Exemplary Examples of Organisms
 1. Atlantic Blue Marlin
Location Found & Habitat Specific Information

Internal Physical Characteristics

External Physical Characteristics

Behavioral Characteristics

2. Beluga sturgeon
Location Found & Habitat Specific Information

Internal Physical Characteristics 

External Physical Characteristics 

Behavioral Characteristics

3. Atlantic Giant Grouper
Location Found & Habitat Specific Information

Internal Physical Characteristics 

External Physical Characteristics

Behavioral Characteristics

The fossils I researched show evolution because all of the fossils displayed have multiple similarities between all of them, but as time progresses, these similar traits are altered. For example, all of the fossils display bones that run down the side of the body, but as time progressed, these bones seemed to thin out, allowing the fish to be more lightweight and swim faster in the waters. Another example is that the size of the tail has increased as well as time passed, which allows the fish to be able to push themselves forward with more force when swimming.

My group is distinct from mammals and amphibians that exist in the ocean because they have gills that allow them to go through cellular respiration underwater without needing to surface for air. This shows that my group has seen evolution over time due to similarities with other classes, being that they have adaptations to survive underwater, along with some amphibians and reptiles. My group is then different from the cartilaginous fish because all members in my group contain bones, which is advantageous over cartilage because it provides sturdier structural support. This shows that a divide happened later that separated these two superclasses that was originally one, due to the two superclasses having some similar traits, but over time evolved to be two distinct traits.

Most vertebrae have limb structures in their bodies, all of them being of similar structures. This is a homologous structure because most limbs follow the 1 digit- 2 digit- many digit structure, showing that at one point, all of these organism had a similar structure. The original use for the ancient structure was to provide organisms to swim in the water and get traction, as the first organisms with these limb structures is thought to be aquatic. Within my taxonomic group specifically, bony fish all have the similar pectoral fin structures, with all having a humeris (1 digit), ulna and radius (2 digits), and then many digits to create the limb, which helps the fish propel faster through the water.

In the Osteichthyes superclass, every embryo looks almost identical to each other, as all grow eyes, heart, spine and skeleton in the exact same place with the exact same structures. After that, the fish begin to develop internal organs, gills, and fins. However, past this stage, differentiation occurs, as some fish begin to develop additional fins, and some fish also grow to be different sizes. For example, the giant grouper (Epinephelus itajara) has eight fins, while the Ocellaris clownfish (Amphiprion ocellaris) has nine (additional anal fin), which shows that divergence of the development of embryology at the same point caused the clownfish to grow to grow the additional fin. This shows that the two fish are related due to having the same internal and external structures present, but then separated through the growth of the additional fin in the clownfish during some point in the embryological development process.
 

At some point during the fish ancestral lineage, the fish acquired the ability to develop strong jaws and paired fins. This allowed these types of fish to be able to eat more varieties of food, as well as swim away from predators with more ease. For this reason, fish had the ability to move to a much wider variety of habitats, including both saltwater and freshwater. After moving, speciation occurred, showing that jawed fish evolved through adaptive radiation due to the ability to live in a wider variety of habitats.

 

 These karyotypes compare the Hoplias lacerdae and the Hoplias aimara. They are very similar to each other due to them having the same number of chromosomes (50 chromosomes, 25 pairs), as well as very similar structures of the actual chromosomes themselves, which most likely carry similar genes in similar places on those chromosomes due to them being very closely related (same genus). Comparing these chromosomes to humans, the two are different because humans only have 23 pairs, while these fish have 25, as well as the structures are a bit different. However, they can be related to humans because both carry the male or female sex chromosomes, as well as humans and some bony fish (Sarcopterygii) carry the gene that make them tetrapods. This relationship shows that tetrapods may have evolved from lobe-finned fish, as their four limbs granted tetrapods the ability to walk on land at one point, allowing for land animals to exist outside of the water, as it is thought that the first animals were aquatic.

For many of the larger fish, biologists have observed the presence of the GH/ IGF1 gene. This gene has been linked to the production of growth hormones that will help the fish to grow more than fish without this gene. This shows evolution because original fish are presumed not to have this gene, but through mutation, a variant was given this gene. From there, since the trait helped these fish to survive and reproduce easier (harder for predators to consume larger fish), fish with the gene evolved and created the many variants of fish with the gene that are seen today in larger fish, such as the ocean sunfish and giant grouper. 

