Adaptation & Evolution: The Basics, Plus Some

Charles Darwin is overrated as much as Alfred Russell Wallace is underrated.

Wallace received little money for his endeavors, yet independently formulated a theory of the origin of species very similar to that of Darwin, who had resources and was well off in comparison.

Their papers were jointly published, but guess who gets the recognition in science classrooms today?

Anyways, Wallace talked about The Great American Interchange – the theory of an event caused by volcanic activity, which created the Isthmus of Panama, which effectively linked North and South America for the first time in hundreds of millions of years. Because of this new land bridge, the species in the north migrated to the south, and those in the south migrated to the north. Some of these species that migrated were unable to propagate, and this influenced the biotic dynamics of the geographic area.

Darwin mainly talked about evolution by means of isolation by continental drift. A more technical term, allopatric speciation, refers to the speciation following the geographic isolation of subpopulations of species.

Both of these theories talked about variation in the gene pool, leading to natural selection, survival of the fittest, evolution, etc. etc.

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What is adaptation? It is the adjustment/change in behavior, physiology, and/or structure of an organism to become more suited to an environment. These new traits are known as adapted traits.

  • An example of this would be aposematic coloration – basically warning colors that scream “don’t eat me or you’ll regret it!” Aposomatism is mimicked all the time in other species. A Batesian species is harmless, and takes advantage of what is known of the species they are mimicking. A Mullerian species will share the same coloration as another species to share the benefits. A common saying in America is “red bordered by yellow kills a fellow”. We associate these colors as dangerous, and with good reason.

Let’s examine the class of mammals, especially the tetrapods (four-footed). Mammals can be characterized by their hair, three bones in their ears, a birth membrane, and the ability of the mother to produce milk.

  • Placentals – these are the mammals that develop in the womb and suckle their mother’s milk.
  • Marsupials – these mammals are supplied by a yolk sac, originated from Asia, migrated to Australia, and could propogate (think wallabys and kangaroos!)

Plants also have some ingenious adaptations to life in the rainforest:

  • Drip tip leaves – in this wet environment, it is important to not have extra water hanging out on the leaves of a plant to prevent mold or fungus or rot, so the leaves cause the water to run down easily.
  • Thorns and spines – pretty obvious, an animal is not going to want to eat you if you’re spiky.
  • Special roots (prop, stilt, butreous) – if you look at the photos of rainforest trees, you may notice that the roots of many trees are oddly shaped. Their purpose is not to gather water, because that’s easy enough to do in the rainforest, but rather to find nutrients, which tend to remain at the surface level.

Howler monkeys are also very cool. I remember waking up early in the morning to their voices during my time in Honduras.

  • They have opposable first and second digits, which makes them like us – we can pick up things and do far more.
  • A prehensile tail – they can grab onto things with their tails. Believe it or not, not all chimps, monkeys, and apes can do this!
  • Trichromatic color vision
  • Enlarged hyoid bone

This list could go on – jaguars, sloths, toucans (famous example with the beak), bromeliads, red-eyed tree frogs (and their poison), and more. Basically in conclusion, even though natural selection is just a theory, through these processes of natural selection and evolution, species have adapted to their environments. Check back for more!

Thanks for reading! ~Gloria

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