How did they evolve? During evolution of chordates, jaws and paired appendages appeared which launched adaptive radiations in the chordate groups. Convergent evolution also happened during this time which means some species have similar characteristics and behaviors as others.
How to they maintain their body temp? Chordates have learn to regulate their body temperature because it is very important to survive. There two main ways dates regulate their body temperature, these are Ectothermy and Endothermy. In Ectomy, the temperature of their environment determines the temperature of their bodies. In othermy, they generate heat from inside their bodies and also regulate that heat.
How do they feed, responses, excrete, circulate, move and respond? Most chordates are filter feeders, which means they move plankton from water through their pharynx. Aquatic chordates use gills for respiration. Land vertebrates have lungs that allow them to breathe. Gills are a form of single loop circulation, and lungs are considered as a double loop circulation. Invertebrates have simple nervous systems, while vertebrates have complex brains. How fish feed, respire, excrete, circulate, move and respond.
Feeding: Fishes have all different types of mode of feeding: herbivores carnivores parasites, filter feeders and detritus feeders. It depends on what type of food they eat. The passage of the fish’s digestive system is: mouth, esophagus, stomach (pyloric ceca- digestive enzymes and absorb nutrients) liver and pancreas which add enzymes. Digestion and nutrient absorption are complete by the intestine. Undigested foods are eliminated through the anus.
Respiration: Fish exchange gases using gills (made of filaments) and has a large space for exchange of O2 and CO2.Also, they have a single gill opening
Circulation: They have closed circulatory system with a single loop (heart→gills→rest of the body→heart). Their heart consist of four parts: sinus, venosus(collect blood from veins), atrium(one-way compartment for blood), ventricle (actual pumping portion of heart), and bulbus arteriosus (connects to aorta through gills)
Excretion:Fish get rid of the wastes in the form of ammonia and some waste diffuse through gills and kidneys. Kidneys help control amount of water in their bodies. Fishes in saltwater lose water by Osmosis.
Movement: Fish have an s shaped structure in their body traveling from head to tail that enables them to move easier with flexibility. the fins are used for balance and they are used to adjust direction. A swim bladder can inflate and therefore is used to adjust buoyancy.
Respond: Fish have well-developed nervous systems and sense organs. The nervous systems are organized around a brain. Cerebrum senses the smell. Cerebellum coordinates body movements. Medulla Oblongata controls many internal organs.The have Chemoreceptors which control the extraordinary senses of taste and smell. Lateral Line system detect gentle currents and vibrations in the water. It can sense the motion of other fishes to protect themselves.
Ecology of Fish Some fish spend a big part of their lives in the ocean and migrate to freshwater to breed. Fish with this behavior are called anadromous and include salmon, lampreys, and sturgeons. For example, salmon start their lives in streams then migrate to sea. After about four years, they to back to stream to spawn. They recognize their stream by smell. Other fish live their lives in freshwater and migrate to the ocean to breed. These fish are called catadromous. For example, eels live in rives then travel up to lay eggs. The eggs are then carried to shallow coastal waters by the currents then go to fresh water when they get older.
Groups of Fish and Characteristics The 3 different groups of fish are jawless fishes, sharks and their relatives, and bony fishes. Jawless fish have no teeth or jaws and they are split into two classes that are lampreys and hagfishes. Lampreys are filter feeders that have sucking disks to attach to their large host fishes. Hagfishes are wormlike and have a 4-6 tentacles around their mouth. Instead of using eyes, they use light sensors in their bodies. They feed on dead fish, have an open circulatory system, produce a lot of slime, have six hearts, and they tie themselves in knots. Sharks and their relatives include sharks,skates, rays, and some other unusual fish. These animals have skeletons made of cartilage and most also have toothlike scales. Most sharks have many big, sharp teeth but some others have more dull and small teeth like the basking shark. Some rays use vacuum like mouths to eat and some are filter feeders. They move by flapping their pectoral fins through the water. Bony fish have skeletons made of bone and most are ray-finned. There are a few bony fish that are considered lobe-finned. The lobe-finned fish include lungfishes which live in salt water and coelacanth that live in salt water. These fish have more substantial support bones in their fins.
Perch Dissection 1. The general body shape of the perch is oval. The body shows adaptations for life in water through its swim bladder and its gills which help it float and breathe.
2. One function of the gill rakers is they separate the gill arches from each other and create spaces between them. They also filter debris from the water to protect the gills
4. The scales point towards the tail. The advantage of this is that when it swims it is more hydrodynamic.
5. The perch has two nostril. They are different from our nostrils because they don’t use their nostrils for breathing but for just smell.
6. The characteristics that we can observe in the gills that make them an efficient respiratory organ are that they have a very large surface area to take in alot of oxygen.
7. The lateral line is to detect vibrations by predators that are threatening them and to detect in the changes in current and water pressure.
1. The endoskeleton is an advantage because it protects the organs and supports the body from the inside.
2. The guppy that fertilizes its eggs internally, produces fewer eggs because each egg has a greater chance of being fertilized. The survival rate between the two is about equal because although the perch produces more eggs, only a few of them get fertilized. The guppy produces less eggs, but most of them get fertilized.
3. The function of the swim bladder is to inflate the bladder so that it floats and can regulate the depth when it’s swimming.
4. These chemicals help them to scare off predators and to communicate.