Sponges, Cnidarians, and Ctenophores

Chapter 33

Phylum PoriferaSection 33.1

Phylum Porifera

Latin for “Pore-Bearing”

Asymmetric Body Structure

Sponges

• Aquatic animals• Represent transition from

unicellular to multicellular life• No true tissue or organs

• 5,000 species (most marine)• Various colors, shapes, sizes, etc.

• Adults are sessile

Sponge Body Plan:

• Two layers of cells separated by mesohyl (jellylike substance)

• Body wall forms a hollow cylinder that is open at the top

More Sponge Parts:

• Choanocytes (collar cells): flagellated cells that draw water into the sponge

• Ostia (pores): pores that penetrate the body wall that allow water into the sponge

• Osculum: opening at the top of the sponge

Sponge Support System

• Simple skeleton made up of spongin and/or spicules• Spongin: tough, flexible protein fibers• Spicules: tiny, hard particles of calcium

carbonate or silicon dioxide• shaped like spikes

Spongin

Spicules

Sponge Anatomy

Feeding & Digestion

Filter feeders of plankton and other small organisms

Steps in feeding & digestion:1. Choanocytes beat & draw water into ostia

• Then collect food from water2. Nutrients pass from choanocytes to

amoebocytes • Crawling cells that deliver nutrients to rest

of the body3. Wastes and CO2 diffuse into the water and

goes out the osculumvideo

Water Flow:

Asexual Reproduction

• Regeneration: • regrowth of missing cells

• Budding:• sometimes the bud breaks off the parent

and becomes a new organism • or it may remain attached to the parent

and develop into a sponge colony

Environment gone bad?

Gemmules: food filled ball of amebocytes protected by protein & spicules• Can survive harsh conditions• Similar to endospore of bacteria

Sexual Reproduction

1. Sperm of one sponge enters pores of a different sponge

2. Choanocytes engulf the sperm3. Sperm transferred to ameobcytes4. Then transferred to egg in mesohyl5. Egg is fertilized6. Swimming larva leaves the

sponge and settles on an object to become an adult

Hermaphrodites

• Why doesn’t self-fertilization usually occur in an hermaphroditic species?

• Answer:• Less genetic diversity thus less of a

change to survive an environmental change (evolution would not occur as much)

Phyla Notecards:

• First side:• Phylum name• Example organisms• Drawing of organism

• With color!

• Opposite side:• Body symmetry• Mobility (adult & larval

stages)• Feeding methods• Reproductive methods• Defense mechanisms• Environment/habitat

Cnidaria & CtenophoraSection 33.2

Phylum Cnidaria

General Characteristics:

• Radial symmetry• Have tissues and simple organs• Aquatic (mostly marine)

Phylum Cnidaria

Body Plans:

• Medusa: bell-shaped specialized for swimming

• Polyp: vase-shaped specialized for sessile living

More Body Parts:

• Two cell layers:•Epidermis: outer

layer•Gastrodermis:

inner layer

• Mesoglea: • jellylike material

between two layers

Continued…

• Gastrovascular cavity: center of body with a hollow gut and mouth

• Tentacles: flexible extensions surrounding the mouth• Moves food in

Feeding & Defense:

• Cnidocytes: specialized cells used for defense and capturing prey• Gives the phylum its name!

• Nematocyst: organelle within cnidocyte with a long filament and a poison tip• Trigger response

Video

Nervous System:

• Nerve net: diffused web of interconnected nerve cells• No brain• No cephalization

• Can respond to stimuli • Nerve net contractile cell contraction of

whole body

• Can control swimming & feeding

Classification:

Four classes:

1. Class Hydrozoa2. Class Cubozoa

3. Class Scyphozoa4. Class Anthozoa

Class Hydrozoa:

• Colonial organisms (combo of polyp & medusa form)• Each organism has a specialized function for the

colony

• Exception: hydras – only polyps, NOT colonial

• Examples: Portuguese man-of-war, hydra, and Obelia

Video

Class Cubozoa:

• Commonly known as box jellies• Cube shaped medusa

• Some have cnidocytes that can cause death to humans• Example: Sea wasps

Class Scyphozoa:

• Commonly known as jellyfish• The medusa form is dominant• Some have poisonous nemotocytes

that can cause pain and death

• Biotechnology with Jellies video

Class Anthozoa:

• Meaning: flower animals• Dominant form = polyp• Examples: coral & sea anemone

• Some have symbiotic relationships with other species:• Coral with algae• Sea anemone with clownfish

Nemo!

Coral And Algae

Phylum Ctenophora

Distinguishing Characteristics:

• Meaning: comb holder• Commonly called comb jellies

• Move by beating cilia

• Contain colloblasts that secrete a sticky substance that blinds prey• Do not have cnidocytes (like other jellies)

Continued…

• Apical organ: sensory structure that determines orientation in the water

• Bioluminescence: production of light through chemical reactions

Phyla Notecards:

• First side:• Phylum name• Example organisms• Drawing of organism

• With color!

• Opposite side:• Body symmetry• Mobility (adult & larval

stages)• Feeding methods• Reproductive methods• Defense mechanisms• Environment/habitat

Class Notecards:

• First side:• Class name• Example organisms• Drawing of organism

• With color!

• Opposite side:• Unique characteristics• Description of

representative organism • Info about an organism

listed in the book

• Environment/habitat