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Animals
What is an Animal?
• Animal – multicellular eukaryotic
heterotrophs whose cells lack walls
• 95% of all animal species are
invertebrates (no backbone or vertebral
column
Embryology
• Embryology – early development
• Zygote undergoes series of divisions to become
a blastula
• Blastula - Hollow ball of cells
• Gastrula - Blastula folds on itself, forming a
single opening (blastopore) and the gastrula.
– Blastopore leads into a central tube that runs the
length of the developing embryo. Tube becomes the
digestive tract.
The Fertilized Egg & Cleavage
• Yolk~ nutrients stored in the
egg
• Vegetal pole~ side of egg
with high yolk concentration
• Animal pole ~ side of egg
with low yolk concentration
• Blastula~hollow ball stage of
development
Gastrulation
• Gastrula~ 2 layered, cup-shaped
embryonic stage
• 3 Embryonic germ layers:
• Ectoderm~ outer layer; epidermis;
nervous system, etc.
• Endoderm~ inner layer; digestive tract
and associated organs; respiratory, etc.
• Mesoderm~skeletal; muscular; excretory,
etc.
• Invagination~ gastrula buckling
process to create the...
– Archenteron~ primitive gut
– Blastopore~ open end of archenteron
Protostomes and Deuterostomes
• Protosomes – an animal whose mouth is
formed by the blastopore (most
invertebrates)
• Deuterosomes – an animal whose anus is
formed by the blastopore ( echinoderms
and all vertebrates)
Animal Embryology
• Protostome-Deuterostome
dichotomy among coelomates:
protostomes (mollusks, annelids,
arthropods); deuterostomes
(echinoderms, chordates)
• a) cleavage: protostomes~ spiral
and determinate; deuterotomes~
radial and indeterminate
• b) coelom (body cavity) formation:
protostomes~ schizocoelous;
deuterostomes~ enterocoelous
• c) blastopore fate: protostomes~
mouth from blastopore;
deuterostomes~ anus from
blastopore
Body Cavity
• Body cavity (coelom) formation – fluid
filled space that lies between the digestive
tract and the body wall.
– Allow internal organs to be suspended –
helpful during movement.
– Provide room for internal organs to specialize
and enlarge.
Body Symmetry
• Asymmetrical – no symmetry (sponge)
• Radial – like a bicycle wheel, no matter how you
divide the animal with imaginary planes you get
two equal halves (jellyfish)
• Bilateral – a single imaginary plane can split the
animal in half (crayfish, human)
– Cephalization – animals with bilateral symmetry have
concentrated sense organs and nerve cells at the
front end of the body (head)
Binomial Nomenclature
• The Linnaeus System works by placing
each organism into a layered hierarchy of
groups. Each group at a given layer is
composed of a set of groups from the
layer directly below. Simply knowing the
two-part scientific name makes it possible
to determine the other six layers.
Linnaeus System
• The groupings (taxa) of taxonomy from
most general to most specific are:
• Kingdom
• Phylum (animals) or Division (plants)
• Class
• Order
• Family
• Genus
• Species
DOMAIN
Eukarya
KINGDOM
Animalia
PHYLUM
Chordata
CLASS
Mammalia
ORDER
Carnivora
FAMILY
Felidae
GENUS
Felis
SPECIES
Felis catus
Fig. 23-1, p. 485
Domain Comparison
Bacteria
Archaea
Eukarya
Prokaryote
Prokaryote
Eukaryote
Unique bacterial rRNA
nucleotide sequence
Unique archaean rRNA
nucleotide sequence
Cell walls with
peptidoglycan
Cell walls with NO
peptidoglycan
“extremophiles”
Cell walls resistant to
osmotic shock
Cell walls in plants and
fungi
Modern Evolutionary Classification
• If you lived in the time of Linnaeus, how would
you have classified dolphins? Barnacles and
crabs?
• Phylogeny – study of evolutionary relationships
o Species in a genus have a common ancestor
o Genuses in a family have a common ancestor,
etc.
o Conclusion: the higher the taxon, the further
back the common ancestor
Phylum: Porifera (“pore bearer”)
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•
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•
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Sponges
Asymmetrical; no coelom; no organs
Sessile (attached to bottom)
Spongocoel (central cavity)
Osculum (large opening)
Choanocytes (flagellated collar cells)
Hermaphroditic (produce both sperm and eggs)
Phylum: Cnidaria
• hydra, jellies, sea anemones,
corals
• Radial symmetry; no coelom
• No mesoderm; gastrovascular
cavity (GVC) (sac with a
central digestive cavity)
• Hydrostatic skeleton (fluid held
under pressure)
• Polyps and medusa forms
• Cnidocytes (cells used for
defense and prey capture)
• Nematocysts (stinging
capsule)
Phylum: Platyhelminthes
• flatworms, flukes,
tapeworms
• Bilateral; no coelom
• Predators, scavengers,
parasites
• Triplobastic; mesoderm
but, GVC with only one
opening
• Some cephalization
• Many pathogens
(Schistosoma,
Cestodidias)
Phylum: Nemotoda
• roundworms
• Very widespread group of
animals (900,000 sp. ?)
• Cuticle (tough
exoskeleton)
• Decomposition and
nutrient cycling
• Complete digestive track;
no circulatory system
• Trichinella spiralis
Phylum: Mollusca
• snails, slugs, squid, octopus,
clams, oysters, chiton
• True coelom
• Soft body protected by a hard
shell of calcium carbonate
• Foot (movement), visceral
mass (internal organs); mantle
(secretes shell); radula (rasplike scraping organ)
• Ciliated trochophore larvae
(related to Annelida?)
