Transcript Phylum Chordata - Blue Valley Schools

Phylum Chordata
Chordata - Background
• Over 45,000 species – a lot??
• Very successful with adaptation and survival
• Range of organisms across aquatic and
terrestrial environments
• Contains most complex subphylum
Chordata - Background
• Some of the greatest diversity:
– Cartilaginous fish
– Bony fish
– Amphibians
– Reptiles
– Birds
– Mammals
Chordata - Diversity
Common Features - Notochord
• At the center of it all…
– Chorda = chord
– Depend on a nuchal cord that runs down
dorsal aspect of body from anterior (front) to
posterior (tail end)
– What do you think that nerve cord becomes??
Common Features - Notochord
Common Features - Notochord
Common Features - Notochord
Let’s explore how the chordates
have evolved…happily together.
Chordata - Characteristics
• Symmetry – bilateral
• Presence of a thyroid (or thyroid like) gland
• Complete digestive tract
• A ventral, contractile blood vessel (heart)
Chordata - Characteristics
Chordates - Characteristics
• Unique combination of the FOUR following
characteristics at some stage of their
development:
– Notochord
– Dorsal tubular nerve cord
– Pharyngeal slits or pouches
– Post anal tail
Chordate characteristics
• Notochord
– Supportive rod that extends most of the antpost length of the animal
– Consists of connective tissue protective
sheath that surrounds tubular cord
– Must provide strength and flexibility
– Large fluid filled vacuoles spaced
intermittingly
Chordate Characteristics
Chordate Characteristics
• Dorsal tubular nerve cord
– Runs along AP axis
– Located on dorsal surface
– Usually expand anteriorly into a brain
– Branches out into complex nerve nets at
EACH level
Chordata - Organization
• Consists of three subphyla:
– Urochordata (sea squirts)
– Cephalochordata (lancelets)
– Vertebrates (jaw-less fish, aves, reptiles…etc)
• Urochordata are the most primitive
• Vertebrates are composed of MANY classes
Urochordata
• Most primitive of all chordates
– Usually gelatinous appearance, free flowing
• Tend to be sessile in adult forms
– What type of feeding do you think they have?
• Notochord is present in the free swimming
larvae stage only (change forms)
Urochordates
• Pharyngeal slits
– Use specialized mesh “baskets” to filter feed
– Incurrent and excurrent siphon
• Heart anomaly
– Pumps by “wringing it out” / multiple directions
• Fertilization
– Hermaphroditic (sperm and egg into sea)
Urochordates
Cephalochordates
• Small tadpole like organisms (1-5 cm long)
• Found throughout the world’s oceans
• Transparent appearance and relatively flat
and streamline
• Able to swim / still rely on filter feeding
Cephalochordates
• Adaptations to notocord
– Largely made of muscle (burrow vs. swim)
• Cilia at anterior head for feeding
• Often bury in sand and take sessile strategy
Cephalochordates
Cephalochordates
Organ System
Special Characteristics
Circulatory
-
Digestive
-
Excretory tubules
-
No true heart
Contractile waves in walls of major vessels
will propel the blood
Blood contains amoeboid cells and bathes
are
Cirri are used in a cilia fashion to feed
Small and edible particles pulled into the
mouth along with water.
Filtered through the pharyngeal slits into
cecum
Modified coelomic cells closely associated
with blood vessels.
Arrangement allows for filtration of blood
Reproductive methods
-
Dioecious (use gonad glands)
Gamates are deposited into atriopore and
leave to allow external fertilization to occur
Respiratory
-
Uses gill slits in conjunction with pharynx to
filter water and gases
Vertebrates
• Most complex subphyla of chordates
• Most notable common feature is the
formation of a back bone type structure
• HUGE evolutionary advances as move across
the classes
– Cross from marine to terrestrial (bridge gap)
Vertebrates - Characteristics
• Clear and definitive back bone
• The skeleton of most vertebrates (excluding most
primitive ones) consists of a skull, the vertebral
column and two pairs of limbs
• The internal skeleton provides support to the
organism during the period of growth, and for this
reason vertebrates can achieve larger sizes than
invertebrates.
