Rucete ✏ Campbell Biology In a Nutshell
Unit 7 ANIMAL FORM AND FUNCTION — Concept 40.1 Animal Form and Function Are Correlated at All Levels of Organization
Animal bodies show a deep connection between form and function, shaped by evolution and physical laws. As animals grow and adapt to their environments, their body structures—from tissues to organ systems—evolve to support survival and efficiency. This concept lays the foundation for understanding how animal form relates directly to function across biological scales.
Evolution of Animal Shape and Size
- Body plans are shaped by physical laws (strength, diffusion, movement, heat exchange).
- Convergent evolution creates similar shapes (e.g., fusiform bodies in swimmers like seals and tuna).
- Larger animals require thicker skeletons and stronger muscles, limiting their speed.
- Even large animals like T. rex evolved efficient locomotion (though running speed is debated).
Environmental Exchange Constraints
- Animals must exchange nutrients, gases, and wastes with the environment.
- Single-celled organisms exchange directly; multicellular ones need adaptations.
- All cells require access to a suitable aqueous environment.
Exchange Surfaces in Animals
- Simpler animals (e.g., hydras, flatworms) use body surfaces for exchange.
- Complex animals have internal exchange surfaces (e.g., lungs, intestines) that are branched or folded.
- These surfaces connect to the external environment via body openings like the mouth.
Body Fluids and Internal Transport
- Interstitial fluid surrounds cells; blood and other fluids transport nutrients and wastes.
- Internal circulatory systems link exchange surfaces to the rest of the body.
Advantages of Complex Body Plans
- Allow for:
- Protection (e.g., exoskeletons)
- Sensory organs for detecting stimuli
- Specialized organs for digestion and excretion
- Help maintain a stable internal environment (especially important on land).
Structural Organization
- Hierarchical structure: Cells → Tissues → Organs → Organ Systems
- Example: The digestive system includes multiple organs with various cell types.
Tissue Types
- Epithelial: Covers surfaces, lines organs.
- Connective: Supports and binds (includes bone and blood).
- Muscle: Enables movement.
- Nervous: Processes and transmits information.
Organ Systems and Functions
- Each system performs a coordinated role:
- Digestive: Breaks down food
- Respiratory: Gas exchange
- Circulatory: Internal transport
- Nervous: Coordination and response
- And more (see Table 40.1 for full list)
In a Nutshell
Animal form is tightly linked to function. Across levels of biological organization, form supports survival through structural adaptations, physiological coordination, and efficient exchange. Whether it’s a flatworm or a whale, the architecture of life reflects its purpose.