Term
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Definition
The phylum Porifera contains the simplest creatures of the animal kingdom. Sponges are aquatic sessile beings (they are not able to move by themselves and they keep themselves attached to substrates), they do not have tissue diversity and their bodies have pores (feature after which their name comes).
They are multicellular, like all beings of the animal kingdom. |
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Term
| What is the way of life of sponges? |
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Definition
| Sponges live exclusively in an aquatic environment and they are attached by their base to a substrate (fixation ground). Sponges are filtering animals, they nourish themselves from nutrients that enter their atrium brought in with water. |
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Term
| What is the typical shape of poriferans? |
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Definition
| Sponges have bodies in the form of tubular vases or globes open in the upper extremity. They have an internal central cavity and porous walls. The central cavity is called spongocoel and the opening in the upper extremity is called osculum. |
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Term
| How does water move inside sponges? What is the function of the pores in these animals? |
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Definition
| Sponges are filtering beings. They make water enter their bodies by their lateral pores. Water then circulates inside the central cavity and exits through the osculum. |
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Term
| How do sponges try to protect themselves against harm from the environment? Is that method efficient or rudimentary? |
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Definition
| Sponges can close their pores to avoid the entrance of water into their bodies in the presence of stimulus that may mean danger. This method however is rudimentary but it is actually a protection attempt against nocent agents. |
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Term
| What are the main cells of which poriferans are made? |
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Definition
Sponges have their outer wall covered by flat cells called pinacocytes and having pores well-delimited by special cells called porocytes. The internal wall is filled with choanocytes, flagellate cells specialized in phagocytosis of food brought to the central cavity; the choanocyte flagella also maintains the water flux inside the sponge.
Between the outer and the inner coverage of the poriferan body there are cells with amoeboid movement (by pseudopods), the amoebocytes; since they are embedded in connective matrix, amoebocytes move and distribute nutrients to othercells and they also produce spicules that like a primitive skeleton fill the tissue and support the body structure. (Some poriferans have an internal skeleton, an endoskeleton, made of spicules and organic fibers.) |
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Term
| Concerning digestion how are poriferans characterized? |
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Definition
| Sponges are different from other animals since they present only intracellular digestion. They do not have a digestive system nor do they release digestive enzymes in the spongocoel to cause extracellular break down of nutrients. |
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Term
| How are animals divided according to their type of digestive process? |
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Definition
| Apart from sponges, that do not have a digestive cavity where extracellular digestion takes place, all other animals have a digestive system with an internal cavity in which extracellular digestion occurs. |
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Term
| How are gases exchanged in sponges? |
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Definition
| The gas exchange in sponges happens by diffusion from the exterior to the cells that absorb molecular oxygen and liberate carbon dioxide. |
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Term
| Do sponges have nervous, circulatory and excretory systems? |
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Definition
| Sponges do not have a nervous system neither circulatory system nor excretory system. |
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Term
| Is reproduction in sponges sexual or asexual? |
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Definition
| Reproduction in sponges can be asexual by budding, gemmation or fragmentation (regeneration) or sexual with larval stage (a ciliated amphiblastula larva). |
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Term
| What is the evolutionary advantage of the occurrence of sperm cells and larval stage in the life cycle of sponges? |
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Definition
| The sexual reproduction in sponges, in addition to contributing to genetic variability, also facilitates the colonization of farther environments by these beings, since spermcells and larvae are mobile and can swim in the exterior to compensate the immobility of the adult individual. |
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Term
| What is the economic importance of sponges? |
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Definition
| Some chemical substances secreted by sponges have anti-inflammatory, antibiotic and anti-tumoral activities and they are used in the production of medicines. Since ancient times the endoskeleton of somesponges has had commercial value, they are used as cleansing implements for baths (bath sponges), to wash animals, objects and so on. |
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Term
| Sponge identity card. How are sponges characterized according to example of representing beings, basic morphology, type of symmetry, embryonic (germ) layers and coelom, digestive system, respiratory system, circulatory system, excretory system, nervous system and types of reproduction? |
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Definition
| Example of representing beings: sponges. Basic morphology: tubular or globular body with spongocoel, sessile; choanocytes, pinacocytes and amoebocytes. Type of symmetry: not established. Germ layers and coelom: do not apply since poriferans do not have true tissue organization. Digestive system: nonexistent.Respiratory system : nonexistent. Circulatory system: nonexistent. Excretory system: nonexistent. Nervous system: nonexistent. Types of reproduction: asexual and sexual with larval stage. |
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