Question

theory 1

The ancestors of giraffes had short necks, and there was great competition for the plant food near the ground. Some of the giraffes kept trying to stretch their necks to reach leaves higher in the trees. As they stretched and stretched, their necks became longer. As their necks became longer, they were able to reach more food. Those ancestral giraffes survived to reproduce, while the giraffes that had not stretched their necks died. The offspring of giraffes with stretched necks inherited the longer necks. This process continued for generation after generation. In this way, giraffes evolved with longer and longer necks.

Theory 2

The ancestors of giraffes had short necks, and there was great competition for the plant food near the ground. Some of the ancestral giraffes naturally had slightly longer necks than others. The individuals with longer necks could reach leaves higher up in trees, and therefore could eat more food. Because those ancestral giraffes ate more food, they survived to produce offspring while the individuals with shorter necks did not. The offspring of giraffes with longer necks inherited the longer necks. This process continued for generation after generation. In this way, giraffes evolved with longer and longer necks.

a. In Theory 1, what caused the giraffe neck to become longer?

b. In Theory 2, what caused the giraffe neck to become longer?

c. According to what scientists now know about genes, could the giraffes’ offspring have inherited longer necks as described in Theory 1? Explain.

d. According to what scientists now know about genes, could the giraffes’ offspring have inherited longer necks as described in Theory 2? Explain.

e. Which of the two theories matches Darwin’s theory of evolution? Explain.

Answer 1

a. In Theory 1, what caused the giraffe neck to become longer?

                          As per Theory 1,the ancestors of giraffes had short necks.So obviously as per the rule in nature there will be existing completion among the same group of species sharing a common habitat.Inorder to survive with the competitors ,some of the giraffes started trying to reach the leaves in height where the other ancestor giraffes normally don’t reach.This habits of some giraffes where repeated with time and slowly they were successful in reaching the height,as a result small changes happened regarding the structure of their neck.The giraffes who were capable of eating from the height had more food and less competition and reproduced more.As the time passed,the population of giraffes had more such changed giraffes than the shorter ones as they were not able to survive due to the lack of adaptations.The ones having longer adapted necks transferred this character to their progenies and this process continued.Thus the giraffes gradually evolved with the longer neck.

b. In Theory 2, what caused the giraffe neck to become longer?

                        So in this theory 2 the case is different unlike in theory 1.Here it has explained that most of the giraffes were with short necks and some giraffes naturally had long necks when born.So these long necked ones had lesser competition and was able to have more food and reproduced at a higher rate than the other ones.They inherited their longer necks to the next generation .So as the time passed giraffes gradually got evolved with the longer neck.

c. According to what scientists now know about genes, could the giraffes’ offspring have inherited longer necks as described in Theory 1? Explain.

                 Genes are considered as the molecular unit of heredity of a living organism.It is the genes that hold the informations to build and maintains the organisms cell and pass this informations or genetic traits to the progeny.

   

                      Heredity is defined as the passing of phenotypic traits from the parents to the progenies and it can happen in both asexual and sexual reproduction.The offspring cells thus acquires the features of the parent cell in an organism.(Phenotype is the set of observable features of the structure and behaviour in an organism – and these traits results due to the interaction of genotype with the environment).

So as per the scientists information on genes,there are chances in which the offsprings of giraffes must have inherited long necks form their parents,because long necks was a phenotypic trait in the parent giraffes,so obviously there are chances for this trait to get transferred to the progenies.How these long necks were formed doesn’t matters.

d. According to what scientists now know about genes, could the giraffes’ offspring have inherited longer necks as described in Theory 2? Explain.

                                                 Here also the understanding the gene concept of scientists as explained in the question above there are chances in which the offspring giraffes have inherited it from the parents.Here the parents naturally have the longer neck trait and will be transferred from the parents to the offsprings when they reproduce.If the parents have a specific or special trait ,the chances of getting it transferred to the offsprings are very high as per the concept of gene and heredity,How they developed this special trait or the reason doesn’t matters.

e. Which of the two theories matches Darwin’s theory of evolution? Explain

Darwinism is a theory on biological evolution –developed by Charles Darwin and several others.

This theory states that – every species of organism arise and develop via natural selections of small and inheritable variations that enables that specific organism to survive, compete and reproduce.

This theory is also called as Darwinian Theory.

Darwin’s most famous theory is the theory of natural selection –

According to this theory – evolution happens when variation occurs in each generation and the individuals survive with the help of different combinations of these variable characters. Individuals having this variable characters will increase their survival probability and will have more chances for successful reproduction,also their offsprings also benefit from this heritable,useful character that spreads the population.

Thus simply it can be explained that – those organisms that are best adapted to their environment have a better chance for reproduction and survival.

A key factor that explained by Darwin is the survival of the fittest.He called the ability of an organism to survive and reproduces in its environment as fitness and explained that fitness results from adaptations.

He through his analysis concluded that – individuals with low levels of fitness die,hence do not reproduce while those with higher levels of fitness survive and reproduce successfully.

Natural selection happens with time and results in the changes of the inherited characters in a population,thereby increasing that species fitness in the environment.

Multiply,vary and let the fittest survive is the principle behind the Darwin natural selection.

                          So on analyzing the above explanations the THEORY 1 matches the Darwin theory of natural selection.As here first arised the competition,then the survival for existence,development of a new character due to the competition ,then fitness of these individuals in that current environment,then transferring this character to the next generation via reproducing successfully and thus spreading the inherited character within the population.

But in theory 2 the giraffe already have this long neck feature with them naturally and they are transferring them to their next generations,which is not much similar to the theory of natural selection explained by Darwin.