Study of Homologous and Analogous Organs in Plants and Animals (Class 12 Biology Practical File)

The study of homologous and analogous organs helps Class 12 students understand evolutionary relationships in plants and animals. Homologous organs have the same basic structure but different functions, such as the thorns of Bougainvillea and the tendrils of a cucumber plant. They indicate divergent evolution. Analogous organs perform similar functions but differ in structure and origin, like wings of birds and wings of insects. These represent convergent evolution. Observing specimens and diagrams during the practical helps students compare structural features and functions clearly. This topic is essential for understanding evolution and preparing accurate Biology practical records.

Aim

Study of homologous and analogous organs in plants and animals

Observation

1) Homologous Organs

The structures of animals and plants under study show homology, ie. similarity in the fundamental (basic) structures due to shared or common embryonic origin but all of these organs/features performs different functions

Homologous Organs in Animals

The structures depict the forelimbs of a man, cheetah, whale and bat in the case of animals.

The hand of a man, limb of cheetah, flipper of a whale and the wings of a bat have common set of bones but all of these structures though appears similar but are involved in different functions like grasping, running, swimming and flying respectively.

Homologous Organs in Plants

The structures depict Bougainvillea (thorn) and Cucurbita (tendrils) the case of plants.

The leaves of the plant Bougainvillea have been modified into the thorns for protection while leaves in Cucurbita are made into tendrils for providing support in climbers.

2) Analogous Organs

The structures of animals and plants under study shows analogy, i.e. they perform similar functions in different organisms but do not share same structure on the basis of origin.

Analogous Organs in Animals

The structures depict the wings of a bat and wings of an insect in case of animals.
The forelimbs of bats, birds and wings of insects are used for flying by these animals however, they are structurally very different from each other

Analogous Organs in Plants

The structures depict Passiflorine (stem tendril)l and pea (leaflet tendril)l in case of plants.
The Passiflorine and pea have leaves modified into tendrils which support the plant during climbing whereas they do not share any structural similarities.