Upload
ksena
View
33
Download
2
Embed Size (px)
DESCRIPTION
Chapter 23. Animals. 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). Groups of Animals. - PowerPoint PPT Presentation
Citation preview
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings.
BIOLOGYA GUIDE TO THE NATURAL WORLD
FOURTH EDITION
DAVID KROGH
Animals
Chapter 23
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)
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)
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)
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
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)
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
sagittalplane
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)
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)
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings.
Acoelomate
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings.
Pseudocoel
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings.
Coelom
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
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings.
Sponges
Figure 23.6
osculum
Inner cells withflagella createcurrents.
The currentscause water toflow into poresand out theosculum at top.
Spiculesstrengthenthe walls.
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings.
Sponges
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
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings.
Nematocysts
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings.
Cnidarians
Figure 23.8
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)
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings.
Planarian Organ Systems
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings.
Planaria
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
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings.
Segmented Worms
Figure 23.13
anus
segments
coelomic space
muscular wallsbetween
segments
pairs of bristles
mouth “hearts”
intestine
brain
dorsalblood vessel
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings.
Annelid Diversity
Figure 23.14
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)
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
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings.
Molluscs
Figure 23.15
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
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings.
Parasitic Roundworms
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
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)
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings.
Arthropods
Figure 23.18
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)
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings.
Echinoderms
Figure 23.24
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings.
Sea Star
Figure 23.25
tiny spines andgills on surface
digestive glands
eye spot
mouth(bottom center)
water intakefor tube feet
tubefeet
interior bulbsof tube feet
direction oflocomotion
Tube feet enablesea stars to “walk”and hold on to prey
bulb
anusstomachs