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The  Deuterostomes Echinoderms and Chordates The  Deuterostomes Echinoderms and Chordates

The Deuterostomes Echinoderms and Chordates - PowerPoint Presentation

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The Deuterostomes Echinoderms and Chordates - PPT Presentation

Developmental Variations During embryonic development the process of gastrulation forms the digestive cavity Gastrulation varies in the animal kingdom No gastrulation placozoans ID: 710115

www https watch youtube https www youtube watch chordates fish mouth cord nerve notochord food sea derived gill dorsal

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Slide1

The Deuterostomes

Echinoderms and ChordatesSlide2

Developmental Variations

During embryonic development, the process of

gastrulation

forms the digestive cavity.

Gastrulation

varies in the animal kingdom

No

gastrulation

(

placozoans

)

Incomplete

gastrulation

Forms a

gastrovascular

cavity with one opening

Complete

gastrulation

Forms a digestive tract with 2 openingsSlide3

Animals with Complete Gastrulation

Complete

gastrulation

forms a true digestive tract with 2 openings, the mouth and the anus

In

protostome

animals, the first opening of the gastrula forms the mouth

In

deuterostome

animals, the second opening of the gastrula forms the mouthSlide4

Deuterostome Phyla

There are 3 phyla characterized by

deuterostome

development

Echinoderms

Sea Cucumbers, Crinoids, Sea Stars, Brittle Stars and Sea Urchins

Hemichordates

Acorn Worms and

Pterobranchs

Chordates

Tunicates, Lancelets, Jawless fish and VertebratesSlide5

Phylum Echinodermata

The echinoderms are unusual in the animal kingdom in that they have a great deal in common with the chordates and hemichordates, but also differ in ways that do not appear anywhere else in the animal kingdom

It seems unlikely that their similarities with other

deuterostomes

are the result of convergent evolution, so it seems that through the course of evolution the

echinoerms

have lost a number of ancestral characters retained in the other phylaSlide6

Characters retained:

Embryonic development &

Gastrulation

Triploblastic

Complete digestive tract

Body Cavity

Eucoelomate

Symmetry

Bilateral during larval stagesSlide7

Characters lost or diminished:

Segmentation

Cephalization

No head, brain or specialized sense organs

Sensory apparatus are not centralized

Bilateral symmetry in the adult form

The bilateral symmetry in the larvae goes through a dramatic metamorphosis, reorganizing the body into a

Pentaradially

Symmetrical adultSlide8

Metamorphosis

The

coelom

forms as a U shape, which pinches off into 3 distinct cavities, 2 of which will become diminished

The digestive tract becomes reorganized, with the formation of new mouth and anal openings and a new orientation (mouth on the left and anus on the right)

The left and right sides of the larvae undergo differential development, with the left side forming the oral surface and the right side forming the

aboral

surfaceSlide9

Derived characters special to the Echinoderms

Water-vascular system

Consisting of a

madroporite

, a system of canals (stone canal, ring canal, radial canals and lateral canals) and sucker tipped tube feet

Dermal endoskeleton

Consisting of calcified plates called

ossicles

and a variety of spines and

pedicellaria

Hemal

system

Poorly understood, it appears to function for distribution of materials

Pentaradial

symmetry

Organs radiate from a central disc, characteristically in a pattern of fivesSlide10

Water Vascular SystemSlide11

Tube FeetSlide12

Crinoids (Sea Lilies)

