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Animal Evolution
Porifera
sponges
• 5,000 living sponge species
• Three Main Groups:
– hexactineuida (glass sponges)
– demospangia
– calcarea (calcareous sponges)
• no coelom, organs, or skeleton
• no urinary, cardiovascular, respiratory or
nervous system
• cellular grade of organization
Evolutionary Time Frame
• Among the oldest known fossils
• began in late Precambrian
• developed from first multi-cellular
organism
Tissues
• Two layers of cells
– layers are separated by gelatinous region
called mesohyl
• Spongocoel
– the central cavity
– internal water chambers
• water flows in and out of the osculum
• coanocytes are flagellated, collar cells
– these line the spongocoel
– help propel water through cell
Reproduction
• Reproduce sexually or asexually
• Hermaphrodites
– this means they are male and female
– produce both eggs and sperm
• gametes arise from choanocytes or amoebocytes
• eggs reside in the mesohyl, while sperm cells are carried out of the
sponge by water current
• fertilization occurs in the mesohyl
• zygotes develop into flagellated, swimming larvae
• in asexual reproduction buds are produced
– are often packets of several cells inside a protective coating
called gemmule
Locomotion
• No muscles
Digestion
• No mouths
• carnivores
• archaiout, cells ingest and
digest food
• suspension feeders
– “filter feeders”
– they collect bacteria
taken from the water
• tiny pores in outer walls
– these draw water
– called ostia
• cells in sponge walls filter water
• water is pumped through the body and out larger opening (oscula)
• flow of water is unidirectional
– driven by beating of flagella which line the surface of chambers
and are connected by a series of canals
Cnidaria
corals, jellyfish, hydra
• Four Main Classes
– Anthozoa (corals, anemones, sea pens, sea
fans, sea anemones)
– Cubozoa (box jellies)
– Hydrozoa (diverse group of siphonophores,
hydroids, five corals, medusae, obella)
– Scyphozoa (true jellyfish, jellies, sea wasps, sea
nettles)
• do not have a cardiovascular system
Evolutionary Time Frame
Cnidaria first appeared during the Pre-Cambrian era
• Corals - first appeared in Vendian
– few fossils in Cambrian period, but identifiable corals
began evolutionary radiation in Early Ordovician
Period
– wiped out at end of Permian Period
• mass extinction event in which 95% of all marine
invertebrate species became extinct
– scleractinian corals appeared in the middle of the
Triassic (15 million years later)
• became dominant hermatypic (reef-building)
organisms in shallow tropical marine habitats
Tissues
• Simplest organisms at tissue level
• cells are organized in true tissues
• two cell layers - outer ectoderm (epidermis) and inner
endoderm (gastrodermis)
• Outer Ectoderm
– contains cnidocysts (stinging cells)
• Inner Endoderm
– lines gut (sometimes divided by septa)
• Mesoglea (between layers)
– layer of jelly-like substance
– contains scattered cells and collagen fibers
Excretion
• Cnidarias have one oral opening
• all secretions, including waste materials,
exit through this
• Undigested remains are sent back through
the anus/mouth
Reproduction
• Alternate between asexual and sexual
– sexual reproduction includes free-swimming
forms
• formation of gametes in medusae and some
polyps
– asexual budding (polyps)
• Gonads are the only organs present in the
body cavity of cnidaria
Locomotion
• Cnidaria move by a decentralized nerve
net and simple receptors
• movement is coordinated by the nerve
net
• move freely in water by passive drifting
and contractions of its bell-shaped body
Digestion
• Cnidaria are carnivores
• they have tentacles in a ring around their
mouth
– these capture prey and push food into the
gastrovascular cavity
• gastrovascular cavity is a sac with a central
digestive compartment
• cnidaria have one opening which
functions as the mouth and anus
Respiratory
• Done by the diffusion of oxygen through
their tissues
Nervous
• Cnidaria contain muscles and nerves in the
simplest form
• Cells of the epidermis and gastrodermis
