lab 9: porifera, cnidaria, platyhelminthes, mollusca

Question 1

porifera: sponges (background info)

Answer 1

-sister group to all other animals
-most body symmetry: asymmetrical
-many have provided structural support by spicules (kind of skeleton), stiff spikes of silica or calcium carbonate secreted by ameobocytes
-adults are sessile but larvae are motile

Question 2

porifera: sponges

Answer 2

-filter feeding heterotrophs
-central cavity (spongocoel) lined by flagellated cells (choanocytes) flagella draw water through pores into spongocoel through ostium cells, intracellular digestion, filtered water exits through osculum
-most are asexual but some are sexual
-asexual: budding or release of stress-resistant aggregates of amebocytes
-sexual: amebocytes / choanocytes differentiate into gametes; sperm release into water, eggs retained in the mesenchyme, sperm are captured by amebocytes / choanocytes. then embryo expelled from the sponge (many hermaphrodites)

Question 3

cnidaria: jellyfish, corals, anemones, hydroids

Answer 3

-majority are marine animals
-radially symmetric
-repetitive body dreads arranged in a circle around central point; sensory organs meet environment all directions
-2 layers: ectoderms (outer) & endodermis (inner) that sandwich a gelatinous layer called mesoglea

Question 4

cnidaria: jellyfish, corals, anemones, hydroids (life cycle)

Answer 4

-life cycle: most have a life cycle including alternating polyp, larval (planula) & medusa forms (can also have only 1 or 2 stages)
-3 stages of life cycle exploit different food sources
-polyp (cylindrical w tentacles around mouth; attached to substrate; single or colonies)
-medusae (umbrella shaped, free floating, mouth points down, surrounded by hanging tentacles; move by jet propulsion caused by rhythmic contraction of the bell structure)
-larvae (look different from adults, live in different habitats, eat different food, sexually immature, & swim by means of cilia

Question 5

cnidaria: jellyfish, corals, anemones, hydroids (reproduction & feeding)

Answer 5

-reproduction: large sessile form (polyp) which reproduces asexually by budding, fission or fragmentation; or sexually
-a sexually reproducing, free floating stage (medusa); a larval stage
-feeding: marine carnivores; specialized stinging cells (cnidocytes) that contain small, barbed harpoon like structures (nematocysts) in tentacles & are used to capture prey; mouth; GVC (gastrovascular cavity); extracellular digestion in GVC; phagocytosis small particles in cells, waste goes out same way food goes in

Question 6

cnidarian class: hydrozoa

Answer 6

-polyp stages dominates life cycle but many also have medusae
-ectoderm & endoderm around GVC separated by mesoglea
-endoderm: secrete enzymes for extracellular digestion
-ectoderm: stinging.cnidocytes & muscular contractile cells

Question 7

cnidarian class: skyphozoa (sea jellies, jellyfish)

Answer 7

-gelatinous medusa dominates life cycle
-polyp: small larvae stage

Question 8

cnidarian class: anthozoa (anemones & corals)

Answer 8

-largest class of cnideria
-solitary / colonial polyps
-no medusa

Question 9

cnidarian class: cubozoa (box jelly)

Answer 9

-box-shaped medusa
-polyp stage inconspicuous, tentacles are found at each corner of the box, strong swimmers, voracious predators of fish in tropical & subtropical waters
-sting of some species can be fatal to humans

Question 10

summary of phylum cnidaria

Answer 10

-class anthozoa: preserved sea anemone (metridium)
-class skypozoa: preserved common, jellyfish (aurelia)
-class hydrozoa: physlia (man of water)

Question 11

chapter 37: phyla platyhelminths & mollusca

Answer 11

-platyhelminths: flatworms
-mollusca: mollusks (clams, snails, octopuses)

Question 12

phylum platyhelminths

Answer 12

-flatworms have a broad, flattened body shape with large surface area for gas exchange (makes them live in moist environments)
-acoelomates (mesoderm is solid mass of tissues with no internal cavity); simple sensory organs
-one opening: mouth & anus; simplest animals with bilateral symmetry
-divided into 3 subgroups:
1) turbellarians: free living flatworms
2) cestodes: endoparastic tapeworms
3) trematodes: endo- or ectoparastic flukes

Question 13

phylum platyhelminths class: turbellaria

Answer 13

-free living hunters or scavengers that live on the substrates of freshwater or marine environments; few are terrestrial
-reproduce asexually (splitting themselves in half) or sexually (mutual & simultaneous fertilization [hermaphroditic])

Question 14

phylum platyhelminths class: cestodes

Answer 14

-parasites are usually much smaller than their victims & often harvest nutrients w/o causing death
-endoparasites: live inside their hosts
-ectoparasites: live outside their hosts
-cestodes (tapeworms) are strictly parasitic & obtain nutrients from hosts by diffusion across their body wall, lack a mouth & digestion system, specialized vertebrate gut parasites, absorb nutrients from host (no mouth), reproduce sexually by cross fertilization/self fertilization, life cycle quite complex, several hosts, gravid (egg-carrying) ones exit body thru feces

Question 15

phylum platyhelminths class: trematoda

Answer 15

-flukes, parasites (endo & ecto), oval (few mm long), feed by gulping host tissues & fluids through a mouth, reproduce sexually (cross fertilization / self fertilization), their life cycles are quite complex, often with several hosts
-in humans, the blood fluke schistosoma mansonis responsible for schistosomiasis (several public health issues)

Question 16

phylum mollusca

Answer 16

-clams to squid; most mollusks live in marine environment, some terrestrial & freshwater forms, have gills or other respiratory structures located in body, minimizing water loss when moving on land
-coelmate: often reduced to small chamber surrounding the heart
-3 major components (some also have the 4th: heart)
1) foot: large muscle, base of animal, used for movement: crawl around surface
2) visceral mass: most internal organ (digestion, excretion, reproduction,