https://

www.youtube.com/watch?v=cZcomBnNKXg&feature=related

https://

www.youtube.com/watch?v=hAdEfdyKBHM

https://

www.youtube.com/watch?v=jg_0UdbSRsM&feature=relmfu

https://

www.youtube.com/watch?v=XR4NnmJfEXcSlide13

Sea Stars

https://

www.youtube.com/watch?v=pSo30lRHaAw

https://

www.youtube.com/watch?v=I8as-z-EShc

https://www.youtube.com/watch?v=-

ardrFZuFkU

https://

www.youtube.com/watch?v=qC89SLOXIvs

https://

www.youtube.com/watch?v=TioCree5axI

https://

www.youtube.com/watch?v=Xm2mF2IgLrASlide14

Brittle Stars

https://

www.youtube.com/watch?v=Myhp8ifW6ig

https://

www.youtube.com/watch?v=Chs8Vk-6hooSlide15

Sea Cucumbers

https://

www.youtube.com/watch?v=vsLBOkYLLeI

https://

www.youtube.com/watch?v=iYSbLr-mVkM

https://

www.youtube.com/watch?v=6mx0GDxfjQ4Slide16

Sea Urchins

https://

www.youtube.com/watch?v=eGixkoZwEUs

https://

www.youtube.com/watch?v=oljZbs5haaY

https://

www.youtube.com/watch?v=WI7ZCK8aWoMSlide17

Echinoderms - Video

Sea Stars

https://www.youtube.com/watch?v=A100m5EpfFI

https://www.youtube.com/watch?v=rE8l-KFQlhY

Sea Urchins

https://www.youtube.com/watch?v=nD7_0obUm0o

https://www.youtube.com/watch?v=D3W4OCnHyCs

Sand Dollars

https://www.youtube.com/watch?v=bSsgDhWpPq0

https://www.youtube.com/watch?v=gLK71-vsi2ESlide18

Phylum Hemichordata

Hemichordates are

deuterostomes

, a characteristic they share with both echinoderms and chordates

As the name suggests, hemichordates have some derived characteristics that are ancestral to the phylum

chordata

Dorsal, hollow nerve cord

Gill slits in the pharynx

These traits are shared with all chordates, but are absent in the echinodermsSlide19

Hemichordate Diversity

The phylum

Hemichordata

consists of two classes

The Acorn Worms (

Enteropneusta

)

The

Pterobranchs

The Acorn Worms and the

Pterobranchs

are similar in body form, but vary with regard to feeding structures

Feeding structures in both are ciliated to collect food particles and direct them to the mouthSlide20

Acorn Worms – Feeding

The acorn worms have a muscular proboscis used for food gathering located anterior to the mouth opening

The mouth is ventrally located

A collar is associated with the mouth, and is used both to direct food into the mouth and to redirect particles too large to ingest

Acorn worms are free living and burrow actively to search for foodSlide21

Pterobranchs - Feeding

The proboscis itself is shield shaped

The base of the proboscis bears several tentacles which extend into the water to create a food gathering surface for filter feeding

Pterobranchs

move freely inside of a

collagenous

tube, but are sessile in that they are restricted to life within that tubeSlide22

Gill Slits in the Pharynx

Hemichordates have one or more pairs of gill slits that allow water from the pharynx to pass out of the animal, rather than being ingested

Cilia maintain water flow through the gill pouches

Aside from providing a mechanism for filtering and concentrating food particles, the gill pouches create a surface for gas exchange. Slide23

Central Nervous System

A point of emphasis in our discussion of the evolution of the central nervous system has been the presence in many invertebrate phyla of ventral nerve cords

A ventral nerve cord persists in the hemichordates, but is accompanied by a dorsal nerve cord

The dorsal nerve cord is hollow because it is formed by an

invagination

of

ectodermal

embryonic tissue, as is the “spinal cord” associated with the chordatesSlide24

Phylum Chordata

The chordates are

deuterostomes

– they possess a complete digestive tract with the mouth forming from the 2

nd

opening of the gastrula

Chordates, like the hemichordates, have a dorsal hollow nerve cord. Unlike hemichordates they do not have a persistent ventral nerve cord

All chordates, at some time in their development, have pairs of pharyngeal gill slitsSlide25

The Notochord

The distinguishing characteristic of phylum

Chordata

is an endoskeleton centered around the formation of a notochord

The notochord is a rod of

mesodermal

tissue located on the dorsal side of the animal that extends almost the full length of the body

The notochord lies just ventral to the nerve cord that forms the central nervous systemSlide26

More notochord stuff

In the simplest of the chordates, the notochord is a simple rod of tissue with a fibrous sheath that provides some level of longitudinal rigidity

In other chordates, the notochord may exhibit pronounced segmentation, and may or may not become ossified (impregnated with calcium, forming bone)Slide27

Ancestral and Derived Characters

Aside from the shared ancestral characteristics that Chordates share with their closest relatives

(

deuterostome

development, notochord, dorsal hollow nerve cord & pharyngeal gill slits)

the Chordates share 2 derived characteristic only with other Chordates:

An

endostyle

(from which the thyroid gland is derived)

A post-anal tailSlide28

The Endostyle

The

endostyle

is a specialized organ associated with the pharynx

In some of the invertebrate chordates the

endostyle

functions largely as a filter-feeding apparatus, secreting mucus for trapping food particles in the pharynx

