This is the second part of my three part series on evolution. In honor of Valentine’s Day approaching, I figured I would talk about baby making. Shout-out to all you November birthdays ;).
When someone says “survival of the fittest”, the first things that come to mind are creatures with impressive physical abilities like super fast cheetahs, incredibly smart chimpanzees, or massively powerful brown bears. SURPRISE! We aren’t talking about Fergie Fitness here.
In biology, we define fitness as an organism’s genetic contribution to the next generation’s gene pool. In order to have that kind of fitness, you have to have a number of successful offspring, AKA, be good at baby making. Following that logic, it doesn’t matter if an animal lives to a ripe old age, has big muscles, or is an exceptionally healthy individual. All that matters is that the lifeform has the traits necessary to live long enough to birth and rear reproductively successful offspring. Period.
Now that we’ve established fitness, lets talk about being the FITTEST. Fitness can take many forms. Some organisms birth offspring and die shortly after, however, their offspring are numerous and usually require no rearing on the part of the parent. This has shown to be a successful life history strategy in the cases of octopus, squids, salmon, and mayflies. Other organisms give birth to few offspring and have to care for them for months or sometimes years (i.e. humans).
An organism is born with traits that make it either successful or not so successful in its environment. The environment supplies selective pressures that act on heritable traits and select for the traits that are the most successful. Selective pressures are things like being hunted by predators, the availability of food and water, mate availability, and changes in habitat.
But what about organisms of the same species in the same populations competing with each other? Remember, we defined evolution as change in the heritable traits of biological populations over successive generations.
More competitive traits increase the likelihood of an organism and its offspring being more reproductively successful than other individuals in the same species displaying different traits like beak size, individual size, or coat color. The organisms with the most successful traits pass them on to the next generation, and the contribution of traits to the next generation can change the composition of the population. Boom. Natural selection/ survival of the fittest. Unsuccessful traits don’t survive long enough to make babies, thus tipping the scale and changing the prevalence of traits in a population at any given point in time. I repeat: change in the heritable traits of biological populations over successive generations.
Part three is going to be about selective pressures and the different ways they can act on populations to create drastic changes over time!