Chordates

Phylum Chordata-Main Characteristics

• Bilateral symmetry
• Segmented body and muscles
• 3 germ layers and a well developed coelom

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• At some point in development they have:
1. Notochord-flexible rod running down dorsal side
2. Hollow dorsal nerve cord
3. Pharyngeal gill slits
4. Post-anal tail

Human embryo (5 weeks)

Notochord – attachment site for muscles

Lancelet (adult)

Deuterostomia

Phylum Chordata

Human embryo (5 weeks)

Notochord – attachment site for muscles

Dorsal, hollow nerve cord – one end forms the brain (if present)

Lancelet (adult)

Deuterostomia

Phylum Chordata

Human embryo (5 weeks)

Notochord – attachment site for muscles

Pharyngeal gill slits

Dorsal, hollow nerve cord – one end forms the brain (if present)

Lancelet (adult)

Deuterostomia

Phylum Chordata

Human embryo (5 weeks)

Postanal tail

Notochord – attachment site for muscles

Pharyngeal gill slits

Dorsal, hollow nerve cord – one end forms the brain (if present)

Lancelet (adult)

Deuterostomia

Phylum Chordata

Invertebrate subphyla:

• Urochordata
• Cephalochordata

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Phylum Chordata

• Tunicates; a.k.a. sea squirts
• The key shared derived characters of chordates are found in the larval stage

Subphylum Urochordata

Subphylum Cephalochordata

• Lancelets
• The key shared derived characters of chordates are found in the adult stage

Phylum Chordata

Craniates:

• Group is divided into those without jaws and those with jaws
• A key shared derived character: neural crest, which gives rise developmentally to cartilage or bones of the skull
• Hagfishes
• Vertebrates

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Phylum Chordata

Hagfish

• Cartilaginous skull and notochord
• No vertebrae
• No jaws
• No paired appendages
• Nervous system lacks specialization

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Phylum Chordata

Vertebrates:

• A key shared derived character: vertebrae
• Lampreys
• Gnathostomes

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Phylum Chordata

Lamprey

• Cartilaginous skeleton, including a structure surrounding the notochord with rudimentary vertebrae
• No jaws
• No paired appendages

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Phylum Chordata

Gnathostomes:

• Key shared derived characters: hinged jaws and mineralization of skeleton
• Chondrichthyes
• Osteichthyes

Class Chondrichthyes

• Over 750 species of sharks, skates, ray, ratfish, or chimaeras
• Notochord present only in embryos
• Predominantly cartilaginous skeleton
• Respire through gills
• Lateral line system for detecting pressure changes
• 2-chambered heart
• Ovoviparous-eggs fertilized inside female; live birth

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Mode of Reproduction

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• Oviparous – embryonic development fueled from nutrients supplied by yolk, and the unshelled eggs hatch outside the mother’s body
• Ovoviviparous – embryonic development fueled by yolk, but the eggs hatch inside the mother’s body
• Viviparous – embryonic development fueled by mother’s blood through a placenta; live birth

Phylum Chordata

Osteichthyes:

• Key shared derived character: ossified skeleton (hard matrix of calcium phosphate)
• Ray-finned fishes
• Lobe-fins

Class Osteichthyes

Ray-finned fish

• Very diverse group; over 30,000 extant species
• Notochord present only in embryos
• Ossified (bony) skeleton
• Respire through gills
• Lateral line system for detecting pressure changes
• 2-chambered heart
• Swim bladder – air-filled sac that helps control buoyancy

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Summary so far

Phylum Chordata

Lobe-fins:

• Key shared derived character: rod-shaped bones in fins or limbs
• Coelacanths
• Lungfishes
• Tetrapods

Phylum Chordata

Order “Coelacanths”

Phylum Chordata

Class “Lungfishes”

Respiration through gills supplemented by lungs

Phylum Chordata

Tetrapods:

• Key shared derived character: limbs in place of pectoral and pelvic fins
• Amphibia
• Amniotes

Phylum Chordata

Class Amphibia

• “Two lives”
• Over 4,800 species
• Larvae usually aquatic, adults terrestrial
• Bony skeleton
• Oviparous reproduction
• Eggs lack a shell and are prone to desiccation through the skin
• Respiration by lungs, skin and gills either separately or in combination
• Three chambered heart
• Eustachian tubes allow rapid adjustment from aquatic to land
• Countershading (frogs)-adaptation for camouflage
• Cloaca

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Frog Facts

• Don’t drink water but soak it into their body through their skin.
• Breathe through their nostrils and skin
• Tongue is attached to the front of their mouths
• Frogs can see forwards, sideways and upwards all at the same time. They never close their eyes, even when they sleep.
• Use their eyes to help them swallow food. When the frog blinks, its eyeballs are pushed downwards creating a bulge in the roof of its mouth. This bulge squeezes the food inside the frog's mouth down the back of its throat.