have bundles of microfilaments arranged
in contractile fibers
• there is no brain, and the nerve net is
associated with simple sensory receptors
that are distributed throughout the body
Platyhelminthes
flat worms
• Means “flat worm”
• thin bodies between dorsal and ventral
surfaces
• Consist of Four Classes:
– Turbellaria (free-living flatworms)
– Monogenea (monogeneans)
– Trematoda (trematodes or flukes)
– Cestoidea (tapeworms)
• no urinary system
Evolutionary Time Frame
• Origin of bilaterians, Precambrian period
– before Cambrian explosion
• early origin of coelom hypothesized by
trace fossils left in Precambrian sediments
Tissue
• Epidermis covers body
– made up of layers of cells
• the middle embryonic layer is the
mesoderm
– here occurs the development of complex
organs and organ systems to true muscle
tissue
• inner layer of cells forms intestine
Reproduction
• Most Reproduce asexually
– while some do reproduce sexually
• the parent constricts in the middle
– each half regenerates its missing end
• cross-fertilization between individuals
Locomotion
• Glide along a film of mucus, secreted by
themselves
• the cilia on the ventral epidermis able
them to move
Digestion
• Have a gastrovascular cavity with one
opening
• they lack a digestive tract
• absorb nutrients across the body surface
• branched gut to transport food
Cardiovascular
• Lack organs for circulation
• fluid filled spaces aid in transport
Respiratory
• Lack organs for gas exchange
• internal tissues are near the surface of the
skin
– this is because of their flattened bodies
– gas and nutrients exchange with environment
Nervous
• Pair of cerebral ganglia
• longitudinal nerve cords connect to
transverse nerves
Nematoda
roundworms
• Nematoda consist of
no distinct classes
• Nema - “thread”
• 90,000 known species
• do not have a
respiratory system
Evolutionary Time Frame
• Found as early as the Carboniferous period
• fossils of nematodes were found in amber, these dated
back to the Cenozoic era
• relatives of nematoda date back to Cambrian
– nematodes remain in the same form since then
• because nematodes are microscopic, fossils are difficult
to find
– they lack hard body parts
Tissue Layers
• Contain internal body cavity
– pseudoderm
• lack cilia and well-defined head
• the epidermis (skin) is composed of a
mass of cellular material and nuclei, these
are not separated by membranes
• a thick outer cuticle which is tough and
flexible is secreted
– this cuticle is shed, usually about four times
before it becomes an adult
– tough exoskeleton
Excretion
• Some nematodes
have specialized
cells that excrete
nitrogenous waste
• canals are present
in others to
excrete wastes
Reproduction
• Reproduce sexually with internal
fertilization
– males use copulatory spines to open female
reproductive tract and inject sperm
• sperm lack flagellae and move by pseudopodia
• females are larger than males and deposit
about 100,000 eggs a day
Locomotion
• Muscles are longitudinal and contract
producing a thrashing motion
– only bend from side to side
– muscle cells branch toward nerve
• the internal pressure is high, this causes
the body to flex, rather than flatten
• nematoda have no cilia or flagellae
Digestion
• Have mouth opening into pharynx
(throat)
– food is pulled in and crushed
– pharynx leads to a long simple gut cavity
lacking muscles
– it is then led to the anus at the tip of the
body
• nutrients and wastes are distributed in
body cavity
– this is regulated by an excretory canal along
each side of the body
Cardiovascular
• No cardiovascular system
• nutrients are transported through the
body by fluid in the pseudocoelom
Nervous
• Ring of nervous tissue around the pharynx
• gives rise to two nerves: dorsal and ventral
– nerve cords
– run the length of the body
– muscle cells branch toward nerve
Mollusca
snails, slugs, oysters, clams, octopuses, squids
• Over 150,000 known species
• molluscous are soft bodied
– protected by a hard shell made of calcium
carbonate
• Classes:
– Plolyplacophora (chitons)
– Gastropoda (snails and slugs)
– Bivalvia (clams, oysters, bivalves)
