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Questions and Answers
What is a characteristic that all animals share?
What event marks a period of rapid animal diversification?
What type of symmetry do most animals exhibit?
What is the term for the succession of cell divisions without growth between divisions in animal embryos?
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What is the characteristic feature of sponges (Porifera)?
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What is the characteristic feature of chordates?
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What is the term for the type of development in which the blastopore becomes the anus?
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Which group of animals has a lophophore for feeding or a trochophore larval stage?
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What is unique about the formation of the anus in Deuterostomes?
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What is a characteristic of Arthropods?
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Which type of tissue is responsible for holding organs and tissues together in place?
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What is the function of fibroblasts in connective tissue?
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What is a characteristic of Chordate embryos?
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What is the primary function of the swim bladder in fish?
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Which group of animals are characterized by their ability to metabolize at a high rate?
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What is the function of the amniotic egg in reptiles and mammals?
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Study Notes
Common Characteristics of Animals
- Animals can move and capture prey, and are multicellular, eukaryotes, and heterotrophic, with no cell walls.
- They are thought to have evolved from flagellated protists, with choanoflagellates being the closest living relatives.
Animal Body Plan
- Radial symmetry vs. bilateral symmetry: most animals have bilateral symmetry, allowing for faster movement and formation of a head with sensory organs and a central nervous system.
Embryo Development
- Animal zygotes undergo cleavage, a series of cell divisions without growth between divisions, forming a blastula.
- The blastula is often a hollow ball of cells.
Animal Tissues
- Only a few groups, such as sponges, have no tissue.
- Most animals have germ layers that give rise to tissues and organs, including:
- Diploblastic: ectoderm and endoderm.
- Triploblastic: ectoderm, endoderm, and mesoderm.
- Body cavity types:
- Coelom: a cavity surrounded by tissues derived from mesoderm.
- Hemocoel: filled with hemolymph.
- Some animals have no cavity at all, such as flatworms.
Protostome vs. Deuterostome Development
- In protostome development, the blastopore becomes the mouth.
- In deuterostome development, the blastopore becomes the anus.
Invertebrate Animals
- Invertebrates are animals without a backbone.
- Examples of invertebrate phyla include:
- Porifera (sponges): simplest animals, filter feeders, no tissue.
- Cnidarians: true tissues, gastrovascular cavity, polyps and medusa life forms, nematocysts, radial symmetry.
- Lophotrochozoans: have a lophophore for feeding or a trochophore larval stage.
- Flatworms (platyhelminthes): flat body form for large surface area.
- Molluscs: muscular foot, visceral mass, mantle.
- Annelids: segmented worms, coelom.
- Ecdysozoans: cuticle, molting.
- Nematodes: have hemocoel.
- Arthropods: segmented body, exoskeleton, jointed appendages, open circulatory system.
Vertebrate Animals
- Common characteristics of chordates: bilateral, deuterostome development, mostly vertebrates with two groups of invertebrates.
- Four characteristics of chordate embryos:
- Notochord.
- Dorsal nerve cord.
- Pharyngeal pouches (slits).
- Post-anal tail.
- Examples of vertebrate groups:
- Hagfishes and lampreys: lacking jaws.
- Shark and ray: oil in the liver to maintain buoyancy.
- Ray-finned and lobe-fin fish: swim bladder for buoyancy.
- Amphibians: need water and land, metamorphosis.
- Reptiles: scales, shelled and amniotic eggs, ectothermic.
- Birds: endothermic, direct descendants of dinosaurs.
- Mammals: mammary glands, hair, endothermy.
Animal Form and Function
- Tissues: groups of cells with a similar appearance and function.
- Four types of tissues:
- Epithelial tissue: covers the outside of the body and lines organs and cavities.
- Connective tissue: holds tissues and organs together in place.
- Muscle tissue: responsible for movement and contractions.
- Nervous tissue: responsible for communication and coordination.
- Functions of specific tissues:
- Fibroblasts: secrete fiber proteins.
- Macrophages: engulf foreign particles.
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Description
Learn about the characteristics of animals, their evolution from protists, and body plan types. This chapter covers radial and bilateral symmetry, and the Cambrian explosion.
