Ecdysozoa

Question 1

Clade Ecdysozoa features? What is their shared, derived trait?

Answer 1

• monophyletic
• 2 major phyla: nematoda, arthropoda
  cuticle that is periodically moulted
• tough outer layer outside epidermis, secreted by epidermal cells
• composed of chitin

Question 2

What are functions of the cuticle?

Answer 2

• barrier against dessication and mechanical injury
• structural support; tough exoskeleton that acts as a framework for muscle attachment
• must be shed through ecdysis for animal to grow

Question 3

3 layers of the cuticle?

Answer 3

Endocuticle + exocuticle (procuticle)
epicuticle - thin waxy
fine ducts run from the epidermis to the top of the cuticle

Question 4

What is ecdysis and its function in arthropods?

Answer 4

Moulting
- cuticle is sclerotized forming a hard, rigid cuticle
- regions of sclerotized cuticle shaped like plates are called sclerites
- used as armour plates and hardened appendages

Question 5

How does ecdysis work?

Answer 5

1) Ecdysozoan becomes inactive and apolysis separates old cuticle from epidermis
2) Inactive enzymatic moulting fluid is secreted into sepration spce and epidermis grows in a folded manner
3) A new proto-epicuticle is secreted on the epidermis
4) Moulting fuid enzyes are activated and old endocuticle is digested but sclerotized exocuticle isnt
5) New procuticle layer is secreten protecting proto-epicuticle from digestion
6) Moulting fluid is reabsorbed and deposition of new epicuticle is complete
7) Old exocuticle is moulted and new cuticle expands

Question 6

Phylum Nematoda characteristics?

Answer 6

• aquatic roundworms without segmentation, eyes or appendages (lost secondarily)
• anterior blunt, posterior pointed
• hemocoel lined with mesodermally-derived tissues but not completely
• movement by side-side contractions of longitudinal muscles
• sexual reproduction, internal fertilization, direct development

Question 7

Phylum Arthropoda evolution is characterized by?

Answer 7

• decreased number of body segments
• increased appendage specialization
• Hox gene sequence regulation

Question 8

6 characteristics of arthropods?

Answer 8

Segmented body
Jointed paired appendages
Sclerotized cuticle
Cephalization
Reduced coelom
Open circulatory system

Question 9

Body segments and limbs are arranged into?

Answer 9

Tagmata

Question 10

What do arthropods have in the head region?

Answer 10

feeding structures and sensory structures
eyes, antenna, olfactory receptors

Question 11

Why do they have a reduced coelom?

Answer 11

Strong, segmented limbs reduce need for hydrostatic skeleton
Hemocoel supports internal organs

Question 12

What does the hemolymph do?

Answer 12

circulates in hemocoel surrounding tissues and organs
may have respiratory pigments for oxygen transport

Question 13

What are the 3 lineages of arthropods?

Answer 13

Subphylum Chelicerata, Clade Pancrustaceans, Subphylum Myriapoda

Question 14

Features of subphylum Trilobita?

Answer 14

• extinct marine arthropods
• 3 tagmata: cephalon, thorax, pygidium (tail)
• compound eyes, flexible antenna
• thoracic segments had one pair of biramous limbs (ventral - locomotion, dorsal - gill)

Question 15

Which feature of trilobites did arthropods lose?

Answer 15

Lost dorsal branch of limbs so their limbs are uniramous

Question 16

Subphylum chelicerata features? (specifically chelicerae)

Answer 16

• claw-like feeding appendages called chelicerae
• mouthparts adapted for feeding and defense
• homologous to antenna
• 2 or 3 segmented pincers
• chelicerae in spiders have venom glands
• spiders, scorpions, mites
• 2 tagmata

Question 17

What are the 2 tagmata of Chelicerata?

Answer 17

Anterior cephalothorax - covered by carapce; dorsal exoskeleton
- 6 pairs of appendages: chelicerae, pedipalps, 4 pairs of legs
- pedipalps are jointed sensory appendages
- no antennae, uniramous limbs
Posterior abdomen - no appendages; contains digestive and reproductive organs

Question 18

Arachnid features?

Answer 18

• fluid-feeding predators
• eye spots called ocelli
• abdomen and cephalothorax with 6 pairs of appendages
• separate sexes

Question 19

Spider features?

