Arthropods 1 Flashcards
1
Q
Describe protostomes.
A
- Means mouth first.
- Embryonic blastopore becomes the mouth. (As opposed to the anal opening in deuterostomes)
- Bilaterally symmetrical.
2
Q
Describe Ecdysozoans?
A
- A group of protostome animals including Arthropoda.
* Grow by moulting exoskeleton and growing a new one.
3
Q
What is ‘heteronomous metamery’?
A
A reduction in metamerism. (Linear series of body segments)
4
Q
Who were the ancestors of Arthropods?
A
Unknown.
5
Q
Describe Onychophorans.
A
- Velvet worms.
- Are Ecdysozoans, but not Arthropods.
- Soft, fleshy, claw-bearing unjointed legs.
- Thin flexible cuticle containing chitin.
- Fluid-filled body cavities act as hydrostatic skeletons.
6
Q
Describe Tardigrades.
A
- Are ecdysozoans but not Arthropods.
- 8 fleshy unjointed legs and hydrostatic skeletons.
- Lack circulatory systems and gas exchange systems
- Can lie dormant for at least a decade.
7
Q
What are the common features of Arthropods.
A
- Lost ancestral coelom.
- Internal cavity has become a haemocoel.
- Exoskeletons thickened by proteins and chitin.
8
Q
Describe trilobites.
A
- First jointed appendages found in the fossil records with beginnings of specialisation.
- Heavy exoskeletons
- Flourished in the Cambrian and Ordovician seas.
9
Q
Describe Myriapods.
A
- Many legs.
- Includes centipedes and millipedes.
- Head and a trunk.
10
Q
Describe Chelicerates.
A
- Bodies divided into two major regions.
- Anterior region bears two pairs of appendages, modified to form mouthparts.
- Many have four pairs of walking legs.
11
Q
Describe Arachnida.
A
- Includes spiders, scorpions, mites, harvestmen and ticks.
* Mites and ticks are vectors for disease.
12
Q
Describe Insecta.
A
•Have bodies with three basic regions:
- head with a single pair of antennae.
- thorax with three pairs of legs.
- abdomen with no appendages. (Unlike other Arthropods)
13
Q
Are Arthropods deuterostomes or protostomes?
A
Protostomes.
