Modification_of_body_plans

Modification of Body Plans

Understanding Body Plan Modification

• Basic body plans of animals and plants were modified to adapt to different environments.

Charles Darwin (1809 - 1882)

• British naturalist known for his contributions to the theory of biological evolution.

• Proposed the theory of evolution by natural selection.

• Defined evolution as "descent with modification."

• Highlights of Darwin's theory:

  • Species change over time.

  • New species arise from existing ones.

  • All species share a common ancestor.

Descent with Modification

• The concept emphasizes how basic body plans were adapted based on environmental needs.

Limb Development in Mammals

Interspecies Limb Diversity

• Variation in limb structure includes:

  • Bone size, shape, and number of bones.

  • Muscular and skin adaptations.

  • Presence of feathers (in some species).

• Limb development reflects the animal's habitat and is crucial for:

  • Movement.

  • Feeding.

  • Social behavior.

Modifications in Vertebrates

Key Aspects of Modification

• Movement and Locomotion:

  • Adaptations for walking, running, climbing, digging, and swimming.

• Feeding Mechanisms:

  • Features enabling animals to grasp food.

• Social Behavior:

  • Influences mating rituals and interactions among species.

Basic Body Plan Components

• Upper Limb Structure:

  • One long bone (humerus).

  • Two long bones (radius and ulna).

  • Lower limb structure includes many small bones (carpals, metacarpals, phalanges).

  • Example configurations include:

    • 5 fingers or toes.

    • Variability in number, shape, and function.

Forelimbs of Vertebrates

Adaptations of the Pentadactyl Limb

• Illustrated adaptations demonstrate various functional roles across species:

  • Bat: adaptations for flying.

  • Horse: adaptations for running.

  • Human: adaptations for manipulation.

  • Seal: adaptations for swimming.

  • Mole: adaptations for digging.

Homologous vs. Analogous Structures

Definitions

• Homologous Structures: Same basic body plan but different functions (e.g., vertebrate limbs).

• Analogous Structures: Different body plans serving similar functions (e.g., wings of birds and insects).

Plant Modifications

Analogous Similarities

• Example of analogous structures in plants:

  • Potato vs. Sweet Potato:

    • Both serve as starchy food sources.

    • Morphological differences yet exist (e.g., tuber vs. root).

  • Bougainvillea and Cucurbita exhibit adaptations for survival in similar environments.

Evolutionary Considerations

Basic Body Plan Modifications

• Modifications provide insights into evolutionary adaptations:

  • Digging (moles).

  • Flying (bats).

  • Running (horses).

  • Swimming (dolphins).

  • Climbing (apes).

• All adaptations relate back to a common ancestor, showcasing functional variations driven by habitat demands.

Vestigial Structures

• Vestigial structures are remnants of structures:

  • Better developed and functional in ancestors.

  • Have lost most or all of their original function and may retain minimal structure.

  • Charles Darwin referred to these as rudimentary features indicative of evolutionary history.