Invertebrate Zoology Flashcards
Talk about the anatomy and state the four cell types in Porifera
They have an outer layer called the pinacoderm, an inner layer called the choanoderm, a central cavity called the spongocoel. The outlet opening is called oculum and the pores are called Ostia. The four main cell types are sclerocytes, porocytes, pinacocytes and amoebocytes
What is the bulk of the body of a sponge made of?
An acellular gel matrix called the mesohyl that contains skeletal elements to reinforce it, such as protein fibres called spongin and mineral spicules e.g. Calcium carbonate and silica.
What are the three roles of amoebocytes?
They are totipotent, they transport nutrients to other parts of the sponge body and they produce spicules.
Describe, in detail how sponges filter feed
Water passes through the pores and into the spongocoel, out through the occulum. The flagellum of the choanocytes beat to create a current that draws the water through the pores and out of the sponge. The choanocytes can also draw water through the collar of finger like projections, where food can get digested or passed onto amoebocytes.
What are the three body structures a sponge can adopt?
Asconoid means surface area to volume ratio is limited, syconoid means a pleated inner wall and leuconoid means a multi chambered spongocoel.
Talk about reproduction in Porifera
It can be asexual or sexual. They are sequential hermaphrodites, which means they produce both gametes and can function as one gender or the other. The water current can draw sperm through the pores and out of the occulum of a small sponge to another neighbouring individual that is a female, in which the egg is fertilised.
Briefly describe feeding in Porifera
No mouth, filter feeders. Unidirectional water flow
Which two groups make up the radiata? What are the features of radiata?
Cnidaria and Ctenophora. Radiata are radially symmetrical and are diploplasts, so they have no body cavity.
Talk about the anatomy of the cnidarians
They have a mouth surrounded by tentacles. They have a three layered body wall; there’s the epidermis, the gastrocnemius and the mesoglea. They have cnidocyte cells in the tentacles that contain cnidae (capsule-like organelles that explode). In nematocysts for example, cnidae have pressurised stinging structures to attack prey.
What are the main groups within the Cnidaria and what body form do they adopt? Briefly describe the body forms and how reproduction works in Cnidaria?
Hydrozoa are hydroids, they alternate between polyp and medusa. Anthozoa are sea anemones, they are polyps. The Scyphozoa are jellyfish, they are medusae. Polyp is a cylindrical form of the cnidaria and medusa is a flattened form. In reproduction, colonies of polyps undergo asexual reproduction or budding to form medusae. The medusae undergo sexual reproduction to form larvae and mature polyps.
How are Ctenophora different to Cnidaria?
They have cilia combs and they do not have cnidocytes
Talk about the nervous system of Cnidaria
They have epitheliomuscular cells in the epidermis that contain contractile myofibrils for movement. There are sensory neurones connected to these cells in the epidermis by nerve cells. Coordination of muscle contractions and cnidocytes firing.
Talk about reproduction in flatworms
Asexual reproduction called spontaneous fission and sexual reproduction is that they are hermaphrodites. They can also regenerate.
Talk about parasitism in flatworms
The Trematoda and Cestoda are tissue and gut parasites respectively. They adopt endoparasitism. The consequences of living in another organism is that they lose their gut, cephalisation and cilia due to a need for a tegument (protective covering from digestive enzymes). Planarians are non-parasitic.
What are the general features of nematodes?
They have an alimentary canal, they have a body wall with longitudinal muscles for thrashing when floating, pseudocoelom for transport of nutrients since no circulatory system, four longitudinal ensheathed nerve cords.
