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Evolutionary Relationships II

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Evolutionary Relationships II - Lesson Summary

These are the hereditary traits transmitted from parent organisms to their offspring.

Characteristics are of two types namely, homologous characteristics or analogous characteristics

         • Homologous characteristics are organs that have the same basic structure and origin, but different functions. For example, mammals, birds, reptiles and amphibians have four limbs with the same basic limb layout because they have inherited the limbs from a common ancestor. These limbs have been modified to perform different functions.

         • Analogous characteristics are organs that have different structures and are of different origin, but perform same functions. For example, the design of the wings of bats and the wings of birds look similar because they have a common purpose – to fly.

Fossils are the remains or traces of a plant or animal that existed in a past geological age, and that has been excavated from the soil.

Fossilisation is the process in which an organism is converted into a fossil.

Biological convergence
This is a phenomenon by which two unrelated organisms become quite alike after a period of time through few generations, if it is assumed that they have a common ancestor. The eyes of the octopus and the eyes of vertebrates have evolved independently. These similarities of structure, despite of different origins provide a classic example of biological convergence.

A characteristic of a particular animal may, post-evolution be useful for performing a totally different function.
For example, long feathers were considered to provide insulation in cold weather. Some reptiles like the dinosaur had feathers but very few were adapted for flying. In the present day, birds use feathers for flight, which is an example of adaptation.

Artificial selection
This is the usage of plants with desirable characteristics to produce new varieties.
Broccoli, kohlrabi and kale are produced from its ancestor wild cabbage by artificial selection.
The tools used to trace evolutionary relationships are excavation, time-dating, studying fossils, and determining DNA sequences. These have been used for studying human evolution.


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