Question

Briefly explain what, if any, aspects of Mayr's 5 theories of evolution are challenged by each of the following concepts: (a) Newman and Müller’s epigenetic mechanisms of character origination in which genetic evolution has more of a consolidating that innovating role, (b) genetic assimilation of an environmentally induced phenotype, (c) character variability as contrasted with character variation, (d) heterotopy, (e) heterochrony by neoteny, (f) homology thinking.

Answer 1

a. Mayer's theory suggested that any mutation or variation occured in the whole genome or the whole organism and not on a single gene. And he also believed in reductionism. On contest to this Newman's theory about epigenetics suggests that mutation occur through environmental changes and occur in a single gene which gets inherited to their offsprings and in this way evolution takes place from one generation to another.

B. Genetic assimilation is a process by which a phenotype is originally produced in response to an environmental condition which later becomes genetically encoded via artificial selection or natural selection. It overcomes the barrier to selection imposed by genetic canalization of developmental pathways. Epigenetics would enhance the results but there is no need. This induction of variation totally defies what Matt support i.e. Darwin's theory which suggested that only existing variations are capable of being inherited.

C. There exists some variation which are observed within the lifetime of an individual or within or between demes, populations, and species that is not under genetic control and thus would not be considered heritable variation. However, this type of variation can cause problems in studies related to the life cycles or histories of organisms which are unknown or where environmental factors influence character variation. Hence can pose a hindrance to Mayr's theory of evolution .

D. Heterotopy refers to the change in the spatial arrangements of some process within the embryo which can lead to evolution. It is achieved by the rewiring of an organism's genome, and can accordingly create rapid evolutionary change. On the other hand Mayr's theory suggest that evolution is a gradual and slow process.

E. Heterochrony refers to a change in the timing of developmental events. For example, a change in timing might slow down the development of the body, but not alter the maturation of the reproductive system. This change yields an adult organism with a form similar to the ancestral juvenile form.

F. Homology thinking suggests that variation is quasi-independent and individuated body parts are inherited and then form a lineage which are referred to as homologies. This aspect is against the theory of evolution because it suggests that variation takes place onto the whole organism/species and not individual homologous body parts.