Introduction to Animals

Overview

• Course: Bio 94 - Lesson 14

• Content: Focus on Figures 30.1, 30.2, Table 30.1

Learning Outcomes

• 14.1: Distinguish animals from other eukaryotes

• 14.2: Recognize key transitions during animal diversification

• 14.3: Describe diversification within animal phyla

• 14.4: Assess types of evidence for studying animal evolution

Definition of an Animal

• Characteristics:

  • Eukaryotic organisms, distinct from fungi and plants

  • Share a monophyletic common ancestor

  • Significant diversification began around 550 mya (Cambrian explosion)

Animal Diversity

• Number of Phyla: ~30-35

• Species Count: Approximately 1.5 million species

Table 30.1: Overview of Major Animal Phyla

• Major classifications and approximate number of described species:

  • Porifera (sponges): 8,500

  • Cnidaria (jellyfish, corals): 11,500

  • Mollusca (clams, snails): 85,000

  • Arthropoda (insects, etc.): 1,200,000

What Makes an Animal?

1. Multicellular:

   • Lack cell walls, have extracellular matrix (ECM)

2. Heterotrophic:

   • Obtain carbon by consuming other organisms

3. Motile:

   • Move under their own power during life cycle

4. Neurons and Muscle Cells:

   • Allow communication and body shape alteration (except sponges)

Investigating Animal Evolution

1. Fossil Evidence

2. Comparative Morphology

3. Comparative Development (Evo-Devo)

4. Comparative Genomics

Key Transitions in Animal Evolution

1. Multicellularity

2. Complex Tissue Layers

3. Bilateral Symmetry

4. Origin of Gut and Coelom

• Coelom: cavity lined by mesoderm housing organs

Themes of Diversification

• Sensory organs: sight, hearing, taste, touch

• Feeding types: detritivore, herbivore, carnivore, omnivore

• Feeding modes: suspension, deposit, fluid, mass feeders

• Movement: development of limbs and skeletons

• Reproductive Strategies:

  • Asexual and sexual reproduction

  • Embryo development and life cycle patterns: viviparous, oviparous, metamorphosis

Important Considerations

• Evolution does not occur in isolation; true muscles develop from mesoderm

• Key innovations emerge gradually

• Convergent evolution relates to homologous genes