(a) How do the following provide evidence in favor of evolution in organisms? Explain with an example for each.(i) Homologous organs(ii) Analogous organs(iii) Fossils(b) Explain two methods to determine the age of fossils.


(i) Homologous organs: are the organs inherited from the common ancestors, having similar basic structures, but performing different functions.

For example, forelimbs of humans, lizards, frogs, birds, etc. have a similar basic design but perform different functions.

The similarity in origin and basic structures is observed as they share a common ancestor but they differ in functions due to evolution. This is also termed divergent evolution.

(ii) Analogous organs: are the organs performing the same functions but have different origins or basic structures inherited from different ancestors.

For example, the wings of insects and birds have the same function of flying but different basic designs.

The organs perform the same function but different structural designs as they do not share a common ancestor, thus termed as convergent evolution.

(iii) Fossils: are defined as the remnants or traces of dead plants and animals that died more than 10,000 years ago.

Fossils are mainly formed when plants and animals die in watery environments or buried in mud and silt. Soft tissues decompose quickly leaving the hard bones or shells afterward. 

As time passes, sediment accumulates over it and hardens to form rock.

For example, archeopteryx.

(b) The age of fossils is determined using the absolute dating method and relative dating method.

In the absolute dating method, a scientist can measure the ratio of remaining Carbon-14 to the unchanged Carbon-12 to see how long it has been since the material's source died. Advancing technology has allowed radiocarbon dating to become accurate within just a few decades in many cases. 

While, in the relative dating method, the age of fossils is determined by comparing them with the other fossils or rocks whose age is pre-determined or recorded.


Simply Easy Learning

Updated on: 16-Jan-2023


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