Transcript You Light Up My Life

Animals: The Invertebrates
Chapter 25
Characteristics of Animals
• Multicelled heterotrophic eukaryotes
• Require oxygen for aerobic respiration
• Reproduce sexually, and perhaps
asexually
• Motile at some stage
• Develop from embryos
Chordates
Major
Animal
Phyla
Echinoderms
Arthropods
Annelids
Coelomate
Ancestry
Mollusks
Rotifers
Roundworms
Bilateral
Ancestry
Radial
Ancestry
Multicelled
Ancestry
Figure 25.2
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Flatworms
Cnidarians
Sponges
Single-celled, protistanlike ancestors
Symmetry
Radial
Bilateral
Figure 25.3
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The Gut
• Region where food is digested and then
absorbed
• Saclike gut
– One opening for taking in food and expelling
waste
• Complete digestive system
– Opening at both ends; mouth and anus
Body Cavities - Acoelomate
epidermis
gut cavity
no body cavity; region between gut
and body wall packed with organs
Figure 25.4a
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Body Cavities - Pseudocoel
epidermis
gut cavity
unlined body cavity
(pseudocoel) around gut
Figure 25.4b
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Body Cavities - Coelom
gut cavity
lined body cavity
(coelom)
peritoneum
Figure 25.4c
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Segmentation
• Repeating series of body units
• Units may or may not be similar to one
another
• Earthworms - segments appear similar
• Insects - segments may be fused and/or
have specialized functions
Animal Origins
• Originated during the Precambrian (1.2
billion - 670 million years ago)
• From what? Two hypotheses:
– Multinucleated ciliate became
compartmentalized
– Cells in a colonial flagellate became
specialized
Phylum Placozoa
• One living species,
Tricoplax adherens
• Simplest known
animal
• Two-layer body,
3 mm across
Figure 25.5
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Sponges - Phylum Porifera
• No symmetry
• No tissues
• No organs
• Reproduce sexually
• Microscopic swimming larval stage
Sponge Structure
water out
glasslike
structural
elements
amoeboid
cell
pore
semifluid
matrix
central
cavity
flattened
surface
cells
water in
Figure 25.7a
flagellum
microvilli
nucleus
Page 419
Phylum Cnidaria
• Only
animals that
produce
nematocysts
• Nerve net
• Hydrostatic
skeleton
• Saclike gut
capsule’s lid
at free surface
of epidermal
cell
trigger
barbed
thread
inside
capsule
nematocyst
Figure 25.8
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Cnidarian Diversity
• Scyphozoans
– Jellyfish
• Anthozoans
– Sea anemones
– Corals
• Hydrozoans
Two Main Body Plans
outer epithelium
(epidermis)
mesoglea
(matrix)
Medusa
Figure 25.9 Page 420
inner epithelium
(gastrodermis)
Polyp
Obelia Life Cycle (Hydrozoan)
reproductive
polyp
male medusa
female medusa
ovum
sperm
zygote
feeding
polyp
polyp
forming
planula
Figure 25.10
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Flatworms:
Phylum Platyhelminthes
• Acoelomate, bilateral, cephalized
animals
• All have simple or complex organ
systems
• Most are hermaphrodites
Three Classes
• Turbellarians (Turbellaria)
• Flukes (Trematoda)
• Tapeworms (Cestoda)
Planarian Organ Systems
flame cell
nucleus
pharynx
cilia
protonephridia
opening of
tubule at
body surface
flame cell
fluid
filters
through
membrane
folds
Fig. 25.11a,b
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Planarian Organ Systems
brain
nerve cord
ovary
testis
oviduct
genital pore
penis
Fig. 25.11cd
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Roundworms (Nematoda)
• False coelom
• Complete digestive system
pharynx
intestine
false coelom
eggs in uterus
gonad
anus
muscularized body wall
Figure 25.13
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Flukes: Class Trematoda
• Parasitic worms
• Complicated life
cycle
– Larval stage
infects a mollusk
– Adult infects a
Worms mate in
human host
Larvae bore
into human
skin
Larvae form,
leave snail
Fertilized egg
Asexual reproduction
in intermediate host
Ciliated larva
vertebrate
Southeast Asian blood fluke
Figure 25.14
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Tapeworms: Class Cestoda
Definitive host
Larvae
encysted in
muscle
tissue
Intermediate
host
Scolex attaches
to host
intestinal wall
Figure 25.15
Mature proglottid with fertilized eggs
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Rotifers
• Bilateral
• Cephalized
• False coelom
• Crown of cilia at
head end
• Complete gut
Figure 25.17
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Two Coelomate Lineages
Protostomes
• Mollusks
• Annelids
• Arthropods
Deuterostomes
• Echinoderms
• Chordates
Cleavage Patterns
Protostome embryo
(spiral cleavage)
Deuterostome embryo
(radial cleavage)
In-text figure
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Mollusks: Phylum Mollusca
• Bilateral, soft-bodied, coelomate
• Most have a shell or reduced version of
one
• Mantle drapes over body and secretes
shell
• Most have a fleshy foot
• Many have a radula for shredding food
Molluscan Diversity
• Gastropods
• Chitins
• Bivalves
• Cephalopods
Torsion
• Twisting of body
parts during larval
development
• Occurs only in
gastropods
mouth
gill
anus
Figure 25.18
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Body Plan of a Snail
heart
mantle cavity
anus
gill
mantle
digestive
gland
foot
radula
Figure 25.18
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Body Plan of a Clam
mouth
left mantle
retractor muscle