Vertebrates - Characteristics
• Central nervous system that is partly located
inside the backbone.
– Head and sensory organs resulting from the
process of cephalization.
Vertebrates – Bridging the gap
• “Although hagfish have no jaws and no
vertebrae, they do have other characters that
identify them as fish. These traits make them
an interesting candidate for being in some
way transitional between chordates and
vertebrates…”
Vertebrates – Change over time
Fish – Vertebrate Beginning
• All contain the essential elements of
chordates
• Develop over time to have bones and more
solidified back bone
• Definitive dorsal neuro tube
• Divided into bony and cartilaginous
Chondrichtyes
• (chondros = cartilage, ichthyos = fish)
• Major class of jawed fish, including rays,
skates, and sharks
• Body made primarily of light weight cartilage
• Skeleton may combine with calcium but never
completely ossified.
Chondrichtyes - Characteristics
• origin on earth some 450 million years ago
• “Their success that has not only assured their
survival, but has required their minimal
evolutionary adaptation over the eons to
assure survival.”
Chondrichtyes - Characteristics
• All are water dwelling / marine (ribs)
• “Rule of two’s” – paired fins, nostrils, eyes, two
sets of teeth, two chaambered hearts
• Chondrichthyes are poikilothermic (cold-blooded)
• Lack swim bladder / must keep moving to float
Chondrichtyes - Characteristics
• HUGE variety of organisms:
Chondrichtyes - Characteristics
• Placoid scales:
– Tough layer of skin that give firm and durable
texture to skin (sandpaper feel)
– Project posteriorly to reduce friction
– Add to weight
• Sleep:
– Motion is key
– Spiracles (located behind the eyes)
– Active vs rest periods of cognition
Chondrichtyes - Characteristics
• Modified Teeth:
– Modified placoid scales, not ossified
– Row of outer teeth replaced by row held on
inner jaw with ligamentous band
– May replace every 7-10 days
Chondrichtyes – Skates and Rays
• Skates and rays– Ocean floor dwelling / shallow water
– Large range of size (<2 foot wingspan to 20
feet)
– Often found near coral or plant life to feed on
invertebrates
– Use camoflauge to hide from predators and a
defensive spine
Chondrichtyes – Skates and Rays
• Modifications for “floor feeding”
– Expansion of pectoral fins laterally – became
wing like appendages
– Dorso-ventral muscular waves result in
locomotion
– Poisonous spine
– Dorsal eye position
Chondrichtyes – Skates and Rays
Sharks – quick facts
• Range from approximately 9 inches (Panama Dwarf
shark) to 50 feet (whale shark)
• Older than most dinosaurs (350 million+)
• Most sharks are scavengers, some of the largest filter
feeders. (Large meals may last up to 2 months /
atypical digestion)
• Buoyancy – …physics in Biology class?!
Chondrichtyes – Characteristics
• Circulatory –
– Use 2 chambered hearts
– Closed circulatory system
– Red blood cells are produced by the spleen
(how is this different from mammals?)
• Respiratory– Use gills to filter oxygen rich water
– Must have persistent current (spiracles behind
eye) or bellows effect
Chondrichtyes – Characteristics
Chondrichtyes – Characteristics
• Fertilization
– Rarely observed
– Internal fertilization is used
– Males often bite female pectoral fins to hold
onto them and maintain necessary alignment
– Claspers, a modified form of pelvic fin, will
insert into female to release sperm
– Most give birth to live young, few lay eggs (2
year gestation possible
Chondrichtyes – Characteristics
Chondrichtyes – Characteristics
• Locomotion
– Propelled by large tail fin
– Rest of the fins are high and low speed
stabilizers
Chondrichtyes – Locomotion
• Hydrodynamic - the force of liquid in motion
• Goal is to generate large amounts of power
with little resistance
– Power: tail can displace 400 lbs of water per
oscillation in Great White Shark
– Speeds of 22 mph typical in Mako Shark (can
be as high as 60mph in attack burst – within
20 feet)
– Minimal drag on unidirectional scales
Chondrichtyes – Locomotion
Osteichthyes - Background
• Osteo = bone, icthyes = fish
• Have bone in parts or all of their skeleton
• Considered more advanced and more evolved
then cartilaginous fish
• Developed well after sharks
• Examples:
– Perch, Salmon, Lungfish
Osteichthyes - Diagram
Osteichthyes - Classes
• Consist of two classes– Sarcopterygii (lungs??)
