Arthropoda Flashcards
(21 cards)
What are the 6 basic characteristics of Arthropods?
- Metamerism
- tagmosis
- exoskeleton
- muscle arrangement
- coelom and blood vascular system
- Moulting and sensilla
What is metamerism?
Serial repetition of body segments
What is Tagmosis
Grouping of adjacent metameres into a coherent morphological unit (tagma) with a specialized function.
What are the general 3 tagma of arthropods?
head, thorax, abdomen
What is the exoskeleton secreted by? What is it composed of? (3)
Secreted by the epidermis
Composed of exocuticle (cross linked), endocuticle (less crosslinked), and epicuticle (prevents water loss)
What are the functions of the arthropod exoskeleton? (4)
- Maintains shape
- Provides Support
- Provides protection
- Facilitates movement
What is the axial skeleton made of? What are the 3 types of these?
Sclerites
- Dorsal Tergum
- Lateral Pleuron
- Ventral sternum
What is the appendicular skeleton made of? How do these move relative to each other?
Articles
-move relative to each other because there is a thin, flexible exoskeleton between the articles (the articular membrane)
What is the thin, flexible exoskeleton between the articles called?
Articular membrane
How is the movement of the articles CONTROLLED? What are these 2 types called?
antagonistic muscles bands
- extensor muscle
- flexor muscle (antagonistic muscle)
What is the evolutionary potential of arthropod appendages?
- endoskeleton can be sculpted into dif shapes for dif functions
- each article of the appendage can be precisely moved by muscles
What type of excretory gland do arthropods have?
Metanephridia
Do they have a true coelom?
Possibly the saccule at the base of their metanephridium
*not analogous with eucoelom of annelids
What circulates the hemolymph through the hemocoel of the body?
Alary muscles that run from the dorsal, contractile heart to the body wall.
What challenges does the exoskeleton present to growth? How are these overcome?
- Cannot grow exoskeleton once hardened
- Overcome by molting
How do they moult? (think of a cicada)
Split down mid-dorsal line
- > takes a while for protein to crosslink within chitinous exoskeleton
- > arthropod pumps up body w water or air, exoskeleton hardens and then organism can shrink back down and have room to grow
How does mechanosensory reception work? Describe the particular structure.
Have mechanosensory bristles for detection of mechanical stimuli
- is bulbous hair in excavation of exoskeleton that has dendrites of sensory neurons in the hair of it
- stretch of that hair causes depolarization of the cell membrane, info transmitted to nervous system
Where are mechanosensory bristles found?
On various appendages, with various specializations
What are mechanical stimuli?
Touch/feel of different objects
How does chemosensory reception from chemical stimuli work?
- have chemosensory pegs
- dendrites of neurons extend up to perforations of exoskeleton to detect chemical stimuli
What is the sister group to arthropods? What is one characteristic that differentiates them from arthropods?
Onychophora (velvet worms)
No jointed appendages
