Principles of darwinism, Biology

Assignment Help:

PRINCIPLES OF DARWINISM -

1.       OVERPRODUCTION (PRODIGALITY) -

  • All organisms have enormous fertility and they multiply in geometric ratio. Examples of over production and rapid multiplication are as follows -
  • A female rabbit gives birth to six young ones in one litter and produces four litters in a single year. If all rabbits were survived and multiplied at this rate, their number would be very large after sometime.
  • Elephant is considered as slowest breeder, which matures at the age of 30 years and alive for about 90 years age.
  • Each female gives rise to about six offsprings and if all survived in 750 years, a single pair would produce about 19 million elephants.

2.       STRUGGLE FOR EXISTENCE -

  • Populations tend to increase in size until the environment supports no further increase and equilibrium is reached.
  • The population fluctuates around this equilibrium. Hence population sizes generally remain approximately con- stant over a period of time related to length of animal's life cycle.
  • The competitions between individuals for environment resources create a struggle for existence. It is three types:
  • Intraspecific : A struggle between the individual of the same species for similar necessities like food, shelter breeding place, light, water etc. is referred to as intra-specific struggle. e.g., Cannabolism.
  • Interspecific : It is a struggle that takes place between the individuals of different species for similar require- ments. E.g., Hunter-prey interaction.
  • Extraspecific or environmental conditions: The natural forces and environmental conditions like excess of mois- ture or drought; heat or cold, earthquakes and volcanic eruptions wipe out thousands of organisms of a species.

3.       VARIATIONS AMONG INDIVIDUALS -

  • No two organisms are exactly alike.
  • Under a given set of environment conditions certain individual of a species posses variations tending to adjust them very advantageously to external conditions, whereas other individuals of the same species possess less favourable variations and thus are at a disadvantage in relation to the same set of environment factors.
  • Variations are small morphological, physiological and behavioristic differences among the individuals.

4.       SURVIVAL OF FITTEST -

  • In the struggle for existence, individuals with favourable or useful variations would be survivors in the competitions, while those with less favourable variation would die.
  • This is called as survival of fittest by natural selection i.e., nature selects only those individuals of a particular species that are capable of surviving in the changed conditions.

5.       NATURAL SELECTION -

  • This is the basis for formation of new species. Hence, he belived evolution as slow gradual and long time process.

6.       PRINCIPLE OF NATURAL SELECTION -

Ultimately the Natural Selection is based on five observations and three inferences as suggested by Ernst Mayr (1982) in the form of following table -

OBSERVATION                                                                                                   INFERENCES

1.

Great potential to reproduce results

(a) High number of individuals cause struggle for existence in which only few survive

 

in population increase exponentially

2.

Most populations stable in size except

 

for seasonal variation

3.

Limited Natural resources

(b) Survival depends upon the hereditary constitution of individual. Those fit as per the environment generate more offsprings

 

 

 

4.

There is variation among individuals

(c) Favourable characteristic in a population will accumulate gradually through generation

 

to a large extent

 

5.

Much of these variations are inheritable

 

Population become well adapted to their local environments through natural selection.

Natural selection is the differential success in reproduction and its product is adaptation of organisms to their environment; it is the result of interaction between environment and the variability.


Related Discussions:- Principles of darwinism

Glucose-6-phosphate, Three molecules of ducose-6-phosphate  yield 3 molecul...

Three molecules of ducose-6-phosphate  yield 3 molecules of CO,  and 3 molecules of five carbon residues (pentose sugar). The latter are converted ultimately to  2 molecules  of  g

What is the goal of risk assessment, What  is  the  goal  of  risk ass...

What  is  the  goal  of  risk assessment? The goal of risk assessment is to provide risk managers, who might be, for example, government regulatory officials, industry health a

Kinds of ovules, Kinds of Ovules Ovules undergo varied degrees of cur...

Kinds of Ovules Ovules undergo varied degrees of curvature during development. The position of micropyle with respect to the funiculus becomes different and constitutes the b

Titration of inverted honey solution, Titration of inverted honey solution ...

Titration of inverted honey solution It involves the titration of the inverted honey solution. Carry out the titration in the following manner. 1) In a conical flask take 5

What is the primary structure of a protein, What is the primary structure o...

What is the primary structure of a protein? What is the significance of the primary structure? The primary protein structure is the linear sequence of amino acids that form the

Neurofilaments and microtubules - nervous system, Normal 0 fals...

Normal 0 false false false EN-IN X-NONE X-NONE

Explain the compound water, Explain the compound water? Water :  Wate...

Explain the compound water? Water :  Water is the most important compound in living cells, making up most of the bulk of living organisms. Our own bodies contain 40% - 60% wa

Explain the s1m filament theory of muscle contraction, Explain the s1M fila...

Explain the s1M filament theory of muscle contraction. What is special of "FlavrSavr" variety of tomato? Why is it preferred to its normal native variety? Illustrate a label

Cat scratch disease, Cat scratch disease It is caused by Bortenella he...

Cat scratch disease It is caused by Bortenella henselae, a gram-negative, non-motile bacterium. The organism is found in all parts of the world. The cat is an important reserv

Determine the synaptic process, Since neurotransmitters are not consumed in...

Since neurotransmitters are not consumed in the synaptic process, what are the mechanisms to decrease their concentrations in the synaptic cleft after they have been used? As t

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd