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BLGY1124 > Insects > Flashcards

Insects Flashcards

1
Q

Are insects arthropods?

A

yes

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2
Q

What features do insects have in common with other arthropods?

A
  • segmented body plans
  • exoskeleton
  • moulting
  • jointed legs
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3
Q

Trends in Arthropod Evolution

A
  • loss of segments
  • specialisation of segments
  • tagmatisation (grouping of segments with related functions
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4
Q

Origin of Insects

A
  • insects are 6 legged crustaceans
  • became specialised for freshwater
  • became specialised for land
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5
Q

Remipedia

Charactaristics

A
  • 30 known extant species
  • live in salt water caves
  • primitive
  • more closely related to insects than other crustaceans
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6
Q

What is the difference between crustaceans and insects?

A

Crustaceans have biramous (branched) limbs and insects have uniamous limbs. The inner branch may have become gills and then wings

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7
Q

Apterygota

A
  • Archaeognatha and Thysanura
  • no wings
  • no metamorphosis
  • remnant abdominal appendages
  • 3 ‘tails’
  • spermatophores
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8
Q

Archaeognatha

A
  • Bristletails
  • single condyle mandibles (unlike all other)
  • often jump
  • members of Apterygota
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9
Q

Thysanura

A
  • Silverfish
  • two condyle mandibles (like all other insects)
  • flattened runners
  • members of Apterygota
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10
Q

Winged Insects

A

Paleoptera and Neoptera

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11
Q

Paleoptera

A
  • Mayflies and Dragonflies
  • cannot fold wings back over abdomen
  • wings have many vains
  • beat independently which is inefficient
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12
Q

Neoptera

A

-Exopterygotes and Endopterygotes
-all other winged insects
-can fold wings back
-

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13
Q

Exopterygotes

A

Blattodea - cockroaches and termites
Orthoptera - grasshoppers
Hemiptera - true bugs

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14
Q

Endoptergotes

A

Coleoptera - beetles
Hymenoplera - wasps, bees, ants
Lepidoptera - butterflies, moths
Diptera - true flies

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15
Q

What are the 3 types of insect life cycles?

A

Ametabolous (Apterygota)
Hemimetabolous (Exopterygotes)
Holometabolous (Endopteryrgotes)

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16
Q

Ametabolous Life Cycle

A
  • larva hatches from egg
  • larva moults going through a series of nymph stages
  • head shrinks proportionally as larva grows
  • adult looks like larva but bigger
  • no metamorphosis
  • keeps moulting in adulthood
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17
Q

Hemimetabolous Life Cycle

A
  • larva hatches form egg
  • larva goes through 5-8 moults
  • wing buds develop on the outside
  • adult has wings and does not moult again
  • partial metamorphosis
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18
Q

Holometabolous Life Cycle

A
  • maggot hatches from egg
  • goes through several moults
  • wing buds develop inside the body
  • pupates
  • adult has wings and does not moult again
  • complete / dramatic metamorphosis
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19
Q

What happens when a maggot pupates?

A
  • no eating or movement
  • -highly metabolically active
  • insides broken down
  • previously dormant cells multiply
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20
Q

Insects Through Time

Devonian

A
  • 400-350 mya
  • early land plants
  • bristletails
  • pre spiders
  • possible first winged insects
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21
Q

Insects Through Time

Carboniferous

A
  • 300-350 mya
  • high oxygen concentrations
  • giant horsetails and tree ferns
  • giant pre dragonflies
  • paleoptera with third sets of wings
  • pre cockroaches
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22
Q

Insects Through Time

Permian

A
  • 250-300mya
  • extinct winged orders still present
  • primitive reptiles
  • horsetails
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23
Q

Insects Through Time

The Great Extinction

A
  • greatest mass extinction event ever
  • ecological space for rise of the dinosaurs
  • many insect orders end
  • holometabolons survive and diversify
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24
Q

Insects Through Time

Triassic

A
  • 200-250mya

- early examples of modern orders

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25
Q

Insects Through Time

Jurassic

A
  • 150–200mya

- modern orders but now extinct families

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26
Q

Insects Through Time

Cretaceous

A
  • 150-64mya
  • feathered dinosaurs
  • Neuroptera and Hymenoptera
  • insects act as pollinators
  • coevolution of insects with flowering plants
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27
Q

Insects Through Time

Eocene

A
  • 55-35mya
  • Baltic amber forest
  • mammals
  • diatryma (birds)
  • hemipteran
  • butterflies
28
Q

Which organisms are insects derived from?

