Lecture 16

Question 1

parazoa

Answer 1

considered to be basal to all other animals, lack true tissues, not monophyletic, almost all belong to Phylum Porifera, rest are Phylum Placozoa

Question 2

Phylum Placozoa

Answer 2

until recently, only one named species, Trichoplax adhaerens

Question 3

Trichoplax adhaerens

Answer 3

shallow marine water, pancake two cell layers thick and a few mm wide, top and bottom but asymmetrical in outline, can change shape, moves via cilia, externally digests food

Question 4

cell-cell recognition

Answer 4

if cells from different sponges mixed together, they sort themselves properly

Question 5

Phylum Porifera (8800)

Answer 5

sponges, model organisms in searches for earliest hints of features present in more highly derived taxa, most marine some freshwater, except for larval stage, are sessile

Question 6

sessile

Answer 6

attached to one spot, do not move

Question 7

5 characteristics of sponge morphology

Answer 7

1. no obvious tissues or organs
2. spicules or spongin
3. amoebocytes and choanocytes
4. numerous openings lead to central spongocoel
5. mesohyl

Question 8

spicules

Answer 8

structural support in sponges, tiny hard needles or rods, calcareous or silicious

Question 9

2 types of support in sponges

Answer 9

1. spicules

2. spongin

Question 10

spongin

Answer 10

structural support in other sponges, tough collagen protein network for support

Question 11

2 types of cells in sponges

Answer 11

1. amoebocytes

2. choanocytes

Question 12

amoebocytes

Answer 12

look like amoebae, form outer surface of sponge, secrete spicules, roam through the insides carrying food to other cells

Question 13

choanocytes

Answer 13

look like single choanoflagellate protists (central flagellum surrounded by microvillar collar), line inside of sponge

Question 14

osculum

Answer 14

large opening in sponge, each has one or more

Question 15

mesohyl

Answer 15

gelatinous acellular layer between the outer ‘skin’ and the choanocyte layer, not a tissue, contains collagen

Question 16

sponge feeding

Answer 16

1. majority are suspension feeders

Question 17

suspension feeding

Answer 17

a subset of filter-feeding where water and suspended materials taken from water column

Question 18

suspension feeding in sponges

Answer 18

1. beating of choanocyte flagella draws water in through ostia
2. through microvillar collar, where food particles are
   removed
3. out through osculum

Question 19

sponge feeding

Answer 19

1. food particles phagocytosed by base of choanocyte cell
2. amoebocytes nudge up and take up food passed on by choanocyte
3. amoebocytes then carry food to other cells, or use energy to make spicules
   or other structural materials

Question 20

sponge reproduction

Answer 20

1. separate sexes, simulataneous hermaphrodites, or sequential hermaphrodites
2. eggs from modified amoebocytes (retained in mesohyl), sperm from modified choanocytes (sent out through oscula)
3. sperm sucked in through ostia of neighbouring sponge of same species
4. zygote retained until it develops into a ciliated larva

Question 21

simultaneous hermaphrodite

Answer 21

male and female at the same time

Question 22

sequential hermaphrodite

Answer 22

first one sex, then change to be the other

Question 23

sponge larva

Answer 23

1. swims out and finds a good place to settle
2. lands on substrate, either turns inside out or external
   ciliated cells migrate inside
3. ciliated cells drop or reabsorb cilia, then
   grow flagella to become choanocytes

Question 24

sponge ecology

Answer 24

1. filter feeding cleans water
2. organisms live inside sponges
3. mutualisms with single-celled algae within photic zone
4. few predatory
5. few predators due to toxic chemicals

Question 25

photic zone

Answer 25

zone in which light can penetrate

Question 26

sponge economic uses

Answer 26

1. bioprospecting for pharmaceuticals (endangered) | 2. spongin networks for bath and art sponges

Question 27

glass sponges

Answer 27

delicate, long-lived, restricted to deep water, can form reefs, populations in BC threatened by shipping, in the Strait of Georgia protected through closure of bottom-fishing

Question 28

2 phyla in "Radiata" (part of Eumetazoa)

