How Fishes Evolved
Fishes were the first vertebrates to ever evolve. Fishes and invertebrate chordates probably evolved from common invertebrate ancestors. Fishes evolved revolutionary traits during the course of their evolution. The most important developments were those of the jaw and paired fishes. The first fishes in the fossil record were jawless and had bodies that were covered in bony plates. These fishes lived in the late Cambrian Period (510 million years ago). The traits of these marine organisms would remain for 100 million years. The same fishes would survive into the Devonian Period, but would start to lose some of the bony armor of their Cambrian counterparts. Some that were armored would eventually become extinct at the end of the Devonian Period. Other armored fishes would begin to adapt jaws, a huge feeding advantage that revolutionized vertebrate evolution. The evolution of jaws would allow fishes to eat a wider variety of foods, such as plants and other animals as opposed to just filter feeding. This adaptation was also helpful in protection. Another revolutionary adaption was that of the paired anterior fins that were attached to girdles made of cartilage. Paired fins allowed fishes more control over body movement, as well as giving them powerful thrust while swimming.
How Fishes Feed, Respire, Circulate, Move, and Respond
Every mode of feeding is seen in fish. They can be herbivores, carnivores, parasites, filter feeders, and detritus feeders. Some fish can function in more than one eating way depending on what resources are available. Food passes from the fish’s mouth, through the esophagus, to the stomach where it is partially broken down. Depending on what kind of species the fish is, it is then either completely broken down in pouches called pyloric caeca, or the liver and pancreas. The intestine then completes the process of digestion and nutrient absorption. All undigested material is eliminated through the anus.
Most fishes exchange gases through the gills on either side of the pharynx. Filaments in the gills provide the area for the exchange of oxygen and carbon dioxide. Fish exchange gases by pulling oxygen-rich water in their mouths, pumping it through their gills and filaments, and then pushing oxygen-poor water out through side openings in the pharynx.
Fishes also have a closed circulatory system. Their heart consists of four parts: the sinus venosus, atrium, ventricle, and bulbus arteriosus. The heart pumps blood around the body in a single loop. The sinus venosus collects blood, the atrium serves as a one way compartment, the ventricle then actually pumps the blood the the large muscular tube, bulbus arteriosus. The blood then flows through a large blood vessel called the aorta, and then moves into the fish’s gills. This is the complete structure/blood path of the heart.
Like many other aquatics animals, most fish rid themselves of waste in the form of ammonia. Waste is either removed by kidneys or diffuses out through the gills. The kidneys help concentrate waste and return as much water as possible back to the body. Kidneys also pump out dilute urine. Some fish are even able to move from fresh to salt water by adjusting their kidney function.
Fishes have a well-developed nervous system organized around their brain. The fish’s brain has 5 different parts. The olfactory bulbs (sense of smell), cerebrum (voluntary body activities), optic lobe (process information from the eyes), cerebellum (coordinates body movements), medulla oblongata (controls functioning of internal organs), and they all lead to the spinal cord. Most fish have highly developed sense organs and are active in daylight. Fish use the lateral line system (vibrations and currents in the water) to detect the motion of other fish and prey swimming by. Some fish even have systems that can sense low levels of electric current or generate their own electricity.
Most fish move by using muscles on either side of the backbone. This causes the fish’s body to move in “S-shaped” curves. As the curves travel from the head toward the tail fin, it creates backward force on the water. This force and the action of the fins is what propels the fish forward. FIns help keep the fish on course, adjust direction, and speed. The streamlined body shape of the fish helps reduce friction as they move through the water.
Many fish also have an internal swim bladder with allows them to adjust their buoyancy, making them sink or float. They need this swim bladder because their bodies are more dense than the water around them so without it, they would sink.The swim bladder is located just beneath the backbone.
How Fishes Maintain Body Temperature
Fishes have to constantly maintain a constant warm blood pressure. Even though they are cold blooded (which means their body temp varies from external temp) they produce this thing called metabolic heat. Which is created from the “burning” of food. But the blood loses a lot of heat when passing through the gills so their body temperature is usually only one or two degrees off of the water. But some fish are warm blooded and are able to keep their body temperature way above the water temperature. What it really comes down to is what kind of fish are you talking about.
Types of Fish and How They Are Different
All living fishes can be classified into three groups: jawless fishes, cartilaginous fishes, and bony fishes. Jawless fishes have no [true] teeth or jaws and their skeletons are composed of fibers and cartilage. They also do not have vertebrae. Instead, jawless fishes keep their notochords into adulthood. Current jawless fishes are distributed into two groups: lampreys and hagfishes. Lampreys are usually filter feeders as larvae and parasites when they mature. An adult lampreys head is almost completely taken up by a circular sucking disk with a round mouth at the center. They usually attach themselves to other fishes. They then suck up the tissues and body fluids of the host, Hagfishes have wormlike bodies and have four to six tentacles around their mouths. Because they do not have eyes, hagfishes have evolved light-sensitive detectors on their bodies. They eat dead and perishing fishes using a toothed tongue. Hagfishes secrete high amounts of slime, have six hearts, and have an open rather than closed circulatory system. Cartilaginous fishes have skeletons made up of cartilage, as the name suggests.
Ecology of Fish
There are two types of fish when it comes to migrating, laying eggs and mating.
anadromous is one type of fish that is born in freshwater then migrate and spend most of their life in salt water and when it comes the time to mate they travel back to the place of their birth and mate. Their journey can take several months and they travel up to 3,200 kilometers. The other type of fish is called a catadromous. This type of fish are live in freshwater but migrate to salt water to mate. They travel up to 4800 kilometer to find the right mating place. The eggs are then carried by the current to shallow coastal waters.
