AP Biology class blog for discussing current research in Biology

Tag: #Whales

The Evolution Of The Largest Animal On Earth

How did Blue Whales get to be as big as they are today? The answer lies in the understanding of evolution and adaptation.

In the past, Baleen whales had a diet fully consisting of plankton that rose to the ocean’s surface. About 5 million years ago, Rorqual whales started to adapt more to their environments, and were able to find that “lunge feeding” was the most efficient way to obtain their food and grow. This new finding lead their diet to change from plankton to krill and small fish. Lunge feeding and upwelling exposed them to a larger availably of food, which ultimalelty caused whales to evolve and have bigger mouths. Through wind motions, upwelling was able to occur, and rich nutrients were brought up from the depths of the ocean, which stimulated “growth and reproduction.” With their bigger mouths, came their bigger bodies, but of course it is not that simple. The evolution of whales can not be fully explained without evolutionary ecology. As whales continue to grow and evolve, their DNA gradually begins to change to continue to allow the whale to survive. The DNA begins to give it different instructions based on their new adaptations.

To get a deeper look into DNA, we can look at nucleic acids. Nucleic acids are the building blocks of DNA molecules. Phosphodiester bonds connect the phosphate and sugar groups of nucleotides, monomers of nucleic acids, to make up the double helices of DNA. A whale’s DNA is quickly evolving and forces the DNA to adjust and change the functions in the whale by changing the order of the bases, adenine, guanine, cytosine, and thymine, that it is made up of.

Whales had to adapt and conquer. The ocean is filled with competition and every animal has to do what they need to survive. Specialization comes into play when there are many animals going for the same foods. Specializing on one specific prey gives the predator an advantage against other predators. Blue Whales specialized in krill, but as whales soon came to find out, krill is not an easy prey to catch. A krill’s ideal environment is a polar ocean with upwelling zones, so in order for whales to catch their food, they must be able to be mobile and quick. Their bodies have adapted to being able to move very fluidly through the ocean and catch their prey with speed and an “element of surprise.”

With environmental problems quickly rising, whales are going to face challenges. Climate change is heating up the oceans and causing a decrease in krill and plankton. Whales’ specialization is going to play a crucial role in not letting them die out. Since they have focused their evolution on eating krill, they will have to adapt to the decrease in availability.


How are animal carcasses beneficial?

Studies prove that carcasses of dead animals are important for plant growth. Researcher, Dr. Roel van Klink, conducted an experiment and concluded that carrion, the decaying flesh of dead animals, is essential for many species. Since, carrion of large animals is an extremely nutrient rich, ephemeral resource. The Oostvaardersplassen Nature Reserve found that the leaving the deceased animals on the ground has had a positive effect on biodiversity. The remains attract more insects and other arthropods and increase plant growth. After five months the plants were significantly larger than usual; the biomass was five times larger and nutritional plant quality was higher than the controlled sites.

Many debates have started from this proposition to keep dead animals in nature reserves. The European legislation requires any dead animal to be removed or destroyed, unless the aim is to provide food for endangered scavengers, like vultures. However, in places like Kenya and Tanzania, the Mara River’s ecosystem relies on rotting carcasses for sustenance. The disposal of wildebeests in the river, not only feeds scavengers, but also releases nutrients (phosphorus and carbon) into the river after their body decomposes and releases algae and bacteria, which also nourishes the fish. Although many nature reserves benefit from this concept, the Oostvaardersplassen nature reserve abused their power in 2017-2018. The reserve starved 3,300 deer, horses and cattle to death. These opposing views cause controversy on whether or not decaying animals are beneficial or detrimental to the economy.

Many ecosystems rely on rotting carcasses for sustenance. In the ocean, over 60 species live off of the “whale-fall” communities. This is when a large whale dies and their body sinks to the seafloor, into a new ecosystem. Scavengers (hagfish, sleeper sharks, amphipods, etc.) in the ocean tear away large pieces of soft tissue from the whale and later, “bone-eating” worms help to digest the whale carcass. These new species, developed from the “whale-fall” communities, can last decades in the deep ocean. Unfortunately, many whales suffer from commercial whaling, which also affects the food chain for animals that eat whales. This time of mass slaughter killed off as many as ninety percent of living whales during the 18th and 19th century. Therefore, some of the first extinctions in the ocean have been from whale-fall communities.

Personally, I believe that animal carcasses are beneficial to nature and should be allowed. Though, some people abuse their power to benefit their own land, by slaughtering animals. For that reason, there should be set regulations to ensure the safety of animals so people won’t just go around killing innocent animals for their own advantage.

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