– Cephalopida (squids, octopuses, hautiluses)
Evolutionary Time Frame
• Lived in freshwater streams as early as
400 million years ago
• developed the ability to be able to live in
most aquatic environments
– 300 million years ago
Tissue
• Three main parts:
– Muscular foot (for movement)
– visceral mass (containing the internal organs)
– mantle (fold of tissue, drapes over visceral
mass, secretes shell)
• houses gills, anus, excretory pores
• some produce a water filled chamber
– called a mantle cavity
Excretion
• Excretory organs called nephridia
– remove metabolic wastes from hemolymph
Reproduction
• Separate sexes with gonads in the visceral
mass
• life-cycle includes ciliated larva
(trochophore)
Locomotion
• Muscular foot
• no bones
• Outer shell made of calcium carbonate
supports and protects
• some also have inner shells for support
– called cuttlebones in cuttlefish
– pen in squids
Digestion
• Feed by a strap like
rasping organ called
the radula to scrap
food
– ribbon like, hooked
teeth
• have jaw, pharynx,
esophagus,
stomach, intestine
and anus
Cardiovascular
• Open circulatory system
• no true heart
• blood is pumped along by vessels and join
with open sinuses
– bathes internal organs
Respiratory
• Gills housed in mantle cavity
– function in gas exchange
• terrestrial snails lack gills
– instead, lining of mantle cavity functions as a
lung
– exchanges respiratory gases with air
Nervous
• Clams and chitons have no nervous
system
• squid and octopus have most sophisticated
nervous system of all vertebrates
– they have large brains and eyes
– giant axon transmits messages
Annelids
earthworms, leeches, marine worms
• 15,000 species
• Three classes:
– Oligochaeta (earthworms)
– Polychaeta (polychaetes)
– Hirudinea (leeches)
• Annelids means “little rings”
• segmented worms
Evolutionary Time Frame
• Originated in Precambrian
Tissue
• Coelom partitioned by septa
– penetrated by digestive tract, longitudinal
blood vessels and nerve cords
Excretion
• Metanephridia
– excretory tubes in each segment
– ciliated funnels
– remove waste from blood and coelomic fluid
– lead to exterior pores, discharges waste
• nephridia excrete waste
– these are coiled tubes with expanded funnel
shape (nephostrome, attached to septum)
– leads to outside on posterior end
Reproduction
•
•
•
•
•
Cross-fertilization
Sperm is stored
clitellum secretes a mucous cocoon
cocoon picks up eggs and stored sperm
some reproduce asexually by
fragmentation
Locomotion
• Two types of
muscles:
circulatory and
longitude
• when muscles
tighten, others
lengthen
Digestion
• Contains specialized regions
– pharynx
– esophagus
– crop
– gizzard
– intestine
•
•
•
•
Cardiovascular
Closed cardiovascular system
has a network of vessels
blood and oxygen carrying hemoglobin
dorsal and ventral blood vessels
– main blood vessels
• blood transported by contractions of the
walls of the vessels
– called peristalsis
• pairs of vessels connect dorsal and ventral
vessels
Respiratory
• The respiratory organ is the skin
• epidermis layer is very thin and moist
– this allows for gas exchange
Nervous
• Cerebral ganglia is located above and in
front of the pharynx
• ring of nerves around pharynx connects to
sub-pharyngeal ganglion
• nerve cords run posterioly
Arthropods
crustaceans, spiders, insects
• Consist of over one million species
• arthropod means “jointed feet”
• make up over 3/4 of all known living and
fossil organisms
• conquered the land, sea and air
• Classes: Triolbita, Chelicerata, Uniramia,
Diplopoda (millipedes), Chilapoda
(centipedes), Insecta (insects)
• do not have a urinary system
Evolutionary Time Frame
• Soft-bodied relatives began during the Vendian
• rapid evolution in Cambrian Period
• Trilobites (the dominant marine group) began
in the Paleozoic
• arachnids moved onto land during Devonian
– 385 million years ago
• oldest insect fossil from the Devonian Period
– 400 million years ago
Tissue
• The cuticle covers the entire body
• exoskeleton
– made of tough compounds, chitin and protein
– outer shell
– structure against which muscles pull
