Life is always changing. Changes in genetics cause new adaptations to arise, and if they benefit the species, they continue on to change the course of life. Throughout the history of life, there have been countless adaptations. Many have disappeared, but some took hold to mold the diversity of life we see today. Some of these adaptations had not only a large impact on the species they evolved in, but the composition of the Earth and the future of life from then on out. So what are some of the most impactful adaptations? Let’s get into it!
The first major adaptation of life was the formation of life itself. It's very difficult to piece together the events that happened so long ago, but it's generally thought that life began on Earth around 3.8 billion years ago. In the primordial atmosphere of methane, ammonia, and hydrogen all mixing around on a primitive earth, all it took was a zap of electricity to form the organic molecules needed to form RNA, which is the most basic form of genetic information. Nucleic acids are able to self replicate, leading to the beginning of evolution and the alterations of genetic code being selected for survival.
But the most basic unit of life is the cell, which is characterized by being enclosed in a membrane. This membrane is made of phospholipids, which are fat molecules with phosphorus in their structure. What makes these molecules so good at forming membranes is because of their amphipathic nature, meaning they have both a hydrophobic and hydrophilic side. Just like oil and water, the fatty hydrocarbon chains of phospholipids don’t mix with water, but their phosphate tops do. This causes them to spontaneously form into a two sided membrane with the hydrophobic fatty sides on the inside and the hydrophilic phosphate sides on the outside. When this protective membrane encircled around self-replicating RNA, the first basic unit of life was formed, which was the last universal common ancestor of all life on earth, aka LUCA.
Another adaptation that changed the formation of life was the development of photosynthesis. Today we associate that adaptation with plants, but it actually began in cyanobacteria. Evidence shows that photosynthesis arose between 3.2-3.5 billion years ago. Photosynthesis works by using sun energy to split water molecules into the hydrogen and two oxygen parts, taking that hydrogen and adding it to carbon from carbon dioxide to form sugar that the organism can then use as a source of energy. The leftover oxygen atoms from the split water and CO2 molecules are discarded as a byproduct of the reaction. Because of this, for the first time, our atmosphere filled with oxygen. But in a world devoid of oxygen before, oxygen was a poisonous gas, killing off many forms of life that had evolved to survive in an oxygenless world. But this set the stage for new life to evolve into an oxygen filled atmosphere. Plants developed photosynthesis when the cyanobacteria that perform this adaptation merged inside of the plant cells, living in symbiosis. This important pairing created the base of the food web for almost all life on earth today.
When did we begin to move? Animal movement began around the beginning of the Cambrian Era around 550 million years ago. This was the beginning of what's called the Cambrian explosion, which was a dramatic increase in biodiversity. This is due to increases in oxygen as well as erosion pulling minerals in the water allowing calcified structures to form like shells and bones. This gave muscles something to hold onto, allowing for movement to evolve. One of the early movers include a species called Dickinsonia, who looked like a giant pancake and used peristalsis to move. This rhythmic muscle movement is the same system our bodies use to guide food through our digestive system. Another early mover was the jellyfish, who were one of the first swimmers in the ocean. This adaptation in animals allowed us to move around and explore new habitats in search of food and to escape dangerous habitats.
We all have gills! Or at least modified gills. Our jaws are vital parts of our bodies that we use to eat, and speak. It allows us to chew food, which increases the variety of foods that we can eat, and gives us the structure for verbal language to develop. The conventional thought of how jaws evolved is that they formed from modified front gills that moved forward and altered their structure. At first, this gave fish the ability to suck in food more easily, but it also may have made their other gills more efficient as well, allowing more water to flow through. Over time the jaws had to become more specialized and stronger, allowing animals to catch, and chew their prey. There are some vertebrates that still exist today who evolved before jaws, including lamprey and hagfish.
Although there have been many adaptations in the history of life, some in particular have had a dramatic effect on the manifestation of the biodiversity we see today. The formation of the cell, the most basic unit of life, the development of photosynthesis, which changed almost all of life into oxygen powered organisms, the evolution of movement giving animals the ability to expand their habitats, and the formation of jaws which diversified hunting and eating techniques and laid the foundation for verbal language to form. There are many other important adaptations that shaped the course of life as well. Can you think of any?
Sources:
Formation of the Cell
Photosynthesis
Movement
Jaws