Animal Systematics
Systematics
• The study of biological diversity and
classification
• classification of living organisms by
evolutionary relationship
Classification
• Carolus Linnaeus (17071778)
– Swedish naturalist
• Developed the modern
taxonomic classification
system
Linnean System of Classification
Kingdom
Phylum
Class
Order
Family
Genus
Species
Animalia
Chordata
Mammalia
Primates
Hominidae
Gorilla
Gorilla gorilla
Revised Linnean System
Division
Kingdom
Phylum
Subphylum
Superclass
Class
Subclass
Infraclass
Order
Superfamily
Family
Subfamily
Genus
Species
Subspecies
Eukarya
Animalia
Chordata
Vertebrata
Tetrapoda
Mammalia
Theria
Eutheria
Primates
Anthropoidea
Hominidae
Ponginae
Gorilla
Gorilla gorilla
Gorilla gorilla beringei
Binomial Nomenclature
• Genus + species
• Examples:
–
–
–
–
Rana catesbeiana: bull frog
Turdus migratorius: American robin
Homo sapiens: modern human
Mucosa domestica: house fly
• Subspecies sometimes included
– Gorilla gorilla beringei: mountain gorilla
What is an Animal
• Eucaryotic
– cells divided into organelles
• Multicellular
• Heterotrophic
– do not produce own nutrients
• Lack cell walls
• Tissues linked by proteins (e.g. collagen)
What is an Animal
• Cells often linked by cell junctions
– gap, adhesion, tight
• Possess electrogenic cells
– nerve cells and muscle cells
• Reproduce sexually (diploid)
– sperm + egg → zygote → blastula → gastrula
→ larva → adult
Major Evolutionary Divergences
Among Animals
• Development of Tissues
• Development of Body
Plans
• Development of Body
Cavities
• Developmental Origin
of the Coelom
Development of Tissues
• Development of aggregations of similar
cells into patterns and layers
• Parazoa (sponges) – lack tissues
• Eumetazoa – possess tissues
Development of Body Plans
• Pattern of body and structure
• Number of embryonic cell layers
• Radiata (e.g. jellyfish, hydra)
– radial symmetry
– diploblastic (2 germ cell layers)
• Bilatera (everything else)
– Blateral symmetry
– Triploblastic (3 germ cell layers)
Development of Body Cavities
• Acoleomates (flatworms)
– no body cavities
• Pseudocoelomates (rotifers,
roundworms)
– body cavity not surrounded by
mesoderm (pseudocoelom)
• Coleomates (everything else)
– body cavity enclosed by
mesoderm (coelom)
Developmental Origin of the
Coelom
•
Coelomates are divided into two gorups
based upon:
1. Pattern of cell cleavage during early
development
2. When cell developmental fate is determined
3. How the coelom is formed
4. How the digestive tract is formed during
gastrulation
Protostomes
• Mollusks, earthworms, insects, etc.
• Spiral cleavage
– cell division diagonal to vertical axis
• Determinant cleavage
– development into tissues determined
very early in cleavage
• Schizocoelous
– coelom forms by splitting solid masses
of mesoderm in
• Blastopore forms mouth
Deuterostomes
• Starfish, vertebrates
• radial cleavage
– cell division at right angles to vertical
axis
• indeterminant cleavage
– development into tissues determined
later in cleavage
• enterocoelous
– coelom forms by mesoderm layer
budding from archenteron
• blastopore forms anus
Parazoa:
Phylum Porifera
•
•
•
•
•
sponges
little cell differentiation
sessile
no nerve or muscle cells
porous body
– enables water circulation
through the body
– flow driven by choanocytes
– food collected and digested
by amoebocytes
Radiata:
Phylum Cnidaria
• Corals, jellyfish,
anemones, corals
• gastrovascular cavity
– central compartment
with single opening
• two basic body plans:
– polyp – usually sessile
– medusa – motile form
Radiata:
Phylum Cnidaria
• tentacles arranged around
opening to the
gastrovascular cavity
• lined with nematocysts
– stinging cells
• possess nerve cells
forming nerve net
– no central nervous system
• possess muscle-like cells
Radiata:
Phylum Ctenophora
• Comb jellies
• Similar in appearance to
jellyfish
• Possess comb-like plates
of cilia used for
locomotion
• Collect food with tentacles
covered with colloblasts
(lasso cells)
Acoelomates:
Phylum Platyhelminthes
• Flatworms
• gastrovascular cavity with one
opening
• true muscle tissue
• primitive excretory system (water
balance)
• sensory organs in head
(photoreceptors, chemoreceptors)
• central nervous system (ganglia in
head w/ ventral nerve cords)
Acoelomates:
Phylum Platyhelminthes
• Major Classes
– Turbellaria
• planarians (free living)
– Monogenea and
Tremotoda
• flukes (parasites)
– Cestoidea
• tapeworms (parasites)
Pseudocoelomates:
Phylum Rotifera
• Rotifers
• complete digestive tract
– separate mouth and anus
• pseudocoelomic fluid
acts as circulatory
system
• cilia lining crown draw
water into the mouth
Pseudocoelomates:
Nematoda
• Nematodes (roundworms)
• complete digestive tract
• pseudocoelomic fluid acts
as circulatory system
• longitudinal muscle
orientation
• aquatic habitats, soils,
plant and animal parasites
Protostome Coelomates:
Phylum Nemertea
• Proboscis worms
• acoelomous body, except
for fluid-filled sac used to
extend proboscis
• similar excretory, sensory
and nervous systems to
flatworms
• complete digestive tract
• closed circulatory system
(blood confined to vessels)
Protostome Coelomates:
Lophophorate Phyla
• possess lophophore
– ciliated fold around
mouth
• no head
• U-shaped digestive
tract
Protostome Coelomates:
Lophophorate Phyla
• Bryozoans
– sessile, resemble
moss, hard
exoskeletons
• Phoronids
– horseshoe worms
• Brachiopods
– resemble bivalves
Protostome Coelomates:
Phylum Mollusca
• Mollusks
• Major Classes:
– Class Polyplacophora
• chitons
– Class Gastropoda
• snails and slugs
– Class Bilvalvia
• clams, oysters, mussels, etc.