A

crustaceans

29
Q

Amber

A
  • fossilised plant resin
  • best known from Baltic area
  • preserves small animals
  • can infer ecological interaction
  • -parasite on organisms
  • -organisms trapped in close proximity to each other
30
Q
  1. Why are insects important?
A
  • dominate terrestrial and freshwater biodiversity
  • can transmit diseases
  • some feed on animals
  • pollination
  • Drosophilia (fruit fly) is THE model animal organism
31
Q
  1. There are lots of them but they are small
A
  • more than 50% of all described species are insects
  • it is estimated that only 1/5 of insects have been describes
  • most are 2-3mm in length
32
Q
  1. Insects are Octhropods
A
  • jointed limbs
  • exoskeleton made up of plates
  • intersegmental membrane that attaches plates together is what allows joints to bend
33
Q
  1. Adult Insects Usually Have Wings
A
  • two pairs of wings on second and third thorax segments
  • wings are probably modified gills, which were modified second leg branches
  • some of the same genes are involved in both larval wing and larval gill development
34
Q
  1. Arthropods Moult
A
  • have to moult or exoskeleton puts a limit on how big they can grow
  • immediately after moulting, lose water more rapidly, unable to fly, find it difficult to walk
  • a less rigid exoskeleton allows insects e.g. maggots to grow in between moults
  • in primitive insects, moults only produce larger almost identical copies
35
Q
  1. Insects Are Segmented
A
  • body plans based on repeating units
  • basic body plan:
  • -head
  • -3 segment thorax
  • -abdominal segments
36
Q

Insect Head

A
  • originally 6 segments, now fused together
  • specialised for feeding and sensory detection
  • antenna
  • eyes
  • ‘teeth’ outside bdy
37
Q

Insect Mouth Parts

A
  • Mandibles - jaws
  • Maxilla - inner branch, small set of jaws and sensory palps
  • Labium - lower lip, like two maxilla fused together, used as a spoon to push food into the mouth, palps
  • Labrum - upper lip, like labium but without palps
38
Q

Nervous System

A
  • ‘Brain’ - collection of ganglia fused from original brain segments
  • ventral nerve cord
  • ganglion (concentration of nerve cells) in each segment
39
Q

Thorax

A
  • specialised for locomotion
  • lots of muscle
  • 3 pairs of legs
  • wings
40
Q

Abdomen

A
  • specialised for metabolism and reproduction
  • appendages mostly lost
  • at the tail end, several segments are fused together and specialised for reproduction
41
Q
  1. Most Insects Display Metamorphosis
A
  • extreme metamorphosis is seen in advanced insects

- maggot -> larger larva -> pupa -> fly

42
Q
  1. Insects Reproduce Sexually
A
  • separate males ad females
  • males and females can look the same or different
  • not all insects are sexually dimorphic
43
Q

9.. Respiration

A
  • more O2 in the atmosphere allow insects to grow bigger due to limitations in their respiratory systems
  • spiracle - external opening to the respiratory system
  • pump bodies to squeeze air sacs approximating breathing
  • air travels down main trachea and then along tracheal branches to tracheoles which get narrower and narrower until they can enter cells
  • very efficient over distances less than 1mm but gets less efficient the bigger the insect is
44
Q
  1. Circulatory System
A
  • open blood stream
  • ‘heart’ - tube lined with muscles that can contract
  • has valves to direct blood flow towards the brain
  • aorta carries blood from heart to brain
  • haemocoel - body cavity, organs hang in the haemocoel which fills with blood
  • oxygen etc. moves by diffusion through haemocoel back to heart
  • almost no veins or arteries
45
Q

