Kingdom AnimaliaPhylum Chordata

The vertebrates and their relatives

Figure 23.02

Phylum Chordata4 Characteristics of a chordate

1. A dorsal hollow nerve cord (spinal cord in

vertebrates)

2. A notochord (most vertebrates only have a

notochord during development – becomes

the backbone in vertebrates)

3. Pharyngeal Pouches (develop into gills in

fish and amphibians and becomes glands

and auditory canal in later chordates)

4. Post-anal Tail (disappears in humans)

**Thyroid Gland-secretes mucus that traps

food in pharyngeal cavity

Four Chordate Hallmarks

• Dorsal tubular nerve cord

Four Chordate Hallmarks

• Notochord – flexible rodlike structure;

extending length of body

Four Chordate Hallmarks

• Pharyngeal pouches and gill slits

Four Chordate Hallmarks

• Postanal tail – tail extends beyond anus

**Fifth** Chordate Hallmarks

• Endostyle or thyroid gland – secretes mucous

that traps food particles in pharyngeal cavity

**Sixth** Chordate Feature

• Ventral Heart – heart located ventrally

Major Characteristics of

Chordates

Phylum Chordata

Subphylum

Urochordata

Subphylum

Cephalochordata

Subphylum

Vertebrata

tunicates lancets Agnathans

Fish

Sharks

tetrapods

Subphylum Urochordata

• Tunicates (also known as “sea squirts”)

– Look similar to other chordates during

development, but completely different as

adults

Phylum Chordata 13

Subphylum Urochordata

• Defining characteristics

– Notochord and

nerve cord are

found only in the

larval stage

• Most of the urochordates

are filter feeders

Filter

FeedingMy how we have changed!

Phylum Chordata 15

Subphylum Cephalochordata

• Defining

characteristics– The notochord extends beyond

the nerve cord to the anterior

end of the animal

– The notochord is contractile,

formed as a longitudinal series

of flattened discs (rudimentary

vertebral column)

Subphylum Cephalochordata

• Lancelets: live in the ocean with their body buried in

sand

– Have a definite mouth and no jaws

– Long pharynx with up to 100 gill slits

– Breathe through their body surface

– Have a simple digestive system, heart, and closed

circulation

– Notochord and nerve chord run entire length of body

Amphioxus

Video Resources for More Info

• Origin of Vertebrate System: https://youtu.be/232wtCuLsoI

• Evolution of Fish: https://youtu.be/DjthfvB47Mc

• Evolution of Vertebrates: https://youtu.be/nqoqxA8p_AM

Subphylum Vertebrata

• 99% of chordates are vertebrates

– Fish >24,000 species

– Amphibian >4,000 species

– Reptiles >6,000 species

– Birds >10,000 species

– Mammals >5,400 species

Phylum Chordata: The

Vertebrates

• Subphylum Vertebrata

• Nine extant classes

• First 3 commonly called fishes

• Remaining 4 called tetrapods (4 feet)

• All possess some form of segmented

vertebra

Vertebrate Higher

Classification Superclass Agnatha - without jaws

Class Myxini – hagfishes

Class Cephalaspidomorphi – lampreys

Superclass Gnathostomata – with jaws Class Chondrichthyes – sharks, rays, chimaeras

Class Actinopterygii – ray-finned fishes

Class Sarcopterygii – lobe-fin fishes

Class Amphibia – frogs, salamanders

Class Reptilia – snakes, lizards, crocodiles

Class Aves - birds

Class Mammalia - mammals

1st fish

Proto-vertebrate

Tunicate larvae Adult tunicate

lancelet

Possible evolution of 1st fish

Adult tunicate Larval tunicate

Amphioxus

1st dinosaur

end of dinosaurs

1st reptiles

1st amphibians

1st land plants

1st fish

1st invertebrates

Millions of YearsGeologic Time Scale

Pikaia

Fossils dates back to

Cambrian 540-500 mya

Early Chordate ancestor may have given rise to 1st vertebrate

Fish Evolution

• Fish were the first vertebrate to evolve

• Evolved about 540 mya

– Were jawless and covered in armored plates

• Devonian Period = Age of the Fishes

– Fish developed both jaws and fins at this time

Evolution of Jaws in fish

agnathostome gnathostome

1st appeared 400 mya

chondocranium

palatoquadrateHyomandibular arch

Meckel’s cartilage

Fishes

• Aquatic vertebrates characterized by:

– Fins (Movement)

– Scales (Protection)

– Gills (Breathing)

– There are fish with exceptions!– Can you name any?

