15'1 The Animal Kingdom

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15.1 The Animal Kingdom
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Objectives

• Describe the main characteristics of animals.
• Explain the major differences in the body plans
  of animals.
• Distinguish between vertebrates and
  invertebrates.

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Characteristics of Animals

• Animals are many-celled, which makes them
  different from monerans and protozoa.

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• They lack chlorophyll in their cells, so they
  can't make glucose through photosynthesis like
  plants and algae.

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• Animals obtain their food by ingesting it.
• They take in food from their environment and then
  digest it.
• Because they eat their food, animals differ from
  fungi, which digest their food outside their
  bodies and then absorb the nutrients.

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• Animals have the ability to move.
• While it is true that many of the animals stay in
  one place as adults, they were able to move at an
  earlier stage in their lives.

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Classification of Animals

• The first animals evolved from single-celled
  protists hundreds of millions of years ago.
• Since then, the animals have evolved a variety of
  different body plans, or kinds of overall body
  structures.
• These different body plans are the basis for
  animal classification.

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• One major way that animal bodies differ is in
  their level of organization.

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• Four levels of organization exist among animals
• cells
• tissues
• organs
• organ systems

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Cells

• The simplest kind of animal body has many cells
  but no true tissues.
• Animals called sponges have this kind of
  structure.

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Tissues

• Another group called the cnidarians (ny DAIR ee
  uhns) includes animals whose bodies are made up
  of tissues but have no organs.

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Organs

• Several groups of animals have bodies in which
  tissues work together as organs.
• These include the flatworms and roundworms.

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Organ Systems

• In the earthworms, flatworms, and roundworms,
  organs work together as organ systems.

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• Animals can also be classified by their shape.

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• Animals with radial symmetry have bodies
  organized around a center, like a wheel.
• They have a top and bottom, but no front, back,
  or head.

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• Animals with bilateral symmetry have bodies with
  two similar halves.
• They have a head end that faces in the direction
  the animal moves.
• The head contains the animal's sense organs.

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• A sponge's body can't be clearly divided into
  parts.
• It has no symmetry.

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• Many of the animals with bilateral symmetry, such
  as dogs and birds, have an extra degree of
  complexity.
• These animals have a backbone.

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• Animals with backbones are called vertebrates
  (VUR tuh brihts).
• You are a vertebrate.
• All the animals without backbones are called
  invertebrates.

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• Based on differences in the bodies of animals,
  scientists have divided the animal kingdom into
  28 large groups called phyla.
• We will discuss discusses only the major phyla.

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Check and Explain

• 1. What characteristics separate the animals from
  the plants, algae, protozoa, monerans, and fungi?
• 2. What is the difference between radial symmetry
  and
• bilateral symmetry?
• 3. Infer What kind of symmetry would you expect
  most animals that hunt for food to have? Explain.
• 4. Make a Graph Invertebrates make up 95 percent
  of all known animal species. Make a circle graph
  that shows this and identifies the other 5
  percent.