BIO2231 - Sponges

Question 1

Definition

Metazoa

Answer 1

• Multicellularity with differentiation of cells
• Blastula stage in development

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Question 2

Definition

Synapomorphies

Answer 2

Characters shared within a group

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Question 3

Definition

Autapomorphies

Answer 3

Characters that define different groups

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Question 4

Key points

Metazoa?

2 points.

Answer 4

Animals

• Multicellular
• Blastula stage in development

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Question 5

Key points

Porifera

3 points.

Answer 5

• Cell aggregates
• No germ layers
• No true tissues, organs or gut

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Question 6

Key points

Eumetazoa

4 points.

Answer 6

• True tissues
• Gastrula stage
• Germ layers
• Digestive cavity (gut)

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Question 7

Cnidaria

3 points.

Answer 7

• Two germ layers (diploblastic)
• Radial symmetry
• No anus

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Question 8

What is diploblastic?

Answer 8

Having a body derived from only two embryonic cell layers

(ectoderm and endoderm, but no mesoderm), as in sponges and coelenterates.

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Question 9

What is the advantages of Multicellularity?

2 points.

Answer 9

• Size
• Complexity

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Question 10

Multicellularity

Why not become one big cell?

Answer 10

• SA/V ratio
• structural integrity of cell membrane and cell division machinery

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Question 11

What is the impact of Increasing complexity?

2 points.

Answer 11

Compartmentalisation

• Specialised cells for certain tasks = greater efficiency
• BUT loss of independence for cells = greater vulnerability to injury

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Question 12

What are the advantages of increased body size?

6 points.

Answer 12

• Efficiencies of scale (bigger is better)
• Buffers against environmental fluctuations
• Easier to retain heat for metabolism
• Development of specialised body compartments
• Better in attack (as predators)
• Better for defence against predators

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Question 13

What are the Consequences of body size?

3 points.

Answer 13

Changes in surface to volume ratios limit exchange of oxygen and nutrients

Necessitates specific body shapes:

• Sponge like
• Flat sheets (bell/cup shape)
• Tubes

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Question 14

How can an animal be a shape other than flat/long/spongy?

4 points.

Answer 14

Need to develop delivery systems

Diffusion no longer adequate → evolution of:

• fluid filled body cavities
• circulatory systems
• respiratory systems
• excretory systems

Note: Has Metabolic costs (e.g. pumping)

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Question 15

What will you not find in sponges?

3 points.

Answer 15

• Gastrula stage with two germ layers
• A digestive cavity (gut)
• True tissues

General rule is above are absent in sponges … but that could be wrong

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Question 16

Describe

Phylum Porifera

6 points.

Answer 16

• Cell aggregates with different cell types
• Embedded in protein matrix (mesohyl)
• Skeletal fibres (collagen, spongin) and spicules
• Gastrulation absent or unusual
  • No mouth
  • No digestive cavity

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Question 17

What is ECM?

Answer 17

Extra Cellular Matrix
(mesohyl)

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Question 18

What are the characteristics of

The Sponges?

6 points.

Answer 18

• Aquatic only (mainly marine)
• Free swimming larvae
• Sessile adults
• Filter feeders (intracellular digestion)
• Ancient (>700 my)
• Diverse (5000 spp.)

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Question 19

What is the form of Phylum Porifera ?

4 points.

Answer 19

• Structurally arranged to maximise surface area
  • Cells are arranged around a canal system
  • Supported by mesohyl with spicules Hickman
• Skeleton composed of coarse spongin fibres (modified collagen) and/or needle like spicules of calcium carbonate or silicon dioxide

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Question 20

What is the body wall of Phylum Porifera?

3 points.

Answer 20

Body wall composed of

• outer layer = pinacoderm
• inner flagellated layer = choanoderm
• connective layer = mesohyl

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Question 21

What are the cell types of Phylum Porifera?

9 points.

Answer 21

• Pinacoderm
  • Pinacocytes = body wall cells
  • Porocytes = pore lining cells
• Choanoderm
  • Choanocytes = flagellated cells that move water and do feeding
• Mesohyl
  • Archeocytes = can differentiate into other cell types
  • Collencytes spongocytes , sclerocytes = secretory cells that produce the matrix
  • Oocytes and spermatocytes = reproductive cells

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Question 22

How do Phylum Porifera feed?

5 points.

Answer 22

• Beating flagellum on choanocytes creates current

    * sucks water through pores in body wall
    * expels from atrium through opening, osculum

• Water current food, gas exchange and waste removal
• Filter feeders fine, suspended organic material microvilli of choanocyte trap small particles

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Question 23

Phylum Porifera

What is the Aquiferous System Morphology?

3 points.

Answer 23

• Asconoid = vase/pipe shaped
• Syconoid = vase with folded walls
• Leuconoid = many chambers

Majority of sponges are Leuconoid

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Question 24

Phylum Porifera

Doe morphology indicate Clade?

2 points.

Answer 24

Grade ≠ Clade

• All classes can show leuconoid grade of construction
• Calcarea shows all grades of construction

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Question 25

## Footnote Phylum Porifera **How do Phylum Porifera reproduce?** 8 points.

Answer 25

Asexual * Budding Sexual * Hermaphroditic * No gonads * Sperm carried into nearby sponges and fertilise eggs * Usually viviparous * Free swimming larva with flagellated cells _{BIO2231 1ay}

Question 26

## Footnote Phylum Porifera **How are Phylum Porifera classified?** 4 points.

Answer 26

By body wall and spicules * Class Calcarea * Calcareous spicules , Pinacoderm present * Class Hexactinellida - glass sponges * Siliceaous spicules , Syncytial body wall * Class Demospongiae * Siliceous spicules with axial filament, Pinacoderm present leuconoid sponges, wide variety of shapes * Class Homoscleromorpha * Siliceous spicules without axial filament, pinacoderm with true basement membrane (incipient tissue) 95% of sponges are Demonsponges _{BIO2231 1az}

Question 27

**Unique Demosponges?** 5 points.

Answer 27

**_Carnivorous Deep Sea Demosponges_** * Discovered in mid 1990s * Several species * Hooklike spicules entrap crustacean and other invertebrate prey * No longer meet the sponge definition of: "sedentary, filter feeding metazoan, which utilizes a single layer of flagellated cells (choanocytes) to pump a unidirectional water current through its body." * Appears to engage in extracellular digestion (as well as the intracellular typical of other sponges) _{BIO2231 1ba}

Question 28

**What are other things you probably never knew about sponges?** 6 points.

Answer 28

* Sponges are important habitats 1 sponge was found with 16000 species in and on it * Extremely efficient biofilters a sponge the size of a 1 litre milk carton could filter a swimming pool in a day * The largest species can reach 5x5m * There are a number of freshwater species * Some sponges can move very slowly creeping * One of the first drugs for treating cancer, cytosine arabinoside, was isolated from a sponge _{BIO2231 1bb}