Arthropoda

Question 1

What are the 6 basic characteristics of Arthropods?

Answer 1

1. Metamerism
2. tagmosis
3. exoskeleton
4. muscle arrangement
5. coelom and blood vascular system
6. Moulting and sensilla

Question 2

What is metamerism?

Answer 2

Serial repetition of body segments

Question 3

What is Tagmosis

Answer 3

Grouping of adjacent metameres into a coherent morphological unit (tagma) with a specialized function.

Question 4

What are the general 3 tagma of arthropods?

Answer 4

head, thorax, abdomen

Question 5

What is the exoskeleton secreted by? What is it composed of? (3)

Answer 5

Secreted by the epidermis

Composed of exocuticle (cross linked), endocuticle (less crosslinked), and epicuticle (prevents water loss)

Question 6

What are the functions of the arthropod exoskeleton? (4)

Answer 6

1. Maintains shape
2. Provides Support
3. Provides protection
4. Facilitates movement

Question 7

What is the axial skeleton made of? What are the 3 types of these?

Answer 7

Sclerites

1. Dorsal Tergum
2. Lateral Pleuron
3. Ventral sternum

Question 8

What is the appendicular skeleton made of? How do these move relative to each other?

Answer 8

Articles

-move relative to each other because there is a thin, flexible exoskeleton between the articles (the articular membrane)

Question 9

What is the thin, flexible exoskeleton between the articles called?

Answer 9

Articular membrane

Question 10

How is the movement of the articles CONTROLLED? What are these 2 types called?

Answer 10

antagonistic muscles bands

• extensor muscle
• flexor muscle (antagonistic muscle)

Question 11

What is the evolutionary potential of arthropod appendages?

Answer 11

1. endoskeleton can be sculpted into dif shapes for dif functions
2. each article of the appendage can be precisely moved by muscles

Question 12

What type of excretory gland do arthropods have?

Answer 12

Metanephridia

Question 13

Do they have a true coelom?

Answer 13

Possibly the saccule at the base of their metanephridium

*not analogous with eucoelom of annelids

Question 14

What circulates the hemolymph through the hemocoel of the body?

Answer 14

Alary muscles that run from the dorsal, contractile heart to the body wall.

Question 15

What challenges does the exoskeleton present to growth? How are these overcome?

Answer 15

• Cannot grow exoskeleton once hardened

- Overcome by molting

Question 16

How do they moult? (think of a cicada)

Answer 16

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

Question 17

How does mechanosensory reception work? Describe the particular structure.

Answer 17

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

Question 18

Where are mechanosensory bristles found?

Answer 18

On various appendages, with various specializations

Question 19

What are mechanical stimuli?

Answer 19

Touch/feel of different objects

Question 20

How does chemosensory reception from chemical stimuli work?

Answer 20

• have chemosensory pegs

- dendrites of neurons extend up to perforations of exoskeleton to detect chemical stimuli

Question 21

What is the sister group to arthropods? What is one characteristic that differentiates them from arthropods?

Answer 21

Onychophora (velvet worms)

No jointed appendages