Answer 19

• 2-segment chelicerae with venom glands
• gas exchange via book lungs in abdomen
• 0-4 pairs of ocelli
• spinnerets - abdominal glands producing liquid protein silk
• maternal care of eggs and sometimes young
• complex courtship

Question 20

Scorpion features?

Answer 20

• pedipalps modified as pincers
• segmented abdomen
• terminates in poisonous stinger
• digest externally and ingest fluid
• complex courtship
• maternal care of eggs and young

Question 21

Mite features?

Answer 21

• no segmentation between cephalothorax and abdomen
• 2-3-segmented chelicerae
• 0-2 pairs of ocelli

Question 22

Subphylum Myriapoda characteristics?

Answer 22

• terrestrial and less tagmatization
• simple eyes, 3 pairs of mouthparts (1 mandibles), one pair of antennae
• over 3 pairs of jointed uniramous legs
• gas exchange via tracheal system; air enters lateral spiracles, through trachea, into tracheoles throughout the body
• lack O2 trasporting pigments in hemolymph
• direct development

Question 23

2 types of myriapods?

Answer 23

Millipedes - detritivores or herbivores with 2 pairs of jointed legs/segment
- diplosegments due to fusion of adjacent segments
Centipedes - predators with 1 pair of jointed legs/segment
- venomous claws

Question 24

What does Clade Pancrustaceans include?

Answer 24

Subphylums Crustacea and Hexapoda

Question 25

Subphylum Crustacea; 3 types of pods?

Answer 25

Isopods - terrestrial, freshwater, marine
Copepods - small, planktonic crustaceans
Decapods - large crustaceans

Question 26

Crustacea tagmata? eyes? exoskeleton?

Answer 26

3 tagmata: head, thorax, abdomen
- cephalothorax covered by carapace - exoskeleton shield
- compound eyes on stalks
- exoskeleton strengthened by biomineralization (calcium carbonate)

Question 27

What kinds of limbs on each tagmata?

Answer 27

Biramous limbs:
Head - 2 pairs of antennae, paired segmented mandibles, 2 pairs of maxillae - tasting food
Thoracic - more than 4 pairs of limbs for locomotion
Abdominal - swimming, gas-exchange, filter-feeding, holding eggs

Question 28

How does gas exchange in different crustaceans work?

Answer 28

• small crustaceans exchange gas through cuticle
• large crustaceans exchange through gills (unsclerotized) and soft
• O2 transported by pigments in hemolymph

Question 29

How do crustaceans reproduce?

Answer 29

• separate sexes, reproduce sexually via copulation
• copulation occurs via intromission or spermatophore deposition
• sessile barnacles are hermaphrodites but dont self-fertilize
• asexual parthenogenesis is common
• direct or indirect development

Question 30

Subphylum hexapoda shared trait?

Answer 30

6-legged arthropods, 3 pairs of legs on thoracic segment only

Question 31

Class Insecta are the only invertebrates to?

Answer 31

evolve flight and wings

Question 32

Tagmatization in Class Insecta?

Answer 32

Head with one pair of antennae and 3 pairs of mouthparts (1 mandibles)
Thorax with 3 pairs of jointed uniramous legs
- may have wings
Abdomen with no appendages

Question 33

Gas exchange in Insecta?

Answer 33

• occurs through tracheal system via lateral spiracles
• branched cuticle-lined tubes carry O2 directly to tissues
• lack O2 transporting pigments in hemolymphs

Question 34

Clade Pterogyta features?

Answer 34

• 1-2 pairs of wings on thoracic segment
• wings are extension of cuticle
• wings are shared, derived trait
• some lost wings secondarily

Question 35

Incomplete vs complete metamorphosis?

Answer 35

Incomplete - juveniles called nymphs resemble adults but undergo several moults before reaching full size
- wings develop over several moults
Complete - insects progress through larval stages which have different morphology ftom adults
- wings develop at specialized pupal stages

Question 36

How do insects reproduce?

Answer 36

• 3 sexes, sexual reproduction
• non-insect hexapods and apterygotes transfer sperm indirectly via spermatophore (package of sperm)
• pterogytes copulate

Question 37

How does insect ecdysis work?

Answer 37

• shed entire exoskeleton including linings of gut and trachea
• insect swallows air or water after moulting to expand new exoskeleton