How many germ layers are in platyhelminthes?
Flatworms have three embryonic tissue layers that give rise to surfaces that cover tissues (from ectoderm), internal tissues (from mesoderm), and line the digestive system (from endoderm).
What is the respiratory system of platyhelminthes?
Flatworms do not have a respiratory system. Instead, they have pores that allow oxygen to enter through their body. Oxygen enters the pores by diffusion. Flatworms have a ladder-like nervous system; two interconnected parallel nerve cords run the length of the body.
How many germ layers make up the body of platyhelminthes how are they classified according to this feature?
How many germ layers make up the body of platyhelminthes? How are they classified according to this feature? Platyhelminthes are the first triploblastic animals (remember that cnidarians are diploblastic), meaning that they contain three germ layers: the ectoderm, mesoderm and endoderm.
What are the 3 body layers in flatworms?
Flatworms are generally hermaphroditic—functional reproductive organs of both sexes occurring in one individual. Like other advanced multicellular animals, they possess three embryonic layers—endoderm, mesoderm, and ectoderm—and have a head region that contains concentrated sense organs and nervous tissue (brain).
What is the three germ layers?
Three primary germ layers Gastrulation is a key phase in embryonic development when pluripotent stem cells differentiate into the three primordial germ layers: ectoderm, mesoderm and endoderm.
How many germ layers do porifera have?
Porifera are diploblastic. They have cells arranged in two germ/embryonic layers— endoderm and ectoderm.
How do Platyhelminthes obtain oxygen?
Flatworms are small, literally flat worms, which ‘breathe’ through diffusion across the outer membrane. The flat shape of these organisms increases the surface area for diffusion, ensuring that each cell within the body is close to the outer membrane surface and has access to oxygen.
Do annelids have a respiratory system?
Respiration. In some annelids, including earthworms, all respiration is via the skin. However, many polychaetes and some clitellates (the group to which earthworms belong) have gills associated with most segments, often as extensions of the parapodia in polychaetes.
Do platyhelminthes mesoderm?
Like cnidarians flatworms have a layer of ectoderm and endoderm, but also a third germ layer called mesoderm. Flatworms are acoelomate because they lack a body cavity (fluid filled layer) and their body construction is solid.
Why do flatworms not have Coelom?
Flatworms, lacking a coelom, were traditionally thought to represent leftovers from the early days of animal evolution, before any animals had a coelom. The author suggests that modern flatworms descended from a coelomate ancestor, which lost its coelom (and its anus!) through the course of evolution.