– reduces water loss (impermeable to water)
– protection
– chitin laid in plates with joints
– exoskeleton is molted (shed) occasionally
• leaves temporarily vulnerable
• legs have two branches (biramous appendages)
– outer branch are flattened gills
– inner branch is used for walking, grasping, chewing, or
reproduction
Reproduction
• Paired reproductive
organs (ovaries and
testes)
• dioecious
• internal fertilization
• most lay eggs and
development proceeds
with some form of
metamorphosis
Locomotion
• Movement of
appendages is controlled
primarily by a complex
muscular system
– muscular system divided
into smooth and striated
components
Digestion
• Mandible or jaws chew food
Cardiovascular
• Open circulatory system
• fluid called hemolymph is propelled by the
heart through short arteries and into
spaces called sinuses surrounding tissues
and organs
– blood flows and bathes tissues and organs
– dorsal tubular heart is perforated by pores
– generally lack blood vessels
• resembles open circulatory system of
mollusks, but arose independently
Respiration
•
•
•
•
•
Organs specialized for gas exchange
– allow diffusion of respiratory gases in spite of exoskeleton
aquatic species
– gills with thin feathery extensions
– place extensive surface area in contact with surrounding water
terrestrial
– have internal surfaces
– insects
• tracheal systems
• branched air ducts, lead into interior from pores in cuticles
gas exchange occurs inside book lungs
– these are stacked plates in internal chambers
its extensive surface area is a structural adaptation
– enhances exchange of oxygen and carbon dioxide between hemolymph
and air
Nervous
• Well developed sensory organs, include:
– eyes
– olfactory receptors for smell
– antennae for touch and smell
– sensory organs concentrated at anterior end
• Three Regions:
– deutocerebrum
– protocerebrum - receives nerves of eyes and other organs
– tritocerebrum
• association with neuropils (antennae)
• nerves innervate mouth parts and anterior digestive canals
• contains annelid-like brain (cerebral ganglion)
– nerve ring surrounding pharynx connects the brain with the pair
of ventral nerve cords
• these cords contain numerous ganglia
Echinodermata
starfish, sand dollars, brittle stars, sea cucumbers, sea urchins
• Pentameral (fivefold symmetry)
– rays or arms in fives or multiples of fives
• echin “spiny” derma “skin”
• suckered tube feet which move and grip
• Classes:
– Concentricycloidea (sea daisies)
– Asteroida (starfish, sea stars)
– Crinoidea (sea lillies, feather stars)
– Ophiuroidea (brittle or snake stars)
– Echinoidea (sea urchins, sand dollars)
– Holothuroidea (sea cucumbers)
• about 7,000 known species
• no urinary system
• poorly developed nervous system
Evolutionary Time Frame
• Fossils are not pentameral
• oldest known Venedian fossil is Arkarua
– soft bodied with unmineralized plates
• modern echinodermata (with mineralized
skeleton) entered the fossil record in early
Cambrian
• Asterozoans date back to Ordivician
• crineids and blastoids are the later Paleozoic
– became extinct at the end of the Permian
Period
Tissue
• Spacious coeloom
– open, fluid-filled body cavity
• large gonads
• complete gut
• interlocking calcium carbonate plates and
spines
– enclosed by epidermis (endoskeleton)
Reproduction
• External fertilization
– egg and sperm are freely discharged into water
• provide no parental care
• go through planktonic larval stages before
settling down
• separate males and females
Locomotion
• Tube feet
– extend, grip, contract and release
• do this over and over again
• hydrualic water vascular system
– network of fluid filled canals
– function in locomotion, feeding and gas
exchange
Digestion
• Some turn stomach inside out through
the mouth
• sea urchins scrape algae from rocks with
five large teeth
• secrete juices that digest soft body of
mollusks in its own shell
Cardiovascular
• Does not have a cardiovascular system
• functions of the cardiovascular system are
taken over by the water vascular system
Respiration
• No respiratory system
• once again, functions of the respiratory
