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