3. Head segments are comparatively small (3 head segments in onychophores but in true arthropods head segments are 5 or 6).
When did all living onychophorans move to land?
All currently living onychophoran species are terrestrial, although the fossil record shows they were likely aquatic at some point, the shift to land probably took place during the Ordovician period.
Which is a link between annelids and arthropods?
Early researchers considered onychophorans to be a link between annelids and arthropods, as they share characteristics with both phyla.