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8 Examples of Evolution in Action
LORDZB NOVEMBER 19, 2011
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Evolution is one of the greatest scientific discoveries of all time. Armed with the knowledge of the interconnectedness of all life on earth, biologists have made startling discoveries. There is so much evidence in favor of evolution, that arguing against it is like denying that there is a moon in the sky. Yet people do still actively deny evolution occurs. Speciation, the formation of a new species from an ancestor species, takes a very long time yet there are evolutionary steps which can be observed. Here are eight examples, amongst many, of evolution in action.8
The Peppered Moth
Peppered-Moth-Evolution-ScienceIÂ’ll start this list with a classic example of evolution which can be found in many textbooks. Originally, the vast majority of peppered moths (Biston betularia) had a light, mottled coloring which was a good camouflage against predators. Before the industrial revolution, a uniformly dark variant of the peppered moth made up 2% of the species. After the industrial revolution, 95% of peppered moths showed this dark coloration. The best explanation as to why this change in the species occurred is that the light moths lost their advantage of camouflage as light surfaces were darkened by pollution, and so light moths were eaten more frequently by birds. The peppered moth as an example of evolution has been attacked recently, usually as to the cause of the shift in coloration, but the example still stands as a major shift in a species caused by mutations leading to variation and natural selection.7
Live Birth in Three-toed Skinks
The-Three-Toed-Skink-Saiphos-EqualisThe example of the peppered moth is a nice one for textbooks because it uses a single trait. Speciation involves many mutations leading to significant changes. The yellow bellied three-toed skink (Saiphos equalis) is a lizard of New South Wales, in Australia, that appears to be undergoing the change from laying eggs to live birth. Since these skinks can either lay eggs or give birth, it gives scientists the chance to study the adaptations necessary for live birth. Skink embryos encased in an egg have an extra source of calcium that the live born skinks lack. It turns out that this nutritional difference is made up by the mother secreting extra calcium for the young held inside her. This looks like the first step on the road to developing a system like the mammalian placenta. Skinks living on the coast tend to lay eggs, probably because the warm weather is predictable and sufficient for embryonic development. Those skinks living in the cooler mountains tend to give birth to live young, the mother’s body providing a more stable temperature. It is to be predicted that these two populations will at some point separate into different species as each population becomes fixed in its reproductive strategy. This brings up a common question in creationists – If man evolved from apes, why are there still apes? Well, with the skinks we would see two species formed, an egg laying and a live birthing species. Each would be best suited for their habitat. If live birthing skinks evolved from egg layers, why are there still egg layers? Because each is adapted for its niche.6
The Arms Race between Crabs and Mussels
Hemigrapsus SanguineusEvolution often happens in tandem; a predator evolves an improved hunting method, and any mutations in the prey species that aid survivability will be selected for leading to a change in the prey population. We do not have to wait for a predator to evolve to observe this, however; modern humans have been transporting species around the world, and thus we can observe new species interactions. The Asian shore crab (Hemigrapsus sanguineus) is an invasive species in New England which feeds on the native blue mussels. It has recently been observed that mussels, when they detect Asian shore crabs, develop thicker shells to stop the crabs eating them. This shell thickening behavior is costly to the mussels, and so is heavily regulated. The evolutionary factor here is that only mussels from regions where Asian shore crabs are endemic will thicken their walls when exposed to the crabs. Those mussels from other regions do not detect the crabs as a threat. Here we observe the starting shots in an evolutionary arms race.
8 Examples of Evolution in Action - Listverse
