NSCELEC 2 Week 5: Phylum Porifera

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Questions and Answers

What characteristic distinguishes Porifera from other invertebrates?

Development of complex organs

Lack of tissue-level organization (correct)

Ability to swim as adults

Presence of vertebrae

Which statement correctly describes the habitat of most Porifera species?

Exclusively in deep-sea trenches

Found mainly in marine waters (correct)

Primarily terrestrial environments

Mostly found in freshwater bodies

What are the structures in Porifera that allow for fluid absorption?

Cellular membranes

Ostia and osculum (correct)

Scleroblasts and spongioblasts

Spongocoel and symmetry

How do Porifera primarily reproduce?

Asexually by budding or fragmentation Signup and view all the answers

What is the central cavity of Porifera called?

Spongocoel Signup and view all the answers

Which of the following best describes the shape of Porifera bodies?

Cylindrical Signup and view all the answers

What type of nutrition do Porifera exhibit?

Holozoic Signup and view all the answers

What ability do Porifera have that is significant for their survival?

Regenerating lost body parts Signup and view all the answers

What is the primary function of choanocytes in sponges?

To generate a water current and trap food particles Signup and view all the answers

What structure allows water to exit the sponge after entering the spongocoel?

Osculum Signup and view all the answers

Which cell type forms the outermost layer of sponges?

Pinacocytes Signup and view all the answers

How does mesohyl contribute to the sponge's morphology?

It maintains the tubular shape and provides support. Signup and view all the answers

In which of the following forms are ostia typically developed?

From folds in the sponge's body wall or porocytes Signup and view all the answers

What is the main role of porocytes in sponges?

To regulate the flow of water through ostia Signup and view all the answers

Which part of the sponge morphology is not organized into tissue layers?

None of the above Signup and view all the answers

What common feature do choanocytes and choanoflagellates share?

Both types possess collar-like structures for feeding. Signup and view all the answers

What is the primary function of gemmules in sponges?

To withstand harsh environments and colonize new areas Signup and view all the answers

Which statement is true about the sexual reproduction of sponges?

Some sponges may change their sex during their lifecycle. Signup and view all the answers

What characterizes the body structure of Class Calcarea in sponges?

Body composed of calcareous spicules Signup and view all the answers

What is the result of the differentiation of choanocytes in sponges?

Production of spermatozoa Signup and view all the answers

In sponges, oocytes are formed from which type of cell?

Amoebocytes Signup and view all the answers

What do sponges primarily rely on for locomotion, despite being sessile as adults?

Creeping along surfaces through cell movement Signup and view all the answers

What kind of symmetry is exhibited by Class Calcarea sponges?

Radial symmetry Signup and view all the answers

Which factor may influence when sponges produce gametes?

Water temperature Signup and view all the answers

Which cells are primarily responsible for trapping bacteria in sponges?

Choanocytes Signup and view all the answers

What is the typical process of asexual reproduction in sponges?

Budding and fragmentation Signup and view all the answers

What type of particles can be phagocytized by pinacocytes?

Food particles that are larger than individual cells Signup and view all the answers

How do sponges primarily perform gas exchange?

By diffusion through water passing through Signup and view all the answers

What role do amoebocytes play in sponge digestion?

Transporting food to other cells Signup and view all the answers

What are gemmules, and where are they found?

Reproductive structures found in freshwater sponges specifically Signup and view all the answers

What happens to nitrogenous waste in sponges?

It is excreted by diffusion into the surrounding water Signup and view all the answers

What limits the type of digestion in sponges?

Food particles must be smaller than individual cells Signup and view all the answers

What is the primary characteristic of the skeleton in Hexactinellids?

Composed of six-rayed siliceous spicules Signup and view all the answers

Which type of canal system is present in Desmospongiae?

Leuconoid Signup and view all the answers

Which of the following is a characteristic feature of Sycon sponges?

They are found in shallow marine waters Signup and view all the answers

What distinguishes Euplectella from other sponges?

Its skeleton has a three-dimensional network of spicules Signup and view all the answers

Which sponge is known for boring into coral skeletons or shells?

Cliona Signup and view all the answers

What is a distinguishing feature of the body shape of Desmospongiae?

