Animal Diversity 2
Multicellular, eukaryotic, heterotrophic organisms
that feed by INGESTION
Nematoda
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Most abundant animal on Earth
Pseudocoelomate
Up to a million different species!!! (only ~50k described)
15,000 species are described as parasitic
Sheds proteinaceous cuticle
LOTS of investment in reproductive organs
Represent 90% of ocean floor species.
Account for 80% of all individual species on earth!
Body cavity
Acoelomate
Pseudocoelomate
Eucoelomate
Nematodes as parasites
Case study: Trichinosis
Phenotypic Plasticity
Spikes in response to
predation
Up-regulation of chemical deterrents in
response to herbivory.
Mouth parts changing in response to
environmental conditions.
Arthropoda
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Animals with exoskeleton, segmented body,
and jointed appendages
Exoskeleton is periodically shed
Four subphyla: Crustacea, Hexapoda,
Cheliceriformes, Myriapoda
Exoskeleton is mainly chitin
First organisms to fly – unoccupied niche (air)
allowed for massive radiation
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Crustacea
Biramous (two-parted) limbs (even barnacles)
Most are free-living aquatic animals
Some (e.g. pill bugs) are terrestrial
Some (e.g. barnacles) are sessile
Ex: Crustacean claws
branch into 2 segments
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Crustacea
Daphnia have five pairs of biramous thoracopods
(thorax appendages)
Hexapoda:
Six-legged arthropods
External insect anatomy
3 distinct body units: head, thorax, and
abdomen
Insect head:
Search for: compound
eyes, ocelli, antennae,
labrum, mouthparts
Insect mouthparts:
Mandible, maxilla, labium
Evolution of mouthpart
morphology
Chewing mouthparts
(e.g. grasshopper)
A: Chewing (e.g. locust)
B: Lapping (e.g. bee)
C: Siphoning (e.g. moth)
D: Sucking (e.g. mosquito)
Arthropod respiration:
Tracheal system
Cheliceriformes
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No antennae, no jaws
Pincer-like appendages called chelicera used
for grasping and fragmenting food
A word on horseshoe crabs….
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Not crustaceans.
2 primary compound eyes, 7 secondary simple eyes
Hemocyanin carries oxygen instead of hemoglobin
(they have blue blood due to high levels of copper)
Only arthropod with “broadcast spawning”
Totally weird.
We collect blood because it coagulates
in the presence of gram-neg bacteria
Myriapoda
Millipedes
2 pairs of legs per segment
Detritivores
Centipedes
1 pair of legs per segment
Predators
Final notes:
Only two more labs:
- Animal Diversity 3 (chordates and starfish)
- and then a final lab practical
(no lecture for the last lab)
I will post a study guide this week on howbiologyworks.com