Phylum Arthropoda

Question 1

Symmetry;

Bilateral

Question 2

Support;

Exoskeleton of chitin over the body provides protection, a degree of water retention, and support.
(presence of an exoskeleton limits the size of arthropods as it needs to be shed
prior to growth).

Question 3

Coelom;

Present

Question 4

Segmentation;

Fixed number of metameric segments in each region of the body,
* head, thorax and abdomen in an insect
* cephalothorax (head and thorax combined) and abdomen in a spider
(arachnid)
Have jointed limbs, three pairs in an insect, four pairs in a spider, one pair on
each segment of the thorax.

Question 5

Gut/feeding;

Arthropods have a one way gut with a separate mouth and anus, ingested and undigested food do not mix.
There is regional specialisation.
All digestion is entirely extracellular in the gut cavity.

Question 6

Arthropods are the most successful animal group on Earth. There are more species of insects and more
insects in total than in any other group.
This is because the basic insect body plan can, in evolutionary terms, be easily adapted to fit a whole range
of niches.
Example
* Insect mouthparts have evolved for chewing, piercing skin, sucking fluids.
* Many insects have wings.
* Many insect species have separate distinct body forms, such as a larval stage and an adult stage
with different food sources.