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Animal Diversity > Lecture 2 RH > Flashcards

Lecture 2 RH Flashcards

1
Q

What are some examples of cnidarians?

A

Hydroids

Corals

Sea anemones

Sea jellies

etc

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2
Q

How are tissues different in cnidarians compared to phylum porifera?

A

More differentiation and formation of true tissues

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3
Q

What are the key features of phylum cnidaria?

A

True tissues

Diploblastic (2 germ layers; endoderm and ectoderm)

2 organised adult layers of tissue the epidermis and the gastrodermis with mesoglea between them.

radial symmetry

Blind gut (no anus)

Hydrostatic skeleton

Simple muscular and nervous systems

Have cnidocytes which capture prey

Carnivorous

All are aquatic and mostly marine

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4
Q

Why are cnidarians said to have true tissues?

A

Cells overlay a basal lamina which is a sheet of collagen

Gap junctions

Presence of an epithelium

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5
Q

What is the mesoglea?

A

Jelly-like layer between gastrodermis and epidermis

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6
Q

What kind of symmetry do cnidarians have?

A

Radial symmetry

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7
Q

Do cnidarians have a gut?

A

Yes a blind gut (entry and exit are both from the same place)

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8
Q

Do cnidarians have a skeleton?

A

Yes a skeleton that relies on water pressure to be effective

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9
Q

Do cnidarians have a muscular and nervous system?

A

Yes, a simple nervous and muscular system

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10
Q

How do cnidarians feed?

A

They capture prey with their cnidocytes.

*This means they are carnivorous

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11
Q

What happens during cleavage?

A

Blastula is formed which is a hollow sphere of cells (blastocoele is the space inside)

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12
Q

What happens during gastrulation?

A

Pouching in of cells to form blastopore and gastrocoele.

Outer layer is ectoderm and inner layer is endoderm

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13
Q

What are the subclasses of Metazoa?

A

Parazoa (no true tissues)

Eumetazoa: Can be either diploblastic or triploblastic

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14
Q

What are the three types of cells that are important for cnidarians to be carnivorous?

A

Myoepithelial cells (epithelium that can contract)

Nerve cells (Nerve nets)

Cnidocytes (unique to this phylum)

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15
Q

What is the function of myoepithelial cells?

A

Locomotion

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16
Q

What kind of muscles can be found in the epidermis?

A

Longitudinal muscle filaments

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17
Q

What kind of muscles can be found in the gastrodermis?

A

Circular muscle filaments

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18
Q

How do cnidarians sense environmental stimuli and respond?

A

No central nervous system so they directly react to environmental stimuli

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19
Q

What is the function of cnidocytes?

A

Subdues prey via its nematocysts which injects toxin into its prey.

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20
Q

What does the nematocyst do and what stimulates its function?

A

Nematocyst

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21
Q

How do nematocysts fire in response to physical stimulation?

A

Cnidocil is sensitive to touch. When it is stimulated it penetrates the skin of its prey and injects poison into it.

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22
Q

What are the body forms that cnidarians occupy?

A

2 body forms which occupy different stages of a cnidarian’s life cycle:

Polyps

Medusa

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23
Q

How is the class of cnidarian determined?

A

The predominance of the medusa stage or polyp stage determines which class it belongs to.

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24
Q

What develops from the gastrula stage?

A

Gastrovascular cavity (blind cavity due to no anus)

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25
Q

Does the gastrovascular cavity exist within the tentacles?

A

Yes

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26
Q

What does medusa dominance indicate about its life cycle?

A

Generally Pelagic

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27
Q

What does polyp indicate about its life cycle?

A

Generally benthic

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28
Q

What are the asymmetric sides of cnidarians called?

A

Oral side

Aboral side

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29
Q

What is the symmetry of cnidarians?

A

radial

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30
Q

How does the hydrostatic skeleton keep the cnidarian functioning?

A

Mouth contains a sphincter which maintains a hydrostatic pressure within the cnidarian’s body

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31
Q

How does the hydrostatic muscle work?

A

Body consists of circular muscle around it and longitudinal muscle. When longitudinal muscle contracts body becomes shorter and fatter and vice versa when circular muscle contracts

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32
Q

How are longitudinal and circular muscles related?

