1

Lab Exercise 4

PoriferaCnidaria

Platyhelminthes

Organization in Animals

• Cellular level: Random assembly of cells

• Tissue level: Cells connected to form distinct tissues

• Organ level: Tissues connected to form organs

Levels of Biological Organization

• Organ system level

– All more advanced organisms

– Multiple organ systems working together form an complex organism

2

Biological Symmetry

• Radial Symmetry

– Body can be divided into mirror image halves through the center

– Examples• Mature Cnidarians

Biological Symmetry

• Bilateral Symmetry

– Body is divisible into left and right halves by a single plane only

– Examples• Flatworms• Arthropods• Vertebrates

Biological Symmetry

• Asymmetry

– Body cannot be divided to produce mirror image halves

– Example• Porifera

3

Embryonic Development

Cell Cleavage

Blastula Gastrula

GastrulaGastrula

(Diploblastic)

Ectoderm

Endoderm

Archenteron-Space within

endoderm

Blastopore

Archenteron: becomes adult digestive tract

Blastopore: becomes the mouth or anus

Gastrula(Triploblastic)

Blastopore

Mesoderm

Phylum Porifera

• Diploblastic

• Asymmetrical

• No digestive tissue-absorbs particles from water

4

Phylum Porifera

• Ostium• Choanocytes• Amoebocyte• Spicules• Spongocoel• Osculum

Ostium

Phylum Porifera— 3 Body Plans

Asconoid Syconoid Leuconoid

Phylum Cnidaria

• Characteristics– Radial symmetry– Cnidocytes– Simple nerve net– Life cycle alternates between two forms

• Medusa• Polyp

5

Cnidaria - body plan

MedusaPolyp

Cnidocyte

Operculum

Cnidocil

Cnidocyte

Nematocyst

Class Hydrozoa - Hydras

• Polyps are the mature form

• Individuals or colonies

• Portuguese Man-o-war special colony

6

Class Hydrozoa - Hydras

• Prey on zooplankton

• You will observe Hydra feeding on Daphnia– Look at locomotion

http://www.youtube.com/watch?v=Kukv0AtIVdU

Class Scyphozoa: Jellyfish

• Marine

• Medusas: dominant life form

• Aurelia

Oral arms

Gastric pouchMesoglea

Tentacles

Gonad

EctodermEndoderm

7

Class Anthozoa

• Anemones and corals

• Most complex cnidarians

• Always polyps

• Symbiosis with dinoflagellates

Class Anthozoa - Anemones

http://www.emc.maricopa.edu/faculty/farabee/biobk/anemone.gif

basal

coelentron

pharynx

Phylum Platyhelminthes- Flat worms

• Triploblastic

• Bilateral Symmetry

• Organs

• Sac-like gut

• Acoelmate– No cavity

• Monoecious

8

Class Turbellaria– Planarian spp.

• Free living

• Cephalization-– You can see where you

are going– Brain center- coordinate

movement

• Bilateral Symmetry = efficient movement

Class TurbellariaPlanarian cross-section

PharynxPharyngeal cavity Gut

Lumen of the pharynx ParenchymaGut

Ectoderm Mesoderm Endoderm

Class Trematoda- Flukes

• Life cycle with multiple hosts

• Parasites– Opisthorchis

sinensis- Human liver fluke

9

Class Cestoda- Tapeworms

• Thin, ribbon-like

• Sections = proglottids

• Parasites

• 1 or 2 Hosts

Hydranth

Gonangia

Class Hydrazoa

Class Scyphozoa

10

Class Trematoda

• Life cycle with multiple hosts