Phylum Arthropoda: Introduction

Question 1

Basic Characteristics

Answer 1

Metamerism and Tagmosis

Question 2

Exoskeleton

Answer 2

Secreted by epidermis
The exocuticle and endocuticle – is made of chitin, with protein crosslinking
The epicuticle is a waxy waterproof layer, made of protein

Question 3

Functions of arthropod skeleton (4)

Answer 3

Protection
Support
Maintain shape
Facilitate movement

Question 4

Axial Skeleton – sclerites

Answer 4

Articles (podomeres) linked together by articular membranes which are thin and flexible

Question 5

Muscle Arrangement

Answer 5

Movements of articles controlled by antagonistic muscle bands
Each article only moves on one plane
Only one set of articles per muscle

Question 6

The adaptive potential of arthropod appendages

Answer 6

Extremely versatile raw material for evolutionary tinkering

Exoskeleton can be sculpted into different shapes for different functions
Each article of the appendage can be precisely moved by muscles

Question 7

Coelom and blood vascular system

Answer 7

Their secondary body compartment is the hemocoel which is the dorsal contractile heart.
The saccule is a coelom that is seen in few marine arthropods

Question 8

Proposed sister group

Answer 8

The Onychophora are proposed as the sister groups for arthropods, based on molecular evidence
Velvet worms