Groups of Extant Fishes

• Class Cephalospidomorphi – lamprey

• Class Myxini – hagfishes

• Class Chondrichthyes – cartilaginous

fishes

• Class Osteichthyes – bony fishes

Hagfish

Class Agnatha

Subphylum

Vertebrata

• Strictly marine

• No bone

• Rasping tongue

• No lateral line organs

• 5-15 pair gills

• Partial open circulatory system

• Holonephros and neotenic pronephros

• Numerous slime glands in skin, secrete copious

amounts of mucus

• Separate sexes, but all individuals have ovitestis,

• Eggs deposited at sea; direct development; totally

marine

Hagfish characteristics

Hagfishes• Thought to feed on dead and dying fish

using a toothed tongue to scrape a hole in

the fishes side, but after autopsies found

only marine worms in digestive tract

• Have 6 hearts and an open circulatory

system

Agnatha (jawless fishes)

• Lack: paired fins, scales, & well developed vertebrae

• Hagfish (slime eels)– Mucus for protection

– Feed on decaying flesh

• Lampreys– Parasitic

– Anadromous

• Marine adults, breed in freshwater

– Vampire fish

Lamprey and Hagfishes

• Are jawless fishes

– Have mouths of soft tissue and no true teeth

• Have no bones

• Are the only vertebrates that do not have

vertebral columns as adults

Lamprey

• Are filter feeders as larvae and parasites

that suck blood and tissues of fish as

adults River Monsters

Lamprey Characteristics

• Oral disc/buccal funnel, with epidermal denticles

and rasping tongue; active "predatory parasites”

• No bone

• Nostril on top of head

• Well-developed vertebrate eyes

• Well-developed Lateral Line system

• Best developed pineal “eye” of any aquatic

vertebrate;

• 2 pairs of semicircular canals;

• Uniformly 7 pairs of gills

• Cranium cartilaginous, open on top

• Opisthonephros

• Eggs deposited in freshwater; freshwater larva;

many species have freshwater adult, but most

migrate to sea and have marine adult stage

(anadromous).

Class Chondrichthyes

• Include sharks & rays

• Very successful class

• Called cartilaginous fishes because skeleton is cartilage not bone

• Approx. 750 species

• Have paired appendages

• Many have acute senses

• Sharks have a lateral-line system

• Allows shark to detect water pressure changes

Fish Senses: Lateral Line

• Fish exhibit cephalization (brain)

• Many fish have Chemoreceptors for an extraordinary sense of taste and smell

• Lateral Line System –allows fish to sense movement and vibration

Shark's Lateral Line Explained

Class Chondrichthyes

Sharks, skates, raysSubphylum

Vertebrata

Cartilaginous Fishes

• Includes sharks, rays, skates, sawfishes, and chimaeras

• “Chondros” = Greek word for cartilage

• A typical shark has 3000 teeth arranged in 6 to 20 rows

• Not all are carnivores, the largest sharks are filter feeders

• Some have flat teeth for crushing mollusks and crustaceans

Characteristics

• Posses jaws with teeth, cartilaginous skeleton, paired fins

• Scales (denticles) have same origin and composition as teeth

• Possesses 5-7 gills

• Spiral valve intestine

• Ureoosmotic strategy

• Lateral line

• No swim bladder

• Heterocercal tail

• Relatively unchanged (480 mybp)

Sharks, skates, rays, chimera

Class Chondrichthyes

Basic Shark Anatomy

Modern Sharks

• Planktivores

• Carnivores

• Parasites

Gill arch from basking shark

Cookie cutter shark

pores

Detects weak magnetic fields produced by other fish

Ovipary- eggs enclosed in

capsule; eggs are laid and

hatched outside the mother

Ovovipary- give birth to

young, eggs develop in

uterus

Vivipary- give birth to

young, placental

connection

• Totally fossil, early jawed fishes;

• Bony armor usually present around head-trunk,

generally flattened body, tend to be bottom-

adapted with eyes rather dorsal (other various

designs);

• No true teeth

• Notochord persistent, un-constricted.

