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2nd Year: Animal Biodiversity > Insects > Flashcards

Insects Flashcards

1
Q

Insects co-evolved with flowering plants. True or false?

A

True.

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2
Q

Approximately how many species are there?

A

~870,000.

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3
Q

If we assume the mandibulata hypothesis:

Phylum: mandibulata
Subphylum: hexapoda
Class: insect

Correct?

A

Yes.

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4
Q

There are 2 distinct groups of insect. What are they?

A
  1. Ectognatha: outside jaws

2. Entognatha: inside jaws

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5
Q

The majority of insects fall into which group?

A

Ectognatha. The entognathans are usually soil-dwelling detritivores.

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6
Q

Define ‘tagmata’.

A

Distinct body regions.

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7
Q

How many body segments do insects have?

A

19.

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8
Q

How many eyes do insects have?

A

2 compound eyes with a simple ‘eyespot’ in between.

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9
Q

How many pairs of antennae do insects have?

A

1

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10
Q

How many legs do insects have?

A

6: they have 3 thoracic segments each with a pair of uniramous limbs on

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11
Q

Define uniramous.

A

Unbranched.

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12
Q

How many legs does the abdomen contain?

A

None.

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13
Q

How do insects perform gaseous exchange?

A

Via a spiracular/tracheal system.

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14
Q

The longitudinal tracheal trunk branches off into many tracheoles that permeate the tissues. True or false?

A

True.

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15
Q

Gas exchange relies on aqueous diffusion. Explain how.

A

O2 dissolves in the tracheal fluid. This is washed over the cytoplasm of cells. CO2 is taken from the cells and dissolves out of the tracheal fluid and is excreted via the spiracles.

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16
Q

Why are insects restricted to being small?

A

Because they rely on diffusion for gas exchange: larger = longer diffusion pathway = less efficient.

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17
Q

Gigantism in insects was widespread during the Palaeozoic. Why?

A

There was hyperoxia, allowing greater efficiency of gas exchange.

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18
Q

There is another theory for why insects dropped in size. What is it?

A

After the cretaceous began body size dropped twice: once 130mya and again 60mya. This coincides with the evolution of birds and bats, thus small size is an adaptation to predation.

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19
Q

What is haemolymph?

A

A fluid that carries nutrients, waste and hormones.

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20
Q

What are the malpighian tubes involved in?

A

Osmoregulation and excretion.

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21
Q

Why is uric acid secreted as a solid?

A

To conserve water.

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22
Q

a) What do wings initially develop from?
b) What is the wing surface formed from?
c) Why are they full of veins?
d) What connects the wings to the body?

A

a) Invaginations of the thoracic integument
b) Thin cuticular membrane
c) The veins carry haemolymph
d) The notum

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23
Q

a) What is the fulcrum?

b) What is the fulcrum full of?

A

a) The hinge-point of the wing

b) Resilin: an elastomeric protein that allows flexible wing movement

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24
Q

There are 2 distinct classes of winged insect. What are they?

A
  1. Palaeoptera

2. Neoptera

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25
Q

What are the wings like in palaeoptera?

A

The wings are veiny and net-like. They cannot be folded back over the body.

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26
Q

What kind of flight do palaeopterans use?

A

Direct flight: the flights muscles attach directly to the wings, thus contraction pulls the wings down.

27
Q

What kind of flight do palaeopterans use?

A

Direct flight: the flight muscles attach directly to the wings, thus contraction pulls the wings down.

28
Q

Give examples of palaeopteran.

A

Dragonflies and mayflies.

29
Q

What are the wings like in neoptera?

A

They are less veiny. The fore and hind wings are intensely modified. They are able to fold the wings back over the body.

30
Q

What kind of flight do neopterans use?

A

Indirect flight: the flight muscles do not attach to the wings, but to the upper tergum and lower sternum in the thorax. Muscle contraction causes the upper thoracic surface to be pulled down, causing the wings to pivot upwards.

31
Q

Do all insects have wings?

A

No.

32
Q

There are 2 hypotheses for the origin of wings. What are they?

A
  1. Paranotal

2. Limb branch

33
Q

Explain the paranotal hypothesis for the origin of wings.

A

Wings evolved from an extension of the tergum originally used for gliding.

34
Q

Give support for the paranotal hypothesis. List 2 reasons.

