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BI2131: Animal Diversity and Adaptation > Arthropods > Flashcards

Arthropods Flashcards

1
Q

What are some common characteristics of arthropods?

A 
Bilateral symmetry.
Chitinous, segmented exoskeleton.
Ventral nervous system.
Open dorsal circulatory system.
Tracheal respiratory system/book lungs.
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2
Q

What are the layers of the exoskeleton?

A

Epicuticle, exocuticle, endocuticle, gland cells and epidermis.

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3
Q

Describe the general circulatory system in arthropods.

A

Hemocoel filled with hemolymph.
Heart = dorsal muscle tube pumping anteriorly.
Heart is perforated by paired ostia with one-way valves.

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4
Q

How does gas exchange differ between chelicerates/true crustaceans and insects?

A

Chelicerates/True crustaceans exchange O2 at gills or book lungs.
Insects perform gas exchange using a tracheal system.

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5
Q

Describe the anatomy of compound eyes.

A

They are made up of many ommatidia with each containing a cornea, lens and photoreceptor cells.

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6
Q

What is the arrangement of the tracheal system in arthropods?

A

Spiracles > Trachea > Tracheoles

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7
Q

How is the arrangement of the tracheal system kept in place?

A

The tracheal tubes are stiffened with bands of chitin.

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8
Q

What is the arrangement of the excretory system in arthropods?

A

Mouth > Crop > Gastric ceca > Stomach > Malphigian tubules > Rectum

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9
Q

In what form is nitrogenous waste excreted?

A

In true crustaceans = ammonia.

In terrestrial arthropods = uric acid.

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10
Q

What is the body plan for chelicerates?

A

1) Prosoma/Cephalothorax (fused head + thorax).

2) Opisthosoma/Abdomen.

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11
Q

How does the body plan of mites differ to typical chelicerates?

A

Mites have no visible division between the 2 segments.

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12
Q

What are the appendages on the front of the mouth of chelicerates known as?

A

Chelicerae. They usually take the form of pincers. In spiders they are fangs.

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13
Q

What are the respiratory systems in chelicerates?

A

Marine chelicerates have gills.

Terrestrial chelicerates have book lungs + tracheae or just tracheae.

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14
Q

How is the nervous system arranged in chelicerates?

A

Ganglia are generally fused into large masses in the prosoma.

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15
Q

What is the limb order in chelicerates?

A

Chelicerae, pedipalps and then 4 pairs of legs.

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16
Q

What is the telson?

A

Posterior-most division of the body of an arthropod.

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17
Q

What are chelicerae used for?

A

Grasping + subduing prey.
Injecting gut enzymes.
Defence.
Processing prey/plant material.

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18
Q

What are pedipalps?

A

They resemble legs as seen in spiders or form massive pincers in scorpions.

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19
Q

What are the segments of a chelicerate’s legs?

A

Coxa > Trochanter > Femur > Patella > Tibia > Metatarsus > Tarsus > Claws

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20
Q

How do the legs of chelicerate’s differ to those of insects?

A

Arachnids possess a patella unlike insects.

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21
Q

Why do spiders have 2 sets of claws on their legs?

A

1 pair to grip the ground.

1 pair to grip the silk of the web.

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22
Q

What are scopulae and how do they function?

A

Dense tufts of hair beneath the claws. They provide adhesion for climbing using Van der Waals forces.

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23
Q

What form of eyes do chelicerates possess?

A

Ocelli (simple eyes) except for horseshoe crabs which possess compound lateral eyes. All chelicerate eyes lack a lens.

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24
Q

How many eyes do spiders have?

A

8 in 4 pairs.

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25
Q

Describe the circulatory system of spiders.

A

Heart + aorta with the heart lying in the pericardium which is linked to the book lung.

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26
Q

Describe the circulatory system of mites.

A

Some mites have no heart. Instead they use cuticular diffusion.

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27
Q

Describe the respiratory system of chelicerates.

A

A system of tubular tracheae + a single “spiracle”. Not homologous to insect tracheae. Book lungs are used for gas exchange in larger chelicerates.

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28
Q

What are book lungs?

A

Internal surface of lamellae providing a large area for GE. Up to 4 pairs in scorpions, up to 2 pairs in spiders.

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29
Q

Where do spiders and scorpions produce enzymes?

A

In the gut.

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30
Q

Where do ticks and mites produce enzymes?

A

In the salivary glands.

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31
Q

What parts of the gut are contained within the foregut in chelicerates?

A

The mouth, pharynx and oesophagus.

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32
Q

What parts of the gut are contained within the hindgut in chelicerates?

A

The nephridia and malpighian tubules.

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33
Q

What are the 3 main classes of chelicerates?

A

Arachnida (arachnids), merostomata (horseshoe crabs) and pycnogonida (sea spiders).

34
Q

What are the 2 main classes of myriapods?

A

Chilopoda (centipedes) and diplopoda (millipedes).

35
Q

What is the body plan for myriapods?

A

1) Head.

2) Elongated trunk (no division between thorax and abdomen).

36
Q

Describe the sensory organs of myriapods.

A

1 antennae pair on head. Simple lateral eyes (loosely scattered ommatidia).

37
Q

What are the 2 forms of anal legs?

A

Antenniform (sensory) and pincer like (aggressive/defensive).

38
Q

What gives the class chilopoda its name?

A

A pair of forcipules - pincer like forelegs. Chilopoda means ‘lip-foot’.

39
Q

Why are myriapods only found in moist environments?

A

They cannot close their spiracles and possess a permeable integument.

40
Q

How many pairs of legs do chilopods and diplopods have per segment?

A

Chilopods have 1 pair of legs per segment whilst diplopods have 2 pairs of legs per segment.