system are done by the water vascular
system
Chordata
vertebrates
• Includes humans and vertebrates
• all have the same features at some point in life
– these features include:
• pharyngeal slits - digestive tube from mouth to anus
– pharynx posterior to mouth, slits
• dorsal, hollow nerve cord - develops into central nervous
system: brain and spinal cord
• notochord - longitudinal, flexible rod between digestive
tube and nerve cord
• muscular post-anal tail - skeletal elements and muscles
– propulsive force in aquatic species
• Echinoderms are the closest living relative of humans
Chordata
• Vertebrates have the ability to regenerate ATP by
cellular respiration
– this is the consumption of oxygen
• adaptations of vertebrate respiratory and circulatory
systems support mitochondrion muscle cells and active
tissues
• all have a closed circulatory system with ventral,
chambered heart
– pumps blood through arteries to microscopic vessels
called capillaries
• capillaries branch throughout every tissue in the
body
• blood is oxygenated as it passes through capillaries in
gills or lungs
Chondricthyes
sharks, rays
• Have cartilaginous skeletons
Evolutionary Time Frame
• Appeared 450 million years ago
• cartilaginous skeleton is a derived
characteristic
– ancestors had bony skeletons, cartilaginous
skeleton characteristic evolved secondarily
Tissue
• Made up of cartilage
– this has a lower density compared to bones
– more flexible
Excretion
• Two kidneys
– hundreds of units of renal corpuscle, deals
with excess water
• in renal corpuscles water and dissolved
substances are squeezed into the end of the
tubule
• cells in this tubule allow certain substances to
pass out and back into capillaries
• tubules join at the end of the urinary duct
– carries urine to urinary sinuses
• urine exits body
Reproduction
• Sexually dimorphic
– separate females and males
• fertilization inside female body
• three ways of reproducing:
– oviparity (female lays eggs)
– oviviparity (eggs hatch in oviduct of female,
develops in uterus)
– viviparity (embryo nourished in placenta)
Digestion
• Jaw and muscles push food down esophagus
• enters stomach
– gastric juices produced by microscopic glands
• then enters intestine
– digestive juices produced by liver and pancreas
– absorb nutrients
– intestines twist around themselves to increase surface
area
• rectal gland filters waste and empties into the rectum
• cloaca opens to the outside
Locomotion
• Powerful swimming muscles in caudal
(tail) fin
– propel them forward
• dorsal fins stabilize
• pectoral and pelvic fins provide lift in
water
• gains buoyancy by storing large amounts
of oil in its liver
– still sinks if it stops swimming
Cardiovascular
• Two chambered heart with one atrium and
one vesicle
– not strong enough to get blood to the gills
– must swim constantly to produce heart
contractions
Respiratory
• Gills pull oxygen from the water
• Ramjet ventilation must occur
– constant flow of water through the gills
• Blood is pumped through brachial arteries
to blood vessels in gills
• oxygenated blood circulates back through
the system
Nervous
• Central nervous system with a brain and
spinal cord
• brain is simple with three parts
– forebrain (obtains information from sight
and smell detectors)
– midbrain (coordinates sensory information)
– hindbrain (coordinates basic life functions
and movement)
Osteoicthyes
ray-finned, lobe-finned, lungfish
• Bony fishes
• ossified endoskeleton with hard matrix of
calcium phosphate
• skin is covered by flattened, bony scales
• appeared in the Devonian and
Carboniferous Periods
Evolutionary Time Frame
• All bony fishes
combined into single
vertebrate class,
osteoichthyes
– based on cladistics, now
recognized in three
extant classes: ray-finned
fishes, lobe-finned fishes
and lungfishes
Tissues
• Have ossified endoskeleton with hard
matrix of calcium phosphate
• skin is covered by flat, bony scales
Excretion
• Two small kidneys work to excrete wastes
Reproduction
• Oviparous
• external fertilization
• female sheds large numbers of small eggs
