Charles Darwin and Alfred Russel Wallace proposed the first accurate theory of evolution, but there were scientists before him who had ideas on what evolution might be. The original thought on evolution was “that simple organisms originate at the base of the scale by spontaneous generation” (Freeman et al., 2017, p. 437). Evolution describes a process in which organisms change over time, this results in passing heritable behavioral and physical traits on to the offspring. Macroevolution is the formation or extinction of species, it is referring to an evolutionary change on a grand scale. A change within a small group of organisms over a short period of time is microevolution. Macroevolution takes place when a lot of micro-evolutionary changes transpire. Factors that influence and change genes pools is migrating, genetic drift, mutation and non-random mating. Migration is when a small group of organisms relocate. Mutations can cause a change within a species only if the mutated organism can successfully reproduce and its offspring must do the same. Organisms cannot be classified as a higher or lower organism because they are related to a common ancestor, species just change over time.
Thousands of species inhabit this earth from microorganisms to terrestrials. All of this diversity derives from a common ancestor. As time passes, inherited traits create speciation, which is the formation of new species due to lineage splitting. Genetic diversity plays a vital role in an organism’s adaptability. If a population’s environment changes, the population will either adapt in order to survive or they will go extinct.
Natural selection is a process that is required for evolution. It is when traits that increase fitness are passed from generation to generation, it also allows all generations to survive. Nevertheless, characteristics that are not fit for the environment and survival are not passed down due to the fact that most individuals carrying the trait will not live to have offspring. Natural selection is a product of changing to adapt more effectively to the environment itself. “Extrapolation of these results suggest that, of the estimated 70,000 species still to be described, more than half already have been collected and are stored in herbaria” (Herbaria are a major frontier for species discovery, 2010). Thousands of new species are discovered every year because of evolution. Especially with global climate change, animals must adapt with the new environment.
Anatomical Adaptations of Aquatic Animals
Cetartiodactyl is comprised of two orders of mammals: Cetacea and Artiodactyla. Dolphins, whales, and other aquatic mammals are more closely related to each other than to any other mammal, thus uniting them in the group Cetacea. “Recent molecular evidence suggests that Cetacea evolved from artiodactyl ancestors, making Artiodactyla non-monophyletic unless Cetacea is included” (Poor, 2014). Artiodactyls (also known as “even toed ungulates”) consist of animals such as deer, camels, hippopotamuses, pigs and other fossil relatives. These animals have an even number of digits on their hands and feet. Early fossil of whales also indicated an even-numbered of digits on their feet, which suggests a relationship towards Artiodactyla. Artiodactyl and Cetaceans don’t resemble to their ancestors. Cetaceans are specialized for an aquatic environment. In order to be equipped for an aquatic lifestyle, they had to inherit traits and give features that would make them adaptable towards a wet environment. Convergent evolution allows organisms that are not closely related to independently evolve similar traits to adapt to similar environments. Due to convergent evolution, these aquatic mammals lost their hind limbs except for their pelvic vestiges, their forelimbs transformed into flippers, they became hairless, a flattened tail for swimming, nostrils relocated to the top of their head (spouts), gained a lot of excess fat (blubber). Other classes such as reptiles and aves evolved different traits. Reptiles evolved watertight ears along the top of the head, third eyelid in some, sensory organs are located on top of the head allows them to have control of their senses when submerged. Aves evolved webbed feet, water diving, feet and bills for water feeding. Seals are remarkably adapted to a sea environment, they have sleek and powerful necks and bodies that is encased in blubber and a flattened tail. Blubber helps insulate them in freezing conditions. They have loosely interlocked vertebrae makes them flexible to surf the currents and navigate through ice and rocky shores. When under water, their nostrils close and shut even tighter as the water pressure increases. Seals can even eat underwater without inhaling water and their corneas are flattened so their pupils can dilate.
First the watertight egg, also known as amniotic eggs, is a feature only found in turtles, lizards, dinosaurs (including birds), mammals, and their relatives (American Museum of Natural History, n.d.). Being that these organisms have a watertight egg tells us that they inherited this feature from a common ancestor. Amniotes are the class of animals that express this characteristic. The watertight contains a fluid-filled membrane that surrounds the embryo and keeps it from drying out. This allowed amniotes to colonize on land, since they no longer needed a wet environment to lay their eggs. Dinosaurs are divided in Saurischians and Ornithischians based on hip structure. Then, the hip structure of Ornithischians dinosaurs is advanced compared to Saurischians. The pubis bone located at the front of the pelvis has an extension that points towards the rear (American Museum of Natural History, n.d.). The hip structure is thought to resemble a bird’s hip. Finally, after the amniotic egg, animals started keeping their embryos within. The placenta’s blood vessels linked the mother’s bloodstream to the embryo. This is known as being viviparous. The embryo develops within the mother with the help of the placenta producing chemicals that regulate the time of birth and soft tissues.
Hall of Saurischian Dinosaurs
First dinosaurs were equipped with a grasping hand. The hand consisted of a strong thumb, a middle finger (longest finger) and two small digits towards the end. Next, the dinosaurs had greater grasping ability with three fingers, so they lost the fourth and fifth digits. Finally, coelurosaurs (including aves, maniraptors, ornithomimids inherit relatively long arms. The 3 central toes allowed dinosaurs to move rapidly and catch prey, the first and fifth toe are small and absent (because of its hind foot). A group of dinosaurs that are still living today are aves. Aves are closely related to maniraptors, velociraptor, and deinonychus. They have homologous structures such as, the claws of a raptor are similar to the claws of a bird, birdlike beaks, long front limbs and wings. The birdlike beak structure derives from Clade Ornithomimids.
Hall of Primitive Mammals
Homologous structures are anatomical signs of evolution that derived from a similar lineage. It displays a similar base structure, but have completely different functions. Mammals are their extinct relatives contain an indentation in the skull behind each eye socket called the synapsid opening. Living mammals have inherited the same opening, except it’s larger. As larger openings evolved, jaw muscles and chewing motions came to be. There is a muscle for chewing that extends from the lower jaw to up to the opening evolved. This might have led to better chewing and digestion. Also, three middle ear bones were an advanced feature. The two additional ear bones helped form a joint between the upper and lower jaws. As time progressed, the ear bones decreased in size and moved towards the lower jaws, forming a new joint. “Other advanced features of mammals include having hair and producing milk for their young. Unfortunately, features like these leave no trace in most fossils. (American Museum of Natural History, n.d.).” Analogous structures are opposite of Homologous Structures, they are convergent features of different species that have structures that preform the same task, but are not alike in structure. These species did not evolve from a common ancestor, they just evolved in response to a similar environment.