A4.1.5 Convergent evolution as the origin of analogous structures Notes

Same Function, Different Structure

1. The wings of birds and insects perform the same function but differ fundamentally in structure and origin.
2. These similarities, arising from independent evolutionary paths, are a result of convergent evolution, which produces analogous structures.

Analogous Structures = Similar Function

1. They are similar in function, performing the same role (e.g., flight, swimming).
2. But arise from unrelated ancestral traits,
3. Adapting and evolving separately due to similar environmental pressures.

Characteristics of Analogous Structures

1. Analogous structures arise not from a shared ancestor, but from similar selection pressures acting on unrelated organisms.
2. They usually appear in organisms that:
   1. Occupy similar habitats (e.g., aquatic environments).
   2. Face similar survival challenges (e.g., need for flight, defense, or water conservation).
   3. Develop functionally equivalent solutions despite unrelated evolutionary pathways.

How Convergent Evolution Works

1. Convergent evolution occurs when unrelated species face similar selection pressures which are environmental challenges that favor specific traits.
2. Over time, these pressures lead to the development of comparable adaptations, even in species with distinct evolutionary histories.

Steps in Convergent Evolution

1. Similar Environmental Challenges: Aerial navigation, aquatic locomotion, or acute vision.
2. Independent Adaptations: Species evolve traits suited to their environment, but starting from different ancestral features.
3. Functional Similarity: Analogous structures emerge, performing similar tasks despite differing origins.

Examples of Analogous Structures

1. Wings of Birds and Insects