 The number of chromosomes and chromosome pairs is different based on the species of the fish. The minimum amount of chromosomes scientists have observed on a fish was 26 (Citharichthys spilopterus), while the most was 100 (Prionotus punctatus and Potamorhina altamazonica). The average amount of chromosomes observed in fish was around 48 (24 pairs), which constituted around 50% of the species of fish studied. This variation in the amount of chromosomes per fish species shows evolution because it is thought that the original ancestor of bony fish was thought to have 24 pairs of chromosomes, but then mutations throughout time have allowed variation in the number of chromosomes. However, more than 90% of fish have between 22 and 26 pairs of chromosomes, showing that the evolution of these types of fish only added or deleted one or a few pairs of chromosomes, and the results were usually never drastic.

Most vertebrates have the presence of hemoglobin, which is a protein that transports oxygen throughout the blood. However, there is one family of bony fish that do not have this protein, being Channichthyidae. Organisms in this family can survive due to them having larger blood vessels, more blood, and bigger hearts than other fish. However, it is interesting to note that fish in this family still have the gene to make hemoglobin, however, it is defective within these organisms. This shows evolution because a mutation could have made these genes containing the creation of these proteins defective, but the organism was adapted to survive without the hemoglobin, and then speciation occurred that allowed organisms in this group to still be able to survive and reproduce without the presence of this protein.

 

This phylogenetic tree shows the difference between lobe-finned fish (Sarcopterygii) and ray-finned fish (Actinopterygii). All bony fish have fins, but this tree separates the development of these two different classes by the type of fins that they have. From there, the classes are broken apart from each other based on number of fins present (can range from 4 to 10) and the size of all of these types of fish, as the placement and existence of the same internal organs is constant throughout all bony fish.

One example is the Lepomis gibbosus, more commonly known as the sunnyfish. In nature, these types of fish can be found in four different colors: blue, orange, yellow, and green. The surrounding habitat mostly influences which color the sunnyfish will be, as the color most frequently used in the surroundings is the one that the sunnyfish will tend to be, in order to blend into its surroundings the most efficiently. My second example comes with the Atlantic blue marlin, also known as the Makaira nigricans, as they can range from any size of 8 to 14 feet, where the variation influences how much food they need to consume. Shorter marlins need to consume less food than longer marlins, which explains why the longer marlins can use its spear-shaped nose to hunt and kill larger predators, such as larger fish and squid. The third example comes with the coloration of the Amphiprion ocellaris, more commonly known as the clownfish. Coloration ranges from orange to reddish-brown. These differences in color reflect the environment surrounding the fish, as orange fish blend in better with the corals surrounding where some of these types of fish live, while reddish-brown allows the fish to blend in better with the mud towards the bottom of the habitat where these types of fish live.

Microevolution

The first example is of any bony fish that is coveted by humans for any reason, such as food. Most places in the world have fishing laws that require for smaller fish to be released back into the water, while the larger fish can be kept. For this reason, many of these types of fish have seen the gene frequency shift towards smaller fish, as the gene pool decreases and prefers small fish, as they have adaptations to survive the fishing. Another reason why smaller fish have been appearing more frequently in the gene pool is the fact food is becoming less plentiful, as humans are constantly “taking away” the habitat and resources of the fish. For that reason, the smaller fish, that take up and use less resources than the larger fish, are becoming more frequent. My final example comes with the temperature of the water. Over the past 100 years, the temperature of the habitats is increasing, which is killing off many of the fish that tend to prefer to live in the colder waters. For that reason, the gene frequency is shifting towards more individuals that prefer to live in warmer waters than those in colder waters. 

Atlantic blue marlins tend to range from 8 feet to 14 feet, with the average being around 11 feet. These differences in length of the fish can reflect the amount of food that the marlin needs to eat. For example, shorter marlins do not have to eat as much, which makes their spear-shape nose shorter, as they may only need to eat smaller fish without using its nose to hunt. However, larger marlins need more food, so they use their longer spear-shaped nose to hunt larger prey, such as squid, which justifies their larger body shape.

Beluga sturgeons range in length from 13 feet to 20 feet. This variation reflects the survival adaptations that the group has faced. On on one hand, the smaller sturgeons do not need to eat as much due to their lower body mass, as well as they can swim faster than larger fish, but they are much easier for natural predators to eat. On the other hand, larger fish are much harder for some predators to eat, but these organisms need to consume more energy for metabolic processes to continue, as well as they cannot swim as fast as the smaller fish in the case that a predator is large enough to eat the large organism.

