Emily's Take on Evolution

 Mutation is a major source of variation that natural selection can act upon to create evolutionary change. Mutations can have positive or negative impacts on the population or organisms themselves. This is connected to Darwin's idea that individuals in a population vary in their traits. I think mutation rates do evolve. Genetic changes from one generation to the next could cause increased mutation. Mutations can cause deleterious alleles to accumulate but it also has the possibility to allow beneficial alleles to be acquired. During cell division, DNA has to be copied. With so much DNA there is an increased risk of typos or mistakes being made in the new copy. This can lead to mutations. Additionally, mutations can be passed from parent to offspring. When someone inherits one abnormal copy of a gene, it makes it all the easier for mutations to build up. This is what happens sometimes in the case of cancer. Mutations in cells accumulate to cause cancerous growths (a.k.a. tumors). S...

 I would define fitness in the context of evolution as an organism's ability to survive and reproduce in its environment. It isn't really physical strength in this context. In a natural population you could measure fitness by observing the number of offspring produced by as many individuals in a species as you can find and then calculating the average number of offspring born. To account for the survival aspect you could use phenotype and specific visible markers to estimate the age of the oldest individuals in the population. If you know approximately how long most organisms in a population survive then you can compare that with the average number of offspring to try and quantify or better understand fitness in that population. Fitness is also going to be impacted by specific aspects of a habitat such as space, food availability, water availability, competition, predation, etc. At times there may be a tradeoff where exerting energy in one area may lead to a decrease of success...

 My favorite prediction that Darwin's idea of descent with modification makes is that lineages split and diverge (speciation). I read an article on ScienceDaily by the University of Cambridge that presented compelling research supporting that statement. The overall claim of the article entitled "Going up: Birds and mammals evolve faster if their home is rising", is that topography is a major driver of evolution even more so than climate change, giving rise to circumstances where species can diverge into new ones. When land elevation increases, temperature decreases, and subsequently habitat complexity is enriched. Higher elevation, such in the case of mountains, can also create situations where species become reproductively isolated due to the fact that they can not inter-mix and move. When reproductive isolation occurs, it is a step towards the forming of new species. This isn't just now an important factor in evolution either. These scientists believe that elevation...