Answer 28

1. Cnidaria | 2. Ctenophora

Question 29

3 characteristics of "Radiata"

Answer 29

1. true differentiated tissues (diploblastic) 2. organs 3. frequently radially symmetrical

Question 30

organs

Answer 30

collections of tissues specialized for different tasks

Question 31

Cnidaria (13 000)

Answer 31

almost all marine few freshwater, includes jellyfish, hydras, sea anemones, and corals

Question 32

3 parts of cnidarian body

Answer 32

1. gastrodermis 2. epidermis 3. mesogloea

Question 33

gastrodermis

Answer 33

endoderm, lines body cavity (gastrovascular cavity)

Question 34

epidermis

Answer 34

ectoderm

Question 35

mesogloea

Answer 35

‘middle jelly’, acellular matrix in between gastrodermis and epidermis

Question 36

cnidaria morphology

Answer 36

1. mouth but no anus 2. two body forms 3. numerous tentacles for prey capture 4. cnidocytes

Question 37

2 cnidarian body forms

Answer 37

1. polyp | 2. medusa

Question 38

polyp

Answer 38

oral end upwards, and aboral end attached to a substrate

Question 39

medusa

Answer 39

oral end downwards and aboral up, moves freely through water

Question 40

cnidocytes

Answer 40

cnidarian synapomorphy, contains very complex endocellular structure (cnida), used for defense and prey capture, when trigger spine touched, cnida shoots out (sticky, stabbing, or poison-tipped)

Question 41

nematocyst

Answer 41

most common cnida

Question 42

4 main classes of cnidaria

Answer 42

1. Class Hydrozoa (most species) 2. Class Scyphozoa 3. Class Cubozoa 4. Class Anthozoa

Question 43

Class Hydrozoa

Answer 43

hydras, both polyp and medusa in life cycle

Question 44

freshwater hydras

Answer 44

hydrozoans, lack medusa stage, "alternation of generations" alternation of sexual with asexual

Question 45

Hydrozoan polyp

Answer 45

sessile, often colonial, reproduces asexually by budding

Question 46

Hydrozoan medusa

Answer 46

budded off asexually, reproduces sexually, larva settles and transforms to polyp

Question 47

Class Scyphozoa

Answer 47

jellyfish, almost all of lifecycle medusa, thich mesogloea, swim by contracting network of fibres around circumference of bell

Question 48

Class Cubozoa

Answer 48

box jellies, medusa dominant, complex light- and movement detecting eyes along perimeter of bell, extremely toxic nematocysts

Question 49

Class Anthozoa

Answer 49

corals and anemones, entirely polyps, live single (anemones) or colonial (coral), corals that produce calcium-carbonate skeletons most important reef-building organisms

Question 50

Cnidaria ecology

Answer 50

1. all predatory (zooplankton, larval fish) 2. symbiosis with zooxanthellae 3. nematocyst toxins dangerous to humans 4. reefs

Question 51

zooxanthellae

Answer 51

symbiotic algae that produce carbohydrates used by the | cnidarians, need for light is why many corals limited to photic zone

Question 52

coral reefs

Answer 52

constructed by corals, provide room and board for tropical marine species, important for human economy (tourism, fishing, aquarium trade), runoff from farming and global warming threats to coral reefs

Question 53

coral bleaching

Answer 53

due to loss of zooxanthellae, first sign of ecological meltdown

Question 54

Phylum Ctenophora (100)

Answer 54

comb jellies, sea gooseberries, all marine, move by beating thousands of cilia arranged in comblike bands, like Porifera appear to lack Hox genes

Question 55

Ctenophora morphology

Answer 55

1. largest organisms to move entirely by ciliary action 2. two tissue layers and a layer of mesogloea 3. mouth but no anus

Question 56

Ctenophora feeding

Answer 56

1. two long tentacles covered with colloblasts used for prey capture 2. prey bump into tentacles, colloblasts explode 3. tentacle with adhering prey wiped across mouth

Question 57

colloblasts

Answer 57

cells filled with sticky substance