Fishes were the first vertebrates to ever evolve. Fishes and invertebrate chordates probably evolved from common invertebrate ancestors. Fishes evolved revolutionary traits during the course of their evolution. The most important developments were those of the jaw and paired fishes. The first fishes in the fossil record were jawless and had bodies that were covered in bony plates. These fishes lived in the late Cambrian Period (510 million years ago). The traits of these marine organisms would remain for 100 million years. The same fishes would survive into the Devonian Period, but would start to lose some of the bony armor of their Cambrian counterparts. Some that were armored would eventually become extinct at the end of the Devonian Period. Other armored fishes would begin to adapt jaws, a huge feeding advantage that revolutionized vertebrate evolution. The evolution of jaws would allow fishes to eat a wider variety of foods, such as plants and other animals as opposed to just filter feeding. This adaptation was also helpful in protection. Another revolutionary adaption was that of the paired anterior fins that were attached to girdles made of cartilage. Paired fins allowed fishes more control over body movement, as well as giving them powerful thrust while swimming.
How Fishes Feed, Respire, Circulate, Move, and Respond
Every mode of feeding is seen in fish. They can be herbivores, carnivores, parasites, filter feeders, and detritus feeders. Some fish can function in more than one eating way depending on what resources are available. Food passes from the fish’s mouth, through the esophagus, to the stomach where it is partially broken down. Depending on what kind of species the fish is, it is then either completely broken down in pouches called pyloric caeca, or the liver and pancreas. The intestine then completes the process of digestion and nutrient absorption. All undigested material is eliminated through the anus.
Most fishes exchange gases through the gills on either side of the pharynx. Filaments in the gills provide the area for the exchange of oxygen and carbon dioxide. Fish exchange gases by pulling oxygen-rich water in their mouths, pumping it through their gills and filaments, and then pushing oxygen-poor water out through side openings in the pharynx.
Fishes also have a closed circulatory system. Their heart consists of four parts: the sinus venosus, atrium, ventricle, and bulbus arteriosus. The heart pumps blood around the body in a single loop. The sinus venosus collects blood, the atrium serves as a one way compartment, the ventricle then actually pumps the blood the the large muscular tube, bulbus arteriosus. The blood then flows through a large blood vessel called the aorta, and then moves into the fish’s gills. This is the complete structure/blood path of the heart.
Like many other aquatics animals, most fish rid themselves of waste in the form of ammonia. Waste is either removed by kidneys or diffuses out through the gills. The kidneys help concentrate waste and return as much water as possible back to the body. Kidneys also pump out dilute urine. Some fish are even able to move from fresh to salt water by adjusting their kidney function.
Fishes have a well-developed nervous system organized around their brain. The fish’s brain has 5 different parts. The olfactory bulbs (sense of smell), cerebrum (voluntary body activities), optic lobe (process information from the eyes), cerebellum (coordinates body movements), medulla oblongata (controls functioning of internal organs), and they all lead to the spinal cord. Most fish have highly developed sense organs and are active in daylight. Fish use the lateral line system (vibrations and currents in the water) to detect the motion of other fish and prey swimming by. Some fish even have systems that can sense low levels of electric current or generate their own electricity.
Most fish move by using muscles on either side of the backbone. This causes the fish’s body to move in “S-shaped” curves. As the curves travel from the head toward the tail fin, it creates backward force on the water. This force and the action of the fins is what propels the fish forward. FIns help keep the fish on course, adjust direction, and speed. The streamlined body shape of the fish helps reduce friction as they move through the water.
Many fish also have an internal swim bladder with allows them to adjust their buoyancy, making them sink or float. They need this swim bladder because their bodies are more dense than the water around them so without it, they would sink.The swim bladder is located just beneath the backbone.
How Fishes Maintain Body Temperature
Fishes have to constantly maintain a constant warm blood pressure. Even though they are cold blooded (which means their body temp varies from external temp) they produce this thing called metabolic heat. Which is created from the “burning” of food. But the blood loses a lot of heat when passing through the gills so their body temperature is usually only one or two degrees off of the water. But some fish are warm blooded and are able to keep their body temperature way above the water temperature. What it really comes down to is what kind of fish are you talking about.
Types of Fish and How They Are Different
All living fishes can be classified into three groups: jawless fishes, cartilaginous fishes, and bony fishes. Jawless fishes have no [true] teeth or jaws and their skeletons are composed of fibers and cartilage. They also do not have vertebrae. Instead, jawless fishes keep their notochords into adulthood. Current jawless fishes are distributed into two groups: lampreys and hagfishes. Lampreys are usually filter feeders as larvae and parasites when they mature. An adult lampreys head is almost completely taken up by a circular sucking disk with a round mouth at the center. They usually attach themselves to other fishes. They then suck up the tissues and body fluids of the host, Hagfishes have wormlike bodies and have four to six tentacles around their mouths. Because they do not have eyes, hagfishes have evolved light-sensitive detectors on their bodies. They eat dead and perishing fishes using a toothed tongue. Hagfishes secrete high amounts of slime, have six hearts, and have an open rather than closed circulatory system. Cartilaginous fishes have skeletons made up of cartilage, as the name suggests.
Ecology of Fish
There are two types of fish when it comes to migrating, laying eggs and mating.
anadromous is one type of fish that is born in freshwater then migrate and spend most of their life in salt water and when it comes the time to mate they travel back to the place of their birth and mate. Their journey can take several months and they travel up to 3,200 kilometers. The other type of fish is called a catadromous. This type of fish are live in freshwater but migrate to salt water to mate. They travel up to 4800 kilometer to find the right mating place. The eggs are then carried by the current to shallow coastal waters.