Class

Placodermi

Class Placodermi

Class Osteichthes

• Posses jaws with teeth

• bony skeleton

• paired fins

• 4 paired gill arches covered by operculum

• Intestine- simple, no spiral valve

• Swim bladder

• Lateral line

• Homocercal tail

• Scales- cycloid, ctenoid, ganoid

Class

Osteichthyes

Class Osteichthes

• Called Bony fish• Most diverse of all fish• Have skeleton made of bone• Have paired fins• Allowed evolution of 4 limbed

amphibians (tetrapods)• Possess scales for protection• Have bony flap called operculum

–Covers fish gills and acts like a water pump each time fish respires

• Have Swim bladder for buoyancy

Basic Fish Structure

Operculum-Gill Cover

Bony Fishes

• Skeletons are made of calcified bone

• Includes fish we are most familiar with:

Sunfish, Trout, Crappie, catfish,

Larghmouth Bass, etc.

Fish Ecology

• Some fish can live in both salt water and

fresh water

– Anadromous Fishes – spend most of their

life in the ocean but move to fresh water to

breed

– Catadramous Fishes – spend most of their

life in fresh water but move to the ocean to

breed

Body Systems of Fishes

• Fish feed in a variety of ways including parasites, carnivores, herbivores, etc.

• Most fish breathe using gills– Gills are feathery filaments containing a network of capillaries to

increase surface area for CO2 and O2 exchange

• Fish have two chambered heart and closed circulation

Body Systems of Fishes

• Fish digestive systems are similar to that of humans

• Excretory system is slightly different

• Ammonia is excreted by diffusion of water through gills and by use of kidneys

Body Systems of Fishes

**How does the action of peeing differ in a marine environment vs fresh water?

I got to go pee!!!

Osmoconformers

vs.

Osmoregulators

What is the difference?

Osmotic Challenges

• Osmoregulation- regulates solute

concentrations and balances the gain

and loss of water

• Osmoconformers, consisting only of some

marine animals, are isoosmotic with their

surroundings and do not regulate their

osmolarity

• Osmoregulators expend energy to control

water uptake and loss in a hyperosmotic or

hypoosmotic environment

Hagfishes

• Osmoconformers

• Only vertebrate that is isotonic to seawater -

much like marine invertebrates

Osmoregulators

• Aquatic vertebrates - gills are chief organs of excretion/osmoregulation

• Kidneys first evolved as osmoregulatory organs in fishes to remove water (freshwater) or conserve water (marine)

Do I

drink

water

?

Do I

drink

water

?

Describe

my pee.

Describe my pee.

Figure 44.3

(a) Osmoregulation in a marine fish (b) Osmoregulation in a freshwater fish

Gain of waterand salt ionsfrom food

Excretionof salt ionsfrom gills

Osmotic waterloss through gillsand other partsof body surface

Gain of waterand salt ionsfrom drinkingseawater

Excretion of salt ions andsmall amounts of water inscanty urine from kidneys

Gain of waterand some ionsin food

Uptake ofsalt ionsby gills

Osmotic watergain throughgills and otherparts of bodysurface

Excretion of salt ions andlarge amounts of water indilute urine from kidneys

Key

Water

Salt

Body Systems of Fishes

**How does the action of peeing differ in a marine environment vs fresh water?

– Salt water fish lose water and thus conserve bodily fluids by having concentrated urine

– Fresh water fish gain water and to have dilute urine

– Fish that move from fresh to salt water alter their kidney function to adapt to tonicity!

Fish Anatomy

Fish Senses

• Swim Bladder – adjust buoyancy

– How does pulling a fish from 40 feet of water

affect the size of its swim bladder?

Exposed Swim Bladder

Fish Reproduction

• Oviparous – egg laying; includes both

internal (some sharks) and external (most

fishes) fertilization

• Ovoviviparous – eggs develop inside

mother’s body and are nourished by egg

yolk; young are born alive

• Viviparous – the mother’s body nourishes

the developing young which are born alive

What’s Exam Going to Look

Like• See examples of practice exams on

website

• Mixture of Multiple choice

• Matching

• Short answer/fill in the blank

• Anatomical section

Great Reading Resource for Vertebrates

Targets to Know

• Major characteristics of Arthropoda,

Echinodermata, and Vertebrata

• Taxonomy within each phylum (unless

otherwise stated in lecture)

