Chapter 3 - Sponges & Placozoa Flashcards
What is the term used for multicellular organisms?
Metazoans
Metazoans include all animals and are characterized by being multicellular.
What does ‘Porifera’ mean?
Pore-bearing
This refers to the sac-like bodies of sponges that have many pores.
How do sponges primarily feed?
By collecting suspended particles from water
Water is pumped through internal canal systems for filter feeding.
What are the three classes of sponges based on spicules?
- Calcispongiae
- Hexactinellida
- Demospongiae
These classes differ in the composition and structure of their spicules.
What type of cells are choanocytes?
Flagellated collar cells
Choanocytes are responsible for maintaining water flow and capturing food particles.
What is the simplest body organization of sponges called?
Asconoid
Asconoid sponges have a tube-shaped structure that allows direct water flow across cells.
What distinguishes leuconoid sponges?
Clusters of flagellated chambers
Leuconoid sponges have the most complex structure with multiple food-collecting regions.
What is the role of archaeocytes in sponges?
They can differentiate into other specialized cell types and are involved in digestion.
Archaeocytes can differentiate into other specialized cell types and are involved in digestion.
What is gemmulation in sponges?
A form of asexual reproduction involving dormant structures
Gemmules can survive harsh conditions and develop into new sponges when conditions improve.
Are most sponges monoecious or dioecious?
Monoecious
Most sponges contain both male and female sex cells within the same individual.
What are the characteristics of Class Homoscleromorpha?
- Marine species
- True basement membrane
- Have adherens cell junctions
This class has unique features that differentiate it from other sponge classes.
What is a notable feature of glass sponges (Class Hexactinellida)?
Six-rayed spicules of silica
Glass sponges are primarily deep-sea organisms with a radially symmetrical body.
What type of spicules do calcareous sponges (Class Calcispongiae) have?
Calcium carbonate spicules
These spicules can have one, three, or four rays.
What is a unique feeding behavior of the carnivorous harp sponge?
Enveloping and digesting prey
This sponge lacks choanocytes and internal canals, contrasting with typical sponges.
What type of organism is Trichoplax adhaerens?
A placozoan
Placozoans are simple, plate-like marine organisms with no symmetry or major organs.
How do placozoans reproduce?
Asexually by budding
They can also produce ‘swarmer’ stages but no sexual reproduction has been observed.
What major systems are absent in placozoans?
No major organs, no muscular or nervous system
Placozoans are simple organisms lacking complex structures.
What type of lamina do placozoans lack beneath their epidermis?
Basal lamina
This absence is notable in the context of their simple structure.
What do placozoans lack in their structure that is typically present in other organisms?
Extracellular matrix
Despite this, placozoans have genes related to the extracellular matrix.
How do placozoans obtain nutrients?
They glide over food, secrete digestive enzymes, and absorb nutrients
This method allows them to feed efficiently despite their simplicity.
How do placozoans reproduce?
Asexually and produce ‘swarmer’ stages by budding
This reproductive method is typical for simple organisms.
Have sexual stages been observed in placozoans?
No sexual stages have been seen but isolated eggs have been found in the laboratory
This indicates a potential for sexual reproduction, yet it remains unobserved in nature.
What is the scientific name for the marine placozoan mentioned?
Trichoplax adhaerens
This species is commonly studied in placozoan research.
