Explaining evolution 7 – ‘Survival of the fittest’


In blog 7 of our  GCSE Science series Explaining evolution we look at the concept of the survival of the fittest.

Explaining evolution 7 – ‘Survival of the fittest’

Darwin’s Theory of Evolution is sometimes summarised in the phrase ‘survival of the fittest’.  In our everyday life as a human being on planet Earth most of us are aware that being fit is a useful attribute, but not essential for survival.  We live in a caring society where the weak and old are protected, and if we become ill or disabled we can expect some medical care and financial support.

Humans have adapted their environments to increase their chances of survival (e.g. building homes, growing crops) and have removed predators (e.g. bears, wolves, etc.) to ensure that we are top of the food chain.  We also complete tasks by working in groups to achieve common aims (e.g. road construction, police, health service, etc.).  Humans have developed some species to act as food sources (e.g. vegetables, cows, cereals, sheep, etc.) by selectively breeding members of these species with desirable characteristics in an artificial environment.

It is very different in the natural world where all organisms endeavour to survive on a day-to-day basis, and all organisms that are not top of the food chain also try to avoid being eaten by predators above them in the chain.  Any weakness in an organism will mean difficulty for it to find enough food to survive and often, if the organism is an animal, its weakness is quickly recognised by ever present predators and the organism is killed.

This is the ‘natural environment’ where fitness is essential, but fitness is not the only attribute contributing to survivability.  An organism’s ability to survive depends on other factors e.g. size, intelligence, speed of reaction, ability to escape, camouflage, defence mechanisms and culture (e.g. living in groups).  These survival techniques also may have to cope with continually changing environments where an organism’s ability to survive depends on how well they are able to adapt.

All organisms need to survive to a breeding stage and herein lies another survivability factor – most organisms breed to produce as many offspring as possible to increase the chance that their species will continue, e.g. a blue tit pair will have 10-12 eggs in a clutch, yet only a few will get to breeding stage.

However ‘fit to survive’ a species may become extinct due to an extreme change to an environment such as new competitors, predators, diseases or environmental change (e.g. an ice age).  Indeed, the evidence for evolution (See the next blog 8 – The Evidence for Evolution) has produced details of some cataclysmic events on planet Earth that have removed the seemingly fittest species.

John Roach

Tutor

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