What type of body plan do cnidarians have?
Table of Contents
What type of body plan do cnidarians have?
Cnidarians have two distinct body plans, the medusa (a) and the polyp (b). All cnidarians have two membrane layers, with a jelly-like mesoglea between them. Some cnidarians are dimorphic, that is, they exhibit both body plans during their life cycle.
What does the class Hydrozoa contain?
Hydrozoa is a class within the phylum Cnidaria, which includes sea anemones, corals, and jellyfish.
What is the order of Hydrozoa?
Hydrozoans are related to jellyfish and corals and belong to the phylum Cnidaria….Hydrozoa.
| Hydrozoa Temporal range: | |
|---|---|
| Subphylum: | Medusozoa |
| Class: | Hydrozoa Owen, 1743 |
| Subclasses and orders | |
| Hydroidolina Anthoathecata Leptothecata Siphonophorae Trachylinae Actinulida Limnomedusae Narcomedusae Tatalidoae |
What body plan did the first cnidarians have?
Although they look like blobs, sea anemones and other cnidarians have a basic anatomical plan called a body axis. That is, they have a top, defined by the mouth, and a bottom.
How do the two body plans of cnidarians differ?
How do the two body plans of cnidarians differ? Poly: sessile, has a cylindrical body with tentacles, first stage of a cnidarian. Medusa: has a motile, bell shaped body with a mouth on the bottom.
What is the life cycle of Hydrozoa?
In many hydrozoan species, the life cycle consists of a free-living planula larva that transforms into a primary polyp. The primary polyp buds other polyps to produce a benthic colonial stage. Upon reproductive maturity, the polyps bud pelagic medusae that ultimately form gametes and spawn in the water column.
Which is characteristics of class Hydrozoa?
Main attributes:
- Internal space for digestion is the gastrovascular cavity.
- Gastrovascular cavity has one opening, the mouth.
- Exoskeleton of chitin.
- Are almoust entirely marine and predators.
- Sexual reproduction produces the planula larvae.
- Two body forms, a polyp and medusea.
- Presence of stinging cells called Cnidocytes.
Does Hydrozoa have exoskeleton?
While a few hydrozoans, such as Hydra, are solitary polyps, most live in colonies made up of anywhere from a few to thousands of individual polyps. Colonies may secrete extensive calcium carbonate skeletons (coenosteum) or be covered with a flexible chitinous exoskeleton (perisarc).
What body cavity does Cnidaria have?
The body cavity (gastrovascular cavity) is sac-shaped, with one opening acting as both mouth and anus. This opening is surrounded by tentacles bearing thread cells. Cnidarians exist both as free-swimming medusae (e.g. jellyfish) and as sedentary polyps.
What are the 2 body forms of cnidarians?
Cnidarians have two body forms—polyp and medusa—which often occur within the life cycle of a single cnidarian. Sea nettle (Chrysaora fuscescens). The body of a medusa, commonly called a jellyfish, usually has the shape of a bell or an umbrella, with tentacles hanging downward at the margin.
What are 2 basic body forms of Cnidaria?
Cnidarians have two basic body forms, medusa and polyp. Medusae, such as adult jellyfish, are free-swimming or floating. They usually have umbrella-shaped bodies and tetramerous (four-part) symmetry. The mouth is usually on the concave side, and the tentacles originate on the rim of the umbrella.
What makes Hydrozoa unique?
They are distinguished from other groups by their complex life cycle, by the growth of medusae from buds rather than strobilae or from metamorphosis, by the presence of a velum inside the bell of the medusa, and by the production of gametes from ectodermal, rather than endodermal, tissue.
What are the three layers of the cnidarian body?
Cnidarians are further characterized by having a body wall composed of three layers: an outer epidermis, an inner gastrodermis, and a middle mesogloea. Tentacles encircle the mouth and are used in part for food capture.
