Lecture 21 Porifera and Cnidaria

Question 1

what are invertebrates?

Answer 1

animals lacking a backbone

- account for 95-97% of known animals species

Question 2

what are the basal animals?

Answer 2

porifera “Parazoa”

Question 3

what are characters of Parazoans (4)

Answer 3

• lack true tissues
• almost all belong to phylum Porifera
• much like colonial protists
• retain a deal of autonomy (single cells can reassemble)

Question 4

what theory did sponges help develop?

Answer 4

• cell-cell recognition theory

Question 5

what are characteristics of the Phylum Porifera?

Answer 5

• lack true tissues
• except for larval stage, are sessile
• model organisms: have earliest hints of features that are present in higher taxa

Question 6

what is the sponge morphology? (4)

Answer 6

• no obvious tissues or organs - partially differentiated
• structural support comes from spicules
• some havetough collagen-protein network for support - spongin
• made of four simple and independent cells

Question 7

what are spicules?

Answer 7

• tiny hard needles or rods made of CaCO3 or Silica

Question 8

what are the four simple and independent cells of sponges?

Answer 8

1. collar cells which line the interior of the sponge
2. epidermal cells which form the skin on the outside of the sponge
3. choanocytes which generate H2O current through sponge and ingest suspended food; bring O2 and nutrients to sponge while also removing waste and CO2
4. Amoebocytes found in mesohyl and play roles in digestion (nutrient transport) and structure (form spicules)

Question 9

what is the mesohyl?

Answer 9

gelatinous matrix between epidermis and choanocyte layer

• contains amebocytes and skeletal elements
• acellular
• resembles type of connective tissue but it is NOT tissue bc acellular

Question 10

how do sponges eat

Answer 10

suspension feeding

Question 11

how does suspension feeding work?

Answer 11

• water is drawn through pores called OSITA into a cavity called a spongoceol and out through an opening called an osculum
• food particles are trapped in a mucus covered microvilli
• engulfed by phagocytosis and digested or transferred to amoebocytes
• amoebocytes carry food and nutrients to other cells or use it for energy to make spicules or other structural materials

Question 12

what kind of reproduction do sponges have?

Answer 12

hermaphroditic – simultaneous or sequential

Question 13

since sponges don’t have testes or ovaries, where do eggs and sperm arise from?

Answer 13

• eggs arise from modified amoebocytes

- sperm arises from modified choanocytes

Question 14

what kind of fertilization do sponges exhibit?

Answer 14

• external - some

- internal - most, eggs are retained in mesohyl, the zygote is retained until it develops into ciliated larva

Question 15

if a sponge loses parts what can it do?

Answer 15

regenerate

- dissociated cells settle, migrate and form active aggregates – form larger aggregates

Question 16

what is the importance and ecology of sponges?

Answer 16

• suspension feeding cleans water
• symbiotic mutualisms with single celled algae (limited to photic zone)
• many live inside sponges

Question 17

what are the two phyla in radiata?

what are characteristics of these two phyla?

Answer 17

• cnidaria and ctenophora
• simple body plan
• eumetazoa: true differentiated tissues
• diploblastic
• organs
• most are radially symmetrical

Question 18

what is the cnidarian body plan?

Answer 18

• diploblastic, radial
• sac with a central digestive compartment called the gastrovascular cavity
• e

Question 19

what is the cnidarian body plan?

Answer 19

• diploblastic, radial
• sac with a central digestive compartment called the gastrovascular cavity
• epidermis
• mesoglea: middle jelly acellular matrix in between
• gastrodermis: endoderm lines gastrovascular cavity
• two forms – polyp sessile form; medusa motile form

Question 20

how does the medusa move?

Answer 20

hydrostatic skeleton

Question 21

how do cnidarians obtain energy?

Answer 21

they are carnivorous so they use tentacles to catch prey

ALL ARE PREDATORY

Question 22

what are cnidarian tentacles armed with?

Answer 22

cnidocytes

• unique cells that function in defense and capture prey
• contain complex endocellular structure, most common is the NEMATOCYST

Question 23

what are nematocysts?

Answer 23

specialized organelles with cnidocytes which eject stinging thread, touch sensitive

Question 24

what are the four classes of cnidaria? which three do we focus on?

Answer 24

• hydrozoa
• scyphozoa
• cubozoa
• anthozoa

HSA

Question 25

what is the class hydrozoa?

Answer 25

• alternates between polyp and medusa form
• ex: hydra: exists only in polyp form and reproduces asexually by budding
• polyp is sessile and often colonial – reproduces via budding
• medusa bud off asexually but reproduces sexually – larvae settles to form polyp

Question 26

what is class scyphozoa?

Answer 26

• jellies (medusae) are the prevalent form of the life cycle
• use hydrostatic skeleton to navigate through contraction-pulsations of the bell-like body
• mostly water
• many bioluminescent

Question 27

what is class anthozoa?

Answer 27

• corals and sea anenomies, occur only as polyps
• corals often form symbioses with algae and secrete a hard external skeleton, limited to photic zone
• anenomies can live as single individuals, corals are often colonial