retractor muscle
foot
palps
left gill
shell
Figure 25.21
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Cephalopods
• Only the nautilus retains external shell
• Other cephalopods are streamlined, active
swimmers
• All move by jet propulsion
– Water is forced out of mantle cavity through a
funnel-shaped siphon
• Have large brains relative to body size
Cuttlefish Body Plan
Closed circulatory system with heart and
accessory heart
esophagus
digestive
kidney stomach
gland
Figure 25.22
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brain
arm
jaw
tentacle
mantle
reproductive internal
siphon
ink sac heart accessory organ
shell
radula
anus
gill
heart
Annelids: Phylum Annelida
Segmented, coelomate worms
• Class Polychaeta
• Class Oligochaeta
• Class Hirudinea
Polychaetes
• Most are marine
• Bristles extend
from paired, fleshy
parapods on each
segment
• Head end is
specialized
“jaws”
toothlike
structures
pharynx
(everted)
antenna
palp
(food handling)
tentacle
eyes
chemicalsensing pit
parapod
Fig. 25.24c
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Leeches - Class Hirudinea
• Predators and parasites
• Less obvious body segmentation
• Most have sharp jaws
Earthworm - An Oligochaete
No parapodia, few bristles per segment
Dorsal blood vessel
Circular muscle
Coelom
Longitudinal
muscle
Nephridium
Nerve cord
Figure 25.25a
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Seta (retracted)
Nerve cord
Earthworm Nephridium
bladderlike storage
region of nephridium
nephridium’s thin loop reabsorbs some
solutes, relinquishes them to blood
blood
vessels
body
wall
funnel (coelomic fluid
with waste enters here)
external pore (fluid containing
wastes discharged here)
Figure 25.25b
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Earthworm Circulatory System
Hearts
Figure 25.25c
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Earthworm Digestive System
Coelomic chambers
Esophagus
Crop
Gizzard
Pharynx
Mouth
Figure 25.25d
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Earthworm Nervous System
Brain
Nerve cord
Figure
25.25e
Page
431
Arthropods:
Phylum Arthropoda
• The phylum with the greatest number of
species
• Four lineages:
– Trilobites (all extinct)
– Chelicerates (spiders, mites, scorpions)
– Crustaceans (crabs, shrimps, barnacles)
– Uniramians (insects, centipedes, millipedes)
Adaptations for Success
• Hardened exoskeleton
• Jointed appendages
• Fused and modified segments
• Respiratory structures
• Specialized sensory structures
• Division of labor
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Figure 25.26
Page 432
Chelicerates
• Originated in seas
• A few are still marine: horseshoe crabs,
sea spiders
• The arachnids are all terrestrial
Spiders
Mites
Scorpions
Chiggers
“Daddy longlegs”
Ticks
Body Plan of a Spider
eye
brain
heart digestive gland Malpighian tubule
poison
gland
book lung ovary silk gland
pedipalp
mouth
sperm receptacle
anus
spinners
chelicera
Figure 25.28
Crustaceans
• Most are marine, some
freshwater, a few
terrestrial
• Head has two pairs of
antenna, three pairs of
food-handling
appendages
Copepods
Crayfish
Barnacles
Lobsters
Shrimps
Crabs
Isopods (pillbugs)
Lobster Body Plan
one of two
eyes
antennae
(two pairs)
fused segments of
cephalothorax
segments of
abdomen
food-handling
appendages
(three pairs)
swimmerets
tail
fin
first leg
five walking legs (five pairs total)
Figure 25.29a
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Crab Life Cycle
Larval and juvenile
stages molt repeatedly
and grow in size
egg
Figure 25.30
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Millipedes and Centipedes
• Segmented bodies with many legs
• Millipedes
– Two pairs of legs per “segment”
– Scavengers
• Centipedes
– Flattened, with one pair of legs per segment
– Predators
Insect Body Plan
• Thorax usually has three pairs of legs
and one or two pairs of wings
• Abdomen contains most internal organs
and specialized structure for
reproduction
• Three-part gut
• Malpighian tubules attach to midgut and
serve in elimination of wastes
Insect Headparts
Butterfly
Mosquito
Grasshopper
antenna
labrum
mandible
Fly
maxilla
palps
labium
Figure 25.32
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Insect Diversity
• The only winged invertebrates
• More than 800,000 known species
• Most successful species are small in
size and have a great reproductive
capacity
Types of
Insect
Development
Growth and molting
egg
young
adult
Incomplete metamorphosis
Different stages exploit
different resources at
different times
egg
adult
nymphs
Complete
metamorphosis
egg
larvae
pupa
adult
Unwelcome Arthropods
• Poisonous spiders
• Disease-carrying
ticks
• Venomous
scorpions
• Agricultural pests
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Corn rootworm (Diabrotica virgifera)
Figure 25.38
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Echinoderms
• Deuterostomes
• Body wall has spines or
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plates
• No brain
• Adults are radial with
Sea urchin
bilateral features
Sea cucumber
Figure 25.39
Brittle star
Page 440
Echinoderm Diversity
• Crinoids (sea lilies and feather stars)
• Sea stars
• Brittle stars
• Sea urchins, heart urchins, sand dollars
• Sea cucumbers
Body Plan of a Sea Star
sieve
plate
gonad
coelom
anus
upper
stomach
lower
stomach
digestive gland
eyespot
Figure 25.40a
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Water Vascular System
sieve plate
ampulla
Figure 25.40b
Page 441