The

endostyle

persists in Chordates that do not filter feed. The thyroid gland is derived from the embryonic

endostyle

, and retains a function related to feeding and metabolismSlide29

Chordate Diversity

The Chordates are a diverse phylum, including both invertebrate and vertebrate classes

The

Protochordates

are invertebrate filter feeders, and consist of the

Urochordates

(tunicates) and the Cephalochordates (lancelets)

The

Agnatha

are the jawless fish. They are the simplest bodied vertebrates, with a cranium and a well developed tripartite brain (three regions: forebrain, midbrain, hindbrain)Slide30

Protochordates: TunicatesSlide31

Tunicate Anatomy

Tunicates are filter feeders

Water enters the mouth, filters through the gill slits in the pharynx, and passes out through the atrial siphon

Food passes through a complete digestive tractSlide32

Protochordates: LanceletsSlide33

Lancelet Anatomy

Lancelets are filter feeders like the tunicates, but they have more fully developed musculature, notochord and dorsal nerve cordSlide34

Vertebrates with Jaws

The most familiar Chordates are the Vertebrates.

Aside from the

Agnatha

, the remaining vertebrate Chordates have jaws derived from the first 2 pairs of gill arches

The ability to process food has evolved independently in many different phyla. Any level of processing has the potential to improve digestion and thus increase the chances of survivalSlide35

Vertebrate Diversity - Fish

Agnatha

– jawless fish (hagfish and lampreys)

Chondrichthyes

– jawed fish with cartilage skeletons (sharks and rays)

The

Chondrichthyes

lack a swim bladder, and maintain

bouyancy

through a large, oily liver

Osteichthyes

– jawed fish with bony, calcified skeletons (most familiar fish)

The bony fish offset the density of their heavy skeleton with an air filled swim bladder on the dorsal side of their body cavitySlide36

Class Agnatha – Jawless FishSlide37

Chondrichthyes – Cartilage FishSlide38

Osteichthyes – Bony FishSlide39

Poikilothermy vs. Homeothermy

Poikilothermic

Temperature varies

“Cold Blooded”

Ectothermic

Body temperature is a function of the outside environment

All invertebrates, as well as fish, amphibians and reptiles

Homeothermic

Temperature is relatively constant

“Warm Blooded”

Endothermic

Body temperature results from within

Body heat derived from metabolism

Dinosaurs (theoretically), birds and mammalsSlide40

Vertebrate Diversity – Poikilothermic

Tetrapods

Class

Amphibia

Includes frogs, toads, salamanders and newts.

Moist, vascular skin functions for gas exchange

The earliest terrestrial vertebrates

Amphibians are tied to moist environments by the need to keep their skin and their eggs moist

Class

Reptilia

Includes lizards, turtles, crocodilians & snakes

Dry, scaly skin is well adapted for life on land

Shelled, amniotic egg frees reptiles from the need to return to the water to lay eggsSlide41

AmphibiansSlide42

ReptilesSlide43

Vertebrate Diversity – Homeothermic

Tetrapods

Class

Mammalia

Mammals are distinguished by a variety of skin gland variations

Hair glands

Milk glands

Class Aves (Birds)

Birds possess a number of adaptations unique to the class Aves, including

Feathers (derived from epidermal scale pouches)

Bipedalism

, with Forelimbs adapted for flight

Sternum with a broad “keel” for pectoral muscle attachmentSlide44

MammalsSlide45

Birds (Class Aves)Slide46

Mammalian Diversity

Class

Mammalia

is divided into 3 groups due to variations in reproductive behavior and anatomy

Monotremes

Include the platypus and the echidna

Marsupials

Include the kangaroo, koala and opossum

Placentals

Include most familiar mammals, including humansSlide47

Monotremes

Monotremes

have reproductive systems and behaviors almost identical to reptiles. They are oviparous (egg layers) and their eggs have leathery shellsSlide48

Marsupials

Marsupials are viviparous. Their young are born live, but immature and poorly developed

Marsupial young continue their development through prolonged lactation within a protective pouchSlide49

Placental Mammals

Placental mammals are live born after a long gestation period

The young are nourished through the placenta, which imbeds in the wall of the uterus and allows exchange of nutrients and wasteSlide50

Marc Kirschner

, Harvard:

How the chordate got its cord

https://www.youtube.com/watch?v=232wtCuLsoI

https://www.youtube.com/watch?v=Y0xfpGdh1_Y

https://www.youtube.com/watch?v=I1yqkSuTwrU