A

They are antagonistic

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33
Q

How do cnidarians reproduce asexually?

A

Budding (Body develops and outpocket which develops into another organism)

Fission (Separation occurs in the middle creating 2 individuals in a similar way to bacteria)

34
Q

What does asexual reproduction often result in?

A

clonal aggregation (linked via gastrovascular cavity)

*Sea anemones do this

35
Q

What is a polymorphism in a colony?

A

Some individuals specialize in doing a certain function while other individuals perform another function

36
Q

What are some examples of specializations that the different individuals of a hydroid colony could perform are?

A

gastrozooid (contain tentacles and are important for feeding)

Gonozoid (responsible for reproduction)

37
Q

Are cnidarians mono or dio ecious?

A

Dioecious (forms larvae)

38
Q

What is the larva of a cnidarian called?

A

Planula larva (swimming gastrula)

39
Q

What are the classes of phylum cnidaria?

A

Hydrozoa (greatest variation in life cycles)

Scyphozoa

Cubozoa

Anthozoa

Staurozoa

40
Q

What are the distinguishing features of hydrozoa?

A

Nematocysts are only present in the epidermis, not the gastrodermis. (can’t sting within the body cavity)

Both polyp and medusa stages are important

41
Q

What is meant when hydrozoans are said to have greatest variations in life cycle?

A

Some hydrozoans have dominant medusa stages whereas others have dominant polyp stage.

42
Q

How do hydrozoans reproduce?

A

Polyp is found in colonies. Polyp buds off to form medusas that can reproduce sexually by releasing sperm and eggs to form planulas.

43
Q

What is the manubrium of a hydromedusa?

A

An extension of the mouth (the neck)

44
Q

What is the velum?

A

lip of tissue around the edge of a hydromedusa which is unique to it.

45
Q

What are the features of the siphonophore class of hydrozoans?

A

drifting colonies of polyps/medussae and show many polymorphisms.

46
Q

What are the structural components of the physalia (AKA portugese Man-O-War or Blue Bottle)?

A

Pneumatophore (a specialized polyp that serves as a float)

Gonozoids

Gastrozooids

Dactylozooids (They just sting)

47
Q

What are the features of the velella velella?

A

One central gastrozooid that does all the feeding

Gonozooids

Dactylozooids

48
Q

What is a unique feature of the physalia?

A

1 specialized polyp called the pneumatophore that functions as a float.

49
Q

What is a unique feature of velella velella (By the wind sailor)?

A

They have a sail which makes them float over the water with tentacles following under.

They have a specialized polyp for feeding.

50
Q

What do some siphonophores with specialized medusae use their medusae for? Name an example of this.

A

Specialized medusae propel the entire colony together while the polyps function to feed.

Erenna (also contain bioluminescent lures)

51
Q

What are features of hydrocorals?

A

Polyps are colonial

Secrete calcarous exoskeleton, very similar to true coral

Nematocyst of fire coral produce burning sensation

Extremely toxic

Most common in Australia (Yay?)

52
Q

What are features of Class Scyphozoa?

A

Medusae dominate the life cycle

Very large medussae (much larger than hydrozoan medussae)

Swim by jet propulsion

Sensory organs are called rhopalia allow them to orient themselves in response to stimuli

53
Q

Describe the scyphozoan life cycle:

A

1) Males and Females spawn sperm and eggs and they fertilize and form a planula.
2) Planula then grows into a scyphistoma polyp which undergoes asexual reproduction forming many copies of itself.
3) The resultant polyps stack on top of each other like cups and form what is called a strobilation.
4) Strobilation then turn upside down and forms a medusa and is called an ephyra which becomes an adult medusa.

54
Q

What are some structural features of scyphozoa?

A

Tentacles at the rim of the bell

Oral arm extensions of manubrium containing nematocysts

Much of the arm consists of mesoglea

gonad is contained within the bell (looks like a 4 leaf clover)

Rhopalia around the edge of the bell

55
Q

How does the rhopalium provide sensory information of direction and

A

Contains a hard ball of calcium carbonate called a statolith. And its hanging down and as the bell tips it swings from one side to another and there is cilia on both sides which controls which direction the hairs face allowing the scyphozoan to detect the location of the surface relative to current position.

