phylum mollusca - waterford mott biology -...

Phylum MolluscaSnails, slugs, oysters, clams, octopuses, and squidsMost are marineSoft-bodied animals, but most are protected by a hard shellThree similar structures: muscular foot, visceral mass, mantleSeparate sexes with gonads in the visceral mass

Fig. 33.16

Nephridium Visceral mass

Heart

Coelom

Mantle

Mantle cavity

Anus

Gill

Gonads

Heart

Intestine

Stomach Shell

Radula

Mouth Esophagus Nerve

cords Foot

Digestive tract

Mouth

Radula

Phylum Mollusca ClassesClass Polyplacophora - oval-shaped marine animals encased in an armor of eight dorsal platesClass Gastropoda - snails (shells), slugs (lack shell or very small shell)

Both marine and freshwaterTorsion - anus and mantle above head

Class Bivalvia - clams, oysters, mussels, and scallops (shell divided in two halves)

Have gills used for feeding as well as gas exchange

Class Cephalopoda - squids, octopuses

Beak-like jaws surrounded by tentacles of modified foot

(a) A land snail

(b) A sea slug (nudibranch)

Mouth

Anus

Mantle cavity

Stomach Intestine

Figs. 33.16 - 33.21

Mantle Hinge area

Digestive gland

Mouth

Shell

Palp Foot

Mantle cavity Gonad Gill

Incurrent siphon

Water flow

Excurrent siphon

Anus

Adductor muscle (one or two)

Gut Coelom

Heart Squid

Octopus

Chambered nautilus

Molluscs: Silent ExtinctionGroup with the largest number of recent extinctions Most threatened groups are freshwater bivalves and terrestrial gastropods Threatened by habitat loss, pollution, and non-native species

Other invertebrates

Insects

Fishes

Mammals

An endangered Pacific island land snail, Partula suturalis

Molluscs

Recorded extinctions of animal species (Data: International Union for Conservation of Nature, 2008)

Reptiles (excluding birds)

Amphibians

Birds

Workers on a mound of pearl mussels killed to make buttons (ca. 1919)

Fig. 33.22

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Phylum AnnelidaSegmented worms (bodies composed of fused rings)Class Oligochaeta - contain chaetae (bristles made of chitin)

Earthworms eat their way through soil extracting nutrients as the soil moves through the canal

Class Polychaeta - possess paddlelike parapodia that function as gills and aid in locomotion Class Hirudinea - blood-sucking parasites (ex. leaches)

Figs. 33.23-33.25Parapodia

Epidermis

Circular muscle

Cuticle

Longitudinal muscle

Dorsal vessel

Chaetae

Intestine

Nephrostome

Fused nerve cords

Ventral vessel

Clitellum

Esophagus

Pharynx Crop

Metanephridium

Coelom

Septum (partition between segments)

Anus

Skin

Metanephridium

Intestine

Gizzard

Ventral nerve cords with segmental ganglia

Circulatory system vessels

Subpharyngeal ganglion

Mouth

Cerebral ganglia

Giant Australian earthworm

Phylum NematodaNonsegmentedAmong the most widespread of animals Found in aquatic habitats, in the soil, in tissues of plants, and in the body fluids and tissues of animalsBodies are covered in a tough cuticleParasites of plants and animals

Figs. 33.26-33.27

Porifera Cnidaria Lophotrochozoa Ecdysozoa Deuterostomia

25 µm

Encysted juveniles Muscle tissue 50 µm

Phylum ArthropodaTwo out of every three known species of animals are arthropodsEarly arthropods (trilobites) show variation from segment to segmentSegmented coelomates that have an exoskeleton made of chitin and jointed appendagesAs they evolved the segments fused and the appendages became more specializedHave an open circulatory system

Fluid called hemolymph is circulated into the spaces surrounding tissues and organs

Figs. 33.28- 33.30

EXPERIMENT

Origin of Ubx and abd-A Hox genes?

RESULTS

Common ancestor

Other ecdysozoans

Arthropods

Onychophorans

Ant = antenna J = jaws L1–L15 = body segments

Cephalothorax

Thorax

Head Antennae (sensory reception)

Abdomen

Swimming appendages (one pair per abdominal segment

Walking legs Mouthparts

(feeding)

Pincer (defense)

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Phylum ArthropodiaFour Subphyla

Cheliceriforms - clawlike feeding appendages (chelicerae) (ex. spiders, ticks, mites, scropions, and horseshoe crabs)

Arachnids have an abdomen and a cephalothorax with six pairs of appendages

Myriapoda - millipedes (two pairs of legs per segment) and centipedes (one pair of legs per segment)

Figs. 33.31-33.34

(a) Millipede

(b) Centipede

Intestine Heart

Stomach

Brain

Eyes

Poison gland

Pedipalp Chelicera

Book lung

Sperm receptacle

Gonopore (exit for eggs)

Silk gland

Spinnerets

Anus

Ovary

Digestive gland

Scorpion

Dust mite

Web-building spider

50 µm


Hexapoda - insectsMore species-rich than all other forms of life combinedFlight key to evolutionary successMany undergo metamorphosis

Incomplete metamorphosis - the young (nymphs) look like adults but go through a series of moltsComplete metamorphosis - larval stages specialized for eating and entirely different from adult stage (maggot, grub, or caterpillar)

Abdomen Thorax Head Compound eye

Antennae

Heart Dorsal artery Crop Cerebral

ganglion

Mouthparts Nerve cords Tracheal tubes Ovary

Malpighian tubules

Vagina

Anus

(a) Larva (caterpillar) (b) Pupa

(c) Later-stage pupa (d) Emerging

adult

(e) Adult

Figs. 33.35-33.37


Crustacea - have biramous, branched, appendages that are extensively specialized for feeding and locomotion

Decapods are large crustaceans (lobsters, crabs, crayfish, and shrimp)Planktonic crustaceans include many species of copepods (may be the most numerous of all animals)Barnacles - sessile crustaceans whose cuticle is hardened into a shell Fig. 33.39

(a) Ghost crab

(b) Krill (c) Barnacles

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Phylum EchinodermataShare characteristics of deuterostomes with chordates (even though they are invertebrates)

Radial cleavageDevelopment of the coelom from the archenteronFormation of the mouth at the end of the embryo opposite the blastopore

Most echinoderms are slow-moving or sessile marine animals

Have a thin, bumpy or spiny skin that covers an endoskeleton of hard calcareous plates

Have a water vascular system which is a network of branching hydraulic canals into tube feet that function in locomotion, feeding, and gas exchange

Fig. 33.40

Porifera Cnidaria Lophotrochozoa Ecdysozoa Deuterostomia

Short digestive tract

Stomach Anus

Central disk

Spine Gills

Madreporite

Radial nerve

Gonads

Ampulla Podium

Tube feet Radial canal

Ring canal

Digestive glands

Phylum EchinodermataRadial symmetry of many echinoderms evolved from bilateral ancestorsSea stars (Class Asteroidea) - undersurfaces of arms have tube feetBrittle stars (Class Ophiuroidea)Sea urchins and sand dollars (Class Echinoidea) - have no arms, but they have five rows of tube feetFeather stars (Class Crinoidea)Sea cucumbers (Class Holothuroidea) - endoskeleton is reducedSea daisies (Class Concentricycloidea) Figs. 33.41-33.45

Vertebrates540 million years ago the first vertebrates began to evolveOne lineage of vertebrates colonized land 365 million years ago52,000 species of vertebrates which include the largest organisms ever to live on Earth

Fig. 34.1

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ChordatesVertebrates are a subphylum of the phylum ChordataHave a notochord and a dorsal, hollow nerve cordBilaterian animals that belong to a clade known as DeuterostomiaTwo groups of invertebrate deuterostomes are the urochordates and cephalochordates are more closely related to vertebrates than to invertebrates

Fig. 34.2

ANCESTRAL DEUTEROSTOME

Notochord

Common ancestor of chordates

Head

Vertebral column

Jaws, mineralized skeleton

Lungs or lung derivatives

Lobed fins

Limbs with digits

Amniotic egg Milk

Echinodermata

Cephalochordata

Urochordata

Myxini

Petromyzontida

Chondrichthyes

Actinopterygii

Actinistia

Dipnoi

Amphibia

Reptilia

Mammalia

Chordates C

raniates Vertebrates

Gnathostom

es O

steichthyans Lobe-fins

Tetrapods A

mniotes

ChrodatesAll have a set of shared derived characters (some only express them during embryonic developmentNotochord - longitudinal, flexible rod located between the digestive tube and the nerve cord

Provides skeletal support throughout most of the length of a chordateIn most vertebrates a complex, jointed skeleton develops

Nerve cord - develops from a plate of ectoderm that rolls into a tube dorsal to the notochord

Develops into the central nervous system

Muscle segments

Notochord

Dorsal, hollow

nerve cord

Muscular, post-anal tail

Pharyngeal slits or clefts

Anus

Mouth

Fig. 34.3

ChordatesMost have grooves in the pharynx called pharyngeal clefts that develop into slits that open to the outside of the body

Function as suspension-feeding structures Modified for gas exchange in aquatic vertebratesDevelop into parts of the ear, head, and neck in terrestrial vertebrates

Chordates have a tail extending posterior to the anus (many lose it during embryonic development)

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ChordataSubphylum Urochordata (tunicates) - deepest-branching lineage of chordates and are marine suspension feeders (sea squirts)

Most closely resemble chordates during larval stageDraws water through a siphon to filter out food particles

Subphylum Cephalochordata (lancelets) - named for blade-like shape

Marine suspension feedersRetain chordate body plan as adultsGene expression in lancelets holds clues for the evolution of the vertebrate form

Cephalochordata Urochordata Myxini Petromyzontida Chondrichthyes Actinopterygii Actinistia Dipnoi Amphibia Reptilia Mammalia

Mouth

Cirri

Pharyngeal slits

Atrium

Digestive tract

Atriopore

Segmental muscles

Anus

Notochord

Tail

Dorsal, hollow

nerve cord

1 cm


Figs. 34.4-34.6

Notochord

Dorsal, hollow nerve cord

Tail

Muscle segments

Intestine Stomach

Atrium

Pharynx with slits

(a) Tunicate larva (b) Adult tunicate (c) Adult tunicate

Excurrent siphon

Incurrent siphon

Water flow

Excurrent siphon

Anus Intestine

Esophagus Stomach

Incurrent siphon to mouth

Excurrent siphon

Atrium

Tunic

Pharynx with

numerous slits

Nerve cord of lancelet embryo

Brain of vertebrate embryo (shown straightened)

Forebrain Midbrain Hindbrain

BF1

BF1

Otx

Otx

Hox3

Hox3

CraniatesChordates with a headEvolved 530 million years ago (Cambrian Explosion)Head allows a new way of feeding and active predationShare common characteristics: skull, brain, eyes, and other sensory organsNeural crest - collection of cells taht appears near the dorsal margins of the closing neural tube in an embryo

Cells give rise to a variety of structures including some bones and cartilage in the skull

Class Myxini (hagfish) - least derived lineage that still survives

Jawless marine animals taht have a cartilaginous skull and an axial rod of cartilage derived from the notochord that lack vertebrae

Fig. 34.9

Dorsal edges of neural plate

Neural crest

Neural tube

Notochord Migrating neural crest cells

(a) (b)

(c)

Skull bones and cartilage derived from neural crest cells Fig.

34.7

Slime glands

VertebratesCraniates that evolved a backboneShared characteristics: vertebrae enclosing a spinal cord, an elaborate skull, and fin rays (in aquatic forms)Class Cephalaspidomorphi (Lampreys)

Oldest living lineage of vertebratesHave cartilaginous segments surrounding the notochord and arching partly over the nerve cord

Conodonts and Ostracoderms are ancient vertebrates where mineralized skeletons first appeared

Fig. 34.10-34.12


Dental elements (within head)

Pteraspis

Pharyngolepis

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phylum mollusca - waterford mott biology -...

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