Adaptive radiation in evolution

Introduction to Adaptive Radiation

Adaptive radiation is crucial in an evolutionary process as it bring in essential changes among the species as we move forward. Every individual must adapt itself in accordance with the changes in the climatic conditions, changing food pattern as well as an increase in the number of predators. In the evolutionary biology, one should clearly understand about whether adaptive radiation is a necessity or a random act within an ecosystem. Nevertheless, it is definitely required for the long term health of a system. It is true that the mechanisms such as mutation and radiation gives individuals - the strength and abilities to transform their body based on the external factors.

 

Darwin`s theory of evolution

As per Darwin’s theory of evolution, all living organisms have to undergo anatomical structures over a period of time. These changes helped them to adjust according to the changing environments, but they are inevitable. In order for the organisms to survive and reproduce, they need to exploit the other organisms in their ecological range. Evolution by mutation, speciation, and the adaptive radiation helps the species to redesign their bodies ,as a result, the organisms get used to the different versions of the changing environment for their survival. For instance, a volcano formed in an aquatic ecosystem leads to the development of a large new lake habitat. Such habitat could serve as an alternative for the species to survive during volcanoes. As the species get through a number of such incidents, they are formed into many variants of themselves by producing offspring. In simpler terms, adaptive radiation is one of the evolutionary process resulting in the formation of many species from their common ancestors. For example, have you ever observed there are many animals that look like cats? They all look similar because of their common ancestors from which they are radiated into many similar species into leopard, tiger, puma etc.  Another example is the diversity of Galapagos finches. Finches, during the course of evolution, have undergone a series of modifications such as change in the size, shape and length of their beaks, as a result, they have evolved into many subcategories. Furthermore,  changes in their beaks led them to prey on different types of food sources as few birds started eating insects, and a few others feed on seeds. Similarly, the majority of them feed on the trees while few of them found their food on the ground.

 

Nature of  Adaptive Radiation

The word radiation refers to the expression of the taxonomic diversity via bodily changes over a period of time. Adaptive radiation is an evolutionary pattern influenced by variety of factors rather than an independent phenomenon by itself. When we look at  14 or 15 species of Galapagos finches, they have emerged into what they are seen today. It took almost 2 million years for this to happen. So, the process of adaptive radiation is very slow and gradual. The phenomenon was first observed by Darwin while he was travelling through Galápagos Island. He found finches with the variety of beaks (as shown in the picture) and he called them Darwin’s finches.

 

 

 

Features of adaptive radiation

  1. The resulting species and its variations must  be derived from the common ancestry.

  2. There must be relevance between the phenotype(morphological features) with the environment. For instance, polar bear developing a lengthy and thick fur due to the harsh whether 

  3. In an adaptive radiation, there should be trait utility, in other words, the specific morphological changes must be exercised only to survive in an adverse situation but not deliberately for any other reasons. For instance, the beers in the polar region use their thick fur to safeguard against the freezing environment.

  4. There is rapid speciation with a high frequency of emergence of new species while the  phenotypic divergence is underway.

 

Examples of adaptive radiation among species

  1.  A classic example of adaptive radiation is the evolution of Darwin`s Finch population. Another example is the radiation of Australian Marsupials out of a single ancestral stock as shown in the image below. This, is in fact, one of the examples of divergent evolution. Marsupials species have diverged into different orders and species from their original order Euaustralidelphia.

 

  1.  Radiation of Hawaiian tetragnathid spiders to build orb webs that help in predation.

  2. Radiations of Caribbean Anolis lizards have repeatedly evolved into chameleon-like ectomorphs.

  3.  The modification of the structure of the limb of placental mammal provides the best example of adaptive radiation. The ancestor of the present-day placental mammal was a five-toed short-legged terrestrial insectivore. 

 

 

Read More

 1        

Succession in ecosystem

2

Ecosystem-introduction

3

Trophic levels in the ecosystem

4

Productivity in an ecosystem

5

Conserving the biodiversity

 

Check your understanding

  1. Explain Darwin`s theory of evolution.

  2. What is adaptive radiation?

  3. In an adaptive radiation, the species must be derived from the common ancestry, is it true or false?

  4. What is the other name used for Galapagos finches?

  5. Name any 4 factors responsible for adaptive radiation.



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