LWB: Lesson - Adaptations (Topic 2.6) 📖
⏳ Estimated Reading/Watching Time: 9 - 11 minutes
Describe how organisms adapt to their environment.
Natural Selection
Most of the individuals in a population will have features that are generally successful. Each organism has a unique set of DNA, and even though we share 99.999…% of our DNA, there are some differences.
These individuals have adaptations, inherited characteristics that increase their chance of survival. Their adaptations increase in frequency in the population each time an individual with the adaptation reproduces.
But there are also outliers in the population that are less fit. These individuals will reproduce at a lower rate than the general population, decreasing the frequency of their inferior traits in the population.
In general, there are three types of selection: stabilizing, directional, and disruptive.
Stabilizing Selection favors the intermediate phenotypes. For example, in the graph to the far right, the intermediate phenotypes are best adapted to the environment, so those phenotypes become most prevalent in that specific population in that specific environment.
Directional Selection favors one extreme or the other. The bottom left graph illustrates an example of this type of selection. The darker phenotypes are best adapted to the environment (perhaps there is a lot of soot covering the forest due to close proximity to an industrial area), so those phenotypes become most prevalent in that specific population in that specific environment.
Disruptive Selection favors extreme phenotypes. Our last example, the graph in the middle, phenotypes at either extreme are best adapted to the environment, so the middle phenotype will become less prevalent in the population and the dark and light fur colors will become most prevalent in that specific population in that specific environment.
The process of individuals best suited to their environment surviving and reproducing is called survival of the fittest and is the mechanism by which evolution by natural selection occurs. Natural selection is continually driving the genetic change of the population, increasing a population’s fitness in their environment.
Explore each tab below to learn more about the three most common methods of natural selection in wild populations.
Non-random Mating
Allele frequencies change when a certain trait becomes more beneficial in a population. The allele for that trait increases in frequency in the population. The most common way this occurs is through non-random mating. Non-random mating occurs when individuals in a population choose their mates based on specific characteristics. When this happens, the allele frequency of the alleles in the chosen mates will increase. This is how natural selection works.
Albino individuals in wild populations are not common. This is because these individuals usually stand out in their environment and cannot camouflage in their environments. This makes them inferior choices for mates, and, as a result, their traits are not passed onto future generations.
The opposite is also true. If an organism cannot reproduce, the alleles in that organism are lost, specifically the allele that made that organism an inferior mate choice.
Nonrandom mating has also created a special type of selection known as sexual selection. With sexual selection, the female chooses her mate based on specific characteristics or traits, even if that trait is not directly useful in the ecosystem.
Peacocks are an excellent example of sexual selection. Male peacocks have beautiful large tails. However, these tails are very heavy and make it difficult for the male to move quickly in the environment.
Scientists suspect that females choose the male peacocks with the largest, most beautiful tails because the tail is beneficial, but because males with the largest, most beautiful tails can survive in the ecosystem despite their large tail. The males with large tails have been able to survive well enough and find enough food to not only grow a large tail, but also to keep themselves alive with the tail, even though it hinders their ability to escape predators. So, the tail has persisted in the population because the females continue to choose the large and beautiful-tailed males.
This phenomenon happens frequently in bird populations, which is why male birds tend to be more brightly colored than female birds.
Adaptations
Organisms adapt to their environment over time, both in short- and long-term scales, via incremental changes at the genetic level. These changes can be passed on to their offspring, and over many generations, they can result in new species or populations. This process is called evolution by natural selection, and it is the main mechanism of biological diversity on Earth.
There are three types of adaptations in organisms: physiological, anatomical, and behavioral. Without adaptations, organisms will go extinct as they fail to adapt to changing environmental conditions.
Explore the types of adaptations below. Think about your pet (if you have one), can you identify which types of adaptations your pet has? For example, I have 4 cats! My cats have fur to keep them warm and claws for hunting, which are anatomical adaptations. My cats are largely nocturnal, which is a behavioral adaptation.
Now that we are familiar with the three types of adaptations, let’s discuss an organism and break down its physiological, anatomical, and behavioral adaptations. Click through the presentation about Emperor Penguins below.
As you can see, organisms can have adaptations from more than one category, helping the organism increase its survivability in their specific environment.
Organisms adapt to their environment over time, both in short- and long-term scales, via incremental changes at the genetic level.
Adapting to Changing Environmental Conditions
As an environment changes, the population living in that environment can either adapt and survive or not. Those are the only two choices. The more adaptable the individuals within a population, the higher the likelihood that the population as a whole will survive. Organisms must adapt to their changing environmental conditions, or they cannot survive.
If the bamboo forests of the Panda were to suddenly get warmer and drier, bamboo would likely not be able to adapt to this change in climate and the Chinese bamboo population could die out. If the Chinese bamboo population dies out, the pandas that are adapted to living in the bamboo forests would also die if they cannot adapt to eating something else.
Natural selection allows for the organisms most suited to their environment to survive and reproduce. If a species cannot compete in its environment, it will die. Species that do not develop superior adaptations to their environment can go extinct because they cannot out-compete other species in the ecosystem or because the environment changes more quickly than they can adapt. This type of extinction is known as background extinction.
Environmental changes, either sudden or gradual, may threaten a species' survival, requiring individuals to alter behaviors, move, or perish.
Evolution by natural selection is the main mechanism of biological diversity on Earth.
Non-random mating, genetic drift, and gene flow are methods of natural selection, with non-random mating being the MOST common method of natural selection.
Always remember - the organisms best suited to their environment will survive and reproduce.
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