BIO 152 Week 11

Chondrichthyes: Cartilaginous Fishes

- Chondrichthyes are diverse group, consisting of sharks, rays, and skates, together with sawfishes and a few dozen species of fishes called chimaeras, or "ghost" sharks - Chondrichthyes are jawed fishes that possess paired fins and a skeleton made of cartilage. They are thought to be descended from the placoderms, which had skeletons made of bone thus, the cartilaginous skeleton of Chondrichthyes is a later development - Most cartilaginous fishes live in marine habitats, with a few species living in fresh water for a part or all of their lives. Shark teeth likely evolved from the jagged scales that cover their skin, called placoid scales.

Gnathostomes two fins

- Early gnathostomes also possessed two sets of paired fins, allowing the fishes to maneuver accurately - Pectoral fins are typically located on the anterior body, and pelvic fins on the posterior. - Evolution of the jaw and paired fins permitted gnathostomes to expand from the sedentary suspension feeding of jawless fishes to become mobile predators. - The ability of gnathostomes to exploit new nutrient sources likely is one reason that they replaced most jawless fishes. -nJaws are also thought to have play a role in improving the efficiency of respiration, aiding in moving water over the gills. Most modern fishes are gnathostomes that belong to the clades Chondrichthyes (cartilaginous fishes) and Osteichthyes (bony fishes).

Osteichthyes: Bony Fishes

- Members of the clade Osteichthyes, also called bony fishes, are characterized by a bony skeleton. The vast majority of present-day fishes belong to this group, which consists of approximately 30,000 species, making it the largest class of vertebrates in existence today. - Nearly all bony fishes have an ossified skeleton with specialized bone cells (osteocytes) that produce and maintain a calcium phosphate matrix - The skin of bony fishes is often covered by overlapping scales, and glands in the skin secrete mucus that reduces drag when swimming and aids the fish in osmoregulation. - Like sharks, bony fishes have a lateral line system that detects vibrations in water. - All bony fishes use gills to breathe. Water is drawn over gills that are located in chambers covered and ventilated by a protective, muscular flap called the operculum. - Many bony fishes also have a swim bladder, a gas-filled organ that helps to control the buoyancy of the fish - Bony fishes are further divided into two extant clades: Actinopterygii (ray-finned fishes) and Sarcopterygii (lobe-finned fishes). - Actinopterygii, the ray-finned fishes, include many familiar fishes—tuna, bass, trout, and salmon, among others. Ray-finned fishes are named for their fins that are webs of skin supported by bony spines called rays. - In contrast, the fins of Sarcopterygii are fleshy and lobed, supported by bone . Living members of this clade include the less-familiar lungfishes and coelacanths.

Gnathostomes: Jawed Fishes

- One of the most significant developments in early vertebrate evolution was the development of the jaw, which is a hinged structure attached to the cranium that allows an animal to grasp and tear its food - Gnathostomes or "jaw-mouths" are vertebrates that possess jaws. The evolution of jaws allowed early gnathostomes to exploit food resources that were unavailable to jawless fishes.

Explain why sponges and Cnidarians do not need complex circulatory systems

- The simplest animals, such as the sponges (Porifera) and rotifers (Rotifera), do not need a circulatory system because diffusion allows adequate exchange of water, nutrients, and waste, as well as dissolved gases. - Organisms that are more complex but still only have two layers of cells in their body plan, such as jellies (Cnidaria) and comb jellies (Ctenophora) also use diffusion through their epidermis and internally through the gastrovascular compartment - Both their internal and external tissues are bathed in an aqueous environment and exchange fluids by diffusion on both sides . Exchange of fluids is assisted by the pulsing of the jellyfish body. - For more complex organisms, diffusion is not efficient for cycling gases, nutrients, and waste effectively through the body; therefore, more complex circulatory systems evolved - the circulatory system is effectively a network of cylindrical vessels: the arteries, veins, and capillaries that emanate from a pump, the heart. Thus the circulatory systems is a mechanism of bulk flow of molecules in animals.

