1. Quick Sponge Quiz
How do sponges differ from other animals? How do they feed, respire, and eliminate wastes?
Sponges:
do not have a mouth or digestive tract (gut)
no true tissue layers (endoderm, ectoderm, mesoderm) or organ systems
Feed: Choaonocytes (collar cells) catch food particles and engulf them; amoebocytes take food particles from the collar cells and carry them to other parts of the sponge.
Respiration and excretion: The current of H2O that flows through the body of a sponge delivers O2 to the cells and removes CO2 and cellular wastes.

2. Warm-up: The Box Jellyfish

3. Phylum Cnidaria: Jellyfish, Sea Anemones, and Corals
Chapter 26: Sponges Cnidarians pp

4. Introduction to Cnidarians
gastrovascular cavity
gastroderm
mesoglea
epidermis
Soft-bodied animals
Radially symmetrical
Body has 2 cell layers (gastroderm and epidermis) separated by a layer of jellylike (mesoglea)
Have stinging tentacles arranged in a circle around mouth -
Most have life cycles that include 2 stages:
Polyp
Medusa

5. Polyp
attached
sessile
Medusa
free-floating
motile

6. Both forms have a gastrovascular cavity with only one opening  food enters the same hole that wastes go out! (a two-way digestive system)

7. Classes of Cnidarians Class Hydrozoa Mostly polyps; short medusa stage
Often live in colonies, where specialized polyps perform particular functions
Example members: hydras (small, freshwater), Portuguese man- of-war (huge, marine; colonial)
2) Class Scyphozoa (jellyfish)
Medusa is dominant stage;
very short polyp stage

8. Classes of Cnidarians 3) Class Anthozoa (sea anemones and corals)
Polyps only, no medusa stage
Corals create protective “cups”; anemones don’t
Some corals are reef building and are ecologically important

9. Form and Function of Cnidarians
Digestive system:
Gastrovascular cavity is where food is broken down
Food is absorbed and further digested by the cells that line the gastrovascular cavity (gastroderm (endoderm) cells)
Cnidoblast cells (in tentacles) contain nematocysts  poison darts that spring out when touched and paralyze prey
Tentacles then pull food into mouth

10. Form and Function of Cnidarians
Respiratory system:
Circulatory system:
Excretory system:
O2, CO2, and wastes get in and out of cells by diffusion through gastrovascular cavity and epidermis (ectoderm).
Direct exchange with surrounding water.
No organized systems for any of these
No need since cnidarians are only a few layers thick
for metabolic waste

11. Form and Function of Cnidarians
Nervous system:
Simple nerve net and sensory cells to detect food/touch
No centralized nervous system
Musculoskeletal system:
No muscles, but epidermal cells can contract
Reproductive system:
Asexual reproduction - budding (in polyps)
Sexual reproduction – medusae produce either eggs or sperm
Broadcast method  eggs and sperm released into water where fertilization occurs; zygote develops into free swimming larva

12. Obelia
life cycle

13. Life cycle of a Cnidarian

14. Lets draw a diagram of the Cnidarian Reproductive Cycle

15. Turritopsis dohrnii

17. Ecology of Cnidarians Sea anemones and small fish are symbiotic
Coral reefs are a major habitat for many organisms They also protect the land from erosion
Coral reefs are very sensitive to pollution!
Some cnidarians are used in medical research (toxins)

18. You will be given two organisms
Read the information
Using these sheets, your text and notes
complete the T-chart worksheet in groups of three
After this, you will be assigned an aspect of the Kingdom Animalia and your group will create a poster/graphic highlighting this area
And your group will present it to the class (~30sec)