Phylum Chordata

3 Subphyla:
• Urochordata – tunicates (sea squirts)
• Cephalochordata - lancets
• Vertebrata - vertebrates

Urochordata
Tunicates (Sea squirts) are
INVERTEBRATES

Cephalochordata
• Lancets are INVERTEBRATES

Vertebrata
• Vertebrates are …VERTEBRATES!

New Characteristics
All members of Phylum Chordata have a
• Notochord
• Hollow Dorsal Nerve Cord
• Pharyngeal Pouches
• Postanal tail

Notochord
A rod-like structure between the digestive system and the Dorsal Hollow Nerve Cord.
In vertebrates, this develops into the BACKBONE
It anchors muscles and allows rapid movements

Dorsal Hollow Nerve Cord
A tube of cells surrounding a fluid-filled canal above the
Notochord.
This develops into the SPINAL CORD.
The anterior portion develops into the brain and pairs of nerves connect to blocks of muscle.

Pharyngeal Pouches
Paired opening located in the pharynx, behind the mouth.
In terrestrial chordates, these develop into the jaw, inner ear, and tonsils.
In aquatic chordates, these develop into gill slits.

Postanal Tail
A tail that extends beyond the anus.
All chordates have a postanal tail at some point in their development – even humans!
Muscle blocks controlling the tail are connected to the notochord.

Subphylum Vertebrata
Includes:
• FISH
• AMPHIBIANS
• REPTILES
• BIRDS
• MAMMALS
Over 50,000 species

Subphylum Vertebrata
All Vertebrates share
• A vertebral column – replaces the notochord during embryonic development
• Epidermis is divided into OUTER and
INNER layer –often modified to produce hair, scales, feathers, glands, horns
• Endoskeleton – bony or cartilaginous

Subphylum Vertebrata
• Muscles attached to endoskeleton to provide movement
• Digestive system with digestive glands, liver and pancreas
• 2 – 4 chambered heart
• Well-developed coelom
• Paired kidneys

Subphylum Vertebrata
• Two sexes with paired gonads
• Head, trunk, two pairs of appendages, and post-anal tail
Myers, P. 2001. "Vertebrata" (On-line), Animal Diversity Web. Accessed May 11, 2009 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Vertebrata.html.

FISH
4 CLASSES:
• Hagfishes
• Lampreys
• Cartilaginous Fishes
• Bony Fishes

All fish:
• Breathe using gills
• Have 2-chambered hearts
• Reproduce sexually
• Have developed sensory systems
FISH
Most fish (cartilaginous and bony):
• Have paired fins
• Have scales
Most fish are BONY fish.

FISH
Jaws evolved in fish.
• can grab and crush prey
• can prey on variety of organisms

AMPHIBIANS
Class Amphibia (amphibia = “double life”)
3 Orders:
• Caudata (salamanders and newts)
• Anura (frogs and toads)
• Apoda (legless caecilians)

AMPHIBIANS
• Adults are terrestrial, but rely on water for reproduction
• Fertilization is external
• Ectotherms – body temp is variable
• Undergo metamorphosis
• 3-chambered hearts, skin is more important for gas exchange – must stay moist

Amphibians
Amphi – double; frogs, toads, caecilians, salamanders
• Thin, moist skin
• 4 legs
• terrestrial, but closely tied to water

Amphibians
• both internal and external fertilization
• eggs lack protective
• membrane and shell – need water to prevent dessication.
red eye tree frog eggs http://nationalzoo.si.edu/Animals/Rep tilesAmphibians/Exhibit/Topics/zoo_b reeding.cfm?inc=o

Ectotherms
• body temperature is dependent on environmental temperature
• become dormant during times of year when it is too hot or too cold - estivate

Metamorphosis

Metamorphosis in frogs
Herbivorous tadpoles hatch with internal gills
• increase in mouth and tongue size
• loss of gills / formation of lungs
• growth of legs, resorption of tail
• new visual pigment in eyes
• hemoglobin protein in blood
• insectivorous adult

Metamorphosis in salamanders
• young aquatic salamanders have gills and a tail fin
• adults do not have gills or fins – breathe through skin or with lungs

Metamorphosis in salamanders
Some salamanders do not have larval stage, but hatch as small versions of adults

Circulatory System
• 3-chambered heart
• one chamber gets oxygen rich blood from lungs
• one chamber gets oxygen poor blood from body tissues
• blood from both go to third chamber – blood goes to body tissues and skin

Order Anura
Frogs
• smooth, moist skin
• long legs
Toads
• bumpy, dry skin
• short legs
Both are tailless and insectivorous

Order Anura
• vocal cords capable of producing a wide range of sounds.
• Vocal cords are sound-producing bands of tissue in the throat.

Order Caudata
• long, slender body with a neck and tail.
• smooth, moist skin
• lack claws
• a few cm to 1.5 m
• carnivorous

Order Apoda
• burrowing amphibians, have no limbs, and have a short, or no, tail.
• primarily tropical animals with small eyes that often are blind.
• eat earthworms and other invertebrates found in the soil.
• have internal fertilization.

Origins of Amphibians
• Most likely, amphibians arose as their ability to breathe air through well-developed lungs evolved.
• The success of inhabiting the land depended on adaptations that would provide support, protect membranes involved in respiration, and provide efficient circulation.

Origins of Amphibians
• Amphibians first appeared about 360 million years ago.
• Amphibians probably evolved from an aquatic tetrapod around the middle of the Paleozoic Era.

Challenges to life on land
• Land life for amphibians held many dangers.
• Unlike the temperature of water, which remains fairly constant, air temperatures can vary greatly.
• In addition, without the support of water, the body was clumsy and heavy.

Challenges to life on land
• Able to breathe through their lungs, gills, or skin, amphibians became, for a time, the dominant vertebrates on land.

REPTILES
Class Reptilia
4 Orders
• Squamata (snakes and lizards)
• Chelonia (turtles)
• Crocodilia (alligators and crocodiles)
• Rhynochocephalia (Tuataras)

REPTILES
• Reptiles have SCALY SKIN
• Reproduce on land – AMNIOTIC EGG
• Legs are more directly UNDER the body
• 4-chambered hearts
• Ectotherms

BIRDS
Class Aves
• 8600 species of modern birds
• Inhabit variety of habitats:
Antarctica
Deserts
Tropical Rain Forests
All birds have WINGS, but not all birds FLY!

BIRDS
All birds have FEATHERS and WINGS
Feathers
• modified protein scale
• molting – shedding of old feathers and growth of new feathers
• wing and tail feathers lost in pairs to maintain balance
Wings
• adaptation for flight
• flight muscles attached to sternum
(breast bone)

BIRDS
Flying requires LOTS of energy!
• 4-chambered heart beats very fast
(chickadee = 500 times/minute)
• respiratory system includes air sacs – oxygenated air is circulated during
INHALATION and EXHALATION.

BIRDS
• ENDOTHERMS – maintain own body temperature, independent of environmental temperature
• Reproduction – internal fertilization, shelled amniotic egg

Phylum CHORDATA
Subphylum VERTEBRATA
Class MAMMALIA

MAMMALS!
Class Mammalia
• Endotherms
• Produce milk for young
• Hair
• Diaphragms
• 4-chambered heart
• Specialized teeth
• Modified limbs
• Highly developed brains

MAMMALS!
Hair is
• made out of keratin (like feathers)
• developed from scales (like feathers)
• arrangement provides insulation / waterproofing
• conserves body heat (endotherms)

MAMMALS!
Endotherms maintain constant body temperatures
• panting (release heat)
• sweating (release heat)
• shivering (generate heat)
• raising hair (conserving heat)

MAMMALS!
Mammals have several types of
GLANDS
• Scent
• Saliva
• Hormones
• Milk
• Digestive enzymes

MAMMALS!
Mammals nurse their young
• Mammary glands – secrete milk that is rich in fats, sugars, proteins, vitamins, and minerals
• This continues until offspring are able to eat and digest solid food

MAMMALS!
The diaphragm aids in breathing
• muscle beneath the lungs, separating the
THORACIC (chest) cavity from the
ABDOMINAL cavity
• Expands the chest cavity, bringing in air
• Contracts and pushes air out

MAMMALS!
Mammals have a 4-chambered heart
• Left and Right Atrium
• Left and Right
Ventricle
• Oxygenated and deoxygenated blood
Circulation removes waste and maintains
HOMEOSTASIS are entirely separated.

MAMMALS!
Mammalogists love teeth!
• you can tell what an animal eats based on its type of teeth
• teeth are adapted to type of food eaten
• teeth are hard and fossilize more often than other parts of the body

MAMMALS!

MAMMALS!
This mole’s pointed incisors are used to grasp and hold small prey

MAMMALS!
A beaver’s incisors are modified for gnawing and can gnaw through almost anything.
These teeth continue growing throughout the animal’s lifetime.

MAMMALS!
A lion’s sharp canines are perfect for slicing and tearing flesh.

MAMMALS!
Premolars and molars are used for slicing, shearing, crushing, and grinding.

MAMMALS!
Other characteristics include
• modified limbs
• complex behaviors – learning and remembering

MAMMALS!
Mammals have complex brains
• Primates (including humans) are possibly most intelligent
• use tools
• communicate

MAMMALS!
3 Orders of Mammals
• Monotremes (platypus and echidnas)
• Marsupials (kangaroos and oppossums)
• Placental Mammals (Chiroptera- bats;
Rodentia – rodents; Carnivora – weasels, skunks, bears, foxes; Cetacea- whales, dolphins; Primates- chimps, apes, monkeys, humans)

MAMMALS!
Monotremes
• Eggs
• Only 3 species alive today (1 platypus,
2 echidnas)
• Found only in Australia and New
Zealand

Flat tail, duck beak, webbed feet Coarse brown hair, covered in spines

MAMMALS!
Marsupials
• short period of development in mother’s body
• period of development inside pouch
• most are found in Australia – opossum is
North American marsupial

MAMMALS!
Placental Mammals
• Over 4000 species (mostly bats and rodents)
• Young develop in the UTERUS
• Nourished by a PLACENTA
• Development inside the mother’s body ensures protection from predators and environment during development.

MAMMALS!
The placenta is derived from the same membranes that surround embryos in amniotic eggs (reptiles and birds)
Marsupials also have PLACENTAE, but is short-lived

MAMMALS!
• smallest mammals are shrews and bats and weigh as little as 3 grams
• largest is the blue whale –
160,000 kg! (352,739 lbs!)

Origin of Mammals
• The first placental mammals appeared in the fossils record about 125 million years ago.
• Scientists trace the origins of placental mammals from a group of mouse-sized animals to a group of reptilian ancestors called therapsids.

Origin of Mammals
• Therapsids had features of both reptiles and mammals.
• They existed between 270 and 180 million years ago.

Origin of Mammals
• The mass extinction of the dinosaurs at the end of the Mesozoic Era, along with the breaking apart of Pangaea and changes in climate, opened up new niches for early mammals to fill.
• The Cenozoic Era (65 million years to present) is sometimes called the golden age of mammals because of the dramatic increase in their numbers and diversity.