What is likely to have been the selection pressure that led to the evolution of jaws and paired fins?

- enhanced swimming capacity (speed and maneuvering) - increased ability to capture needed resources (food)

Describe the limitations of an open circulatory system

- in an open system, an elongated beating heart pushes the hemolymph through the body and muscle contractions help to move fluids - In an open circulatory system, the blood is not enclosed in the blood vessels but is pumped into a cavity called a hemocoel and is called hemolymph because the blood mixes with the interstitial fluid. - As the heart beats and the animal moves, the hemolymph circulates around the organs within the body cavity and then reenters the hearts through openings called ostia- This movement allows for gas and nutrient exchange - An open circulatory system does not use as much energy as a closed system to operate or to maintain; however, there is a trade-off with the amount of blood that can be moved to metabolically active organs and tissues that require high levels of oxygen. CLOSED: - In a closed circulatory system, blood is contained inside blood vessels and circulates unidirectionally from the heart around the systemic circulatory route, then returns to the heart again. - Arthropods, bivalves and gastropods all have open circulatory systems, while annelids and cephalopods have closed systems - All vertebrates have closed circulatory systems. There is however, variation in the structure and complexity of their systems, which reflect diversity in body plans, habitats and body size

What are unique adaptations of the circulatory systems of crocodiles?

-two main arteries that leave the heart but go to different parts of the body - specialized tissues that slow blood flow to the lungs - a hole in the heart between the two ventricles allowing blood flow between them Crocodiles and alligators are the most primitive animals to have a four chambered heart. The additional adaptations in blood flow also allow them to remain submerged for extended periods of time. This enhances their abilities as predators.

The phylogenetic tree shown here displays the major groups of chordates. Which of the statements below about this phylogenetic tree are true?

Jaws evolved before lungs and lobed fins Notochords evolved before craniums (heads on this tree) Organisms with vertebral columns have notochords

The phylogenetic tree shown here displays the major clades of chordates. Which of the statements below about this phylogenetic tree are true?

Organism (a) is a common ancestor of all chordates Rays and frogs have a vertebral column Birds and ray-finned fishes have a notochord and jaws Descendents of organism (d) have legs

What do all craniates have that earlier chordates did not have?

Partial or complete skull

Explain the differences between single circuit and two circuit circulatory systems

SINGLE -fish: The atrium collects blood that has returned from the body and the ventricle pumps the blood to the gills where gas exchange occurs and the blood is re-oxygenated; this is called gill circulation. - The blood then continues through the rest of the body before arriving back at the atrium; this is called systemic circulation - This unidirectional flow of blood produces a gradient of oxygenated to deoxygenated blood around the fish's systemic circuit -The result is a limit in the amount of oxygen that can reach some of the organs and tissues of the body, reducing the overall metabolic capacity of fish. TWO CIRCUIT - In amphibians, reptiles, birds, and mammals, blood flow is directed in two circuits: one through the lungs and back to the heart, which is called pulmonary circulation - the other throughout the rest of the body and its organs including the brain (systemic circulation) - In amphibians, gas exchange also occurs through the skin during pulmonary circulation and is referred to as pulmocutaneous circulation.