– Class Cephalopoda
• octopus, squid, nautiluses
Protostome Coelomates:
Phylum Mollusca
• Muscular foot
• visceral mass
– contains organs
• gills (respiration)
• complete digestive tract w/
specialized organs
• open circulatory system
(blood not confined to
vessels)
• mantle
– covers visceral mass, secretes
shell
Protostome Coelomates:
Phylum Annelida
• Annelids (segmented worms)
• hydrostatic skeleton
• coelom in repeating segments
with alternating longitudinal and
circular muscles, setae, and
metanephridia (excretion)
• closed circulatory system
• several specialized regions in
digestive tract
• cerebral ganglia with ventral
nerve cord
Protostome Coelomates:
Phylum Annelida
• Major Classes
– Class Oligochaeta
(earthworms)
– Class Polychaeta
(polychaetes)
– Class Hirudinea
(leeches)
Protostome Coelomates:
Phylum Arthropoda
• specialization of body
segments
– specialized limbs, etc.
• hard exoskeleton
– protein and chitin
• high cephalization of
sensory organs
• open circulatory systems
– blood (hemolymph) not
confined to vessels
Arthropods:
Chelicerates
• claw-like feeding appendages
(chelicerae), lack antennae
• Class Arachnida (spiders,
scorpions, ticks, mites)
– 2 body segments (cepahlothorax
and abdomen)
– 6 pairs of appendages
• chelicerae, pedipalps, 4 pr walking
legs extend from cephalothorax
– book lungs
• enhances gas exchange btw
hemolymph and air
Arthropods:
Uniramians
• jaw-like feeding appendages
(mandibles), 1 pair of antennae,
unbranched appendages
• Class Diplopoda – millipedes
• Class Chilopoda – centipedes
• Class Insecta – insects
– three body segments (head, thorax,
abdomen)
– many possess wings
– specialized digestive system
– Malpighian tubules (excretion)
– tracheal system (respiration)
Arthropods:
Crustaceans
• mandibles, 2 pair of antennae,
branched appendages
• Class Crustacea
– possess gills
– salt glands (hemolymph salt
balance)
• Groups
– Isopods (e.g. pill bugs)
– Copepods (e.g. Cyclops)
– Decapods (crabs, lobsters, etc.)
Deuterostome Coelomates :
Phylum Echinodermata
• sea stars, sea urchins, sea
cucumbers
• adults have radial
symmetry
– bilateral larvae
• endoskeleton of hard
plates
• water vascular system
– used to manipulate tube
feet
Deuterostome Coelomates :
Phylum Chordata
•
•
Lancelets tunicates, vertebrates
Characteristics of embryos:
1. possess notochord
•
longitudinal, flexible rod between
digestive tract and nerve cord
2. possess dorsal hollow nerve
cord
3. have pharyngeal slits
•
modified for gas exchanges, jaw
support, hearing, etc.
4. have muscular postanal tail
Invertebrate Chordates
• Subphylum Urochordata
– tunicates
– sessile marine animals
– chordate characters seen
only in larvae
• Subphylum
Cephalochordata
– lancelets
Subphylum Vertebrata
• Characteristics
– neural crest formation during embryonic
development
– vertebral column + skull
– pronounced cephalization of sensory and
neural apparati
– closed circulatory system
• Agnathans
– lack hinged jaws, notochord present
throughout life
• Gnathostomes
– possess hinged jaws, notochord replaced by
vertebrae, paired appendages
• Tetrapods
– Possess two pairs of appendages
Superclass Agnatha
• lack hinged jaws,
• notochord present
throughout life
• no paired appendages
• lampreys and hagfish
Superclass Gnathostoma:
Jawed Fish
• Class Chondrichthyes
– Sharks, rays
– cartilaginous skeletons
• Class Osteichthyes
– bony fish (bone skeletons)
– Subclass Actinopterygii
• Ray-finned fish
– Subclass Sarcopterygii
• Lobe-finned fish
Superclass Tetrapoda:
Class Amphibia
• Characteristics
– tetrapods (4 limbs)- terrestrial
movement
– aquatic larval stage
– moist, permeable skin
• Anurans
– frogs and toads
• Urodeles
– salamanders and newts
• Caecilians
– legless, fossorial amphibians
Superclass Tetrapoda:
Class (?) Reptilia
• Reptiles
• Scaly, impermeable skin
• Amniotes
– Lay shelled amniotic eggs
• Chelonians (Testudines)
– Turtles
• Lepidosaurians
– Tuatara, snakes, lizards
• Archosaurs
– Crocodilians, dinosaurs, birds
Superclass Tetrapoda:
Class Aves
•
•
•
•
•
Birds
Amniotes
Possess feathers
Possess wings (flight)
Endothermic
– most body heat generated
internally
• Two-circuit circulatory
system
Superclass Tetrapoda:
Class Mammalia
•
•
•
•
•
•
Mammals
Possess hair
Possess mammary glands
Endothermic
Two-circuit circulatory system
Most give birth to young
(amniotic)
• Diaphragm for active
ventilation of lungs
Superclass Tetrapoda:
Class Mammalia
• Groups
– Monotremes
• lay eggs
• platypuses, echidnas
– Marsupials
• embryo completes development in
pouch
• kangaroos and opossums
– Eutherians
• form placenta
• cats, humans, squirrels