Evolution Blog

 Sexual Reproduction and its Advantages When it comes to reproduction, we can see two types persisting. There is asexual reproduction which requires only one individual (usually) and through parthenogenesis or the development of an unfertilized egg, results in an essential clone of the parent. The other we are discussing is sexual reproduction. This process requires at least two parents, resulting in the recombination of genes that are then passed to their offspring.  Asexual reproduction has a lot of advantages, namely, you don't need a partner! As soon as the individual is ready to reproduce they can do so without the ovum needing to be fertilized. Many methods of parthenogenesis can allow for the production of both males and females. A downside to asexual reproduction is that sometimes an individual must incorporate new genes into their offspring thus requiring sexual reproduction, this is cyclic parthenogenesis. Another downside is that it becomes difficult to lose or gain...

What is a species and how do we define  what determines a species? Several concepts help scientists categorize species, and all are correct depending on the project's scope. So many concepts exist because of the vast diversity of life on Earth! Scientists have been working for hundreds of years to compile and categorize said diversity. Just as organisms evolve by external factors, science has evolved to become more complex and precise as new discoveries are made such as genetic sequencing. A general definition can be a group of organisms that can successfully interbreed with each other and produce viable offspring. Let's look deeper at some concepts to see how they can be beneficial and what limits they have.  Firstly the Biological Species Concept (BSC) describes species as groups of actually or potentially interbreeding populations that are reproductively isolated from other such groups. This concept can be useful when you are making preliminary observations of a population...

What is Genetic Drift?  Genetic drift is a shift in a population's allelic frequencies due to random chance events. It can lead to the loss of alleles and a decline in genetic diversity.  Until this week, I was uncertain about the mechanism of drift. I knew it was due to random chance but I wasn't able to fully wrap my head around the concept. The example of Northern Elephant Seals helped me to understand that drift is not as complicated as I thought. I also now understand how the bottleneck and founder effects contribute to genetic drift and the loss of certain alleles.   

  It Gets Complicated What is phenotype plasticity and how does it affect evolution and selection? Plasticity refers to the ability of an organism to change a characteristic of itself in response to environmental stimuli or disturbances.  When examining a trait and determining if it is plastic, it is good to start by seeing if the organism can change the trait. If they can modify a trait, can they do so when stimulated? Can they revert to their original trait expression? If the answer to most or all of these is yes, then you can determine if the trait exhibits plasticity. 

  Genotypes and Phenotypes How does selection act on the phenotype when its really the genotype that is passed to the next generation? Phenotype is the physical expression of a trait and genotype is the gene that causes the expression of the trait. The phenotype is very important to survive in an environment and can be one of the many factors that contribute to the overall success of the organism. For example, if we take a look at the anoles from Improbable Destinies we see that the physical expression or phenotype of each anole is what helps them to truly thrive in their niche. The twig anoles have short and stout legs that hold tightly to twigs and branches while hunting prey and hiding from predators. Garman's anole is larger and stronger, being able to easily navigate the tree trunks and upper branches of trees, even being able to consume other, smaller anoles.  These physical expressions of the genotype are what allows the gene to be successful or not. The genotype goes ...

 Fitness and Survival An individual can have an absolute fitness higher than their relative fitness. This is because relative fitness compares the individual to the population's average and absolute fitness compares the individual to a perfect member. An individual who is different from the population could have a better chance of surviving and reproducing than an average member.  The first generation of individuals below have just moved to a new location. Where they are from they have tan, sandy beaches with clear water and plenty of places to hide. The new location is a bit less sunny, the beaches are less pristine, and have stones and debris with darker murkier water. Both individuals are successful and can reproduce with the lighter coat continuing with more success.  Over the next few generations, the darker offspring can go out during the not-so-sunny day allowing them to gather more resources to give them an edge. The darker water complements their darker coloratio...