phylum cnidaria

Question 1

habitats and lifestyle: cnidaria

Answer 1

• marine and freshwater
• benthic and pelagic
• solitary and colonial
• two structures/modes: polyp and medusa
• ALL predators (corals photosynthetic and predators)

Question 2

two body forms of cnidaria

Answer 2

polyp and medusa

polyp = tentacles up
medusa = tentacles down

Question 3

example of polyp and solitary

Answer 3

anemone

Question 4

example of polyp and colonial

Answer 4

coral

Question 5

example of medusa and solitary

Answer 5

jellyfish

Question 6

example of medusa and colonial

Answer 6

portuguese man of war

Question 7

outside layer of anemone

Answer 7

epidermis

Question 8

layer inside the epidermis (anemone)

Answer 8

gastrodermis

Question 9

what is between epidermis and gastrodermis and what is it composed of ?

Answer 9

mesoglea - comprised of collagen and extracellular matrix

Question 10

cnidaria: major characteristics

Answer 10

1. true internal gut
2. diploblastic - two embryonic cell layers (ectoderm and endoderm - no mesoderm)
3. nerve net, w nerve plexuses but NO central brain
4. have cnidocytes - which have nematocysts (stinging cells)
5. some have alternation of generations between polyp and medusa forms (asexual and sexual forms)
6. bilateral symmetry

Question 11

how do cnidocytes work?

Answer 11

cnidocytes have nematocysts which are stinging cells

they are stored inside out and triggered mechanically by a cnidocil. when triggered, will release thread and barb to increase surface area of stinging

the increased surface area helps to increase the amount of transmission of toxins

Question 12

alternation of generations in cnidaria

Answer 12

sexual and asexual phase, physically separated - like 2 different animals but not

adult medusa stage can reproduce sexually. these adult male and female produce egg and sperm which are halpoid. when fertilization happens, it is back to diploid

Question 13

cnidarian cell types

Answer 13

epitheliomuscle cells

nerve cells

cnidocytes

gland cells

interstitial cells

Question 14

cnidarian life cycle - hydrozoans

Answer 14

polyps reproduce asexually by budding off medusae, and then medusae give rise to polyps by sexual reproduction

when polyp strobilates — segmenting its body to reproduce — it releases tiny ephyra into the water which grow into adult jellyfish

Question 15

what is considered a coelom ?

Answer 15

defined by being enclosed in mesoderm — therefore cnidarians cannot have a TRUE coelom bc dont have mesoderm

Question 16

are coelentrata coelomates ?

Answer 16

no, dont hv enclosed coelom by mesoderm

Question 17

acoelomate, pseudocoelomate, eucoelomate

Answer 17

eucoelomate is the same as coelomate - triploblastic animal w coelom

Question 18

origins of cnidaria: cnidaria-first vs comb-jelly first

Answer 18

cnidaria first: based on characteristic features and least number of evolutionary events (including losses of characteristics)

comb jelly first: comb jellies have more genes, they hv neurotransmitters, internal gut

Question 19

overview of cnidaria phylogeny:

Answer 19

classical view = porifera first —> phylogeny still under development

Question 20

what is the main difference in polyp and medusa stages ?

Answer 20

reproduction:

polyp = asexual
medusa = sexual (produce gametes)

Question 21

hydrozoan features:

Answer 21

complex life cycles

presence of velum

gametes produced in epidermis vs endodermal tissue

Question 22

hydrozoa morphological feature:

Answer 22

polymorphism:

colonial organisms that are genetically identical but perform different functions

Question 23

polymorphic hydrozoan colony components and an organism example

Answer 23

gonozooid - reproductive polyp

gastrozooid - feeding polyp

dactylozoids - defense polyp

medusa - sexual stage

example : siphonophora - portuguese man of war

Question 24

what are the main differences between hydrozoan and schyphozoan life cycle?

Answer 24

hydrozoan - can have polymorphic colony of diff polyp forms

schyphozoan - has strobila — releases ephyra (grows into medusa)

Question 25

how does environmental change affect medusazoans vs anthozoans

Answer 25

1. eutrophication
   — medusazoan larva takes up all the nutrients, more larva produced
   — anthozoans are overrun by algal growth on coral
2. global warming
   — medusazoans supported by warmer temp
   — anthozoans : warming breaks down symbionts, coral bleaching
3. overfishing
   — medusazoans: overfishing reduces fish eating larvae