41
Q

How does locomotion differ between chilopods and diplopods?

A

Chilopods use an alternating gait whilst diplopods possess a symmetrical gait.

42
Q

What are some defences possessed by diplopods?

A

Drab colouration, rolling into a ball/spiral, stink glands, caustic secretions, sedative secretions and toxicity.

43
Q

Where does the term crustacean come from?

A

‘crusta’ refers to the calcified exoskeleton.

44
Q

What is the carapace of a crustacean?

A

A mantle-like fold of the body wall from the last head segment bearing the maxillae. It may be fused with some/all segments covered.

45
Q

What segments make up the cephalothorax of a crustacean?

A

The thorax and head.

46
Q

What are biramous legs and what are some benefits of them?

A

Crustacean legs have an exopod and endopod forming 2 branches. This allows for increased modification and variation.

47
Q

What occurs before moulting in crustacea?

A

Prior to moulting, calcium is absorbed and deposited into the new cuticle.

48
Q

Why have crustacea been unsuccessful on land?

A

They lack a waxy cuticle to prevent water loss and rely on gills for respiration - gills are inefficient out of water. All crustacea have an aquatic larval stage.

49
Q

Which group of crustaceans have successfully colonised the land? Why is this?

A

Isopoda (woodlice). They possess pleopodal lungs which act like spiracles. They are still limited to moist areas.

50
Q

What is the body plan for insects?

A

1) Head.
2) Thorax.
3) Abdomen.

51
Q

What are the benefits of a tracheal respiratory system?

A

It provides a large cuticular area for GE.
Spiracles possess closing valves to prevent water loss.
Tracheae branch into musculature.

52
Q

How do larger insects increase the efficiency of their tracheal respiratory system?

A

Larger insects utilise the active pumping movements of the abdomen to ventilate the outer tracheae.

53
Q

Is the circulatory system in insects open or closed?

A

Open.

54
Q

What is transported in the hemolymph in insects?

A

Nutrients, salts, waste, hormones etc.

55
Q

What are some defensive roles of hemolymph?

A

Clotting, pathogen encapsulation and sequestration of distasteful chemicals.

56
Q

What are the 3 cavities of the hemocoel in insects?

A

Pericardial, perivisceral and perineural sinuses. They are divided by the dorsal and ventral diaphragms.

57
Q

How is musculature arranged in insects?

A

Muscles attach to the exoskeleton’s inner surface through tonofibrillae (fine connecting fibrils).

58
Q

What are apodemes?

A

Ridges at the attaching site of the legs to strengthen the inner cuticle.

59
Q

Are insect skeletal muscles synchronous or asynchronous?

A

Synchronous - one contraction per nerve impulse.

60
Q

Are insect flight/tymbal muscles synchronous or asynchronous?

A

Asynchronous - more than one contraction per nerve impulse.

61
Q

What is the function of the foregut in arthropods?

A

Ingestion, storage and grinding.

62
Q

What is the function of the midgut in arthropods?

A

Excreting digestive enzymes and digesting/absorbing food.

63
Q

What is the function of the hindgut in arthropods?

A

Absorbing water, salts, amino acids and sugars.

64
Q

What is the peritrophic membrane and its function?

A

A thin semi-permeable sheath that compartmentalises digestion, ensheaths the food and acts as an infection barrier.

65
Q

How do you calculate the ovigeny index (OI)?

A

Initial egg load X No. of eggs ready to lay / Lifetime potential fecundity

66
Q

What does a high ovigeny index show?

A

Highly predictable oviposition site availability.

67
Q

What does a low ovigeny index show?

A

Less predictable oviposition site availability.

68
Q

What is parthogenesis and what are the benefits of this reproductive strategy?

A

Producing clones. There are zero time and energy costs for gamete production and courtship.

69
Q

What are the 4 main methods of insect flight?

A

Gliding flight, flapping flight, downwash and wake capture.

70
Q

Describe insect wing structure.

A

No muscles/tendons in the wings.
2 layers of exoskeleton ‘sandwiched’ together.
Girder system of tubular ‘veins’.

71
Q

What are the 2 mechanisms of flight generation in insects?

A

Direct and indirect flight

72
Q

Which insect groups use direct muscle flight?

A

Dragonflies, damselflies and mayflies.

73
Q

Which insect groups use indirect muscle flight?

A

All members of neoptera.

74
Q

How does direct muscle flight?

A

Up + down wing movement is caused by the contraction of muscles connecting the wing base to the thorax ‘floor’. Each wing has independent power from 2 antagonistically acting muscles.

75
Q

What are the pros and cons of direct muscle flight?

A

Pro: wings do not have to beat in unison.
Con: wing beat frequency limited to 25bps (rate of nerve impulses going to muscles).

76
Q

How does indirect muscle flight?

A

Horizontal + vertical muscle set act on the thorax (not wings). Thorax ‘roof’ is less flexible. When muscles contract the whole thorax ‘box’ changes shape (states switch).

77
Q

What is the main advantage of indirect muscle flight?

A

It overcomes the constraint of wingbeat frequency.

78
Q

Why do most indirect muscle fliers use asynchronous muscles?

A

They allow higher wing beat frequency as they automatically contract after extension.

79
Q

What are halteres and what is their role in insect flight?

A

Small club-shaped organs that provide information to the insect by acting as gyroscopes.

80
Q

What flight fuel is used by hymenoptera and diptera?

A

Carbohydrates.

81
Q

What flight fuel is used by grasshoppers, aphids and migratory insects?

A

Lipids in sustained flight; carbohydrates in short-duration flight.

BI2131: Animal Diversity and Adaptation (19 decks)

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