Topic 3: Animals Ch.17 Characteristics of Animals p.338. Distinguishing Characteristics pp

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1 Topic 3: Animals Ch.17 Characteristics of Animals p Animals are: - Multicellular. - Ingestive heterotrophs. - Have a division of labour (tissues, organs, systems). - Motile at some stage in their life. Characteristics of Animals - Animal cells: - Do not have a cell wall. - Do not have chloroplasts. - Have a cell membrane, mitochondria, er, golgi, nucleus, ribosomes, vacuoles, lysosomes, and vessicles. - Sometimes they have cillia or flagella. - Are diploid, with haploid sperm and eggs. Fig. 4.5 Distinguishing Characteristics pp The phylogeny of animals traditionally relied on three key characteristics of their body plan: 1. Symmetry 2. Tissues (Germ layers) 3. Body cavity (Coelom) Fig Symmetry Symmetry refers to how many identical parts an organism can be divided into. Bilateral symmetry One plane can divide an organism into two identical parts. E.g. Humans Radial symmetry Several planes can divide an organism into many identical parts. E.g. Starfish Asymmetrical An organism which can not be divided into identical parts. E.g. Sponge 1

2 2. Tissues (Germ layers) During the development of an animal embryo, three tissue (germ) layers form. Endoderm Forms on the inside. It will become the digestive system in humans. Mesoderm Forms in the middle. It will become the skeleton and muscle in humans. Ectoderm Forms on the outside. It will become the skin and nervous system in humans. Note: These tissues exist only in embryos. Tissues in adults come from (are derived from) these tissues. 3. Body Cavity (Coelom) If an animal has three tissue layers, it can be placed into one of three groups based on its body cavity. Body cavity (or coelom) A fluid filled space inside of an animal. 3. Body Cavity Acoelomate No body cavity. Fig Body Cavity Pseudocoelomate There is a fluid filled space but it has mesoderm on only one side. Fig Fig Body Cavity Eucoelomate There is a fluid filled space lined by mesoderm on all sides. Invertebrate Phyla p.341 Animals are arbitrarily divided into two groups based on presence of a backbone. If they have a backbone they are called vertebrates, and if they don t they are called invertebrates. Over 95% of animal species are invertebrates. We will examine only nine phyla of invertebrate animals. 2

3 Phylum Porifera p.341 E.g. sponges. ~ 9000 species Sponges are asymmetrical. They only have a cellular level of organization. There are no germ layers nor body cavity. Phylum Cnidaria p.342 E.g. Jellyfish, coral, anemone ~10,000 species - Cnidarians are radially symmetrical. - They have two tissue layers but no body cavity. Fig Fig Phylum Platyhelminthes p.344 E.g. Tapeworms, liver flukes, planarian ~ 20,000 species - Platyhelminthes are bilaterally symmetrical. acoelomate. Phylum Nematoda p.346 E.g. Heartworm, pinworm ~25,000 species - Nematodes are bilaterally symmetrical. - They have three tissue layers and a pseudocoelom. Fig Fig Phylum Annelida pp E.g. Earthworm, leech, tubeworm ~16,000 species - Annelids are bilaterally symmetrical. Fig Phylum Mollusca p.343 E.g. squid, snails, scallops ~93,000 species - Mollusks are bilateral symmetry. eucoelomates. - Most diverse invertebrate group, and contain the most intelligent invertebrates (octopus). Fig

4 Fig Phylum Arthropoda p E.g. Insects, spiders, lobsters ~ 1,500,000 species - Arthropods are bilaterally symmetrical. - Most bestest animals. Fig Phylum Echinodermata E.g. starfish, sea urchins, sea cucumbers ~7000 species - Echinoderms have radial symmetry. - Of the groups covered so far, these are the most closely related to humans. Challenge What is this organism? How did it cause the Vietnam war? Fig Fig Vertebrates p Vertebrates have backbones that protect their spinal cord. This group includes part of only one phylum: Chrodata. Fig

5 Phylum Chordata pp E.g. Humans, crows, salmon ~60,000 species - Chrodates are bilaterally symmetrical. - They have three germ layers and are - Unique characteristics: 1. Dorsal hollow nerve cord 2. Notochord 3. Pharyngeal gill slits 4. Post anal tail Phylum Chordata We are going to examine five groups of chordates: 1. Fish 2. Amphibians 3. Reptiles 4. Birds 5. Mammals 1. Fish p.356 Largest group of vertebrates. ~28,000 species. Fish includes two classes: 1. Osteichthyes Bony fish. Most fish. 2. Chondrichthyes Cartilaginous fish. Includes sharks, rays, and skates. Fish have scales, streamlined bodies, and fins. They have gills that is covered by an operculum in the bony fish. Bony fish also have a swim bladder that helps them float. Lateral line system picks up vibrations in the environment similar to ears. 2. Amphibians p. 357 E.g. Frogs, salamanders ~ 6000 species. - Belong to class Amphibia. - Most amphibians are born in the water and spend their adult life on land. - They have four legs and lungs. Fig Reptiles p.p E.g. lizards, snakes, turtles ~ 9000 species. - Belong to class Reptilia. - Reptiles are well adapted to life on land with waterproof eggs and waterproof scales. - Reptiles also have a more complete and stronger skeleton than amphibians, so they can move on land easier. Fig

6 4. Birds p. 359 E.g. Crows, penguins, puffin ~ 10,000 species. - Belong to class Aves. - Birds have feathers for flight and insulation. - Birds have hollow bones, solid urine, and lay eggs to reduce mass so they can fly. Fig Birds Aves is considered a class based on historical classification. Aves is actually a subgroup of Reptilia. 5. Mammals p. 360 E.g. Humans, rats, whales ~ 6,000 species. - Belong to class Mammalia. - Mammals have modified sweat glands that produce milk and fur. Fig Mammals There are three mammal subgroups: A) Monotremes Lay eggs. E.g. playtpus. B) Marsupials Give birth to offspring during early development, with development continuing in a pouch. E.g. kangaroo. C) Eutherians Placental mammals. Give birth to fully developed offspring. E.g. Humans. 6