Lecture
27
Support and Movement
Overview
of lecture
Functions
of Skeletons
Movement
Hydrostatic
Skeletons of Hydra and Earthworm
Suitability
for Aquatic Habitat; Drawbacks
Exoskeleton
of Grasshopper
Preadaptation
for life on land
Success
and Plasticity of Form of Insects
Endoskeleton
of Fish and mammal
Adaptations
for water or land
Functions
of Skeletons
Support
Movement
Protection
Functions
of Skeletons
Support
If
weight bearing resists gravity
Framework
for structure
Functions
of Skeletons
Movement
Acts
as mechanical resistance for muscles
Provides
firmness for muscles to work against
Functions
of Skeletons
Protection
Hard
skeleton protect against mechanical injury
Exoskeletons
can also protect against water lost
Movement
(locomotion)
Ciliary
movement or by contraction of muscles
Accomplished
by microtubules in cilia
Muscles
work by shortening in length
Microfilaments
(actin and myosin) in muscle cells
Levers
cause actin and myosin to slide across each other’s surface
Expenditure
of ATP
Two
antagonistic muscles work against each other, cause opposite movements
Examples
of Skeletons
Hydrostatic
Skeleton of Hydra and Earthworm
Exoskeleton
of Grasshopper
Endoskeleton
of Fish and Mammals
Hydrostatic
Skeletons
Water-filled
closed compartment under pressure
Muscles
surround compartment: provide pressure
Contraction
of antagonistic muscles causes distortion of shape for movement
Circular
muscles contract decrease diameter
Water
is non-compressible: diameter decrease increases length
Longitudinal
muscles contract to decrease length
Water
is non-compressible: length decrease increases diameter
Drawbacks
of Hydrostatic skeletons
Limited
to aquatic or soil dwelling animals
Water
provides buoyancy, soil some support
Offers
no protection
Not
weight bearing: limits size
Hydrostatic
Skeleton of Hydra
Hydrostatic
skeleton is GVC
Mouth
must be closed
Longitudinal
muscles in epidermis
No
circular muscles
Movement
of Hydra
Water
taken in by flagella in GVC expand GVC
Longitudinal
fibers in epidermis contract to become short and fat
If
mouth is open water is expelled
Tentacles
move independently of body to allow prey capture
Hydrostatic
Skeleton of Earthworm
Coelom
is divided by septa
Individually controlled
hydraulic chambers
Both
circular, and longitudinal muscles in body wall
Movement
of Earthworm
By
peristalsis
Waves
of muscle contraction travelling along length
Alternating
contraction and lengthening of segments
Setae
provide anchorage
Contraction
of long. muscles shortens segments
Pulls
body forward
Contraction
of circ. muscles lengthens segments
Pushes
body forward
Exoskeleton
of Grasshopper
Non-living
non-cellular layer on surface of body
Secreted
by epidermis
Composed
of chitin and protein
Movement
of Grasshopper
Jointed
appendages move for locomotion
Thinner
at joints to allow movement
Appendages
are weight bearing: allows for crawling and jumping
Muscles
are not associated with body wall
Muscles
bundles on inside, attached to exoskeleton
Antagonistic
pairs allow movement of appendage in both directions
Third
pair of legs are long with powerful muscles for jumping
Two
pairs of wings for flight
Anterior
pair stiff like fixed wings of planes
Posterior
pair are membranous provide lift and propulsion
Significance
of Exoskeleton
Driving
force behind evolution of insects
Most
successful group of animals (over 50%)
Plasticity
of form and appendages
High
diversity
Waxy
layer on cuticle makes it waterproof
Highly
adapted for land
Growth
requires molting of exoskeleton
Weight
of exoskeleton limits size
Fish
and Mammal Endoskeletons
Cartilage
or bone
Living
tissue
Solid
core vs hollow tube (exo)
Allows
endo to have more mass therefore are better at weight bearing
Largest
animals have endo
Muscles
are antagonistic and attached to outside of bones
Appendages
are jointed allows for crawling, walking, jumping, running
Axial
skeleton is skull, spine, rib cage
Appendicular
skeleton is appendages and pectoral and pelvic girdles
Swimming
by fish
Perch
has swim bladder for buoyancy
Sinusoidal
movement: side to side, in wave
Thrust
provided by tail fin
Pectoral,
pelvic fins for steering
Mammalian
Movement
Thorax
and abdomen lifted off ground by appendages
Propelled
by paired appendages
Comparison
of Land and Water for Support and Movement
Water
is 1000X more dense than air
Water
provides buoyancy
In
water skeleton is not weight supporting
On
land skeleton is weight bearing
Fish
Skeleton
Vertebral
column positioned centrally
Ribs
numerous and weak
Sternum
absent: no ribcage
Lack
of bones in appendages [fins]
Mammalian
Skeleton
Vertebral
column is more dorsal: weight hangs from vertebral column
Chest
with strong ribs and sternum: weight bearing
Cantilever
suspension: vertebral column is supported by pelvic and pectoral girdles