56
Q

How do scyphozoans detect light?

A

Ocellus in rhopalium detects location of light

57
Q

How does jet propulsion work?

A

Longitudinal muscle contract making the jellyfish wider and then the circular muscles contract forcing water outwards and in turn creating thrust.

58
Q

What are the features of Class Cubozoa?

A

Medusa dominates life cycle

No strobiltion

Most toxic of all cnidarians

Contain eyes with a lens, cornea, and retina

59
Q

What does the cubozoan lifecycle look like?

A

1) Sexually reproduces to form a planula.
2) Planula grows up to form a larval polyp (B scyphistoma)
3) Budding may produce more polyps
4) metamorphosis occurs to form a medusa that swims freely

60
Q

What are features of anthozoans?

A

Sessile

No medusa stage at all

61
Q

What is the anthozoan life cycle like?

A

Polyp spawns sperm and eggs which fertilize into planula and then polyp again.

62
Q

What are some anatomical features of anthozoan polyps?

A

Sphincter runs around oral disk.

Pharynx leads to gastrovascular cavity

63
Q

How does a sea anemone that has expelled all its water fill up with water again?

A

It draws water into gastrovascular cavity via the cilia to inflate itself again.

64
Q

What are the septa within anthozoans for?

A

Flaps of tissue form complete and incomplete septa around the pharynx. The septa are open at the bottom of the pharynx at the gastrovascular cavity which allows a larger surface area.

These septa contain lots of nematocysts to sting inside.

65
Q

What are acrorhagi?

A

Inflated individuals with lots of nematocysts found between colonies so that they can sting each other to destroy the competition. Ridge develops between them called “no man’s land”

66
Q

What are stony corals?

A

Hard corals. scleractinian corals have a surrounding external skeleton of CaCO3 secreted from the epidermis of the base.

Polyp can retract into the base of CaCO3 during the day and then filter feed at night.

67
Q

What are the features of subclass zoantharia?

A

subclass Zoantharia (hexocorallia) tentacles are always in multiples of 6.

Sea anemones and some corals are in this group.

Acrorhagi are typical of these groups (agressive tentacles)

Stony corals also belong to this group

68
Q

What are the subclasses of anthozoans?

A

Subclass zoantharia (6 tentacles per set)

Subclass Octocorallia (8 tentacles with pinnules and an internal skeleton)

69
Q

What are pinnules?

A

a secondary division of a pinnate leaf, especially of a fern.

70
Q

What are features of subclass octocorallia?

A

8 tentacles per set

internal skeleton (collagen or CaCO3 surrounding an axial rod)

pinnules

contain spicules

One specialized inflated polyp supports the colony

71
Q

Why are cnidarians bio-luminescent?

A

Many cnidarians bioluminesce in several different patterns due to symbiotic algae. (Sea pens luminesce when touched)

72
Q

What are hermatypic corals?

A

Reef-building corals

73
Q

What are some examples of hermatypic corals?

A

Hexacorals and Octocorals

74
Q

How do hermatypic corals typically reproduce?

A

spawning of hermatypic corals are synchronized and gametes are released at the same time

75
Q

What are zooxanthellaes?

A

endosymbiotic dinoflagellates

76
Q

Where can zooxanthellaes be found?

A

All hermatypic corals

77
Q

What do zooxanthellaes do?

A

Intracellular symbionts in gastrodermis.

Release photosynthate to coral; coral waste provides nutrients to the algae.

78
Q

What is coral bleaching?

A

Happens when corals lose symbiotic algae due to environmental stress. This causes algae to migrate through gut wall and to leave through mouth.

79
Q

What causes coral bleaching?

A

Environmental stressors such as:

Rising sea water temperature

Increased UV radiation

Elevated CO2

Reduced salinity

Pollution

Diseases

Result is loss of zooxanthellae. However symbionts can be replaced with other algae.

80
Q

What is class staurozoa?

A

Newly recognized class

Life cycle similar to anthozoans

Solitary polyp with 8 tentacles each with a cluster of smaller tentacles at hip

81
Q

What are cteophores?

A

Small phylum very similar to cnidarians but they don’t have cnidocytes.

No contractile bell but instead use cilia.

Use colloblasts to immobilise prey

Animal Diversity (22 decks)

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