Insect Feeding Through Time

A
  • scavengers feeding on decayed plants and animals or detritus
  • chewing evolved before sucking
  • dead plants eaten before live plants as living plants are often well defended but nutrient poor
46
Q

Larval Feeding

A

-stage where most growth happens so where most biomass is removed from environment (most damage done)

47
Q

Exopterygote

Definition

A

larvae and adults eat similar food

48
Q

Endopterygote

Definition

A

larae and adults eat different food

49
Q

Biting and Chewing

Basal Mouthparts

A

Labrum - upper lip
Labium - lower lip (palps)
Maxilla - palps
Mandible - jaw

50
Q

Mouthparts in Predators

A
  • usually have large mandibles

- legs can be used instead of jaw so insects don’t have to have large mandibles to be predators

51
Q

Weevil

A
  • mouthparts at the end of a long proboscis
  • chew deeply into plants
  • lay eggs inside hole in plant
52
Q

Liquid Diets

A
  • phloem and xylem
  • individual cell contents
  • insides of prey
  • blood
53
Q

Modification of Mouthparts for a Liquid Diet

A
  • mandibles and part of maxillae modified to form stylets
  • stylets are cartlidge rods that can be stabbed into prey
  • rest of maxillae form inner/maxillary stylets
  • there is a salivary canal between the inner stylets
  • saliva is pumped down a ventral channel and digested food is sucked up the dorsal channel
  • sensory palps lost
  • labium and labrum enlarged to protect stylets
  • Cibarial pump - vaccum pump, muscles contract creating a partial vaccum inside the mouth drawing liquid up
54
Q

Filter Chamber

A

-loop in gut
-food passes around the loop
-but water is able to skip the loop by crossing the small gap between the beginning and end of the gut
-

55
Q

Why do liquid feeding insects need a filter chamber?

A
  • liquid food is very high in water content
  • in order to ingest enough nutrients, insects end up taking in way to much water
  • this is bad for many reasons e.g. enzymes don’t work as well at low substrate concentration
  • filter chamber allows excess water to be quickly passed out of the body
56
Q

Uses of Excess Liquid in Insects

A
  • sweat
  • cuckoo spit - soap added to water as it leaves the body causing it to froth and insect can hide in it
  • honeydew - phloem feeding insects also ingest excess sugar so release water and sugar, ants eat honeydew, and ants distract parasitic wasps from insects
57
Q

Lepidoptera Mouthparts

A 
Caterpillars
-primitive chewing type with mandibles and maxillae
Butterflies
-mandibles lost
-maxillae form short proboscis
58
Q

Why feed on nectar?

A

-easier to reach than phloem, xylem or blood as the skin doesn’t have to be pierced

59
Q

Hawk Moths Mouthparts

A
  • proboscis elongated
  • evolution of plants to have longer flower led to coevolution of the hawk moth
  • proboscis curls up when not being used to protect it
  • this happens when there is no pressure inside the tube, it automatically curls
60
Q

Diptera (Robber Fly) - Feeding

A
  • spiky legs to catch and kill prey

- sucks liquid contents of prey

61
Q

Mosquitoes

A
  • feed on blood
  • relatively specialist, feed on specific species
  • abdomen fills with blood
  • presence of blood in abdomen required for egg development
  • lays eggs in/on water
  • transmit many diseases
  • females only feed on blood
62
Q

Mosquito Larvae Feeding

A
  • feed in liquid
  • filter feeders
  • complex set if spines/hairs on mouthparts
  • mouthparts move and hairs draw water across the head
  • other mouthparts act as sieves and others scrape the collected food into the mouth
63
Q

Mosquito Pupa

A
  • doesn’t feed
  • is alive
  • can swim
  • has eyes and respiratory tube
64
Q

Male Mosquito Adaptations

A
  • many branches on antenna

- increase in surface area to detect female ferimones

65
Q

Female Mosquito Mouthparts

A
  • maxillary and mandibulary mouthparts both for cutting
  • stylets stick into prey
  • labium protects stylets when not feeding
  • hypopharynx = straw

BLGY1124 (8 decks)

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