Evolution - BIOL520

     Darwin’s evolution through natural selection states that organisms in a population have a degree of genetic diversity and thus some are born with slightly different traits. The traits that are more conducive to their environment and thus help them to better survive, gain resources, and reproduce may be passed on to their progeny, while traits that are not conducive to their survival and reproduction are not generally passed on as much. This means that the favorable traits are selected for by nature. If they are better adapted to their environment, then they have a better ability to reproduce and reproduce more, thus increasing their genetic fitness and the frequency of this trait. Their offspring will have these traits and will also be better suited to adapt to their environments.  How can the presence of natural selection NOT necessarily lead to an evolutionary change? There can be a selecting presence that favors certain traits, but if those traits are not i...

     Fitness is how successful an individual organism is at reproducing and thus creating more of their genetic material. The better the individual is able to adapt and survive in their environment, the better they are able to reproduce and potentially care for their young. The more they reproduce, the more they will be able to create more of their specific genes. Their offspring can in turn reproduce, given the right conditions, and thus further strengthen their genetic fitness.      To measure fitness, I would look at the genetic frequency or specific frequency of an allele in a population. I would select an allele and genotype that corresponded to a particular phenotype.       Let’s make a hypothetical situation to demonstrate how we can measure the fitness of cats - I say hypothetical because this should definitely not be done IRL; everyone needs to spay/neuter their cats. Let’s put them out in the country in an area full of squirrel...

       Lamarck focused on the individual organism and the changes in traits that occurred through its life. He believed the changes in the individual would affect its offspring. Darwin focused on the changes of traits within a population, and he believed that trait changes took place over the many generations. Darwin believed that all organisms had a common ancestor, while Lamarck believed that all organisms had independent origins. Lamarck also believed that an organism can take the initiative to change it’s own characteristics, its own behavior and physical traits, to better adapt to its environment and survive. He then believed that these changes would be heritable to the organism’s offspring, and the offspring could continue to enhance these changes during the course of its life.   Lamarck did get one aspect right, which is that traits are heritable. Heritability is an important aspect of evolution. If parents were unable to pass on the traits that made t...

       One of Darwin’s key predictions of evolution was that species change through time. This is dubbed as microevolution. When considering current evidence of evolution, I like to think about how humans have affected the evolution of other species. Most effects are done inadvertently. As I said in one of my previous posts, I love elephants. I remember reading a couple years ago that the amount of poaching of elephants in Africa for their ivory tusks has led to more elephants not developing trunks. Humans have poached and killed the elephants that have tusks to take their ivory, but they do not kill the elephants that do not have tusks. The poachers have thus selected for the tusk-less elephants. National Geographic reported that between 1977 and 1992, 90% of elephants living in a national park in Mozambique were killed for their ivory. Before 1992, 96-98% of female elephants developed tusks, but after 1992, only about 32% of female elephants developed tusks. Even m...