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Example Organisms in Osteichthyes Superclass

Mola mola (ocean sunfish)

Regaleus glesne (giant oarfish)

Makaira nigricans (Atlantic blue marlin)

Istiompax indica (black marlin)

Epinephelus lanceolatus (giant grouper)

Epinephelus quinquefasiatus (Pacific goliath grouper)

Pandaka pygmaea (dwarf pygmy goby)

Huso huso (sturgeon)

Amia calva (bowfish)

Epinephelus itajara (Atlantic goliath grouper)

Amphiprion ocellaris (Ocellaris clownfish)

Paracanthrus hepatus (blue tang)

Physical characteristics

Body shape is roughly cylindrical and tapering at both ends

All bony fish have pigmentation that can allow it to change color (cells called iridocytes allow it to change color)

All bony fish have fins

All bony fish secrete a layer of mucus that overs its entire body

All bony fish have bones to support body instead of cartilage

Behavioral Traits

Many species swim together in coordinated fashion (schooling)

Propel themselves throughout the water using their fins

Many produce sounds either for reproductive, social, or territorial behaviors in a given instance

Many species eat proportional to their size, as smaller organisms eat smaller organisms in smaller amounts, while larger fish eat larger organisms in larger amounts

Wide variety of organisms that bony fish consume, as they can be carnivorous, omnivorous, herbivorous, and detriverous

Many fish produce sexually; however,  a small percentage can produce asexually, as they can produce both the sperm and the egg

Habitat Requirements

They can live in almost any type of water, from temperate to tropical to polar, and can live in freshwater, saltwater, and brackish

Must live in an aquatic environment

They can live in an extreme range of temperatures, from extremely cold to extremely hot

They must live in a setting where oxygen for respiration is available

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

Mostly found in western Atlantic

Seasonal migration along western Atlantic coastline to move to warmer waters

Internal Physical Characteristics

Upper jaw is elongated to look like a spear

24 vertebre helps organism move quickly through water

Cold-blooded

Swim bladder allows fish to change at what depth it can float

External Physical Characteristics

Body- blue on top, silvery white on the belly

15 blue vertical bars on the sides

Dorsal and anal fins are pointed

Behavioral Characteristics

Average lifespan of male- 18 years; female- 27 years

Females lay up to 7 million eggs during mating season (late summer/early fall)

Migration to warmer waters is common

Prefer to swim in pairs

Uses spear-shaped jaw to “spear” fish, which allows marlin to get its food

2. Beluga sturgeon
Location Found & Habitat Specific Information

Mostly found in the Caspian Sea in Europe, where many are born in Volga River

Also can be seen in Black, Azov, and Adriatic Seas as well

Internal Physical Characteristics

5 rows of bony plate along the body

Have branchiostegal membranes (long, curved bones below the operculum) that join to create flaps

Cold-blooded

Swim bladder allows fish to change at what depth it can float

External Physical Characteristics

Long body (up to 16 feet) with flat snout

Short sensory projections near mouth that are feathered at the ends

Body is either greenish or dark gray, while belly is white

Behavioral Characteristics

Individuals can live up to 100 years

Only group together during mating times- more independent

Use environmental factors (such as water temperature, flow velocity, etc.) to determine when to mate

3. Atlantic Giant Grouper
Location Found & Habitat Specific Information

Eastern Atlantic Ocean from Senegal to Congo

Western Atlantic Ocean from Florida to Brazil

Only live in areas with warm water, along the shoreline where depths do not exceed 150 feet

Internal Physical Characteristics

Jawbone extends beyond eyes in length

Cold-blooded

Swim bladder allows fish to change at what depth it can float

External Physical Characteristics

Very large body

Head is broad with small eyes

Pectoral and tail fins are rounded

Color ranges from dull green, grey, yellow, or brown

Behavioral Characteristics

Some individuals prefer to be alone, while others swim in groups of up to 50

Most only mate between July and September

Feed on crustaceans by swallowing them whole

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Exemplary Organism 1: Atlantic Blue Marlin 

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Exemplary Organism 1: Atlantic Blue Marlin 

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This species is known for its long bill that grows from the front of its head. Blue marlin use this bill to stun their prey by slashing their heads in a side-to-side motion, knocking potential prey unconscious, and making it easier to catch. The blue marlin's bill differs from the swordfish 's by being round and pointed, rather than flat and blunt. Like many open ocean bony fishes, blue marlin start out as extremely tiny larvae, no more than a few millimeters long and weighing only a few hundredths of a gram. Soon after hatching, they already have a visible bill. Blue Marlin grow rapidly, and in the course of their lives they may increase their body weight by at least one million times!

