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3A Zoology - Invertebrates > Advances and Functional Aspects of Platyhelminthes > Flashcards

Advances and Functional Aspects of Platyhelminthes Flashcards

1
Q

What are platyhelminthes?

A

Flatworms

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2
Q

What is their basic morphology now known to be due to?

A

Secondary simplification

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3
Q

What are the two forms of platyhelminthes (life strategy)?

A

Free-living and parasitic

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4
Q

What animals were thought to be the first of the bilateria?

A

Free-living platyhelminthes

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5
Q

What is the body plan of platyhelminthes?

A

Dorso-ventrally flattened and all remaining groups are bilaterally symmetrical

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6
Q

What two factors allowed platyhelminthes to become the first hunters?

A

Cephalisation and differentiation

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7
Q

What is the advantage of cephalisation and differentiation?

A

Anterior end meets environment first, meaning able to move in a forward direction and hunt for food and mates

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8
Q

What does differentiation mean?

A

Have an upper surface (dorsal) and lower surface (ventral). Ventral surface becomes the locomotory surface and allows for movement.

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9
Q

What are the 4 classes of platyhelminthes generally in use?

A

Turbellaria, monogenea, cestoda and trematoda

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10
Q

Which platyhelminthes are free living and which are parasitic?

A

Turbellaria - free living
Monogenea, cestoda, trematoda - parasitic

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11
Q

How do Turbellaria move?

A

Smaller turbellaria generally glide over secreted mucous using ciliary action.
Larger species are too heavy and use muscular contraction of longitudinal and circular muscles. Longitudinal muscles contract and extend the body whereas circular cause it to shorten and widen. The use of both in succession allow turbellaria to swim or creep, raising and lowering their ventral surface.

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12
Q

What are the excretory organs of platyhelminthes known as?

A

Flame cells

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13
Q

How is ammonia diffused out of the body of platyhelminthes?

A

Osmoregulation

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14
Q

What allows platyhelminthes to make decisions?

A

Concentration of nerve cells at the anterior end, forming the cerebral ganglia (brain)

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15
Q

What are the advantages of having a cerebral ganglia (brain) in platyhelminthes?

A

Allows them to make decisions of where the body moves, control how much slime they are putting down, move away from predators and towards prey

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16
Q

What are the 4 sensory organs of platyhelminthes?

A

Photoreceptors, statocysts, mechanoreceptors and chemoreceptors

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17
Q

What do the photoreceptors of platyhelminthes do?

A

Sense changes in light

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17
Q

What do the statocysts of platyhelminthes do? (only found in a few groups)

A

Aid balance

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18
Q

What do the mechanoreceptors of platyhelminthes do?

A

Sense touch and vibration to aid in predator avoidance, prey detection and navigation

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19
Q

What do the chemoreceptors of platyhelminthes do?

A

Detect chemical stimuli to locate food sources, identify potential mates and navigate towards suitable habitats

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20
Q

What are the potential effects of parasites on hosts?

A

Nutrient deprivation, micropredation, behavioural manipulations, parasitic castration, parasitoidism

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21
Q

What is micropredation of parasites on hosts?

A

Blood feeding (hematophagy) parasites

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22
Q

What is parasitoidism?

A

Parasitoids are organisms that eventually kill their host

23
Q

What are monogea?

A

Ectoparasites on skin, gills or fins of fish

24
Q

What classes does the group Neodermata include?

A

Trematoda, Monogenea and Cestoda

25
Q

What is the smallest of the Neodermata?

A

Monogenea

26
Q

What is the life cycle of monogenea?

A

Direct life cycle with free living larvae - no intermediate hosts

27
Q

What do organisms of the class Monogenea use to attach to their host?

A

Haptor - structure containing hooks, clamps, suckers located at the posterior end

28
Q

What are Trematoda?

A

Endoparasites, often called Flukes

29
Q

How many hosts do organisms of the class Trematoda have in a full life-cycle?

A

At least 2

30
Q

What are the 2 subclasses of Trematoda?

A

Digenea and Aspidogastrea

31
Q

What parasite within the class Trematoda causes Schistosomiasis? Describe its life cycle.

A

Schistosoma mansoni.
Egg -> Miracidium -> Enters mollusc (usually snail) and becomes sporocyst -> Cercaria -> Enters humans or livestock and becomes an adult -> lays eggs in definitive host

32
Q

What parasite within the class Trematoda causes Sheep Liver Fluke? Describe its life cycle.

A

Fasciola hepatica
Egg -> Miracidium -> Enters snail and becomes sporocyst -> Redia -> Cercaria -> Metacercariae on vegetation is ingested by definitive host (usually livestock like cattle or sheep) -> develops to adult

33
Q

What feature is a vital parasitic adaptation of Trematoda?

A

Tegument

34
Q

What is the tegument?

A

Non ciliated, cytoplasmic surface coating surrounding body

35
Q

How does the tegument aid Trematoda in invading hosts?

A

Can undergo surface modifications and produce various surface antigens to evade detection and destruction

36
Q

How does the tegument allow intestinal survival of parasites?

A

Inhibits digestive enzymes of host

37
Q

What function of the tegument allows acquisition of nutrients?

A

Absorptive function - absorb nutrients from host bodily fluids

38
Q

What does the sensory function of the tegument allow?

A

Parasite can locate host tissues and navigate body, respond to changes in host environment

39
Q

What adaptations, other than the tegument, have Trematoda made for parasitism?

A

Two suckers (oral and ventral) to help adhesion
Digestive system still present, but tegument absorbs nutrients as well
Nervous system similar to free-living species but sensory organs often reduced

40
Q

What are the two subclasses of Cestoda?

A

Eucestoda and cestodaria

41
Q

What are Eucestoda, the subclass of Cestoda?

A

Tapeworms - generally endoparasites with vertebrates as a definitive host

42
Q

Where do adult tapeworms live?

A

In the digestive tract of vertebrates

43
Q

How are tapeworms generally transmitted?

A

Generally via predator-prey interaction

44
Q

Do Cestoda or Trematoda have more major adaptations to parasitic life?

A

Cestoda

45
Q

How is the surface area of the tegument of Cestoda increased?

A

Fine internuncial processes

46
Q

How are nutrients absorbed in parasites of Cestoda?

A

Directly through the tegument, fully dependent on nutrients from the host

47
Q

What operates as the sensory organs of Cestoda?

A

Nerve endings projecting through the tegument work as sensory organs for tactoreception and chemoreception

48
Q

Describe the digestive system of Cestoda.

A

No mouth or digestive system

49
Q

Describe the sensory system of Cestoda.

A

Lacks specialised sensory organs.

50
Q

What are the proglottids of Cestoda?

A

Sections of the strobilia (main body)

51
Q

How do Cestoda reproduce?

A

Sexually or asexually

52
Q

Describe sexual reproduction in Cestoda.

A

“Penis fencing” - have both reproductive organs so fight to take on father role as mother has greater responsibility, needing more energy, food

53
Q

Describe asexual reproduction in Cestoda.

A

Regeneration - can regrow from as little as 1/10. Sometimes regrow wrongly (e.g. too many heads)

54
Q

How much of the body of Cestoda is made up of stem cells?

A

1/5

3A Zoology - Invertebrates (12 decks)

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