The Atlantic giant grouper can be a wide variety of colors, from dull green, grey, dark yellow, or brown. The variation of the color is heavily dependent on the habitat of that particular organism. For example, if the species lives closer to the floor of the body of water, the frequency tends to be more brown. This is because the floor is covered in brown mud, and groupers that are brown have a higher chance of surviving by hiding its brown coloration in the brown mud.

In a recent study conducted by scientists, they looked at three separate populations of Sebastiscus marmoratus, which live off the coast of China. In this study, they have concluded that at one point, migration between the groups was heavy and common, but no longer is the case. This shows us that at this point, the genes, which may have not been present in the populations before, had spread to allow for the populations to be able to survive at a more efficient rate. However, the lack of migration today has lead to the groups diminishing in size. This is largely due to the lack of genetic variety and the heavy environmental pressures, such as invasive species, being too much for the species to handle, and this lack of genetic variety isn’t allowing for these populations to be resistant to the environmental pressures present, whereas when there was genetic diversity at one point, resistance to these pressures could occur.

 

Atlantic blue marlins mate at any point of the day. However, the time of year varies, as some mate before migration in the North Atlantic between the July and September months, while some mate after migrating to the warmer waters of the South Pacific in February and March. Marlins can spawn up to four times per mating season, and lay around 7 million eggs per time, but a very small percentage end up being born and reaching a reproductive age, as predators tend to consume the eggs as food. Marlins choose mates base on size, length of nose, and preference of breeding time. 

Beluga sturgeons usually can mate at any time of the day during the winter or spring, based on the preference of the individuals and the temperature of the water. Sturgeons tend to first migrate to where freshwater exists before mating. Belugas tend to only have offspring once every four to eight years during their reproductive life cycle. Beluga sturgeons choose mates based on when the other mate prefers to mate, as some sturgeons migrate and mate during the winter months, while other migrate later and mate during the spring months.

Atlantic giant groupers can mate at any point of the day during their breeding season, which is from July to September. They breed by first gathering in groups of about 100, then choosing their mate within the group, and then the female spawns the eggs semi-frequently. The groupers then repeats this process every year for as long as the reproductive years last. Again, groupers choose their mates based on what if offered in the group, and then traits such as size are used to find the appropriate mate.

Natural Selection
The type of natural selection is heavily dependent on if the fish is caught by humans or not. If it is, then it can be considered as directional selection because humans are required to throw the fish back into the water if it is too small, meaning that smaller fish are selected over larger ones. Otherwise, it would be disruptive selection, and this is because smaller fish are harder to find, and larger fish are harder to consume. For this reason, the medium fish that don't have these traits are eaten, while the smaller and larger fish are selected instead.

The Atlantic blue marlin is similar to the Beluga sturgeon, in that both went through disruptive selection at some point. However, the Atlantic blue marlin is not as heavily hunted today, which allows for the pattern of disruptive selection to continue. On the one hand, smaller fish can swim away from predators faster than medium or large fish can, as well as they don’t need to consume as much food as medium or large fish. On the other hand, larger fish are much harder for predators to eat than small or medium fish. For this reason, small and large fish have advantages that the medium fish don’t have, which can explain why medium fish are not being seen as frequently as small and large fish are. 

Before the existence of humans, beluga sturgeons went through disruptive selection because the two extreme sides had survival adaptations that the average size didn’t. For smaller fish, it was the ability to consume less food and swim away faster from predators. However, now that humans undergo fishing everyday, the trend is more directional selection today. This is because human laws regulate that smaller fish caught must be released back into the water, and only bigger fish can be kept and (presumptively) eaten, so the fish observed naturally today are usually much smaller than what they were before humans could fish.

For Atlantic giant groupers that are living near the floor of the environment, the fish there are undergoing stabilizing selection. The variations of colors of groupers in these area are from light brown, brown, and dark brown. Usually, the medium brown is the most successful because their shade of brown allows for those types of fish to better blend into their environment and hide from predators more efficiently. However, the light and dark brown organisms tend to be eaten more frequently because they cannot blend into the environment as easily as the medium brown fish can, so the frequency generally tends to be much more medium brown fish (average trait) than the light brown and dark brown fish (extreme traits).

