the deuterostomes

50
The Deuterostomes Echinoderms and Chordates

Upload: taya

Post on 24-Feb-2016

72 views

Category:

Documents


0 download

DESCRIPTION

The Deuterostomes. Echinoderms and Chordates. Developmental Variations. During embryonic development, the process of gastrulation forms the digestive cavity. Gastrulation varies in the animal kingdom No gastrulation ( placozoans ) Incomplete gastrulation - PowerPoint PPT Presentation

TRANSCRIPT

Page 1: The  Deuterostomes

The DeuterostomesEchinoderms and Chordates

Page 2: The  Deuterostomes

Developmental VariationsDuring 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 openings

Page 3: The  Deuterostomes

Animals with Complete GastrulationComplete 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 mouth

Page 4: The  Deuterostomes

Deuterostome PhylaThere 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

Vertebrates

Page 5: The  Deuterostomes

Phylum EchinodermataThe 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 phyla

Page 6: The  Deuterostomes

Characters retained:Embryonic development &

Gastrulation◦Triploblastic◦Complete digestive tract

Body Cavity◦Eucoelomate

Symmetry◦Bilateral during larval stages

Page 7: The  Deuterostomes

Characters lost or diminished:SegmentationCephalization

◦No head, brain or specialized sense organs

◦Sensory apparatus are not centralizedBilateral symmetry in the adult form

◦The bilateral symmetry in the larvae goes through a dramatic metamorphosis, reorganizing the body into a Pentaradially Symmetrical adult

Page 8: The  Deuterostomes

MetamorphosisThe 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 surface

Page 9: The  Deuterostomes

Derived characters special to the EchinodermsWater-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 pedicellariaHemal system

◦ Poorly understood, it appears to function for distribution of materials

Pentaradial symmetry◦ Organs radiate from a central disc,

characteristically in a pattern of fives

Page 10: The  Deuterostomes

Water Vascular System

Page 11: The  Deuterostomes

Tube Feet

Page 17: The  Deuterostomes

Echinoderms - VideoSea Starso https://www.youtube.com/watch?v=A100m

5EpfFIo https://www.youtube.com/watch?v=rE8l-KF

QlhYSea Urchins

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

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

Sand Dollars◦ https://www.youtube.com/watch?v=bSsgD

hWpPq0◦ https://www.youtube.com/watch?v=gLK71-

vsi2E

Page 18: The  Deuterostomes

Phylum HemichordataHemichordates 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 echinoderms

Page 19: The  Deuterostomes

Hemichordate DiversityThe 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 mouth

Page 20: The  Deuterostomes

Acorn Worms – Feeding The acorn worms have a muscular

proboscis used for food gathering located anterior to the mouth opening

The mouth is ventrally locatedA 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 food

Page 21: The  Deuterostomes

Pterobranchs - FeedingThe proboscis itself is shield

shapedThe 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 tube

Page 22: The  Deuterostomes

Gill Slits in the PharynxHemichordates 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.

Page 23: The  Deuterostomes

Central Nervous SystemA 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 chordates

Page 24: The  Deuterostomes

Phylum ChordataThe chordates are deuterostomes –

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

Page 25: The  Deuterostomes

The NotochordThe 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 system

Page 26: The  Deuterostomes

More notochord stuffIn 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)

Page 27: The  Deuterostomes

Ancestral and Derived CharactersAside 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 tail

Page 28: The  Deuterostomes

The EndostyleThe endostyle is a specialized organ

associated with the pharynxIn 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 metabolism

Page 29: The  Deuterostomes

Chordate DiversityThe 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)

Page 30: The  Deuterostomes

Protochordates: Tunicates

Page 31: The  Deuterostomes

Tunicate AnatomyTunicates are

filter feedersWater enters the

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

Food passes through a complete digestive tract

Page 32: The  Deuterostomes

Protochordates: Lancelets

Page 33: The  Deuterostomes

Lancelet AnatomyLancelets are

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

Page 34: The  Deuterostomes

Vertebrates with JawsThe 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 survival

Page 35: The  Deuterostomes

Vertebrate Diversity - FishAgnatha – 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 liverOsteichthyes – 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 cavity

Page 36: The  Deuterostomes

Class Agnatha – Jawless Fish

Page 37: The  Deuterostomes

Chondrichthyes – Cartilage Fish

Page 38: The  Deuterostomes

Osteichthyes – Bony Fish

Page 39: The  Deuterostomes

Poikilothermy vs. HomeothermyPoikilothermic

◦ 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 mammals

Page 40: The  Deuterostomes

Vertebrate Diversity – Poikilothermic TetrapodsClass 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 moistClass 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 eggs

Page 41: The  Deuterostomes

Amphibians

Page 42: The  Deuterostomes

Reptiles

Page 43: The  Deuterostomes

Vertebrate Diversity – Homeothermic TetrapodsClass 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

attachment

Page 44: The  Deuterostomes

Mammals

Page 45: The  Deuterostomes

Birds (Class Aves)

Page 46: The  Deuterostomes

Mammalian DiversityClass 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 humans

Page 47: The  Deuterostomes

MonotremesMonotremes have reproductive systems

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

Page 48: The  Deuterostomes

MarsupialsMarsupials are

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

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

Page 49: The  Deuterostomes

Placental MammalsPlacental

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 waste

Page 50: The  Deuterostomes

Marc Kirschner, Harvard: How the chordate got its cordhttps://www.youtube.com/watch?

v=232wtCuLsoIhttps://www.youtube.com/watch?

v=Y0xfpGdh1_Yhttps://www.youtube.com/watch?

v=I1yqkSuTwrU