ANIMAL CHALLENGES

Animals (Metazoans)

Definition and Characteristics

• Animals, also known as Metazoans, are characterized by a set of defining features known as synapomorphies.

  • synapomorphies*: SYN (together)-APO (apart from, separate)-MORPHY (form)

  • metazoans*: EU (true, good)-META (after, becoming, later, higher, more developed)-ZOA(animals)-NS
      - Multicellular: Composed of multiple cells that work together.
      - Heterotrophs: Organisms that cannot produce their own food and instead consume (ingest) organic and inorganic compounds.
      - Ingestion: Animals obtain nutrients by ingesting other organisms or organic material.
      - Movement: All animals exhibit some form of movement at a certain point in their life cycle, distinguishing them from plants and fungi.

    •     move under their own power at some point in life style

Diversity of Animal Life

• The estimated numbers of various animal groups include:
    - Aves (Birds): Approximately 10,000 species.
    - Insects: Estimated between 6 to 10 million species, indicating their vast diversity.
    - Squamates (Lizards and Snakes): Roughly 7,900 species.
    - Amphibians: About 6,340 species.
    - Sea Stars: Approximately 1,800 species.

Taxonomy and Organization of Life

• Organizing the diversity of animal life can be approached from different perspectives:

• Carolus Linnaeus

  • assumes life is static

  • no changes over time

  • taxonomic scheme arising from this conception groups organisms based on overall similarity in appearance

• Charles Darwin

  • different than Linnaeus: life is dynamic

  • taxonomic scheme arising from this conception groups organisms based on ancestral relationships… then reflected in similarity of appearance

COMMON CHALLENGES OF LIFE

• All animals encounter a number of common challenges throughout their lives.
    - These challenges are addressed with unique solutions specific to each species.
       ### Common Challenges
    - Reproducing: Ensuring the continuation of species.
    - Acquiring Nutrients: Obtaining food and oxygen necessary for survival.
    - Distributing Nutrients: Transporting nutrients and information throughout the body to cells.
    - Removing Wastes: Eliminating waste products like carbon dioxide (CO2) and nitrogenous wastes.
    - Responding to the Environment: Reacting to both internal and external stimuli.
    - Supporting, Protecting, and Moving the Body: Maintaining structural integrity and interaction with the environment.
    - Regulating Salt Concentrations: Maintaining homeostasis in various environments.

Solutions to Common Challenges

• The solutions to these challenges are dependent on the environment and the complexity of the animal's body structure.
    - ### Small, Simple Animals
    - In small, flat, and simple animals, individual cells are capable of performing each necessary task.
      - Particularly effective due to:
        - Rapid Diffusion: Nutrients, gases, and wastes can diffuse quickly over short distances.
        - Direct Contact: Most cells are in direct contact with the environment.
        - Low Metabolic Needs: These animals tend to have minimal metabolic requirements.
        - Moist Environment: Typically found in environments that remain moist, supporting their physiological processes.
       - ### Larger, Complex Animals
    - Larger and more complex animals rely on specialized tissues to manage various tasks.
      - Key characteristics include:
        - Slower Diffusion: Diffusion becomes less efficient as distances between cells increase.
        - Distance from Environment: Most cells are not in direct contact with the external environment or exchange membranes.
        - Higher Metabolic Needs: Greater metabolic demands necessitate specialized systems.
        - Potential for Desiccation: These organisms may live in environments prone to drying out, requiring adaptations for moisture retention.