Download Phyla of Invertebrates - Trimble County Schools

Invertebrates
The Most Important Characterstics
18.1 What is an animal?
– eukaryotic,
– multicellular
– heterotrophs that ingest their food
– cells lack cell walls
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Body Plan
– Animal body plans vary in symmetry, body cavity, and
number of germ layers
– A radially symmetrical animal has a
top and bottom but lacks back and
front or right and left sides
– Animals with bilateral symmetry have
mirror-image right and left sides, a
distinct head and tail, and a back
(dorsal) and belly (ventral) surface
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Dorsal surface
Top
Anterior
end
Posterior
end
Ventral surface
Bottom
Body Plan
Most animals are diploid with haploid sex cells:
Gastrulation-zygote developmental stage that
gives rise to digestive tract
Endoderm-cell layer lining digestive tract
Ectoderm-gives rise to outer covering;nervous
system
Mesoderm-forms muscles and internal organs
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Body Plan
– The body cavities (coelom) of animals vary
– Acoelomate – no body cavity
– A pseudocoelom is partially lined by
tissue derived from mesoderm
– A true coelom is completely lined by
tissue derived from mesoderm
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Tissue-filled region
(from mesoderm)
Body covering
(from ectoderm)
Digestive sac
(from endoderm)
Body covering
(from ectoderm)
Muscle layer
(from mesoderm)
Digestive tract
(from endoderm)
Pseudocoelom
Body covering
(from ectoderm)
Coelom
Digestive tract
(from endoderm)
Tissue layer
lining coelom
and suspending
internal organs
(from mesoderm)
No true
tissues
Sponges
Radial
symmetry
Cnidarians
Echinoderms
Chordates
Flatworms
Protostomes
Bilateral
symmetry
Bilaterians
Eumetazoans
True
tissues
Deuterostomes
Ancestral
colonial
protist
Molluscs
Annelids
Arthropods
Nematodes
18.5 Sponges
–Sponges (phylum Porifera) are
simple, sedentary, sessile
animals without true tissues
–suspension feeders filtering
food particles from water
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18.6 Cnidarians
– (phylum Cnidaria) have two tissue layers:
– use tentacles to capture prey and push
them into their mouths
– Cnidocytes on tentacles sting prey and
function in defense
– Polyp stage and medusa stage
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18.7 Flatworms
- phylum
Platyhelminthes are the
simplest bilateral animals
– There are three major groups of
flatworms:planarians, flukes,
tapeworms
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Gastrovascular
cavity
Nerve cords
Mouth
Eyespots
Nervous
tissue
clusters
Bilateral symmetry
Units with
reproductive
structures
Scolex
(anterior
end)
Hooks
Sucker
18.8 Roundworms
– phylum Nematoda- have bilateral
symmetry and three tissue layers
– The complete digestive tract
has a mouth and anus
– Humans host at least 50 species of
nematodes
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18.9 Molluscs
- phylum Mollusca -have a true coelom and a circulatory
system
– Many feed with a rasping radula, used to scrape up
food
– have
– A muscular foot that functions in locomotion
– A visceral mass containing most of the internal organs
– A mantle, which may secrete a shell that encloses the
visceral mass
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Visceral mass
Coelom
Kidney
Heart
Mantle
Reproductive
organs
Digestive
tract
Shell
Digestive tract
Mantle
cavity
Radula
Anus
Radula
Mouth
Gill
Mouth
Foot
Nerve
cords
Eyes
18.10 Annelids
– phylum Annelida - have a closed
circulatory system in which blood
is enclosed in vessel
– nervous system includes a simple
brain and ventral nerve cord
– coelom functions as hydrostatic
skeleton
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Epidermis
Anus
Circular
muscle
Segment wall
(partition
between
segments)
Segment
wall
Longitudinal
muscle
Dorsal
blood
vessel
Mucus-secreting
organ
Bristles
Excretory
organ
Intestine
Bristles
Nerve cord
Dorsal
blood
vessel
Coelom
Excretory
organ
Digestive
tract
Ventral blood vessel
Segment
wall
Brain
Ventral blood vessel
Mouth
Nerve cord
Pumping
segmental
vessels
Giant
Australian
earthworm
18.11 Arthropods
– phylum Arthropoda: including
crayfish, lobsters, crabs, barnacles,
spiders, ticks, and insects
– segmentation, a hard exoskeleton, and
jointed appendages
– open circulatory system
– head, thorax, and abdomen
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Cephalothorax
Head
Abdomen
Thorax
Antennae
(sensory
reception)
Swimming
appendages
Walking legs
Pincer (defense)
Mouthparts (feeding)
A black widow
spider (about
1 cm wide)
A scorpion
(about 8 cm long)
A dust mite
(about 420  m
long)
18.11 Arthropods
 Millipedes and centipedes
– 2 legs per segment in herbivorous
millipedes
– 1 pair legs per segment in
carnivorous centipedes
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18.12 EVOLUTION CONNECTION: Insects are the
most successful group of animals
– 70% of all animal species are insects
– There may be as many as 30 million insect species
– The body of an insect includes a head, thorax, and
abdomen; three sets of legs; and (in most insects)
wings
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Head
Antenna
Thorax
Abdomen
Forewing
Eye
Mouthparts
Hindwing
18.13 Echinoderms
– phylum Echinodermata: include slow-moving or
sessile radially symmetrical adult organisms
such as sea stars and sea urchins
– water vascular system has water-filled canals
branching into tube feet, which are used for
respiration, feeding, and locomotion
– Echinoderms and chordates -bilateral animals
called deuterostomes
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Anus
Spines
Stomach
Tube feet
Canals
Chordates
• Dorsal hollow nerve cord
• Notochord
• Pharyngeal slits
• Post-anal tail
Excurrent
siphon
Post-anal tail
Dorsal, hollow
nerve cord
Pharyngeal
slits
Mouth
Muscle
segments
Notochord
Adult
(about 3 cm high)
Larva