1. Sponges and Cnidarians
Biology II: Chapter 26

2. The Animal Kingdom Multicellular Eukaryotic Heterotrophs
Cells lack cell walls
95% are invertebrates

3. What Animals Do to Survive
Feeding
Respiration
Circulation
Excretion
Response
Movement
Reproduction

4. Trends in Animal Evolution
Cell specialization and levels of organization
Early development
Body symmetry
Cephalization
Body cavity formation

5. SPONGES

6. Sponges Phylum Porifera
Have tiny openings, or pores, all over their bodies
Sessile: they live their entire life attached to a single spot
They are animals! Why…?

7. Sponges are Animals!!! Multicellular Heterotrophic No cell walls
Contain a few specialized cells

8. Form and Function in Sponges
Have nothing resembling a mouth or gut
Have no tissues or organ systems
Simple functions are carried out by a few specialized cells

9. Asymmetrical Have no front or back ends, no left and right sides
A large, cylindrical water pump
The body forms a wall around a large central cavity through which water flows continually

10. Choanocytes
Specialized cells that use flagella to move a steady current of water through the sponge
Filters several thousand liters/day

11. Osculum
A large hole at the top of the sponge, through which water exits
The movement of water provides a simple mechanism for feeding, respiration, circulation and excretion

12. Simple Skeleton
Spicule: a spike-shaped structure made of chalk-like calcium carbonate or glasslike silica in hard sponges
Archaeocytes: specialized cells that make spicules

13. Feeding Filter feeders Sift microscopic food from the water
Particles are engulfed by choanocytes that line the body cavity

14. Respiration, Circulation, & Excretion
Rely on the movement of water through their bodies to carry out body functions
As water moves through the cavity:
Oxygen dissolved in the water diffuses into the surrounding cells
Carbon dioxide and other wastes, diffuse into the water and are carried away

15. Response No nervous system
Many sponges protect themselves by producing toxins that make them unpalatable or poisonous to potential predators

16. Reproduction Sexually or asexually
A single spore forms both eggs and sperm; usually at different times

17. Sexual Reproduction
Internal fertilization: Eggs are fertilized inside the sponge’s body
Sperm are released from one sponge and carried by currents to the pores of another sponge

18. Asexual Reproduction Budding
Gemmules: groups of archaeocytes surrounded by spicules

19. Ecology of Sponges
Ideal habitats for marine animals such as snails, sea stars, sea cucumbers, and shrimp
Mutually beneficial relationships with bacteria, algae and plant-like protists
Many are green due to these organisms living in their tissues

20. Ecology of Sponges
Attached to the seafloor and may receive little sunlight
Some have spicules that look like cross-shaped antennae
Like a lens or magnifying glass, they focus and direct incoming sunlight

21. CNIDARIANS

22. Cnidarians Phylum Cnidaria Hydras, jellies, sea anemones, and corals
Soft-bodied
Carnivorous
Stinging tentacles arranged in circles around their mouths
Simplest animals to have body symmetry and specialized cells

23. Cnidocytes Stinging cells that are located on their tentacles
Used for defense and to capture prey

24. Nematocyst
A poison-filled, stinging structure that contains a tightly coiled dart
Found within cnidocytes

25. Form and Function in Cnidarians
Only a few cells thick
Simple body systems
Most of their responses to the environment are carried out by specialized cells and tissues

26. Radially Symmetrical
Central mouth surrounded by numerous tentacles that extend outward from the body
Life cycles includes a polyp and a medusa stage

27. Body Plan
Polyp: cylindrical body with arm-like tentacles; mouth points upward
Medusa: motile, bell-shaped body; mouth on the bottom

28. Feeding
Polyps and medusas have a body wall that surrounds an internal space: the gastrovascular cavity
Gastrovascular cavity: a digestive chamber with one opening
Food enters and wastes leave the body

29. Respiration, Circulation, & Excretion
Following digestion, nutrients are usually transported throughout the body by diffusion
Respire and eliminate wastes by diffusion through body walls

30. Response
Specialized sensory cells are used to gather information from the environment
Nerve net: loosely organized network of nerve cells that together allow cnidarians to detect stimuli
Distributed uniformly throughout the body in most species
In some species it is concentrated around the mouth or in rings around the body

31. Response
Statocysts: groups of sensory cells that help determine the direction of gravity
Ocelli: eyespots made of cells that detect light

32. Movement
Hydrostatic skeleton: a layer of circular muscles and a layer of longitudinal muscles that enable cnidarians to move

33. Reproduction: Sexually and Asexually
Polyps can reproduce asexually by budding
External sexual reproduction
The sexes are separate-each individual is either male or female
Both egg and sperm are released into the water

34. Groups of Cnidarians Jellies (formerly jellyfishes)
Hydras and their relatives
Sea anemones
Corals

35. Ecology of Corals The worldwide distribution is determined by:
Temperature
Water depth
Light intensity
Many suffer from human activity
Coral bleaching has become common
Global warming may add to the problem