Because blue marlin undergo such an amazing transformation in size (from being nearly microscopic to being one of the largest open ocean predators), they eat a wide variety of prey, throughout their lifetimes. At a young age, they eat tiny zooplankton, and their prey increases in size as they do. As adults, they eat fairly large bony fishes and squids. Similarly, blue marlin are eaten by a wide variety of predators. When they are newly hatched, they are eaten by other fishes that specialize on eating plankton. The size of their predators increases as they grow, and adult blue marlin are not eaten by anything other than large open ocean shark species.

The blue marlin is a highly migratory species, with individuals migrating across entire ocean basins and even between oceans. One individual, for example, was tagged off the east coast of the United States (western Atlantic Ocean) and recaptured in the Indian Ocean. Like many migratory species, the females are larger than males. In fact, adult female blue marlin are as much as four times the size of the largest males. All of the largest individuals are female. blue marlin reproduce through external (rather than internal) fertilization, where the female releases her eggs into the water column while the male releases his sperm. Once the sperm find the eggs, fertilization occurs. While spawning, a single female may release several million eggs, increasing the likelihood that some will be fertilized and that at least one hatched larva will grow to reach adulthood. Though almost all fishes are cold blooded, blue marlin and the other billfishes have a specialized blood vessel structure - called a countercurrent exchanger - that allows them to warm their brains and eyes. This adaptation provides them with a major advantage when hunting, by allowing them to think more quickly and see more clearly.

The blue marlin is a targeted fishery species in only a limited number of areas but is captured as accidental bycatch in fisheries targeting other species throughout its range. In some areas, this accidental capture is threatening blue marlin populations, and scientists consider the species vulnerable to extinction. Generally speaking, blue marlin populations are decreasing in numbers. Though it is not targeted commercially throughout much of its range, the blue marlin is one of the most highly sought after big game fishes in the world. Sport fishing enthusiasts spend tens of thousands of dollars to catch large blue marlin, and they are typically released alive (though recent data suggests that released individuals may frequently die after the fact). If numbers continue to decline, this highly valuable sport fishery may be in danger of collapse.

Taxonomy note: Several times throughout the history of studying marine fishes, researchers have divided the blue marlin into multiple species, but recent genetic studies leads scientists to believe that all blue marlin around the world are the same species.
To help support our work protecting sea life from dangerous threats, click here to donate today! Additional Resources: http://www.iucnredlist.org/details/170314/0

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This species is known for its long bill that grows from the front of its head. Blue marlin use this bill to stun their prey by slashing their heads in a side-to-side motion, knocking potential prey unconscious, and making it easier to catch.

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Exemplary Organism 3: Atlantic Giant Grouper

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Exemplary Organism 3: Atlantic Giant Grouper

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The Atlantic goliath grouper, like most groupers, is an ambush predator and eats fairly large fishes and invertebrates and even small sharks. Reefs with large numbers of predators, like Atlantic goliath groupers, are known to be healthier than reefs with no predators, so this species may represent an important part of the reef food web. Atlantic goliath groupers feed by swallowing their prey whole; they do not chew. They use their very large mouths to create enough negative pressure to suck in whole fishes or large invertebrates, and they swallow them quickly and efficiently.

Throughout most of the year, low numbers of Atlantic goliath groupers are observed in any one place. They are at the top of their food web and are therefore naturally rare. However, during reproduction (immediately after the full moons between June and December), they come together in groups of at least 100 individuals. These groups are known as spawning aggregations, and they form at relatively few places throughout the species' range. Individual Atlantic goliath grouper likely travel many miles to reach their preferred spawning sites and form part of the spawning aggregation. At these sites, the groupers reproduce by a method known as broadcast spawning, where females release eggs and several males release sperm into the water column above deep reefs all at the same time. This method increases the likelihood that eggs will become successfully fertilized and that fertilized eggs will not be eaten by egg predators on the reef surface.

Though they were likely naturally rare, scientists believe that destructive fishing practices have reduced the numbers of Atlantic goliath groupers by at least 80% and that the species is now critically endangered. In other words, it is very highly vulnerable to extinction. These fish utilize the same, few locations and same, few days for spawning every year, so their presence is quite predictable. Furthermore, a total lack of fear of people makes them an easy target for spear fishers. Finally, the Atlantic goliath grouper's large size, slow growth, and ease of capture all contribute to slow its recovery, even where laws have been put in place to give it some or complete legal protection from fishing (e.g., in the USA and Brazil). It is important to continue to monitor Atlantic goliath grouper population trends in order to determine whether or not the species is recovering or if stronger legal protection may be required.

