Annelids, Molluscs, Nematodes and Arthropods

Question 1

Why do arthropods need to moult?

Answer 1

Arthropods have an exoskeleton, hard and rigid and restricts growth. moulting is the shedding of the exoskeleton.

Question 2

What is tagmatisation?

Answer 2

the organisation of segments into different groups with differing structures and functions

Question 3

What is the importance of an exoskeleton?

Answer 3

provides support and protection
initially flexible but usually hardens and is rigid.
Hardening prevents dehydration and allows adaptation for aridity.

Question 4

Why are molluscs important for humans?

Answer 4

Food (oysters, mussels, clams, squid)
Currency (shell money)
Shells (collectors – high prices)
Jewellery (pearls)

Question 5

What are some of the advantages and disadvantages of arthropods for humans?

Answer 5

Can be used as bait for fishing
food in the future will be insects
insects carry diseases
some are poisonous.

Question 6

What are the key characteristics of spiders, crustaceans and insects?

Answer 6

Main body parts: Arachnids have two main body parts - abdomen and cephalothorax. Crustaceans and insects have three main body parts - head, thorax and abdomen.
Legs: Arachnids contain four pair of legs Crustaceans have 6 to 14 pairs of jointed legs Insects have three pairs of jointed legs.
Antennae: Arachnids have no antennae. Crustaceans and insects have antennae.
Wings: Arachnids and crustaceans have no wings while insects have wings.
Breathing: Some arachnids have book lungs. crustaceans breathe through gills, smaller ones breathe through their skin. Insects breathe through holes on their sides.
Eyes: Arachnids have simple eyes. Crustaceans d insects have compound eyes.

Question 7

What are the key characteristics of spiders, crustaceans and insects?

Answer 7

Main body parts: Arachnids have two main body parts - abdomen and cephalothorax. Crustaceans and insects have three main body parts - head, thorax and abdomen.
Legs: Arachnids contain four pair of legs Crustaceans have 6 to 14 pairs of jointed legs Insects have three pairs of jointed legs.
Antennae: Arachnids have no antennae. Crustaceans and insects have antennae.
Wings: Arachnids and crustaceans have no wings while insects have wings.
Breathing: Some arachnids have book lungs. crustaceans breathe through gills, smaller ones breathe through their skin. Insects breathe through holes on their sides.
Eyes: Arachnids have simple eyes. Crustaceans d insects have compound eyes.

Question 8

What are the advantages for social insects?

Answer 8

accomplish feats impossible for solitary insects
construction of big nests
widespread foraging
constant vigilance against predators