Question

a. First, discuss three causes for the Cambrian explosion. Then address this question: Multicellularity evolved right before the Cambrian explosion; how do you think multicellularity enabled the Cambrian explosion (base your response on our discussion regarding the evolution of multicellularity).

b. Evolution has produced interesting scaling relationships between energy use and body size. Why was it predicted that the scaling relationship of metabolic rate to body size is 2/3? Why is the scaling relationship closer to 3/4? Prove that you have a critical understanding of the metabolic theory of ecology.

Answer 1

a) By some reason the mutation rate in those times were higher (10x) than now, maybe that’s related to the fact that in this period the concentration of oxygen in atmosphere started to raise, whilst in previous era the ozone layer didn’t exist and the mutation rate was abnormally high and the ionizing radiation was very high therefore almost everyone died easily, but with the apparition of the ozone layer they could live peacefully. Also, the increased mutation rate is correlated to the expansion in the HOX family genes which coordinate the development of the antero-posterior axis, this changes in the HOX complex raise a whole type of adaptations (active swim, vision for example) that allowed life to introduce in a lot of ecological niches.

b) The principal reason is related to a mistake when representing the exponents in the following expression where n is a unidimensional measure of length.