1. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings. BIOLOGY A GUIDE TO THE NATURAL WORLD FOURTH EDITION DAVID KROGH Animals Chapter 23

2. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. What is an Animal? Animals are eukaryotic, multicelled heterotrophs that do not have a cell wall pass through a blastula stage (a hollow, fluid-filled ball of cells that forms once an egg is fertilized by sperm)

3. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Groups of Animals The animals most familiar to us are vertebrates (have a backbone) But most of the ~2 million known species of animals are invertebrates (without backbones)

4. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Major Groups of Invertebrates 1.Sponges 2.Cnidarians (jellyfish, sea anemones) 3.Flatworms (tapeworms) 4.Segmented worms (earthworms, leeches) 5.Molluscs (snails, clams, squid) 6.Roundworms 7.Arthropods (spiders, insects, crustaceans) 8.Echinoderms (starfish, sea urchins)

5. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Comparing Animal Groups Animals can be categorized based on three traits: 1.Symmetry 2.Type of gut 3.Body cavity

6. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Symmetry can the body be cut into mirror images? Asymmetry – the animal cannot be divided into mirror images (sponges) Radial symm. – more than one way to produce mirror images (cnidarians) Bilateral symm. – can form mirror images only one way - into right and left halves (all others)

7. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Symmetry Figure 23.3 Radial symmetry: Symmetry around a central point Asymmetry: No planes of symmetry Bilateral symmetry: Symmetry across the sagittal plane dorsal posterior ventral anterior sagittal plane

8. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Type of Gut (= Digestive System) Region where food is digested and then absorbed Sponges lack a dig. syst. Cnidarians and flatworms have a sac-like gut (or incomplete digestive system) has only one opening that serves for both taking in food and expelling waste All others have tube-like gut (or complete dig. syst.) has an opening at both ends (mouth and anus)

9. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Body Cavities Bilat. sym. animals may have an open space (or cavity) between the gut and the outer body wall Flatworms lack this cavity (are acoelomate) Roundworms have a cavity that lacks a membrane lining (a pseudocoel) All other bilat. sym. animals have a cavity lined with a membrane (a coelom)

10. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Acoelomate

11. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Pseudocoel

12. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Coelom

13. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Sponges Are all aquatic Have a very simple body plan – are little more than a tube of cells that filter food particles out of water Water is drawn through the body of the sponge and expelled out through a central opening

14. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Sponges Figure 23.6 osculum Inner cells with flagella create currents. The currents cause water to flow into pores and out the osculum at top. Spicules strengthen the walls.

15. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Sponges

16. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Cnidarians All are aquatic Jellyfishes, corals, and sea anemones Their incomp. dig. syst. is called a gastrovascular cavity (GVC) They use it as a hydrostatic skeleton (a cavity filled with a pressurized fluid) to support themselves Have tentacles covered with nematocysts, stinging structures that provide defense and catch prey

17. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Nematocysts

18. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Cnidarians Figure 23.8

19. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Flatworms Mostly aquatic Free-living planarians, parasitic tapeworms and flukes Simplest animals with organ systems Have a GVC Are often hermaphrodites (have both male and female reproductive organs)

20. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Planarian Organ Systems

21. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Planaria

22. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Segmented Worms Show segmentation – the division of the body into many repeating units Mostly aquatic Includes earthworms and leeches Fluid in the coelom acts as a hydrostatic skeleton

23. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Segmented Worms Figure 23.13 anus segments coelomic space muscular walls between segments pairs of bristles mouth “hearts” intestine brain dorsal blood vessel

24. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Annelid Diversity Figure 23.14

25. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Molluscs Mostly aquatic Include a variety of groups: 1.gastropods (snails and slugs) 2.bivalves (oysters, mussels, clams, etc.) 3.cephalopods (squid, octopus, nautilus)

26. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Mollusc Traits Molluscs have 3 defining traits: 1.A mantle drapes over the body and usually produces a shell 2.A fleshy foot is used for movement 3.Most have a rasping mouthpart (or radula) for shredding food

27. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Molluscs Figure 23.15

28. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Roundworms Mostly aquatic Use their pseudocoel as a hydrostatic skel. Parasites or free-living decomposers Human parasitic roundworms include: 1.pinworms and hookworms 2.the worm that causes trichinosis (often from undercooked pork) 3.the worm that causes elephantiasis

29. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Parasitic Roundworms

30. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Arthropods Mostly terrestrial Is the largest group of animals (more than 1 million species) Have a segmented body and paired jointed appendages for efficient movement on land Have a hard but flexible exoskeleton that provides support and limits water loss It must be shed (or molted) for the animal to grow

31. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Arthropod Groups Three main groups: 1.Uniramians (insects, centipedes, millipedes) 2.Crustaceans (crabs, shrimps, barnacles) 3.Chelicerates (spiders, mites, scorpions)

32. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Arthropods Figure 23.18

33. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Echinoderms All aquatic Sea stars, sea urchins, sea cucumbers, etc. Larvae start off with bilateral sym. but adults have radial sym. Have an endoskeleton (internal skel.) with spines or plates of calcium carbonate Have a water-vascular system with tube feet (is a hydraulic system used for movement, feeding, and gas exchange)

34. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Echinoderms Figure 23.24

35. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Sea Star Figure 23.25 tiny spines and gills on surface digestive glands eye spot mouth (bottom center) water intake for tube feet tube feet interior bulbs of tube feet direction of locomotion Tube feet enable sea stars to “walk” and hold on to prey bulb anus stomachs