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Frog Dissection

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• Why are we dissection frogs?!
• Frogs and humans have similar organ systems, so dissecting frogs helps us learn about human anatomy

Frog Anatomy

• Dorsal side? Vs. Ventral side?

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External Anatomy Dissection and Structures!

External anatomy review

Mouth cavity

Today: Internal Anatomy

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• Liver
• Heart
• Fat bodies
• Stomach- cut open
• Small and large intestine
• Spleen
• Esophagus
• Use dissection guides to help you!!!!

Today: Internal Anatomy

• Male Female

Internal Anatomy

Phylum Chordata

Class Amphibia

• Order Anura (“tail-less ones”) – frogs, toads
• Order Urodela (“tailed ones”) – salamanders, newts
• Order Apoda (“legless ones”) – caecilians

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Phylum Chordata

Class Amphibia

• Order Anura (“tail-less ones”) – frogs, toads

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Phylum Chordata

Amniotes:

• Key shared derived character: amniotic egg, which contains specialized extraembryonic membranes
• Reptilia
• Mammalia

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Phylogeny of Amniotes

Phylum Chordata

Class Reptilia

• About 6,500 species (excluding birds)
• Leathery shell around egg
• 3-chambered heart (4 in crocodilians)
• Scales-waterproof
• Ectothermic-behaviorally thermoregulate metabolism
• Internal fertilization
• Amniotic egg-removes dependence on water for reproduction
• Respiration by lungs and specialized muscles

• Fluid filled sac
• Extraembryonic membranes ( and a shell in many species) are not part of the embryo’s body
• aid gas exchange, waste storage, and nutrition

Amniotic Egg Structure

Phylum Chordata

Class Reptilia

• turtles, tortoises
• squamates - snakes and lizards
• crocodilians

Phylum Chordata

Class Aves

• About 8,600 species, �in about 28 orders
• Eggs with hard shells (calcium carbonate)
• Feathers – highly modified scales
• Endothermic
• 4-chambered heart
• Skeleton fully ossified with air cavities
• Respiration by slightly expansible lungs with thin air sacs
• Advanced cerebellum (flight) and optic lobes (vision)

Emu

Kiwi

Cassowary

Phylum Chordata

Class Aves

• Some groups lost the ability to fly

Penguins

Phylum Chordata

Now let’s consider the mammals…

Phylum Chordata

Class Mammalia

• About 4,500 species in about 16 orders
• Body covered in hair
• Endothermic
• Homeothermic
• Respiration with lungs
• 4-chambered heart
• Mammary glands
• Differentiated, specialized teeth
• Mammary glands present
• Increased cerebral development-capacity to learn
• Viviparous

Phylogeny of Mammalia

Phylum Chordata

Mammalia

• Order Monotrema
• Egg-laying mammals
• Platypus
• Echidna

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Phylum Chordata

Mammalia

• Infraclass Marsupialia
• Embryonic development occurs outside the mother, often in a marsupium

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At birth

After 17�weeks in pouch

Phylum Chordata

Mammalia

Subclass Eutherians (Placental Mammals)

• Embryonic development occurs inside the mother’s uterus, joined by the placenta
• Carnivores, herbivores
• Terrestrial, freshwater, marine
• Some are even volant!

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Mammalia, Order Primates

• A special group (from our human perspective)

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Phylum Chordata

Millions of years ago

Ancestral primate

Lemurs, lorises, and pottos

Tarsiers

New World monkeys

Old World monkeys

Gibbons

Orangutans

Gorillas

Chim-�panzees

Humans

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Class Mammalia

Order Primate

• Homo sapiens
• Opposable thumbs
• Highly developed cerebral cortex

Phylum Chordata

Millions of years ago

Ancestral primate

Lemurs, lorises, and pottos

Tarsiers

New World monkeys

Old World monkeys

Gibbons

Orangutans

Gorillas

Chim-�panzees

Humans

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First Nations Storytelling Project

• Based on First Nations principles of respect, responsibility, reciprocity, reverence, wholism, inter-relatedness, synergy
• Based on interconnectedness-sense of place, traditional place names, story
• TEK (Traditional Ecological Knowledge)
• Local knowledge based on people’s relationships to place
• Includes an intimate and detailed knowledge of plants, animals, and natural phenomena
• Development and use of appropriate technologies for hunting, fishing, trapping, agriculture, and forestry
• A holistic knowledge, or ‘worldview’ which parallels the scientific disciplines of ecology
• life cycles/spiritual connections and relationship with environment
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First Nations Storytelling Project

• Choose an animal
• Find an origin story and include the story or video
• Write a paragraph on why you chose the story and another on how the story relates to the principles of TEK.

Mini-Test Outline

• What are the four main characteristics all chordates have?
• How have the chordates evolved
• Discuss appendages, internal skeleton, respiration, circulatory system, reproduction
• Know the differences in modes of reproduction
• Why are mammals and particularly Homo sapiens at the top of the evolutionary chain?