Cylindrical and asymmetrical Signup and view all the answers

Where are Spongilla primarily found?

In freshwater ponds and streams Signup and view all the answers

What type of reproduction do most marine sponges utilize?

Both sexual and asexual reproduction Signup and view all the answers

Study Notes

Common Characteristics of Phylum Porifera

Invertebrates, known as Parazoans, lack bony structures; Porifera includes sponges as the simplest invertebrates.
Sponges do not exhibit tissue-level organization; they have specialized cells performing specific functions.
Adult sponges are non-motile; they remain fixed to substrata while their larvae are capable of swimming.
Approximately 5000 species of sponges known as “pore bearers” due to their pore-filled structure (ostia).
Identified as the lowest multicellular animals in the Animalia kingdom based on embryological studies.
Found primarily in marine environments, with a few species inhabiting freshwater.
Body forms can be radially symmetrical or asymmetrical, typically cylindrical in shape.
Spicules are secreted by scleroblasts, while spongin fibers are secreted by spongioblasts.
Lack of organs; demonstrate a cellular grade of organization.
Central cavity referred to as spongocoel or atrium, which opens externally through the osculum.
Asexual reproduction occurs through budding and fragmentation mechanisms.
Nutritional process is holozoic; they possess neurosensory cells but lack a distinct nervous system.
Notable regenerative abilities to replace lost parts.

Morphology of Sponges

Sponges exhibit a cylindrical shape, enclosing a large central cavity (spongocoel) through which water circulates.
Water enters via numerous ostia and exits through the osculum, facilitating filtering and nutrient absorption.
Cell types include:
- Pinacocytes form the outer layer and encase the mesohyl, an extracellular matrix that maintains structural integrity.
- Choanocytes line inner cavities and help create water currents for trapping food particles through phagocytosis.
Mesohyl functions as an endoskeleton, providing support to sponges.
Cellular differentiation allows sponges to perform essential biological functions despite lacking complex systems.

Digestion

Sponges lack complex systems for digestion, respiration, and excretion; these functions rely on diffusion.
Choanocytes trap bacteria and nutrients while larger particles are managed by pinacocytes.
Amoebocytes assist by transporting ingested food throughout the sponge.
All cellular types utilize diffusion for oxygen uptake and waste release.

Reproduction

Sponges reproduce both sexually and asexually; asexual methods include fragmentation and budding.
Freshwater sponges can form gemmules, durable structures for environmental survival and recolonization.
Sponges are monoecious, producing both eggs and sperm; gamete development may vary seasonally based on water temperature.
Sperm ejection occurs through osculum, where water currents facilitate the fertilization of oocytes retained in mesohyl.
Larval development occurs internally, with free-swimming larvae released into the environment.

Locomotion

Sponges remain sessile as adults, with minimal movement limited to cellular creeping along substrates.
Experimental evidence suggests that sponge cells can exhibit directed movement to adapt to microenvironments.

Classification of Phylum Porifera

Class Calcarea:
- Marine, shallow waters; skeletons made of calcium carbonate spicules; various body organizations (asconoid, syconoid, leuconoid).
Class Hexactinellids:
- Deep-sea dwellers; characterized by six-rayed siliceous spicules; body shapes are cylindrical with a sycon or leucon canal system.
Class Desmospongiae:
- Found in marine or freshwater; asymmetrical bodies with leuconoid canal systems; skeletons include spongin fibers and siliceous spicules.

Notable Examples of Porifera

Sycon: Solitary/colonial sponges in shallow waters; cylindrical with numerous pores; reproduce sexually and asexually.
Hylonema: Glass rope sponges; round or oval shape with twisted root tufts.
Cliona: Boring sponges that inhabit calcareous structures; exhibit a leuconoid canal system.
Euplectella: Known as Venus flower basket; deep-water species with a unique skeletal network.
Spongilla: Common in freshwater habitats; possess a rhagon-type canal system; reproduce both sexually and asexually.

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Description

This quiz focuses on the characteristics of Phylum Porifera, which includes sponges, the simplest forms of invertebrates. It delves into their lack of tissue-level organization and unique biological features. Test your understanding and knowledge of these fascinating organisms.