Transcript Chapter 19: Invertebrates

Invertebrates
Anatomy and Physiology in
Invertebrates
Support and Movement
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Almost all animals have muscle-like
tissue for movement
Three types of skeletons:
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Hydrostatic skeleton
Exoskeleton
Endoskeleton
Hydrostatic Skeleton
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Muscles supported by a water-filled
body cavity
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No hard structures for muscles to pull
against
Push against the water in the body cavity
Cnidarians, flatworms, nematodes,
mollusks, annelids
Exoskeleton
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External skeleton, muscles attached inside
Arthropods have exoskeletons made of chitin
Exoskeletons are thin and flexible at joints,
allowing for flexion and extension
Very adaptable, very strong
Drawbacks are that the animal must shed it
and grow a new one as it gets larger, and it
is heavy
Endoskeleton
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Present in sponges and echinoderms
(also in vertebrates)
Internal skeleton
Feeding and Digestion
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Intracellular digestion vs extracellular
digestion
Sponges filter food particles from the
water and digestion is intracellular
with nutrients being distributed among
cells
Feeding and Digestion
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Cnidarians and flatworms have a
gastrovascular cavity
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Digestive sac with a single opening – food
enters, wastes leave
Food particles broken down into smaller
pieces, then are taken up by cells lining the
cavity and digestion is intracellular
Feeding and Digestion
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Extracellular digestion takes place in annelids,
mollusks, arthropods, invertebrate chordates
Tube within a tube digestive system – food
enters through mouth and leaves through
anus, digestive tract forms a separate tube
within the body
Food is digested extracellulary in digestive
tract and nutrients are absorbed
Internal Transport
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Constant supply of oxygen and
nutrients necessary for survival
Carbon dioxide and posionous wastes
need to be eliminated
Invertebrates like sponges, cnidarians,
flatworms, and nematodes do not have
circulatory systems – all done by
diffusion
Internal Transport
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More complex invertebrates (and
vertebrates) have circulatory systems,
which include one or more pumps and
tubes that move things around within
the body
Open and closed circulatory systems
Open Circulatory System
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Blood from heart is not entirely contained
within blood vessels
Heart pumps blood through a series of
vessels, and it is released directly onto body
tissues
Flows through tissues and is collected in
sinuses, eventually flowing back to heart
Seen in some types of mollusks (clams,
oysters), arthropods, echinoderms
Closed Circulatory System
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Blood contained within a system of
closed vessels that pass through various
parts of the body and return to the
heart
Blood does not come in direct contact
with tissues – more rapid and efficient
Seen in some mollusks (squids,
octopuses), and annelids
Respiration (gas exchange)
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Small soft-bodied invertebrates exchange
oxygen and carbon dioxide by diffusion
through body surfaces
Two respiratory problems:
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Respiratory system must have large surface area
to allow for enough gas exchange to support
organism’s demands
Surface of organs must be kept wet because
diffusion can only take place across moist
membranes
Respiration (gas exchange)
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Animals that live in water do not have
these problems (sponges, cnidarians,
flatworms, nematodes, echinoderms)
Mollusks and crustaceans have gills,
which are rich in blood vessels and
provide a large surface area for gas
exchange
Respiration (gas exchange)
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Terrestrial invertebrates have special
organs for breathing air
Spiders have book lungs – sheet-like
layers of thin tissue that contain blood
vessels
Insects have trachea – tubes that
bring air to each body cell
Excretion (waste elimination)
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Related to maintaining proper water
balance
Ammonia is a highly toxic, water soluble
byproduct of the breakdown of amino
acids – carried in blood and body fluids
Eliminating ammonia means eliminating
water
Excretion (waste elimination)
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Marine invertebrates (like sponges,
cnidarians) have thin bodies and get rid of
ammonia by diffusion through body surfaces
or gill surfaces
Freshwater flatworms have flame cells,
which remove water and water soluble
wastes
Flame cells form a network that empties
water and wastes through opening in the skin
Can also diffuse waste
Excretion (waste elimination)
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Annelids, mollusks, invertebrate
chordates have nephridia – structures
that remove wastes from body fluids
and return water and solutes to the
body
Waste products eliminated as urine
Excretion (waste elimination)
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Land invertebrates convert ammonia
into urea (less toxic) which is
concentrated into urine and expelled
Insects and some spiders convert
ammonia into uric acid, which is
removed by Malpighian tubules –
uric acid excreted with solid waste,
conserving water
Response
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All animals have some sort of nervous
system, with individual nerve cells functioning
the same
Primitive invertebrates have a nerve net
spreading through their body
Some cnidarians (jellyfish) show
centralization where nerve cells are more
concentrated, forming nerve cords or rings
around the mouth
Response
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Cephalization comes with
concentrations of nerve and sensory
cells in the head
Primitive flatworms have ganglia
(clumps of nerve cells) while insects
and some mollusks have actual brains
Brains lead to nerve cords
Response
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Along with nervous development comes
increased sensory development
Flatworms have eye spots
Insects have well developed, compound
eyes
Reproduction
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All invertebrates are capable of sexual
reproduction, though some also
reproduce asexually
Sexual reproduction creates and helps
maintain genetic variation