Lecture 5 DA Flashcards
Which phylum is the most diverse (percentage)?
Arthropoda, at over 75%.
What are the key features of arthropoda (10)?
- Triploblastic
- Bilaterally symmetric
- Protostomes
- Molt
- Coelomates, with a reduced coelom
- Chitinous exoskeleton
- Metameric, segmented
- Tagmatisation
- Highly cephalised
- Internal fertilisation
What is heteronomous and homonomous segmentation?
Hetero - segments differ
Homo - segments are the same
What is tagmatisation?
Multiple segments fuse into distinct regions.
What is a cuticle, what two forms does it have, and for what kind of environment?
Made of chitin, and can be reinforced with calcium for aquatic environments, and waxy for terrestrial.
What are the functions of the cuticle (3)?
Protection
Anchors muscles
Prevents water loss
What is a disadvantage of having an exoskeleton/cuticle?
Must molt periodically.
What is ecdysis, and how does it occur?
Molting process. The arthropod first engores on water to expand, cracking the exoskeleton.
Will then crawl out, and continue to engorge to stretch its underskeleton, which will later harden. It will then shrink.
How does molting put the arthropod at a disadvantage?
Is vulnerable during this stage, from predators, competition from its own species, or exhaustion from crawling out.
Predation is the biggest threat.
How is the arthropod tracheal system structured?
Cuticle extends into the body to deliver oxygen to the tissue. The hollow tubes are an invagination of the cuticle.
What are the external openings in the tracheal system of arthropods called?
Spiracles.
Do spiracles have valves?
Some do, aids in water loss.
What are wings believed to be formed from?
Evagination of the cuticle.
What are ommatidia?
Compound eyes, which arthropods have.
What are antennae and anntenules used for?
Mechano- and chemoreceptors.
What are the subphyla of arthropoda (5)?
Trilobita Crustacea Chelicerata Myriapoda Hexapoda
What are the general characteristics of trilobites?
Biramous appendages, and one pair of anntenae.
What are the general characteristics of crustaceans?
Biramous appendages, two pair of anntenae, and a nauplius larva.
What are the general characteristics of chelicerates?
Uniramous appendages, no antennae.
What are the general characteristics of myriapods?
Uniramous appendages, and one pair of antennae.
What are the general characteristics of hexapods?
Uniramous appendages, one pair of antennae, and no abdomen appendages.
What environment do crustaceans live in?
Mostly aquatic, some terrestrial.
Are barnacles crustaceans?
Yes.
How many tagmata do crustaceans have, and what are they?
3, a head, thorax and abdomen.
In some, the head and thorax is fused.
What is a tagmata that is a fused head and thorax called?
Cephalothorax or carapace.
How many pairs of appendages do crustaceans have on their head?
5.
The first pair are antennules, and are small.
Second pair are antennae, much larger.
Next pair are mandibles.
Next two pairs are maxillae for manipulating food.
Are crustacean thorax segments number constant? Can these segments be used to manipulate food?
Segment number is variable, the most common is 8. First 3 can be turned forward, specialised to manipulate food.
The first 3 segments of a crstacean’s thorax is used for food. What about the other 5?
They are called pereopods, used for locomotion.
What segments are large claws formed from in some species?
First pair of the pereopods on the thorax.
How many appendages do crustaceans have on their abdomen?
6, called pleopods.
What is a telson?
A tail, found on the abdomen.
What is meant by a biramous appendage?
Each appendage has two lobes.
The lobe closer to the midline is called endopod, while the outer one is the exopod.