Descent With Modification
Descent with modification is the passing of traits from parents to offspring. Over time, we can see that the organisms have changed over time due to a shift in gene frequency, resulting in evolution over time. This is most evident with the development of lungs in some types of fish, such as lungfish, and swim bladders in most bony fish. At first, primitive fish solely had air sacs, which deflated to release water and inflated to allow for water to come in that had the oxygen necessary for life. However, gradually over time, as geographic isolation began to separate some species due to continental drift, the “fittest” species began to adapt to different environments they were newly accustomed to, which some of these species developed lungs and others developed swim bladders over the course of millions of years, which is the organs that these fish use today.

Geographic Isolation

The Atlantic giant grouper and the Pacific giant grouper (Epinephelus quinquefasciatus) were once the same species before the Atlantic and Pacific Oceans were separated 2.8 million years ago, when the North American and South American plates collided and formed the entirety of the Americas. When this happened, what was once just one species of blue marlin was separated by land mass, and from there, speciation occurred that resulted in two “non-interbreedable” species forming since the divide, the Atlantic giant grouper and Pacific giant grouper.  

Atlantic blue marlins have been affected by reproductive isolation. That is because there are two different mating seasons for this species, one from July to September, and another from February to March. This shows that organisms that are breeding in the summer months are going through speciation that are separating that group of marlins from ones that breed exclusively in the winter, as interactions (mating-wise) are decreasing over time because of the difference in mating times.

The different mating seasons of the Atlantic blue marlin have started the process of speciation in these types of marlins. For example, these types of marlins have started to select mates based on their preference of when to mate, which has lead to the groups becoming more and more reproductively isolated because of the less interaction between the two different groups. For this reason, scientists are predicting that at one point, the groups will not be able to mate with each other, which would cause the species to break apart based on when they can breed. However, the impact now is that the offspring see less genetic variety, as winter mates are only breeding with other winter mates, and summer mates are only breeding with other summer mates.

I believe that bony fish have evolved through gradualism. Along with the example provided earlier with the air sacs into lungs or swim bladders, there also is the example of thickness of the side bars. Up until the Eocene epoch, fish had much thinner side bars that helped the fish be lighter and swim quicker. However, in the Eocene epoch, fish had their bones thicken tremendously, as thickness was needed for structural support of the fish. This shows gradualism because we can see that the development of the trait took millions of years to happen, showing that the trait evolved very slightly over time.

Bony fish belong in the kingdom known as animalia. All animals have characteristics that separate them from other kingdoms. First, animals have multiple cells (multicellular), and these cells are eukaryotic. This separates animals from bacteria and most protists, as these organisms are usually unicellular and/or prokaryotic. Second, most animals digest their food (heterotrophic), separating themselves from plants and algae, which are instead autotrophic. Third and finally, animals don’t have cell walls, which separates themselves from plants, algae, and fungi in this way.

Taxonomic Classifications of Exemplary Organisms
1. Common Name: Atlantic Blue Marlin
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Perciformes
Family: Istiophoridae
Genus: Makaira
Species: nigricans
2. Common Name: Beluga Sturgeon
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Acipenseriformes
Family: Acipenseridae
Genus: Huso
Species: huso
3. Common Name: Atlantic Giant Grouper
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Perciformes
Family: Seranndae
Genus: Epinephelus
Species: itajara

The taxonomic classification can show us how related two organisms are based on how many classifications are shared. For example, we can determine that all three of these organisms are related to each other because they share the same kingdom (Animalia), phylum (Chordata), and class (Actinopterygii). However, from there, we can conclude that speciation has occurred due to differences in the orders that can be observed. There are about 17 known orders of bony fish, but more than 80% of these organisms are of the order Perciformes, showing that the other classes came from the divergent evolution of organisms in the Perciformes order. Looking at my organisms specifically, one can conclude that the Atlantic blue marlin and Atlantic giant grouper are more related to each other than either is related to the beluga sturgeon because both share the same order (Perciformes), while the sturgeon doesn’t (Acipenseriformes). From there, the fish evolved separately due to there being difference in the family, genus, and species. However, just by looking at the taxonomic classifications, we can assume the Atlantic blue marlin and Atlantic giant grouper held the same common ancestor for a longer time than the beluga sturgeon due to the first two fish having more common classifications than the sturgeon has.