1. Kingdom animalia Invertebrates
Chapters 24, 25, 26, and 27

2. Invertebrate phyla 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)

3. Invertebrate Evolution
Phylum Porifera
Phylum Cnidaria
Phylum Platyhelminthes
Phylum Nematoda
Phylum Mollusca
Phylum Annelida
Phylum Arthopoda
Phylum Echinodermata
Phylum Chordata

4. Phylum porifera *Cellular Level of Organization
Organisms in the phylum Porifera are among the simplest animals
Many sponges are radially symmetrical
Their parts are arranged around a central axis
Choanocytes are specialized cells that make up poriferans.
Central axis

5. Phylum porifera Filter feeders:
Flagellated choanocytes filter food from the water passing through the porous body
Sessile: stay in one place
Choanocyte in contact with an amoebocyte
Pores
WATER FLOW
Skeletal fiber
Central cavity
Choanocyte
Flagella
Amoebocyte
Figure 18.3C

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

7. Phylum Cnidaria *Tissue level organization
Cnidarians are the simplest animals with tissues.
These animals exist in two radially symmetrical forms:
Polyp
Medusa

8. Phylum Cnidaria 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.

9. Phylum Platyhelminthes *Organ level of Organization
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.
Digestive tract (gastrovascular cavity)
Nerve cords
Mouth
Eyespots
Nervous tissue clusters
Bilateral symmetry

10. Flukes and tapeworms are parasitic flatworms with complex life cycles
Mature flukes in blood vessels of intestine
Male
Human host
Female 1
Sexual reproduction of flukes in human; fertilized eggs pass out in feces 6
Larva penetrates skin and blood vessels 2
Eggs hatch in water 5
Larva that infects human 3
Larva that infects snail 4
Asexual reproduction of flukes in snail
Snail host

11. Phylum Platyhelminthes
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.
Units with reproductive structures
Head
Hooks
Sucker

12. Quick evolution checkpoint
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.

13. Body covering (from ectoderm)
Muscle layer (from mesoderm)
Pseudocoelom
Digestive tract (from endoderm)
Body covering (from ectoderm)
Coelom
Tissue layer lining coelom and suspending internal organs (from mesoderm)
Digestive tract (from endoderm)

14. Phylum nematoda *Pseudocoelom
AKA: Roundworms
Nematodes 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.
Trichinella juvenile
Muscle tissue

15. Phylum Mollusca *Coelom
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

16. Phylum Mollusca Mollusks have a true coelom and a circulatory system
All mollusks have a muscular foot and a mantle
The mantle may secrete a shell which encloses the visceral mass
Mollusks have a true coelom and a circulatory system
Many mollusks feed with a rasping radula

17. 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
Brain
Main heart
Coelom
Digestive tract
Segment walls
Mouth
Accessory heart
Nerve cord
Blood vessels
Excretory organ

18. Segmentation probably evolved as an adaptation for movement

19. Quick Evolution checkpoint: 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.

20. Phylum Annelida *body segmentation & protostomes
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.

21. Phylum arthropoda *jointed appendages
Cephalothorax
Abdomen
Arthropods are the most numerous and widespread of all animals.
They are segmented animals with exoskeletons and jointed appendages.
Thorax
Head
Antennae (sensory reception)
Swimming appendages
Walking legs
Pincer (defense)
Mouthparts (feeding)

22. Phylum arthropoda
In terms of numbers, distribution, and diversity, they are the most successful phylum of animals.
Diversity:
Insects
Crustaceans (marine arthropods)
Arachnids
Millipedes & centipedes
Horseshoe crabs are ancient marine arthropods

23. Phylum arthropoda 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.
Head
Thorax
Abdomen
Antenna
Forewing
Eye
Hindwing
Mouthparts

24. Phylum arthropoda Metamorphosis:
Larvae: specialized for eating and growing
Adults: specialized for dispersal and reproduction

25. Phylum Echinodermata *deuterostome, endoskeleton, radial symmetry
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

26. Phylum echinodermata
The water vascular system has suction-cup-like tube feet used for respiration and locomotion.
Anus
Spines
Stomach
TUBE FEET
CANALS

27. Phylum chordata *notochord
Notochord: flexible, tough rod that provides support for the animal and gives muscles a place to attach

28. Phylum chordata *notochord
Organisms in this phylum (LIKE US) are segmented animals with four distinctive features:
Dorsal hollow nerve cord
Stiff notochord
Pharyngeal slits behind the mouth
Muscular post-anal tail
We’ll study this phylum
separately.