Ethology And It’s Role In Evolution
Throughout the chain of evolution, a plethora of organisms has had certain periods where they reigned supreme for millions & millions of years, whether it be dinosaurs that existed for around 126 million years or modern-day humans that thrive today. However, there are specific reasons for how they evolved not only due to the differences in their geological time scale but also in the way they evolved and how their ethology played an important role to thrive in the ecosystems they existed in.
This begs the question:
“Was there was any impact that these organisms had on their surroundings and if so did their behavior play an impact on their survival or cessation?” Such questions stem from a wide range of theories based on their behavior and the ecosystems they flourished in. While most of the heavyweights such as the dinosaur or organisms before them went extinct due to circumstances that weren’t under their control, since the start of the Holocene there has been a huge decline in variety of megafauna species. If I would start anywhere, I would start with one of my favorite animals Orcinus orca or Killer Whales.
One of the most successful apex predators of our planet’s oceans, killer whales are a menace to their prey, they live in social groups and hunt this way, their unity and teamwork is so good that it will bring Dom Toretto to tears saying “This is family" But what if I tell y’all that their ancestors were land dwelling? or their closest living relatives are hippopotamus? Before you readers start scratching your heads and jump on Google to “feel lucky" I’ll share some interesting things about these organisms.
Mammals
Killer whales and Hippopotamus share a lot of resemblances, firstly they come under the same order which is Artiodactyla or even-toed ungulates. These include toothed whales such as Belugas and land-living ungulates such as Antelopes. But the most fascinating thing these two intriguing organisms share is a common ancestor named pakicetus who existed around 50 million years ago and its remains were found in modern-day Pakistan.
This medium-sized animal was supposedly the ancestor of modern-day toothed whales such as killer and beluga whales. As mentioned above these medium-sized animals were found in modern-day Pakistan around 50 million years ago and were semi-aquatic mammals, this means just like amphibians of today they lived on land and water. But something intriguing occurred around 54 million years ago, these animals diverged into modern-day dolphins and toothed whales such as killer whales we know today. But why did this divergence occur? For starters, look closely at the word “semi-aquatic”. As I mentioned earlier Pakicetus lived on land and water, they possessed webbed feet and dense bones. An adaptation that is beneficial for swimming in the waters of that time along with an ability to walk and hunt on land, but while the pakicetus evolved into ambulocetus natans further evolving into the modern-day cetaceans we know today, the hippopotamus took a different path of evolution. These animals evolved from anthracotheres
There were around 10 subspecies of the anthracotheres mostly concentrated around Central Europe existing from the oligocene to the miocene period. They gave rise to a widespread speciation of Hippopotamuses that existed throughout Europe and Asia until it went extinct after the middle pleiocene.
Now leaving the introductions aside, the main reason behind such divergence and change in ecosystem comes down to their feeding pattern and social hierarchial behaviour. If you see, the killer whales (which are apex predators but quite charming in their own regards) are found in pods of around 5 to 30.
They form one of the most social and complex groups that communicate with each other by means of clicks and whistles, their pods are led by a matriarch whose responsibility is to lead them to feeding grounds and hunt for food. While the younger females and males move towards different pods to breed and increase the pod health, surprisingly enough the male killer whales return back to the pod after mating with females from different pods, this is a different behaviour altogether compared to what is observed with land dwelling mammals such as lions where the younger males leave their pride in search of gaining their own pride. This behavior of living in social groups might be common place for organisms as this is also observed with herbivores that live in strengths of around 150 to around 1000s in order to prevent predation from predators.
Another reason might have been competition and the availability of eats. Unlike land-dwelling herbivores that are generalist feeders, whales especially baleen whales and toothed whales are specialists meaning they eat specific food. This means that scarcity of food especially for animals like pakicetus might have been the reason that drove them towards the high seas meanwhile evolving flippers and changing their diet with accordance to their new surroundings not only improved their chances of survival but also gave rise to the group of cetaceans stemming into the modern-day whales that swim the great oceans of today.
Insects
Another classic example of such evolution based on behaviour and changes in physiological changes to their environment is that of millipedes and centipedes. These creepy crawlies are pretty much found everywhere you go except in the Arctic and Antarctic regions. There are certain species of centipedes that can grow upwards of 30 centimetres, this might run chills down the spine of some people, but what if I tell you that you’re lucky? I might sound crazy here but hear me out during the Carboniferous period these 30 centimetres centipedes would be as tall as 6 feet in length.
Creepy isn’t it but the difference between the sheer size is just mind boggling. How are the creepy crawlies of today that are small insects such as centipedes and dragonflies that were large in size during the Carboniferous, what got them to that size?
Well the answer lies in the form of oxygen levels of that time. If we compare the oxygen levels of today and back then there’s a huge drop in oxygen levels of today at around 21 percent compared to 35 percent during the Carboniferous days. This allowed insects to reach massive sizes despite their respiratory systems being smaller they were efficient enough to provide enough oxygen to these giant creepy crawlies.
This is the prehistoric dragonfly meganeura, these dragonflies had a wingspan of around 65 to 70 cm. These dragonflies were a pretty dominant sight in the Carboniferous jungles and marshlands. Interestingly enough the sizes have not been observed in these insects since then, one of the main causes could be a decrease in oxygen levels that has resulted in smaller sizes of the respiratory system of the insects of today allowing reasonable intake of oxygen concerning their size allowing them to survive today in the modern world.
These two organisms portray the lamarkism theory at its best. Lamarkism theory stated in simple words that physical changes that occurred in an organism’s lifetime can be passed down to its offspring. In the case of pakicetus, hunting in water and land allowed pakicetus to develop webbed feet, providing them better locomotion in water due to which they decided to change their habitats and food preferences with these webbed feet developing into flippers that we see in modern-day whales. Whereas for insects, low oxygen levels contributed to the demise of the larger insects but certain insects like arthropleura developed smaller spiracles (organs through which certain insects perform respiration) that allowed them small amounts of oxygen intake with regards to their size. This is my take on how behavior played its role in the evolution of certain organisms. If you like what I write do consider going through the other articles present on my page, and like and share these with fellow wildlife enthusiasts. As always, take it easy
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