Cnidaria and Ctenophora
Terms in this set (23)
What are the general characteristics of Cnidarians?
All have two tissue layers, a single digestive opening, and stinging cells called nematocysts. They have radial symmetry.
What are the General characteristics of ctenophores?
All have two tissue layers, two digestive openings, and sticky cells called colloblasts. They possess rows of combs that they control to move. They have biradial symmetry
What two evolutionary advances appeared with the Cnidarians?
Tissues and body symmetry
Describe the muscles and nerves of Cnidaria and ctenophores
Primitive and the simplest of tissues
What are the differences between radial and bilateral symmetries?
Radial means you can cut an organism in half many different ways. Bilateral means you can only cut them in half a single way. As a result, radial animals do not have left and right or head and tail sides , but only oral and aboral surfaces.
Describe the two tissue layers that Cnidarians possess. What is found between them?
The outside layer, the epidermis, is derived from the ectoderm. The inner layer, the gastrodermis, is derived from endoderm. In between is the jelly-like mesoglea
What is a nerve net? What does it allow Cnidarians to do?
A simple network of nerves that allows Cnidarians to move.
Describe the motion of jellies and explain why they move this way
Jellies pulse in a single motion. They can only do one type of motion because the nerve net fires all at once. They cannot move just one side of their body.
Describe a nematocyst
The stinging cell of Cnidarians, it is contained in cnidocytes. It fires mechanically by trigger, the jelly does not purposefully "sting"
colonial animals that are usually polyps. They have zooids that complete
different tasks for the good of the colony. The entire animal comes from a single fertilized zygote and all parts share the same DNA. When reproducing, they typically go from Polyp->Medusa->Polyp. The polyp makes small medusa that produce sperm and eggs, which develop into a planula then eventually another adult polyp. The planktonic animals in this group (siphonophores) are one the longest on Earth.
Corals and Anemones. No medusa form at any time of their life cycle.
These often live in colonies, but are groups of independent organisms rather than coming from a single egg. They suck food in by making a current with a structure called a siphonoglyph.
True jellies. They contain lots of mesoglea, and are always medusa forms as adults. They reproduce by producing polyps that produce small ephyra (larval
jellies). They go from medusa->polyp->medusa.
the box jellies. Have 4 sets of tentacles and are ridiculously venomous.
They kill more people than sharks in Australia.
What is the difference between Gastrozooids and Ganozooids?
Gastrozooids are for feeding and nutrition, Gonozooids for reproduction.
What are the two evolutionary characteristics that arose with the Ctenophora?
A one-way digestive tract and biradial symmetry
Describe a Ctenophoran comb
A group of fused cilia used as a paddle.
When Ctenophores move their combs, they sometimes show a rainbow of light. Why is this?
They refract and reflect white light, resulting in a rainbow effect. They do not produce this light themselves.
Describe a colloblast
A sticky cell used by Ctenophores to capture prey.
How many gastrovascular openings do Ctenophores have?
Two: oral and anal
What is the larval form of a Ctenophore called?
What is the larval form of Cnidarians called?
List the similarities between Ctenophores and Cnidarians
Both have two tissue layers and mesoglea, Both have gastrovascular cavities
List the differences between Ctenophores and Cnidarians
Cnidaria has radial symmetry, Ctenophora biradial; Cnidaria has one digestive opening, Ctenophores have 2; Cnidaria has stinging cells, Ctenophores have sticky cells; Cnidarians have nerve nets to move, Ctenophores control their combs with apical sense organs
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