SHARE
The honeycreeper bird beaks develop different shapes after many generations on what they feed on. Source: courses.candelalearning.com

Darwin didn’t ‘discover evolution’. Evolutionary ideas had been proposed and debated long before Darwin came along. Darwin proposed the mechanism which brought about evolutionary change which is called ‘natural selection’. The idea of evolution in words is simple. Things change gradually with time. The process of computers, changing over the past 50 years can be thought of as an evolution in technology. Likewise, when an organism changes over many generations, it might be better suited to live, or more likely to die. To describe what happens, scientists have a few terms.

Evolutionary framework   
For natural selection to work, it has to occur along with a bunch of other things. Darwin outlined five points in his book,’ Origin of  Species’ which brought out his theory of evolution. They are, species come and go through time, and while they exist they change (evolving).Organisms are descended from one or several common ancestors, and have diversified from this original stock (common descent), the diversification or variations of life involves populations of one species diverging with time until they become two separate species (species multiply), evolutionary change occurs through incremental small changes within populations; new species are not created suddenly (gradualism), evolutionary change occurs through variation between individuals; some variants give the individual an extra survival probability (natural selection). Darwin considered all these processes as parts of one grand idea; they all occur together.

Different mechanisms
Evolution over time can follow several different patterns. Factors such as environment and predation pressures can have different effects on the ways in which species exposed to them evolve. There are three main types of evolution: convergent, divergent and parallel evolution.

Convergent evolution is when two totally different species develop similar traits. They have come up with the same solution to a problem, but from different directions. It’s not a conscious choice to develop an eye or a way of hearing. Outside natural factors create a situation where that skill is a benefit. For example, flight has evolved in both bats and insects, and they both have wings, which are adaptations to flight. However, the wings of bats and insects have evolved from very different original structures.
When people hear the word ‘evolution,’ they most commonly think of divergent evolution; this is when your development starts at one place and splits in different directions.

A group of animals starts as the same species, but then as more generations develop, one group becomes good at one thing and others at another. Bird beaks are a good example for this one. One species of bird can develop in different directions depending on what type of food it eats. Their beaks develop different shapes after many generations on what they feed on. Charles Darwin used bird development in many of his scientific papers.

Coevolution  is when two different species change and evolve over time together. They are usually dependent on each other for survival. Flowers and insects are good examples for this type of coevolution. If you have seen really fancy orchids, they often depend on a single species of bug to help them reproduce. A species of moth called the Morgan’s sphinx moth has a proboscis, or tongue, that is almost 12 inches long. This is more than three times of its entire body length. Why would a moth need such a long tongue? Because of the flower it feeds on.

The flower is called a Darwin’s orchid, and its nectar is stored at the bottom of a really long tube. The only animal that can reach this nectar to feed is the Morgan’s sphinx moth. Darwin’s orchids, like many flowers, rely on animals to pick up their pollen and transfer it to another flower. This is called pollination and allows the orchid to reproduce. So, in coevolution as one species changes, the other will make mirror changes so that it can continue to survive.

Santhushya Hewapathiranage

Darwin’s flower and Morgan’s Sphinx moth Source: mrsbioblog.blogspot.com
Darwin’s flower and Morgan’s Sphinx moth
Source: mrsbioblog.blogspot.com

Darwinism and evolution (4) Darwinism and evolution (3)

The wing of a honeybee is similar in shape to a bird wing and bat wing, and it serves the same function. However, the honeybee wing is not composed of bones and has a distinctly different structure. |  Source: cnx.org
The wing of a honeybee is similar in shape to a bird wing and bat wing, and it serves the same function. However, the honeybee wing is not composed of bones and has a distinctly different structure. | Source: cnx.org