Lecture 5

Question 1

What is the scientific phyla of sponges

Answer 1

Porifera

Question 2

What are sponges and example of

Answer 2

Metazoa

Question 3

What theory is used to explain the origin of metazoa

Answer 3

Colonial theory

Question 4

What is the colonial theory

Answer 4

Speocialisation within the colony - develop specific roles so depend on each other

Question 5

Evidence for colonial theory

Answer 5

1. Flagellated cells found in metazoa - sperm
2. Many flagellates form colonies
3. Molecular evidence - developmental genes expressed in some animals including sponges

Question 6

What is a likely ancestor

Answer 6

Choanoflagellates

Question 7

What is the structure of the phylum Porifera

Answer 7

Simple structure (no tissues or organs - cellular level of organisation)

Question 8

Where are they found

Answer 8

Oceans and freshwater

Question 9

How old are the sponges

Answer 9

Ancient

Question 10

Are they motile or sessile

Answer 10

Sessile - move about 4mm a day

Question 11

They have 2 forms depending on where they are found - describe

Answer 11

1. Very big = deep sea (slow movement of water)
2. Smaller = lots of wave action - flat and encrusting
   Filter feeders so need large SA to draw water in and out

Question 12

Describe the structure of the sponge (7 ish points)

Answer 12

1. Water drawn in through ostium and out through osculum
2. Choanocyte cells line spongocoel and waft water through sponge using flagella
3. Water gets trapped in collar of cells and engulfed and processed inside the cells
4. Some can close osculum in response to stimuli
5. Amoebocytes responsible for digestion and secrete totipotent spicules
6. Spicules create shape and structure and protect (like skeleton)
7. Made of calcium carbonate, silicates or sponge

Question 13

Describe structure of glass sponges

Answer 13

75% syncytial - no cell boundaries
Spicules formed of silicates - rigid structure
Electrical impulses transmitted through sheet of cells - changed beat of choanocyte flagella
Shrimps live inside them

Question 14

Sponges

Answer 14

Filter feeders
Some carnivorous - harp sponge
-> Spicules modified to trap prey
Amoebocytes engulf prey
Help coral reefs thrive - play important role in recycling nutrients in coral reef
Sponges shed cells - fall to bottom and eaten by other animals - transfer of nutrients

Question 15

Sponges are size limited - what can they do to increase SA

Answer 15

Infolding of choanocyte layer and flagellated chambers in spongocoel -> water canals

Question 16

Explain asexual reproduction in sponges

Answer 16

Budding or gemmules (amoebocytes middle layer surrounded by spicules, hole in middle called micropile) - gemmules = resting stage, when conditions better amoebocytes climb out and form new sponge

Question 17

Explain sexual reproduction in sponges

Answer 17

Most hermaphrodite but cross fertilisation
Gametes produced by amoebocytes
Sperm expelled via osculum and engulfed by choanocytes and transferred to egg
Larvae (flagellated) retained until blastula stage

Question 18

What biochemical agents associated with sponges

Answer 18

Some sponges produce biotoxins - warning colouration (protect from predators)
Some chemicals = antibacterial - prevents bacteria growing on them

Question 19

Eumetazoa are divided into what 2 branches (symmetry)

Answer 19

1. Radiata - radial symmetry (sessile)

2. Bilateria- bilateral (active)