A
  1. Wings are flat like a gliding structure

2. Some species exhibit gliding behaviour e.g. arboreal ants

35
Q

Give a flaw in the paranotal hypothesis.

A

Little evidence for the formation of wing joints.

36
Q

Explain the limb branch hypothesis for the origin of wings.

A

Wings evolved from an existing dorsal limb branch. Proto-wing structures may have been used as gills/paddles/gliding apparatus.

37
Q

Give support for the paranotal hypothesis. List 2 reasons.

A
  1. Palaeopteran fossils display dorsal gills

2. Arthropod respiratory structures express genes orthologous to those in the drosophila wing.

38
Q

Which genes are found in both arthropod respiratory structures and drosophila wings?

A

pdm and apterous.

39
Q

What does the limb branch hypothesis for wing origin suggest and why? Why does this make it less likely?

A

Suggests they evolved in water if they evolved from gills. Insects evolved on land and their larvae returned to water.

40
Q

Give another flaw of the limb branch hypothesis.

A

It suggests the 4 wingless lineages of hexapods lost their wings in parallel. This is non-parsimonious.

41
Q

Insect trace fossils originate from?

A

The Silurian.

42
Q

Winged insect fossils date back to?

A

The Carboniferous

43
Q

Insects have 2 methods of development. What are they?

A
  1. Hemimetabolous

2. Holometabolous

44
Q

Define hemimetabolous development.

A

There are 3 distinct life stages: egg, nymph, adult. There is no pupal stage.

45
Q

What is the difference between nymphs and adults?

A

They are pretty much identical except nymphs do not have wings or functional reproductive organs yet.

46
Q

Define holometabolous development.

A

There are 3 distinct life stages: larva, juvenile and adult. There is a pupal stage where the juvenile undergoes complete metamorphosis. All 3 life stages are radically very different.

47
Q

What tissues in the larvae form the adult tissues in metamorphosis?

A

The imaginal discs (embryonic stem cell reserves).

48
Q

Define ecdysis.

A

Cuticle shedding.

49
Q

Define an instar.

A

Developmental stages divided by rounds of ecdysis.

50
Q

What is JH?

A

Juvenile hormone: it encourages larval growth and prevents metamorphosis. Levels of JH decrease throughout the lifetime.

51
Q

Define holometabolous development.

A

There are 3 distinct life stages: larva, juvenile and adult. There is a pupal stage where they undergo complete metamorphosis. All 3 life stages are radically very different.

52
Q

What is ecdysone?

A

A moulting hormone.

53
Q

Give a benefit of holometabolism.

A

There is no competition between different life history stages as they vary so widely.

54
Q

What are the 4 most diverse insect taxa?

A
  1. Coleoptera: the beetles
  2. Lepidoptera: butterflies and moths
  3. Hymenoptera: wasps, bees and ants
  4. Diptera: flies
55
Q

Describe the wings of the coleopterans.

A

The fore wings are hardened by scleratin into wing cases. The hind wings are soft and membranous.

56
Q

Describe the adult morph of a lepidopteran.

A

They are soft-bodied and their wings are covered in pigmented scales or setae.

57
Q

In lepidopterans a) what are the setae and b) what are they for?

A

a) Hair-like structures

b) Insulation, facilitates flight and for colour patterning

58
Q

How do lepidopterans feed?

A

Juvenile caterpillars have distinct mandibles for leaf-cutting but adults have a curled proboscis for drinking nectar.

59
Q

What is a characteristic features of the dipterans?

A

Well developed compound eyes.

60
Q

Describe the wings of diptera.

A

The fore-wings are membranous and functional, whereas the hind wings have been modified into halters that function as gyroscopes.

61
Q

What do gyroscopes do?

A

Help to steer.

62
Q

Insect sex consists of ‘weapons and ornaments’. Give examples of each.

A

Weapons: horns and antlers in male-male competition

Ornaments: eye stalks and hammerheads, for sexual selection by females

63
Q

Both weapons and ornaments are ‘condition-dependent characters’. What does this mean?

A

They are only expressed under optimal conditions by those with the fittest genotypes.

64
Q

Why are condition-dependent traits an honest indicator of good mate choice?

A

You cannot fake them, you only have them if you are genetically well-adapted.

2nd Year: Animal Biodiversity (16 decks)

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