Insects 1

Question 1

Give some generalised features of insects

Answer 1

Usually have 6 legs at some point of its life

Body is divided into 3 regions/tagmata (head, thorax, abdomen)

Head is often made from mandibles, maxillae, maxillipeds, antennae, labrum

Head has one pair of atennae

Most adults thorax has 2 pairs of wings (ALL WINGED INVERTS ARE INSECTS)

Question 2

Why are insects important?

Answer 2

600M people are affected by insect vectored diseases

15% crops worldwide are lost to insects

70% of flowering crops benefit from insect pollination whereas 20% of plants need insects

Often major biocontrol agents

Question 3

What are some hypotheses for the origin of insects?

Answer 3

Hypothesis 1 - Arthropods are multiply derived from different worm ancestors

Hypothesis 2 - Insects have a single origin from crustacea

Question 4

Are insects uniramous or biramous?

Answer 4

Uniramous - like myriapods

Question 5

How did they decide which hypothesis for insect origin is correct?

Answer 5

First looked at the legs of the insects

If insect legs were never branched in the past and always been uniramous then it proves that hexapods and myriapods are close relatives and hypothesis 1 is correct

Could not find many fossils of insects to look at the legs to started to look at the neuroanatomy instead

Then looked at developmental genetics - both hexapoda and crustacea have the distal-less gene but is it regulated differently

Finally used molecular phylogenetic systematics and found crustaceans did invade onto land to form the insects

Question 6

Give some examples of intermediate habitats where evolution onto land may have taken place

Answer 6

Estuary

Marsh

Intertidal zone

Mangrove

Question 7

What are some challenges to life on land for insects?

Answer 7

Water loss and osmoregulation due to size - solved with cuticle

Electrolyte homeostasis is solved with malpighian tubules

Respiring in air - insects evolved the trachea

Reproduction and fertilisation - internally fertilise

Support/movement - select for smaller size and insects have a stable gait

Question 8

What is the insect integument?

Answer 8

Composes of the exoskeleton and the cuticle

Chitin based

Has extensive sclerotisation - crosslinking between chitin and proteins

Tough and flexible

Question 9

How does the hexapoda integument differ from the crustacea?

Answer 9

No calcite

More extensive protein x-links

Waxy epicuticle

Question 10

What are the malpighian tubules? Give some features of them

Answer 10

Excretory system for maintaining electrolyte balance

Blind tubules arise in abdomen, terminate in gut

Less developed or absent in early terrestrial insects