Introduction to Animal Kingdom
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Basic Characteristics
• Multicellular eukaryotes• Heterotrophic• Movement • Sexual Reproduction
Multicellular Organization is Important
• Most animals contain many cells– Example: humans have ~50 trillion cells
• Most have specialized cells that form tissues and organs; think of it as a division of labor– Has allowed animals to evolve and
adpat to certain environments
Heterotrophy…• All depend on autotrophs for food
directly or indirectly
• They have to ingest their food, meaning they must digest it
• Digestion is internal, allowing animal to get proteins, carbohydrates and lipids
Movement • Most animals are able to
move, which is a result of specialized nervous and muscular tissue
• Animals that cannot move are sessile, very few animals are sessile
Sexual Reproduction & Development• Most reproduce sexually
• Sexual reproduction increases genetic variation• Fertilized egg cell is called a zygote, all animals
develop from• Fertilization can be internal or external (sperm cell
must penetrate egg cell) • During development, zygote undergoes many mitotic
divisions… these cells must then undergo differentiation
• Differentiation is when cells become specialized
Development
• Protostome– Opening in gastrula
becomes mouth of animal
– Examples: mollusks, annelids, arthropods
• Deutrostome– Mouth develops from
second opening– Examples:
echinoderms, chordates
Body Structure
• Symmetry • Germ Layers • Body cavities
Symmetry
Symmetry describes the arrangement of body structures that enable animals to move in
different ways
Animals have 3 patterns of symmetry: 1. Asymmetry – no symmetry2. Radial Symmetry – similar parts branch in all
directions from a central point3. Bilateral Symmetry- similar halves on either
side of a central plane.
Identify the Type of Symmetry:
Germ Layers
• Tissues found in all animals, except sponges– Ectoderm (outside
layer, forms skin)– Endoderm (forms
digestive tract)– Mesoderm (forms
muscle tissue and most other organs)
Body Cavities
• A fluid filled space separating the digestive tract from the outer body wall; this space is known as coelom
• Functions: – Suspends organs to prevent internal
injury– Enables organs to grow and move
independent of outer body wall
Types of body cavities: • Acoelomate (no body cavity)
– Solid body, no cavity separating digestive tract from outer body wall
– least complex body plan– Examples: flatworms
• Pseudocoelomate – cavity not completed lined by mesoderm tissue– Examples: roundworms and rotifers
• Coelomate – True body cavity; completely lined by tissue of
mesoderm– most complex body plan – Examples: mollusks, annelids, arthropods,
echinoderms, and chordates
Origin of Animals
• 1st evolved from the sea
• Zoologists today recognize ~35 phyla based evolutionary relationships
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