Locomotion
• Glands in skin secrete mucus giving
sliminess, reduces drag during swimming
• flexible fins steer and propel
Digestion
• Digestive tract includes: liver, stomach,
intestine, anus
Cardiovascular
• Swim bladder
– air sac
– helps control buoyancy
– transfer of gases between swim bladder and blood
– varies inflation of bladder and adjusts density of fish
• Three chambered heart
– consists of two atria, one ventricle
– little mixing of oxygenated and deoxygenated blood
– allows animal to control blood flow
• is able to shunt deoxygenated and oxygenated
blood to body or lungs
Respiratory
• Draw in water over gills located in
chambers covered by protective flaps
– overculum
• water is drawn in through pharynx and out
between gills by movement of operculum
and contraction of muscles surrounding
gill chambers
• many different forms of lung ventilation
– squamates - axial musculature
– crocodilians - muscular diaphragm
Nervous
• Two pairs of
cranial nerves
• advanced nervous
system
• compared to
amphibians
Amphibia
salamanders, frogs, caecilians
• Orders: Urodela (salamanders)
– Anura (frogs)
– Apoda (Caecilians)
• Amphibian means “two lives”
– close ties with water, most abundant in damp
habitats (swamps and rainforests)
– rely heavily on moist skin
Evolutionary Time Frame
• Earliest amphibia found in early Devonian
period
– 363 millions years ago
• modern amphibia didn’t appear until
Mesozoic era
– 248 million years ago
Tissue
• Coelom
– houses all internal organs
Excretion
• Ureters carry liquid waste to bladder
• leaves through cloaca and cloacoe vent
– same way as solid waste
Reproduction
• External fertilization
• male grasps female and spills sperm over
eggs of female as she sheds them
• lay eggs in a moist environment
• some reproduce on land where eggs are
deposited
• some give live birth
• most fertilized eggs are deposited in water
– eggs hatch into larvae
Locomotion
• Salamanders move by side-to-side
bending
• frogs have powerful hind legs
Digestion
• Mouth
• esophagus (tube to stomach)
• stomach (food is mixed and partly
digested)
• small intestine (most digestion takes
place, absorbs nutrients)
– digestive juices come from liver and pancreas
• Frogs
– long sticky tongue, nabs insects
• attached to front of mouth
Cardiovascular
• Three chambered heart
– two atria, one ventricle
• double circulation
– blood is pumped twice
– provides blood flow to brain, muscles and
other organs
Respiratory
• Rely on moist skin
– network of blood vessels run through skin
– this carries out gas exchange with
environment
• some lack lungs and breathe through the
skin and oral cavity
Reptilia
snakes, lizards, crocodiles, turtles, birds
• Have scales containing the protein keratin
– this water proofs the skin
– prevents dehydration in dry air
• 6,500 species of extinct reptiles
• Four Groups:
– Testudines (turtles
– Sphenodontia (tuatara)
– Squamata ( lizards and snakes)
– Crocodilia (alligators and crocodiles)
Evolutionary Time Line
•
•
•
•
•
•
•
•
Reptilia were more numerous and diverse during the Mesozoic era
go as far back as the late Carboniferous Period
– 350 million years ago
the oldest fossils were found in Kansas in the late Carboniferous period
– 300 million years ago
ancestors are the Devonian amphibians
first major reptilian radiation occurred during the dawn of Permian
– last Paleozoic era
– gave rise to three main branches: Synapsida, Aapsida, Diapsida
second great radiation by late Triassic
– 200 millions years ago
– dinosaurs (land) and pterosaurs (flying reptiles)
dinosaurs extinct at the end of Cretaceous
– last period of Mesozoic
turtles appeared during the Mesozoic era and haven’t changed since
Excretion
• Two small kidneys
• main nitrogenous waste product is uric
acid
Reproduction
• Lay shelled amniotic eggs on land
• fertilization is internal as eggs pass
through the reproductive tract of the
female
Locomotion
• Agile and fastmoving
• very diverse
– swim, slither,
crawl, run, fly
Digestion
• Dinosaurs:
– Ornithischians are herbivores
– saurichians are herbivorous and carnivorous
• birds
