Transcript Bauplan 2

Invertebrate Zoology
Lecture 2: Bauplans (cont.)
Lecture outline
 Animal Bauplans
Key features of body plans (cont.)
 Locomotion and support
 Feeding
Bauplans: key features
 Locomotion and support
Type of locomotion limited by type of
support system
 Example: Peristaltic movement requires a hydrostatic
skeleton
Locomotion depends upon medium through
which an animal moves as well as its size
 Reynold’s number Re = plU
v
 Large animals: high Re (>1.5): Inertial forces rule
 Small animals: low Re (<1.5): Viscous forces rule
Bauplans: key features
 Locomotion and support
Four key locomotory methods
 Amoeboid
 Cilia/flagella
 Hydrostatic propulsion
 Use of limbs
Bauplans: key features

Locomotion and support: amoeboid movement
 Many cell types move this way

Amoebocytes of sponges
Extension of
pseudopodia
 Fluid “endoplasm”
pushes the more
viscous “ectoplasm” in
a particular direction.
 Endoplasm and
ectoplasm are the
same… ∆ viscosity
 Movement involves
actin and myosin
Bauplans: key features

Locomotion and support: cilia/flagella
 Operate effectively at low Re

Sometimes associated with secreted mucus
 Several Functions

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Propulsion of larvae and small adults
Create fluid currents for feeding and gas exchange
Propel food particles and/or waste particles
Role in sensory structures
Bauplans: key features

Locomotion and support: cilia/flagella
Structure
 9 + 2 microtubule
arrangement
 Dynein arms
ATP-powered
 Microtubules slide past
each other slightly
 Protein cross-links limit
sliding  bending
Bauplans: key features

Locomotion and
support: cilia/flagella
 Patterns of movement
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Flagella: may beat back and
forth, or may move in a helical
(or “rotary”) motion
Push or pull along axis of
flagellum
Bauplans: key features

Locomotion and support:
cilia/flagella
 Patterns of movement
 Cilia: oar-like movement
 Power stroke vs. recovery
stroke
 Metachronal waves
 Coordination of
metachronal waves is
usually mechanical
 Cilia and flagella are very
specific terms (not “hairs!”)
Bauplans: key features

Locomotion and support: hydrostatic
 Key principle: body fluids are not compressible:
 can be pushed into structures  expansion.
 can provide support/structure
 Complementary action of circular and longitudinal
muscles
 Circular: decrease diameter with contraction
 Longitudinal: shorten with contraction
 Fluids move in response to muscle contraction
 Helical muscles prevent twisting and kinking
 Anchor points important
Bauplans: key features

Locomotion and support: hydrostatic
 Peristalsis of earthworm
Phylum Echiura
 Fat innkeeper worm: also moves by
peristalsis within tube
Bauplans: key features

Locomotion and
support: limbs
 Involves rigid skeleton
 Exoskeleton: usually
epidermally-derived
 Endoskeleton: usually
mesodermally-derived
 Some are articulated:
with joints
 Did skeletons arise “by
chance” from
accumulation of metabolic
wastes? (nitrogenous
waste  chitin)
Bauplans: key features

Locomotion and
support: limbs
 Muscles attach to and
push against skeletal
elements in order to
move
 Origin vs. insertion
points
 Often in pairs of
antagonistic muscles
(i.e. flexor/extensor
pairs)

Note interior attachment
points for exoskeleton
Bauplans: key features

Feeding
 Digestion

Extracorporeal digestion: occurs outside body
 Example: some sea stars open up mussel shell
and secrete enzymes to liquefy tissue
 Use cilia and mucus to draw fluids into mouth
Bauplans: key features

Feeding
 Digestion
 Intracellular
digestion: occurs
within cells
 Phagocytosis
(particles)
 Pinocytosis (fluids)
 Role of lysosomes
 Absorption of DOM
Bauplans: key features

Feeding
 Digestion

Extracellular digestion:
within gut chamber
 Incomplete
 single opening
 Complete
 two openings
 Advantages of
complete digestive
system?
Bauplans: key features

Feeding
 Modes of feeding (briefly)
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Suspension feeding: remove food particles
from the water column
Deposit feeding: obtain nutrients from the
sediments
Herbivory
Carnivory
Scavenging
Direct intake of dissolved organic materials