• Evolutionary advances in respiration,

circulation, locomotion and reproduction

across the phyla

• Know anatomical structures of both

external and internal from exemplars used

in class

Class Amphibia

• Amphibians gave rise to all other land

vertebrates

• Amphibian means “double life”

– As larvae they are typically aquatic filter

feeders or herbivores breathing through gills

– As adults most species are terrestrial

carnivores that breathe through their moist

skin and have lungs

Adaptations to Life on Land

• As the amphibians developed in the late Devonian Period 360 mya they needed to adapt to terrestrial life

– Keep from drying out

– Breathe using lungs, not gills

– Bones in limbs allow movement

– Ribs to support and protect internal organs

• Amphibians dominated the Carboniferous Period 345 to 285 mya

Amphibian Body Systems• Amphibians have a well developed

digestive system similar to that of humans

• As most amphibians develop lungs as adults, some are lung-less and only breathe through their skin

• They have closed circulation and a 3 chambered heart with a double loop system similar to that of a human

• Ammonia is disposed of in urine through the use of kidneys

Amphibian Reproduction

• Most amphibians lay their eggs in water;

fertilization is external

• Some salamanders fertilize internally

Amphibian Reproduction

• In most cases of external fertilization, the male will attach itself to the female. Eggs and sperm are released simultaneously and encapsulated in a jelly that attaches to aquatic plants.

• The jelly nourishes the developing embryos

• Tadpoles hatch and metamorphose into adults

Amphibian Reproduction

• Most amphibians

abandon their eggs

once they lay them.

• Some care for both

eggs and young

• Some incubate their

eggs in unusual

places: in their mouth,

on their back, or in

their stomach

Amphibian Senses

• Amphibians have a well developed brain

and spinal cord similar to that of a fish

• Eye’s are protected by a nictitating

membrane

• A tympanic membrane, or eardrum, is

located on either side of the head

• Many have a lateral line system similar to

that of a fish

Groups of Amphibians

• Order Urodela: Salamanders and Newts

• Order Anura: Frogs and Toads

• Order Apoda: Caecilians

Salamanders and Newts

• Have long bodies and tails

• Both adults and larvae are carnivores

• Most adults are terrestrial and live in damp

forests

• Some salamanders, such as mud puppies,

keep their gills and live in water all their

lives

Frogs and Toads

• Have the ability to jump

• Frogs have longer legs and can jump

farther than toads

• Frogs are closely tied to water; toads are

more terrestrial

Caecilians

• Least known of the amphibians

• Are legless and burrow in moist soil or

sediment

• Feed on small invertebrates such as

termites

• Some have scales

Amphibian Ecology

• Most are a great meal for birds and

reptiles

• Some have toxins to poison predators

• Some have bright colors to warn of their

toxins

• Some mimic the bright colors of others

and are harmless

Amphibian Ecology

• Amphibian populations are declining worldwide due to several factors with 1/3 of 6,000 species listed as threatened over 100 species have gone extinct in last 30 yrs.

• Global Warming

• Decreasing Habitat

• Depletion of the Ozone

• Water Pollution

• Introduced Aquatic Predators

• Fungal Infections

• Increasing human population!

Amphibian Anatomy

• We can use amphibian anatomy to model

our own complex anatomical systems

• Many of the systems we have already

discussed, but we now cover them a bit

more in depth

Respiratory System

Exchanging of gases via two well developed lungs

Major Structures:

1. Mouth

2. Trachea

3. Lungs (left & right)

Cardiovascular SystemProcess of exchanging oxygenated blood

with deoxygenated blood via a heart a

series of arteries and veins

Cardiovascular SystemProcess of exchanging oxygenated blood

with deoxygenated blood via a heart a

series of arteries and veins

Digestive System

Class Reptilia

Characteristics

• Ectothermes- used to be

known as cold blooded

• Have scales

• Amniotic egg

• Dry skin

• 3 chambered heart (except

crocks)6,500 species

Class Reptilia

• Land vertebrates with a well developed

skull, a backbone and tail, and four limbs

– Exemptions: snakes have no legs, and turtles

have a shell formed of fused vertebrae?

• Can a turtle lose its shell?

