Lecture 18

Question 1

Ectdysozoa characteristics

Answer 1

moult cuticle in order to grow (ectdysis)

Question 2

ectdysis

Answer 2

entire cuticle shed at once

Question 3

4 main phyla of ectdysozoa

Answer 3

1. onychophora (110)
2. tardigrada (800)
3. nematoda (25 000)
4. arthropoda (1 million)

Question 4

epidermis

Answer 4

below cuticle, living cells that secrete substances that become cuticle

Question 5

3 layers of cuticle

Answer 5

1. epicuticle (includes layer of waxes)
2. exocuticle
3. endocuticle

Question 6

sclerites

Answer 6

hardened plate-shaped regions

Question 7

moulting 10 steps

Answer 7

1. apolysis
2. inactive moulting fluid secreted by epidermis
3. thin protective layer deposited between moulting fluid and epidermis
4. enzymes activated, endocuticle digested
5. new undifferentiated layer of cuticle deposited under protective layer (greater surface area, wrinkled)
6. moulting fluid reabsorbed
7. epicuticle laid down
8. old exocuticle and epicuticle moulted (ectdysis)

Question 8

moulting 10 steps

Answer 8

1. apolysis
2. inactive moulting fluid secreted by epidermis
3. thin protective layer deposited between moulting fluid and epidermis
4. enzymes activated, endocuticle digested
5. new undifferentiated layer of cuticle deposited under protective layer (greater surface area, wrinkled)
6. moulting fluid reabsorbed
7. epicuticle laid down
8. old exocuticle and epicuticle moulted (ectdysis - may swallow water or air)
9. new cuticle expanded
10. exocuticle sclerotized

Question 9

phylum onychophora

Answer 9

velvet worms, tropical terrestrial

Question 10

phylum onychophora

Answer 10

velvet worms, tropical terrestrial, Cambrian ancestors were marine

Question 11

haemocoel

Answer 11

no closed blood vessels, organs bathed in haemolymph, pumped by open-ended tubelike heart

Question 12

onychophora morphology

Answer 12

1. soft-bodied, segmented
2. lobopods
3. little cephalization
4. haemocoel
5. single pair of sensory antennae on head
6. exchange gases using tracheal system
   7.

Question 13

onychophora morphology

Answer 13

1. soft-bodied, segmented
2. lobopods
3. little cephalization
4. haemocoel
5. single pair of sensory antennae on head
6. exchange gases using tracheal system

Question 14

tracheal system

Answer 14

stigmata lead to tracheae which terminate in many fine tubes, O2 and CO2 diffuse

Question 15

stigmata aka spiracles

Answer 15

openings in sides of onychophoran body

Question 16

tracheae

Answer 16

large-bore tubes

Question 17

onychophora feeding

Answer 17

all predators, capture prey by shooting glue from glue glands next to mouth

Question 18

onychophora reproduction

Answer 18

1. separate sexes
2. normal copulation or hypodermic insemination
3. females oviparous, ovoviviparous, or viviparous

Question 19

hypodermic insemination

Answer 19

spermatophore placed on female’s skin, digests through into haemocoel, sperm released and crawl to eggs

Question 20

oviparous

Answer 20

lay eggs that undergo embryonic development outside female’s body

Question 21

ovoviviparous

Answer 21

eggs retained in mother’s body where the young develop, nourished by egg yolk, and hatch inside the mother or immediately after eggs are laid

Question 22

viviparous

Answer 22

young not in eggs undergo development inside mother where they receive nutrients, typically via a placental connection to mother’s tissues

Question 23

phylum tardigrada

Answer 23

water bears, most freshwater some marine,

Question 24

tardigrada morphology

Answer 24

1. 4 pairs of claw-tipped lobopod limbs, move by stepping slowly
2. no antennae or gas exchange system
3. periodically moult
4. able to enter a state of suspended animation in response to drying of habitat

Question 25

phylum nematoda

Answer 25

roundworms, threadworms, morphologically tedious, most free-living in organic substrates, many parasites, medically important

Question 26

nematoda morphology

Answer 26

1. no segmentation, appendages, nor eyes 2. slightly blunt at one end, slightly pointy at the other 3. do moult 4. pseudocoelomate

Question 27

nematode reproduction

Answer 27

1. separate sexes, some hermaphrodites 2. sperm transferred directly by intromission 3. eutelic

Question 28

intromission

Answer 28

(male inserts sperm-transferring structure inside female’s genital opening

Question 29

eutelic

Answer 29

post-embryonic growth occurs by each cell growing, not by addition of cells

Question 30

Caenorhabditis elegans

Answer 30

nematode that is model organism for studying development, can knock out one cell from older embryo and see what is missing in adult (eutelic)

Question 31

phylum arthropoda

Answer 31

most species rich, most ecologically important for decomposition and pollination

Question 32

arthropod morphology

Answer 32

1. jointed limbs 2. sclerotized cuticle made out of chitin acts as exoskeleton 3. segmented 4. well cephalized 5. tagmata in addition to head

Question 33

sclerotized exoskeleton

Answer 33

provides support and a rigid surface for muscles | to attach to, sometimes incorporates minerals

Question 34

tagma

Answer 34

collection of adjacent segments specialized for some function

Question 35

5 main groups of arthropods

Answer 35

1. trilobita 2. chelicerata 3. myriapoda 4. crustacea 5. hexapoda