Chapters 24, 25, 26, and 27

KINGDOM ANIMALIA

INVERTEBRATES

Phylum Porifera (ex. Sponge & sea cucumber)Phylum Cnidaria (ex. jellyfish & hydra)Phylum Platyhelminthes (ex. Planaria &

fluke)Phylum Nematoda (ex. hookworms &

pinworms)Phylum Mollusca (ex. Octopus, snail, & oyster)Phylum Annelida (ex. Earthworm & leech)Phylum Arthropoda (ex. Insects, arachnids, &

crustaceans)Phylum Echinodermata (ex. Sea urchin &

sand dollar)Phylum Chordata (ex. Lancelet & tunicates)

INVERTEBRATE PHYLA

INVERTEBRATE EVOLUTION

1.Phylum Porifera 2.Phylum Cnidaria3.Phylum

Platyhelminthes4.Phylum Nematoda5.Phylum Mollusca6.Phylum Annelida7.Phylum Arthopoda8.Phylum

Echinodermata9.Phylum Chordata

Organisms in the phylum Porifera are among the simplest animalsMany sponges are radially symmetricalTheir parts are arranged around a central axis

Choanocytes are specialized cells that make up poriferans.

PHYLUM PORIFERA *CELLULAR LEVEL OF ORGANIZATION

Central axis

PHYLUM PORIFERA

Filter feeders:Flagellated choanocytes filter food from the water passing through the porous body

Sessile: stay in one place

Pores

WATERFLOW

Skeletalfiber

CentralcavityChoanocyte

Amoebocyte

Choanocyte incontact withan amoebocyte

Flagella

PHYLUM PORIFERA

Single cell

Stalk

The sponge lineage arose very early.They probably evolved from multicellular choanoflagellates, the group that most likely gave rise to the animal kingdom.

Cnidarians are the simplest animals with tissues.

These animals exist in two radially symmetrical forms:PolypMedusa

PHYLUM CNIDARIA*TISSUE LEVEL ORGANIZATION

Cnidocytes on their tentacles sting prey– The tentacles,

controlled by nerves, then push the food through the mouth into a gastrovascular cavity.

– In the cavity, the food is digested and then distributed.

– Only one opening in digestive system.

PHYLUM CNIDARIA

Flatworms are the simplest bilateral animals.

Flatworms have organs.Planarians have a simple nervous system

consisting of a brain, sense organs, and branching nerves.

As in cnidarians, the mouth of a flatworm is the only opening for its gastrovascular cavity.

PHYLUM PLATYHELMINTHES*ORGAN LEVEL OF ORGANIZATION

Digestive tract(gastrovascularcavity)

Nerve cords

Mouth

Eyespots

Nervoustissue clusters

Bilateral symmetry

Flukes and tapeworms are parasitic flatworms with complex life cycles

Mature flukes in bloodvessels of intestine

Humanhost

Male

Female

Snail host

1 Sexual reproductionof flukes in human;fertilized eggs passout in feces

2 Eggs hatchin water

3 Larvathatinfectssnail

4 Asexual reproductionof flukes in snail

5 Larva thatinfects human

6Larva penetratesskin andblood vessels

PHYLUM PLATYHELMINTHES

Units withreproductive

structures

HeadHooksSucker

Tapeworms can be eaten by cattle and burrow into the intestines and muscles.

If meat is not properly inspected, humans can be infected by eating rare or undercooked beef.

Porifera, Cnidaria, and Platyhelminthes lack a body cavity.

Nearly all other animals have a body cavity called a coelom.

This cavity is a fluid-filled space between the digestive tract and the body wall.– The cavity aids in movement, cushions

organs, and it may help in circulation.