Reptile Evolution

• The oldest reptile fossils date back to the

early Carboniferous Period some 350

million years ago

• Dinosaurs of the Triassic and Jurassic

Period ruled the earth until 65 million years

ago

Reptile Body Systems

• Reptiles are ectotherms – rely on interactions with the environment to control their body temperature

• Reptiles have well developed lungs, three chambered hearts, and a well developed brain and spinal cord

• Reptiles’ legs are rotated farther under their body than amphibians allowing them to carry weight and walk on land more efficiently

Anatomical comparison between

Sarcopterygian, amphibian, and reptile.

Reptile Reproduction

• Internal Fertilization – males have a penis

to place sperm in the female’s cloaca

• Most are oviparous

– Turtles leave their nests unattended while

alligators protect their nest

• Some snakes are ovoviviparous

Ovipary- eggs enclosed in

capsule; eggs are laid and

hatched outside the mother

Ovovipary- give birth to

young, eggs develop in

uterus

Vivipary- give birth to

young, placental

connection

Reptilian Eggs

• Reptiles have amniotic eggs – named after

one of the four membranes around the

developing embryo

– Amnion: produces watery environment

around embryo

– Yolk Sac: contains nutrient rich yolk that

feeds embryo

– Chorion: allows gas exchange

– Allantois: stores waste

Amniotic Egg

Yolk sac

Amnioticcavitywithamnioticfluid

Chorion

Amnion

Albumen

Yolk(nutrients)

Allantois

Embryo

Shell

Groups of Reptiles

• Order Squamata: lizards and snakes

• Order Crocodilia: alligators, crocodiles,

caimans, and gavials

• Order Chelonia: turtles, tortoises,

terrapins

• Order Rhynchocephalia - tuataras

Orders not important

Lizards and Snakes

• Most lizards have legs, clawed toes,

external ears, and movable eyelids

• Some lizards do not have legs and look

more like a snake

Alligators, Crocodiles, and their

Relatives• Alligators and Caimans

live only in fresh water and almost exclusively in North and South America

• Crocodiles live in both fresh and salt water and are native to Africa, India, and Southeast Asia

Turtles, Tortoises, and Terrapins

• Turtles – live in or near water

• Tortoises – are terrestrial

• Terrapins – live in brackish water

– Carapace: Dorsal side of Shell

– Plastron: Ventral side of Shell

Ecology of Reptiles

• Many are in danger due to loss of habitat

• Humans also hunt them for food, pets, and

their skins (for bags and boots)

• Many conservation efforts are underway,

but more are needed worldwide

Evolution of Birds

• Oldest known

fossil is

Archaeopteryx

which lived

during the

Jurassic Period

150 mya.

• Birds are very

closely related to

dinosaurs, with

new DNA

sequencing

advancements

placing stronger

statistical support

for birds evolving

from early

dinosaur-like

reptiles.

Evolution of Birds

Class Aves

Characteristics

• Endotherms- Warm blooded

• Feathers and wings

• Hollow bones

• Horny bill

• Lungs have air sacks

• Hard egg shell

Class Aves

• Characteristics of

most birds

– Maintain a constant

internal body

temperature

– Covered in feathers

– Have two legs for

walking and perching

– Front limbs are wings

– Most are adapted for

flight

Feathers

• Used for flight and warmth; several types

– Contour Feathers: provide the lifting force and

balance needed for flight

– Down Feathers: trap air close to the body and keep

the bird warm

– Powder Down: found on ducks and other birds that

live on or in water; release a fine powder that repels

water

Body Systems of Birds

• Endotherms: can generate their own body

heat; warm-blooded

• Smaller birds must eat more in relation to

its size due to Surface Area to Volume

Ratio

Feeding habits of Birds

• They lack teeth and therefore do not chew

• Beaks are adapted to the types of food

they eat

• Bird Digestion

– Crop: enlargement of the esophagus used to

store food

– Gizzard: has muscular walls and small bits of

gravel used to grind food

Respiration

• Birds have very efficient lungs that provide oxygen rich blood during both inhalation and exhalation

• Inhaled air enters posterior and anterior air sacs it then travels through the lungs and is exhaled

• Therefore the air flows into the air sacs and out of the lungs in one single direction, always providing oxygen rich air