– Actinopterygii (swim bladders)
• Developed around 350 million years ago
• Have evolved a fair amount
– Crossed over to land
Sarcopterygii Class
• Have muscular lobes associated with fins
• Ancestors of current amphibians
• Sometimes use lungs when water becomes
stagnant. Able to “breathe”?
Actinopterygii Class
• known as the "ray-finned fishes”
• The actinopterygian fin rays attach directly to
the proximal or basal skeletal elements, the
radials.
• These radials represent the link or connection
between these fins and the internal skeleton
• serve as both prey and predator
Body Plan - Osteichthyes
• Bones throughout– relatively stable arrangement of cranial bones
– medial insertion of mandibular lower jaw
– pectoral girdles are covered with large dermal
bones (similar to ribs)
– Eyeball is even supported by a ring of four
small bones
Body Plan - Osteichthyes
• Never worked so hard to sit still…
– Have a unique swim bladder that help with
buoyancy. (will not automatically sink like
cartilaginous fish)
– Operculum – unique flap that generates a
wave like current for water to move past gills
Body Plan - Osteichthyes
• “The fin-limbs of sarcopterygiians show such a
strong similarity to the expected ancestral
form of tetrapod limbs that they have been
universally considered the direct ancestors of
tetrapods (four-legged vertebrates) in the
scientific literature.”
Locomotion - Osteichthyes
• has a streamlined body for rapid swimming
(covered in unidirectional scales)
• Strong, powerful (caudal) tail fin
• Alternating and rhythmic twisting motion of
body for extra speed
• Sarcopterygii class can support body weight
on flippers in jointed appendages (clumsy
walking)
Respiratory - Osteichthyes
• Most use 2 sets of gills. (which may be aided
when still by operculum)
• Gills consist of threadlike structures called
filaments
– Sometimes use a counter current exchange
• May have more than 1 pair of gills
Respiratory - Osteichthyes
Circulatory - Osteichthyes
• have a closed-loop circulatory system
• the heart consists of four parts, including two
chambers and an entrance and exit.
– Sinous venosus
– Atria
– Ventricle (muscular portion)
– Bulbous arteriosus
Circulatory - Osteichthyes
Digestive Tract - Osteichthyes
• Complete digestive tract
– (mouth, jaw, esophagus, stomach, intestine,
colon, anus)
• pyloric caeca - secrete digestive enzymes and
absorb nutrients in stomach
• the liver and pancreas add enzymes and
various chemicals as the food moves through
the digestive tract
Digestive Tract - Osteichthyes
Nervous System - Osteichthyes
• Fish typically have quite small brains relative
to body size
• Brain does possess various sensory and motor
lobes
– Olfactory = smell
– Optic = vision
– Cerebellum = coordination
– Telencephalon = thinking and behavior
Nervous System - Osteichthyes
• Most fish possess highly developed sense
organs used to protect and hunt
– Nearly all daylight fish have color vision that is
at least as good as a human's
– Many fish also have chemoreceptors that are
responsible for extraordinary senses of taste
and smell (max distance for shark to smell
blood??)
– lateral line system: detects gentle currents
and vibrations, and senses the motion of
nearby fish and prey
Nervous System - Osteichthyes
• Problem solving skills are present
• Memory is thought to be selective (markers
for orientation / mazes vs. memory regarding
bait)
• Responders NOT planners
Nervous System - Osteichthyes
Chordate Part I – DONE!!