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Difference between natural selection and adaptation can be understood through the theory of evolution. All living organisms are continuously undergoing evolution to suit their surrounding environment. Natural selection plays a key role in the evolution of a species and affects the entire population or group, which is termed as Macroevolution. Adaptation is a slow-paced and gradual process, which results in genetic change of individual organisms over a period of time. It is often termed as Microevolution.
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Key Terms: Evolution, Natural selection, Adaptation, Extinction, Predator, Traits
Natural Selection
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Natural Selection is the process in which living organisms change genetically over time and form a new species. In natural selection, adaptation takes place due to environmental pressure or conditioning. The guiding principle of natural selection is that nature selects only those individuals that are fittest individuals for survival and continues their future generations.
Conditions essential for natural selection to take place are:
- Variation within population – organisms of the same species exhibit difference in appearance and behavior
- Inheritance – while some heritable traits are consistently passed through generations some other traits which are dependent on environmental influence are seldom passed on.
- Reproduction - high rate of population growth leading to struggle for locally available resources.
- Variation in fitness of organisms – leading to individuals with better suited traits to survive the struggle for resources and reproduce.
Adaptation
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Adaptation is the ability of a living organism to change in order to suit the surrounding environment which in turn increases its chances of survival and it increase the fitness of an individual in a population. Adaptation is the mechanism to develop changes in characteristics at genetic, physiological, psychological, reproductive, morphological and anatomical levels to suit the surrounding environment.
Adaptation to survive harsh climatic condition
Adaptation to avoid predators through camouflage
Adaptation to scare away predators through Mimicry
Difference between Natural Selection and Adaptation
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| Natural Selection | Adaptation |
|---|---|
| It is the mechanism of adjustment of genes over generations by passing on advantageous heritable traits giving rise to a new species (speciation) | The development of behavioral or physiological characteristics that help the organism to adjust to the environment increasing its chances to survive and reproduce is called adaptation. |
| Natural selection may occur at different levels like individual, genetic, population and species | Adaptation mainly occurs at genetic level and then reflect as a change in individual, population and species |
| Natural selection causes evolution | Adaptation is the characteristic exhibited during evolution |
| Natural selection based on Predator Preference For example, in a particular habitat with orange and brown worms, if the birds prefer the taste of brown worms more than the orange worms then there will be fewer brown worms to reproduce and eventually their number will reduce in that habitat as compared to orange worms. But if the color foliage is dark the bright orange worms will be more visible to the predator birds and they will go for the orange worms that will be an easier prey to catch eventually leading to a reduced population of orange worms. | Adaptation to Avoid Predators through Mimicry and Ability to Camouflage/ Change colors Example: Change in color of the peppered moth due to the industrial pollution in England (Industrial melanism in Biston Betularia), Chameleon changing colors as per surrounding, grasshoppers hiding in green grass, butterflies with eye shaped dots on wings to scare away predators, white fur arctic animals can hide in snow. |
| Natural selection based on Mating Preferences The peahens preferred to mate with peacocks having beautiful long tails. Over a period of time the short-tailed peacocks became extinct and the long-tailed peacocks overtook the population as they got more chances of mating and reproducing. | Adaptation based on Mating Preferences The peahens preferred to mate with peacocks having brighter plumage. This resulted in peacocks adapting to develop shimmering colorful plumage to attract the female and peacocks with dull plumage became rare. |
| Natural selection in case of Access to food without adaptation Example: In a habitat with both long and short necked giraffes, having plenty of tall trees will result in survival of long necked giraffes. Whereas if the same habitat has only short shrubs, then the short-necked giraffes stand a better chance of survival and reproduction. | Adaptation based on Access to food Example: Giraffes with long necks reach leaves high up on the trees. In earlier times there were populations of giraffes with short and long necks. The giraffes with short necks became extinct as the low-lying shrubs and plants died causing a food shortage for them. So, over a period of time, all the giraffes adapted to the situation by developing long necks. |
Adaptation based on Access to food
Industrial melanism an example of Natural Selection
Things to Remember
- Variation is the difference in traits of individuals of the same species.
- Natural selection is a mechanism in which the individuals with traits better suited to their environment are able to survive and reproduce.
- Adaptation is the development of a new beneficial trait over generations which helps the descendant organism to survive and reproduce in the given environmental conditions better than its ancestor.
- In natural selection, adaptation takes place due to environmental pressure or conditioning.