– food isn’t chewed in mouth, ground in
gizzard (digestive organ near stomach)
– crocodiles and dinosaurs also have gizzards
Cardiovascular
• Closed circulatory system
• three chambered heart
– two atria, one ventricle
– little mixing of oxygenated blood and deoxygenated
blood in heart
– blood flow can be altered to shunt deoxygenated
blood to the body or oxygenated blood to the lungs
• Birds
– four chambered heart
• keeps tissues supplied with oxygen and nutrients
Respiratory
• Cannot obtain oxygen through their skin
which is keratinized and dry
• Obtain oxygen using lungs
• many turtles obtain gas exchange through
the moist surface of their cloaca
Nervous
• Advanced nervous system compared to
amphibians
• consists of 12 cranial nerves
Mammalia
• Characteristics of mammalia
– Possession of mammary glands
– produce milk
– hair
– endothermic
– efficient respiratory and circulatory systems
– live birth
• Three Major Groups:
– Monotremes (egg-laying mammals)
– Marsupials (mammals with pouches)
– Eutherian (placental)
Evolutionary Time Frame
• Evolved from reptilian stock during Mesozoic era, even
before birds did
– 180 million years ago
• became dominant form of life 65 million years ago
• oldest mammalian fossils date back to 200 million years
ago (Triassic Period)
• fossils from Permian and Triassic connect mammals with
reptilian ancestors
• Mesozoic mammals were small and probably ate insects
• Great adaptive radiation occurred during the Cenozoic
era, dawned in the wake of Cretaceous extinction
Tissue
• Four types of tissue
– epithelial
• covers external surfaces, internal cavities and
organs
– connective
• binds and supports body parts, protects, fills
spaces, transports materials and stores fat
• two kinds - loose and dense
– nerve
• responds to stimuli and transports impulses from
one part of the body to another
– muscle
• contracts in response to stimulation
Excretion
• Kidney
– main excretory organ
• blood enters kidneys through nephrons
• capillaries and tubules filter blood
• first water, ions and small organic molecules are
removed
• next, water and selected minerals are reabsorbed,
returned to bloodstream
• urine is the final product
– carried out through the ureter
– stored in bladder
– exits through urethral opening
• Internal fertilization
• separate sexes
• male
– two testes lie in skin covered sac
(scrotum)
– sperm is produced in testes and deposited
in female genital tract
• female
– two ovaries, produce ova
– embryos develop inside uterus of female
reproductive tract
– placenta (the lining of the mother’s uterus
and extraembryonic membranes)
• nutrients diffuse into embryo’s blood
• Monotremes - platypuses and echidnas
– only living mammals that lay eggs
• Marsupials are born early in development
– they complete embryonic development
while nursing inside mother’s pouch
Reproduction
• Bones
– axial and appendicular
skeleton
• muscles include:
– diaphragm, separates
thoracic cavity from
abdominal
– musculation of jaw
region and limbs help
with getting food and
movement
– muscles associated with
outer hairy skin allow
automatic responses and
facial expression
Locomotion
Digestion
• Differentiation of teeth for different foods
• stomachs vary in complexity
• herbivores have more complex stomachs
and produce certain bacteria for breaking
up cellulose
• carnivores have relatively simple stomachs
Cardiovascular
• Active metabolism
• four chambered heart
• complex way to distribute oxygen,
digested food, hormones and other
chemicals
• carries away waste products
• oxygenated blood carried away from heart
to body
• deoxygenated blood pumped back to lung
Respiratory
• Diaphragm ventilates lungs
• external openings in head region
• passes through pharynx, trachea, bronchi
and into lungs
• lungs are the main organ of gas exchange
– carbon dioxide and oxygen exchanged
• deoxygenated blood pumped to lung
• tiny air sacs
– location of gas exchange
Nervous
• Larger brains
• contains two primary
parts
– central nervous system
– peripheral nervous
system
• mammals have a larger
cerebrum
– many are capable
learners