QUICK EVOLUTION CHECKPOINT

Body covering(from ectoderm)

Muscle layer(from mesoderm)Pseudocoelom

Digestive tract(from endoderm)

Body covering(from ectoderm)

Tissue layerlining coelomand suspendinginternal organs(from mesoderm)

Coelom

Digestive tract(from endoderm)

AKA: RoundwormsNematodes have a body cavity

not completely lined by mesoderm called a psuedocoelom.

Like most animals, they possess a complete digestive tract.This is a tube with a mouth and an anus. (One-way tract)

Many nematodes are free-living.

Others are parasites.

PHYLUM NEMATODA*PSEUDOCOELOM

Trichinella juvenileMuscle tissue

Phylum Mollusca is a large and diverse phylum that includes gastropods, such as snails

and slugs bivalves, such as clams

and scallops cephalopods, such as

squids and octopuses

PHYLUM MOLLUSCA*COELOM

All mollusks have a muscular foot and a mantleThe mantle may secrete a shell which encloses the visceral mass

Mollusks have a true coelom and a circulatory systemMany mollusks feed with a rasping radula

PHYLUM MOLLUSCA

QUICK EVOLUTION CHECKPOINT:AFTER A BODY CAVITY EVOLVED…Segmentation is the subdivision of some or

most of the body into a series of repeated parts, or segments.

Anus

Segmentwalls

Excretory organ

Digestivetract

Coelom

Mainheart

Brain

Mouth

Accessoryheart

Nerve cord

Blood vessels

Segmentation probably evolved as an adaptation for movement

Protostomal larval development: Earliest type of larval development according to evolution

Mouth is the first opening to develop.

Cells of the embryo cannot be altered.

QUICK EVOLUTION CHECKPOINT:PROTOSTOMAL LARVAL DEVELOPMENT

Earthworms and other annelids are segmented worms whose mouths develop first in the larval stage.

The segmented bodies of annelids give them added mobility for swimming and burrowing. An earthworm eats its way

through soil. Most leeches are free-living

carnivores, but some suck blood.

PHYLUM ANNELIDA*BODY SEGMENTATION & PROTOSTOMES

Arthropods are the most numerous and widespread of all animals.

They are segmented animals with exoskeletons and jointed appendages.

PHYLUM ARTHROPODA*JOINTED APPENDAGES

Antennae(sensoryreception)

Cephalothorax Abdomen

Head

Thorax

Swimmingappendages

Walking legs

Mouthparts (feeding)Pincer (defense)

In terms of numbers, distribution, and diversity, they are the most successful phylum of animals.

Diversity: Insects Crustaceans (marine arthropods) Arachnids Millipedes & centipedes

PHYLUM ARTHROPODA

Horseshoe crabs are ancient marine arthropods

Insects are the most diverse group of organisms.They have a three-part body consisting of head,

thorax, and abdomen.The development of many insects includes

metamorphosis.

PHYLUM ARTHROPODA

Antenna Forewing

MouthpartsHindwing

Head Thorax Abdomen

Eye

Metamorphosis: Larvae:

specialized for eating and growing

Adults: specialized for dispersal and reproduction

PHYLUM ARTHROPODA

Echinoderms have spiny skin, an endoskeleton, and a water vascular system for movement.

Phylum Echinodermata includes organisms such as sea stars and sea urchins These organisms are radially symmetrical as adults

PHYLUM ECHINODERMATA*DEUTEROSTOME, ENDOSKELETON, RADIAL SYMMETRY

The water vascular system has suction-cup-like tube feet used for respiration and locomotion.

PHYLUM ECHINODERMATA

Stomach

Anus

Spines

TUBE FEET

CANALS

Notochord: flexible, tough rod that provides support for the animal and gives muscles a place to attach

PHYLUM CHORDATA*NOTOCHORD

Organisms in this phylum (LIKE US) are segmented animals with four distinctive features:Dorsal hollow nerve cordStiff notochordPharyngeal slits behind the mouthMuscular post-anal tail

PHYLUM CHORDATA*NOTOCHORD

We’ll study this phylum

separately.