A note on a closely related species: the Atlantic goliath grouper lives on both sides of the Atlantic Ocean - in the Caribbean Sea and adjacent waters and off the west coast of Africa. A closely related species, the Pacific Goliath Grouper, is restricted to the eastern tropical Pacific Ocean from Mexico to Peru. Scientists only recently divided the species into two, based on their slightly different genetic makeup. The two species are similar in both appearance and behavior, but little is known about the population trends or conservation status of the Pacific goliath grouper.
To help support our work protecting sea life from dangerous threats, click here to donate today! Additional Resources: http://www.iucnredlist.org/details/195409/0

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The Atlantic goliath grouper, like most groupers, is an ambush predator and eats fairly large fishes and invertebrates and even small sharks. Reefs with large numbers of predators, like Atlantic goliath groupers, are known to be healthier than reefs with no predators, so this species may represent an important part of the reef food web.

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History of the Earth and Evidence of Evolution

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History of the Earth and Evidence of Evolution

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How Fossils Relate to Evolution

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.

Anatomical Similarities and How They Relate to Evolution

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.

Homologous Structures in Kingdom Animalia and Original Use in Different Species

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.

Embryological Evidence of Two Organisms in Osteichthyes and How They Are Related

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.

Examples of Adaptive Radiation/ Divergent Evolution

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.

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Name: Holocentrum macrocephalumis
Age of Fossil: 40 mya (Eocene epoch in Cenozoic era)

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Name: Mene obluuguss
Age of Fossil: 40 mya (Eocene epoch in Cenozoic era)

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Name: Knightia alta
Age of Fossil: 56 mya (Eocene epoch in Cenozoic era)

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Name: Priscacara serrata
Age of Fossil: 40 mya (Eocene epoch in Cenozoic era)

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Name: Mene rhombea
Age of Fossil: 45 mya (Eocene epoch in Cenozoic era)

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Name: Priscacara cockerellites
Age of Fossil: 52 mya (Eocene epoch in Cenozoic era)

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Protein Synthesis, Chromosomal Structure & Genetics

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Protein Synthesis, Chromosomal Structure & Genetics

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Chromosomal Comparisons
I found that each species of fish tend to have differing amounts of chromosomes, as well as the chromosome types vary per fish. For example, out of a study that marine biologists have conducted on more than 100 species (a very small sample size compared to the 34,000+ species of Osteichthyes observed), they found that chromosome numbers ranged from 26 (Citharichthys spilopterus) to 100 (Prionotus punctatus and Potamorhina altamazonica). Another difference is the chromosome types, as fish even with the same number of chromosomes will have different types. For example, the Mugil curema and the Mugil liza, both members of even the same genus, have the same number of chromosomes, but yet they still have different types of chromosomes. The Mugil curema has 44 metacentric (centromere at center) and 4 submetacentric (centromere slightly offset), while the Mugil liza has 48 acrocentric (centromere heavily offset). This shows that chromosomes are heavily different from each other, even if the fish are in the same genus. However, what s not different is the location of certain genes based on chromosomes. For example, it is thought that the GH/ IGF1 gene is in the exact same location for very large fish such as the giant grouper and ocean sunfish. Even though the two species are in different orders, we can assume that the trait was passed down from a common ancestor with the gene, which shows evolution because speciation would have had to occur for the species to become different.

Karyotype and Relationship to Humans

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.

Chemical/ Biochemical Evidence of Evolution

a)  DNA/ RNA Analysis

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.

b)  Chromosomal Analysis

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.

c)  Protein analysis

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.

Phylogenetic Tree

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.

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Species: Hoplias lacerdae (top) and Hoplias aimara (bottom)

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Natural Variations

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.

Genetic Variations of Exemplary Organisms

1. Atlantic Blue Marlin

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.

2. Beluga Sturgeon

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.

3. Atlantic Giant Grouper

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.

Impact of Immigration/Emigration On Gene Flow

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.

Mating Habits Of Exemplary Organisms

1. Atlantic Blue Marlins

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.

2. Beluga Sturgeons

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.

3. Atlantic Giant Groupers

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.

Natural Selection of Exemplary Organisms

1. Atlantic Blue Marlins

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.

2. Beluga Sturgeon

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.

3. Atlantic Giant Grouper

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.

Reproductive Isolation

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.

How Geographic/Reproductive Isolation Has Affected Populations

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.

Punctuated Equilibrium or Gradualism?

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.

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Unifying Characteristics of Organisms in Kingdom Animalia

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

Taxonomic Classifications And Relatedness To Each Organism

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.

# data[].attributes.body
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