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Sample Questions
Ques. How did Darwin’s theory of natural selection explain the appearance of new forms of life on earth? [All India 2008] (3 marks)
Ans. The conditions that led to natural selection as per Darwin’s theory are as follows:
- Variation within population – organisms of the same species exhibit different characteristics allowing them to be a better fit to the surrounding.
- Inheritance – traits leading to adaptability are passed on through generations.
- Reproduction - high rate of reproduction and limited resource availability leads to survival of the fittest.
- Variation in fitness of organisms – leading to individuals with better suited traits to survive the struggle for resources and reproduce.
Ques. Explain Natural selection and adaptation based on mating preferences. (3 marks)
Ans. The mating preferences of the females of some living organisms were based on the physical appearance of the male. The females preferred males with attractive features like the example of a peahen which preferred to mate with bright feathered long tailed peacocks, leaving the dull short tailed ones with no chance to reproduce. Gradually, the bright feathers and long tails became a prominent trait in all peacocks of the next generations showing adaptation and peacocks with short dull tails became extinct showing the effect of natural selection.
Ques. ‘Nature selects for fittest.’ Explain with suitable examples. [All India 2009 C] (3 marks)
Ans. Darwin’s finches which have around 18 varieties and all have different beaks to suit their environmental surroundings are an example of natural selection. The large beaked finches survived the droughts and the small beaked finches survived the heavy rainfall periods of Galapagos islands. This shows how the same feature which might have proved useful during one climatic condition may not be as useful to survive in another climate. Thus, different climatic conditions lead to the natural selection and survival of different beaked finches.
Ques. Natural selection operates when nature selects for fitness. [Delhi 2010] (3 marks)
Ans. The individuals of the same population show variation in characteristics. As they reproduce the numbers increase but the resources remain limited. This leads to survival of only the fittest individuals with the ability to adapt. This ability gives them the chance to produce more and more offspring and helps in their survival. Thus, nature selects only the fittest to survive leading to their natural selection.
Ques. What is micro and macro evolution? (1 mark)
Ans. Natural selection is termed as macroevolution as it takes place at a very large scale and manifests as speciation or rise of a new species. Adaptation is termed as microevolution, as it is a small-scale process which may or may not be clearly noticeable.
Ques. What is the main difference between adaptation and natural selection? (1 mark)
Ans. Natural selection indicates that beneficial heritable traits necessary for survival are more dominant in a population whereas adaptation indicates the change in the entire population to suit their surroundings by developing beneficial traits.
Ques. How does fitness of a population help in evolution? [Delhi 2008 c] (2 marks)
Ans. In a population, the fitness of an individual to adapt better to the environment allows the individual to grow well, reproduce and survive. These individuals outbreed the others in the population and get naturally selected by nature for survival. Darwin called it natural selection and established it as a mechanism of evolution.
Ques. Explain the increase in the numbers of melanic (dark winged) moths in the urban areas of post-industrialization period in England. [Delhi 2012] (3 marks)
or
Explain how natural selection operates in nature by taking an example of white winged and dark winged moths of England [2014 c] (2 marks)
or
Prior to industrialisation, there were more white-winged moths on trees than melanised moths in England. However, after industrialisation, the distribution pattern of these two kinds of moths reversed. What does the above observation indicate? Explain giving reasons. [All India 2008 C] (2 marks)
Ans. Prior to the industrial revolution, the moths in England were mostly white or dull gray colored. The white color helped them easily camouflage on the lichen covered trees. But the onset of the industrial age covered the trees with black soot and the white moths started becoming easy prey to predators who could spot them easily against the dark background. The moths then adapted to the situation and eventually more dark colored moths grew in number. This exhibits adaptation leading to survival and this event was termed as industrial melanism.
Ques. Explain Natural selection based on Climate conditions. (3 marks)
Ans. Darwin’s finches have around 18 varieties and all have different beaks to suit their environmental surroundings. In 1977, drought affected Galapagos islands and the finches with tough large beaks survived the droughts by eating large sized seeds whereas the ones with smaller beaks could not break the big seeds and starved to death. While during the heavy rain spells of 1984, the small beaked birds survived on the soft small seeds produced due to rain and the ones with large beaks were struggling for survival.
Ques.Explain Adaptation based on Climate conditions. (1 mark)
Ans. Allen’s rule states that animals in colder climates have shorter ears, tails, limbs and snouts to minimize heat loss and conserve energy.
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