Homologous Structures vs. Analogous Structures

Altering traits of species at different time is called evolution. The two concepts, Homologous and analogous constitution are present to you as an example of evolution. The main difference between homologous and analogous structures is, homologous trait is when two organisms share a trait because they have same ancestors while Analogous trait is when two organisms share a trait, but it is not due to familiar ancestry.

Homologous Structures

homologousHomologous mannerism has a same fundamental arrangement but then is modified for diverse function. Though identical in structure the function of the structure is opposite in organism. For example let’s talk about the animal homology, the bat limb and mouse limb, the structure of the bone is similar in both the animals because both carry a common progenitor. Both bat and mouse are considered a tetra-pod. Due to their same lineage they are homologous to each other. Another is four limbs of animals of same origin that are modified into different ways to support them as for their survival. We can observe that although the shape and size are not similar of bats wing, wings of bird, seals flipper, forelimb of a horse and a human arm, there is still a friction of resemblance in their structure. They have same set of bones like humans for example, radius, ulna, humerus, carpels and even Meta-carpals. Human use hands for grasping and doing work. Seal use flipper for swimming and bat and birds use wings to fly. Everyone fulfill different purposes of life. Homology is also seen in plants. Like if we see pea and barberry leaves, it shows different function, the tendrils of pea plant gives mechanical support, and spines of barberry to protect the leaves are homologous to each other as leaves but shows different objectives.

Analogous Structures

analogousAnalogous have similar capacity or behavior but have an unlike evolutionary basis. For example, take a look at octopus and human eye. Both of them have similar eye structures but they do not belong to same ancestors, they evolved discretely. This is also called convergent evolution. These usually result due to species living in related environment, fill equal ecological task, and through natural selection the same type of structure is favored in different ancestors. Another example in animal can be wings of insect which are originated from inner and outer surface of the body, feather of birds which are originated from the forelimbs and wings of bat which are originated from both the wings and membranous skin of the abdomen have common function but different origins. Analogous example in plant can be opuntia and peepal plant. In opuntia stem is modified into broad succulent leaf like makeup which can photosynthesize same as leaves. While peepal leaves are normal performing normal photosynthesis. Thus, both of them are performing same function but are of different origins.

Key Differences

  • In homologous anatomy is similar while in analogous anatomy is dissimilar.
  • In homologous functions are dissimilar while in analogous it is similar.
  • In homologous developmental pattern is followed while in analogous there is no such pattern.
  • In homologous there is similar structure while in analogous it is different.
  • In homologous origin is same while in analogous origin differs.
  • Homologous develops in related animals while analogous is in unrelated animals.
  • Homologous have different morphology while analogous have same morphology.
  • Homologous have similar internal structure while analogous does not.
  • Homologous organs show adaptive radiation (divergent evolution) analogous organs show non- adaptive behavior called convergent evolution.

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