Invertebrate Animals CHAPTER 17 What is an Animal? Early Animals Significant Invertebrate Animal Features Invertebrate Groups (Phyla) Sponges (Phylum Porifera)
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Invertebrate Animals CHAPTER 17Invertebrate Animals CHAPTER 17•What is an Animal?
•Early Animals
•Significant Invertebrate Animal Features
•Invertebrate Groups (Phyla)•Sponges (Phylum Porifera)
•Cnidarians (Phylum Cnidaria)
•Flatworms (Phylum Platyhelminthes)
•Roundworms (Phylum Nematoda)
•Segmented Worms (Phylum Annelida)
•Arthropods (Phylum Arthropoda)
•Molluscs (Phylum Mollusca)
•Echinoderms (Phylum Echinodermata)
What Is an Animal?
• Animals
– Eukaryotic, multicellular, heterotrophic organisms that obtain nutrients by ingestion
– Mostly reproduce sexually and then proceed through a series of developmental stages
– Usually have muscle cells, as well as nerve cells that control the muscles
– Have distinct specialized cells (tissues)
– Digest their food within their bodies
Figure 17.3
Life Cycle of An Animal
Dominant diploid stage
Early Animals and the Cambrian Explosion
• Animals probably evolved from a colonial flagellated protist that lived in Precambrian seas
• At the beginning of the Cambrian period, 542 million years ago, animals underwent a rapid diversification.
Survey of Organisms Grid
• The development of true tissues
– Specialized cells living in sheets or masses within an organism
Major Evolutionary Novelties in the Evolution of Invertebrate Animals
• The development of radial or bilateral symmetry
• The development of a true body cavity (coelom)
– A fluid-filled, muscle-lined space separating the digestive tract from the outer body wall.
• The development of segmentation
– Body is subdivided into separate parts which can then develop specialized functions
• The development of a complete gut
– Incomplete digestive tracts have a mouth but no anus
Figure 17.7
Types of Body Symmetry Seen in Animals
Major Invertebrate Phyla
• Invertebrates
– Are animals without backbones.
– Represent 95% of the animal kingdom
– Each invertebrate group we will study is in a different phylum:
• Domain Eukarya
– Kingdom Animalia
Phylum X
Invertebrate Animals CHAPTER 17Invertebrate Animals CHAPTER 17•What is an Animal?
•Early Animals
•Significant Invertebrate Animal Features
•Invertebrate Groups (Phyla)•Sponges (Phylum Porifera)
•Cnidarians (Phylum Cnidaria)
•Flatworms (Phylum Platyhelminthes)
•Roundworms (Phylum Nematoda)
•Segmented Worms (Phylum Annelida)
•Arthropods (Phylum Arthropoda)
•Molluscs (Phylum Mollusca)
•Echinoderms (Phylum Echinodermata)
Figure 17.6
Evolutionary Tree of Kingdom Animalia
Sponges (Phylum Porifera)• Includes sessile (non-motile)
animals Lacks true tissues
• Is asymmetrical in body shape
– Porous, bulbous mass with hollow interior and exit hole at the top
• Composed of only three cell types, the most important are collar cells (choanocytes)
– Flagella drive water current inward to hollow space and out osculum
– Food particles are trapped on sticky collars and passed to other cells
• Some sponges produce spicules (skeletal rods) of silica to help support shape