Phylum: Annelida
• earthworms, leeches, marine
worms
• True body segmentation
(specialization of body
regions)
• Closed circulatory system
• Metanephridia: excretory
tubes
• “Brainlike” cerebral ganglia
• Hermaphrodites, but crossfertilize
QuickTime™ and a
Cinepak decompressor
are needed to see this picture.
Phylum: Arthropoda
• trilobites (extinct); crustaceans
(crabs, lobsters, shrimps);
spiders, scorpions, ticks
(arachnids); insects
(entomology)
• 2 out of every 3 organisms
(most successful of all phyla)
• Segmentation, hard
exoskeleton (cuticle)~ molting,
jointed appendages; open
circulatory system
(hemolymph); extensive
cephalization
Arthropoda: Insect characteristics
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•
•
•
•
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Outnumber all other forms of life
combined
Malpighian tubules: outpocketings
of the digestive tract (excretion)
Tracheal system: branched tubes
that infiltrate the body (gas
exchange)
Metamorphosis…...
•incomplete: young resemble
adults, then molt into adulthood
(grasshoppers)
•complete: larval stages (looks
different than adult); larva to adult
through pupal stage
QuickTime™ and a
Cinepak decompressor
are needed to see this picture.
Phylum: Echinodermata
•
sea stars, sea urchins, sand dollars,
sea lilies, sea cucumbers, sea daisies
•
Deuterostomes
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•
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Spiny skin; sessile or slow moving
Often pentaradial
Water vascular system by hydraulic
canals (tube feet)
QuickTime™ and a
Cinepak decompressor
are needed to see this picture.
Chordates
• Notochord: longitudinal, flexible
rod located between the
digestive and the nerve cord
• Dorsal, hollow nerve cord;
eventually develops into the
brain and spinal cord
• Pharyngeal slits; become
modified for gas exchange, jaw
support, and/or hearing
• Muscular, postanal tail
Invertebrate chordates
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•
•
•
Both suspension feeders…..
Subphy: Urochordata (tunicates; sea squirt); mostly sessile & marine
Subphy: Cephalochordata (lancelets); marine, sand dwellers
Importance: vertebrates closest relatives; in the fossil record, appear 50
million years before first vertebrate
Subphylum: Vertebrata
• Retain chordate characteristics with
specializations….
• Neural crest: group of embryonic
cells near dorsal margins of closing
neural tube
• Pronounced cephalization:
concentration of sensory and
neural equipment in the head
• Cranium and vertebral column
• Closed circulatory system with a
ventral chambered heart
Vertebrate diversity
• Phy: Chordata
• Subphy: Vertebrata
• Superclass: Agnatha~
jawless vertebrates
(hagfish, lampreys)
• Superclass:
• Gnathostomata~jawed
vertebrates with 2 sets of
paired appendages; including
tetrapods (‘4-footed’) and
amniotes (shelled egg)
Superclass Agnatha
• Jawless vertebrates
• Most primitive, living
vertebrates
• lamprey and hagfish
• Lack paired
appendages;
cartilaginous skeleton;
notochord throughout
life; rasping mouth
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Superclass Gnathostomata, I
Class: Chondrichthyes~ Sharks, skates, rays
Cartilaginous fishes; well developed jaws and paired fins; continual water flow over
gills (gas exchange); lateral line system (water pressure changes)
Life cycles:
Oviparous- eggs hatch outside mother’s body
Ovoviviparous- retain fertilized eggs; nourished by egg yolk; young born live
Viviparous- young develop within uterus; nourished by placenta
Superclass Gnathostomata, II
• Class: Osteichthyes
• Ossified (bony) endoskeleton; scales operculum(gill covering); swim
bladder (buoyancy)
• Most numerous vertebrate
• Ray-fined (fins supported by long, flexible rays): bass, trout, perch,
tuna, herring
• Lobe-finned (fins supported by body skeleton extensions): coelocanth
• Lungfishes (gills and lungs): Australian lungfish (aestivation)
Superclass Gnathostomata, III
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Class: Amphibia
1st tetrapods on land
Frogs, toads, salamanders, caecilians
Metamorphosis; lack shelled egg;
moist skin for gas exchange
Superclass Gnathostomata, IV
• Class: Reptilia
• Lizards, snakes, turtles, and crocodilians
• Amniote (shelled) egg with extraembryonic membranes (gas exchange,
waste storage, nutrient transfer); absence of feathers, hair, and mammary
glands; ectothermic; scales with protein keratin (waterproof); lungs;
ectothermic (dinosaurs endothermic?)
Superclass Gnathostomata, V
• Class: Aves
• Birds
• Flight adaptations: wings
(honeycombed bone); feathers
(keratin); toothless; one ovary
• Evolved from reptiles (amniote egg
and leg scales); endothermic (4chambered heart)
• Archaeopteryx (stemmed from an
ancestor that gave rise to birds)
Superclass Gnathostomata, VI
• Class: Mammalia
• Mammary glands; hair (keratin);
endothermic; 4-chambered heart;
large brains; teeth differentiation
• Evolved from reptilian stock
before birds
• Monotremes (egg-laying): platypus
• Marsupials (pouch): opossums,
kangaroos, koalas
• Eutherian (placenta):
all other mammals