51. What is species turnover? 52. How is gradualistic species evolution differen

Question

51. What is species turnover?

52. How is gradualistic species evolution different from punctuated equilibrium?

53. How are mass extinctions different from background extinction?

54. How can duplicated genes be used by evolution?

55. Is it more likely that a gene is made from scratch of re-used? Give an example of how this works.

56. Are all forms/shapes possible to evolve? What are constraints or limits that may influence evolutionary trajectories?

57. How can we get very large changes in morphology?

58. Can you observe a difference in phenotype if there is no difference in the DNA coding region of a gene? How might this happen?

59. What pattern do we see in their phylogenies when hosts and parasites co-evolve?

60. What is reciprocal monophyly and what does it tell us?

Explanation / Answer

Please find the answers below:

Answer 51: Species turnover is a bio-geographical qualitative and quantitative term which deciphers the extent of species extinction or population increase in a geographical area under a given time span. For example, consider an isolated island with a finch species and species of grasshoppers. The finches feed on the grasshoppers. Initially, the population of both species was nearly equal. With due course of time, finches dominated over the grasshopper variety and in next 15 years, the population of grasshoppers decreased drastically as compared to finches. It can be said that the species turnover of finches increased whereas that of grasshoppers decreased.

Answer 52:

Gradualistic evolution: Gradualistic evolution of species is an idea which supports that evolution of species with time was a result of gradual accumulation of minute evolutionary changes in individuals rather than sudden appearance of changes. It is believed that evolution is slow, step-wise but gradual in nature. However, lack of appropriate fossil records for such proofs makes it impractical to follow that gradualistic species evolution indeed took place in past.

Punctuated evolution: In contrast to gradualistic evolution, the punctuated species evolution is an idea which supports that although the species residing in a main geographical area remain mostly stable for long time (millions of years), but those individuals or population of the species residing in the peripheral/outskirts or geographically isolated locations show more signs of sudden onset of genetic variability, variation among individuals of same kind and thus evolution. This is called punctuated species evolution.

Presently, the punctuated evolution is more pronouncely appreciated because of presence of fossil records for it.

Answer 53:

Mass extinction: Mass extinction is the term which states sudden and vast irreversible disappearance of a complete species all over the earth due to biological, natural or accidental reasons. For example, extinction of dinosaurs from earth altogether due to lack of food, space and possible celestial events lead to their mass extinction. It is a rapid process and eliminates a complete species from the earth at once.

Background extinction: Background extinction is a rather radom, slow and continuous process which takes place either by replacement of an old species with a new species, slow disappearance of individuals of a species from majority of the geographical area due to biological or environemental reasons. For example, the species of bird Dodo disappeared slowly due to over-hunting by humans.

Answer 54:

Gene duplication is a mode of evolution where molecular relavance of genetic material is highly important. Gene duplication is a strategy where the cell/organism with duplicated genetic material shows increased/decreased fitness over the normal individuals and successfully survives in the same geographical area. The redundancy in gene number and hence expression contributes to increase in physical characteristics of that individual and even if sudden mutational changes take place in these duplicated genes, the organism will continue to survive because it retains a normal copy of the gene as well. Gradually, these changes are established in the genome is these individuals and give rise to evolution.

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