Circulation and Excretion

• Two loop circulatory system, similar to that of

humans

• Ammonia is removed by the kidneys, converted

to high concentration uric acid and defecated

(bird droppings); similar to reptiles

Senses of Birds

• The brains of birds are very well

developed

– Birds can see color very well and UV light

– Birds can hear very well

– Smell or taste are not well developed

Bones and Muscles

• Most birds can fly. Others are adapted for

swimming and running

• Bones are light, strong, and adapted for

flight; many bones are fused to provide a

study base for flight adaptations

Bird Reproduction

• Both male and female reproductive tracts

open into the cloaca

• The sex organs, internal in both sexes,

increase in size during mating season

• Birds rub their cloacas together during

mating to transfer sperm

Eggs and Incubation

• Eggs are amniotic but unlike reptile eggs

have a hard outer shell

• Eggs must be incubated by the parents

since they are endotherms

• Young must be cared for after hatching

Ecology of Birds• Birds are very ecologically important

– Hummingbirds are involved in pollination

– Some birds eat seeds without digesting them and therefore spread the seeds

– Many birds keep insect populations in check

• Many birds migrate by guidance of stars, Earth’s landmarks, and Earth’s magnetic field

• Birds are good indicators of environmental health; bird numbers dwindled with the use of DDT

Class Mammalia

• Characteristics of mammals

– Endotherms

– Have mammary glands and nurse young

– Have hair

Evolution of Mammals

• The earliest mammals evolved about the same time as the early dinosaurs but remained in the shadows until the giant reptiles disappeared

• First ancestors of mammals appeared during the Permian Period about 290 to 250 mya

• First true mammals appeared during the Jurassic Period 210 mya

Mammal Evolution

• When the continents

split about 60 mya,

three groups of

mammals were

isolated from one

another.

Staying Warm

• Animals have hair to help insulate their bodies.

• They also have subcutaneous fat to keep them warm and many have sweat glands to cool them off.

• Smaller mammals have higher metabolism than larger ones in order to create enough body heat to keep warm.

• Mammals eat about 10 times as much food as a reptile in order to stay warm.

Comparison of Vertebrate

Forelimbs

• When comparing the bones and bone

structures of all vertebrates - birds,

amphibians, reptiles, and mammals – you

can see many of the same bones with very

similar functions

• Refer to Figure 32-7 in the text (Page 826)

Mammal Reproduction

• Internal Fertilization occurs in mammals

• Mammals are divided into three groups

based on methods of development and

birth

– Oviparous: egg-laying mammals are called

monotremes

– Viviparous: includes both placental mammals

and marsupials

Caring for Young

• All newborn mammals feed on their

mother’s milk

• Some newborns are helpless at birth and

must be cared for

• Others are able to see and walk within

minutes after birth

Monotremes

• Monotremes are the egg laying mammals

• They share two notable characteristics with reptiles

– Both the reproductive and urinary systems open into a cloaca

– “Monotreme” means single opening

• Only three species of monotremes exist today: they are found in Australia and New Guinea

– Duckbill Platypus and two species of Spiny Anteaters

Laying eggs and caring for young

• Monotremes lay eggs that are incubated

outside the body

• They hatch into young animals in about 10

days

• The young are nourished by their mother’s

milk that they lick from pores on the

mother's abdomen

Marsupials

• Marsupials give birth to live young that complete their development in an external pouch

• Examples include kangaroos, wombats, koalas, and Tasmanian devils

• A short time after internal fertilization a small embryo leaves the mother’s body, crawls across the fur, and enters the marsupium (pouch) where it attaches to a nipple to nurse

Placental Mammals

• Placental Mammals are those that are most familiar to us.

• Placenta – organ in placental mammals through which nutrients, oxygen, carbon dioxide, and wastes are exchanged between embryo and mother

• Gestation – the time it takes from conception to birth in mammals (can vary from 2 weeks to 2 years depending on the mammal)

Orders of Mammals

What’s Exam Going to Look

Like• See examples of practice exams on

website

• Mixture of Multiple choice

• Matching

• Short answer/fill in the blank

• Anatomical section

Great Reading Resource for Vertebrates

Targets to Know

• Major characteristics of Arthropoda,

Echinodermata, and Vertebrata

• Taxonomy within each phylum (unless

otherwise stated in lecture)

• Evolutionary advances in respiration,

circulation, locomotion and reproduction

across the phyla

• Know anatomical structures of both

external and internal from exemplars used

in class