Arthropods including insects and arachnids are characterised by their jointed limbs and bilateral symmetry with a fixed number of metameric segments e.g. head, thorax, abdomen.
They have both a mouth and an anus as part of a digestive tract with specialised regions (the caecae are appendages that contain gastric juice). The arthropod body form has enabled vast diversification of this animal group, including flight i.e. because the extra limbs could change without affecting the function carried out by the rest.
Their outer body is supported via the exoskeleton, which is a strong chitin structure.
This has led to arthropods, more specifically insects, dominating other animals in terms of highest number of different species as well as overall number of individuals. Extensive evolutionary potential was encased in this body form, giving rise to the most diverse animal group on the planet.
I got A* in A-level biology (Cambridge), thanks! I love your videos
Sherif Negm Facebook
Thank you!! Your site is so helpful!
Thank you for making all the content btw!
Serena Kutty YouTube
You explain everything so simply!
SecretDuck The Student Room
Hi! I have recently finished my first year doing biology at uni and I subscribed to you back when I was doing AQA A levels (glad I don’t live in Wales after watching this vid lol) and you and your website helped me so much. Just wanted to say it’s so nice to see you
Mr Peanutbutter YouTube