Compare the advantages of a two chamber, three chamber and four chamber heart

TWO: - Fish have a single circuit for blood flow and a two-chambered heart that has only a single atrium and a single ventricle - Fish have a two-chambered heart with unidirectional circulation. THREE *amphibians* - Amphibians have a three-chambered heart, which has some mixing of the blood, and they have double circulation - Amphibians have a three-chambered heart that has two atria and one ventricle rather than the two-chambered heart of fish - The two atria (superior heart chambers) receive blood from the two different circuits (the lungs and other body systems), and then there is some mixing of the blood in the heart's ventricle (inferior heart chamber), which reduces the efficiency of oxygenation - The advantage to this arrangement is that high pressure in the vessels pushes blood to the lungs and body - The mixing is mitigated by a ridge within the ventricle that diverts oxygen-rich blood through the systemic circulatory system and deoxygenated blood to the pulmocutaneous circuit. For this reason, amphibians are often described as having double circulation. *reptiles* - Most non-avian reptiles have a three-chambered heart, but have little mixing of the blood; they have double circulation. - Most reptiles also have a three-chambered heart similar to the amphibian heart that directs blood to the pulmonary and systemic circuits - The ventricle is divided more effectively by a partial septum, which results in less mixing of oxygenated and deoxygenated blood - One adaptation includes two main arteries that leave the same part of the heart: one takes blood to the lungs and the other provides an alternate route to the stomach and other parts of the body - two other adaptations include a hole in the heart between the two ventricles, called the foramen of Panizza, which allows blood to move from one side of the heart to the other, and specialized connective tissue that slows the blood flow to the lungs. Together these adaptations have made crocodiles and alligators one of the most evolutionarily successful animal groups on earth. FOUR: - Mammals and birds have a four-chambered heart with no mixing of the blood and double circulation. - In mammals and birds, the heart is also divided into four chambers: two atria and two ventricles - The oxygenated blood is separated from the deoxygenated blood, which improves the efficiency of double circulation and is probably required for the warm-blooded lifestyle of mammals and birds. - The four-chambered heart evolved independently from three chambered hearts in birds and mammals. The independent evolution of the same or a similar biological trait is referred to as convergent evolution

Which of the following statements about common features of chordates is true?

The dorsal hollow nerve cord is part of the chordate central nervous system.

Which of the following is true of the Chordates?

They are coelomates They are deuterostomes They have bilateral symmetry

Why are open circulatory systems advantageous to some animals?

They use less metabolic energy. The limitation is that an open system has a hard time getting the oxygenated fluid to the specific cells that need it the most.

Contrast the circulatory systems of amphibians and reptiles

amphibians: - Amphibians have a three-chambered heart that has two atria and one ventricle rather than the two-chambered heart of fish. The two atria (superior heart chambers) receive blood from the two different circuits (the lungs and other body systems), and then there is some mixing of the blood in the heart's ventricle (inferior heart chamber), which reduces the efficiency of oxygenation. The advantage to this arrangement is that high pressure in the vessels pushes blood to the lungs and body. The mixing is mitigated by a ridge within the ventricle that diverts oxygen-rich blood through the systemic circulatory system and deoxygenated blood to the pulmocutaneous circuit. For this reason, amphibians are often described as having double circulation. reptiles: - Most reptiles also have a three-chambered heart similar to the amphibian heart that directs blood to the pulmonary and systemic circuits . The ventricle is divided more effectively by a partial septum, which results in less mixing of oxygenated and deoxygenated blood - Some reptiles (alligators and crocodiles) are the most primitive animals to exhibit a four-chambered heart. - Crocodilians have a unique circulatory mechanism where the heart shunts blood from the lungs toward the stomach and other organs during long periods of submergence, for instance, while the animal waits for prey or stays underwater waiting for prey to rot. - One adaptation includes two main arteries that leave the same part of the heart: one takes blood to the lungs and the other provides an alternate route to the stomach and other parts of the body. - two other adaptations include a hole in the heart between the two ventricles, called the foramen of Panizza, which allows blood to move from one side of the heart to the other, and specialized connective tissue that slows the blood flow to the lungs - Together these adaptations have made crocodiles and alligators one of the most evolutionarily successful animal groups on earth.

In gill circulation in fishes, the_______collects_____________blood that has returned from the body and the__________pumps the blood to the gills where the blood is__________.

atrium; de-oxygenated; ventricle; re-oxygenated

Which of the following is true of closed circulatory systems?

blood distribution is equal to tissues and regulated blood is moved a high pressures the volume of blood move is smaller than closed systems In closed circulatory systems, the blood remains within vessels/veins/arteries.

In which group(s) of organisms is oxygenated blood completed separated from de-oxygenated blood?

crocodiles, mammals and birds

By what process do flatworms, which are acoelomate animals, move gases and nutrients?

diffusion

????Amphibians have a___________circulatory system. Blood travels from the_________to the________to become oxygenated, and then back to the________. This circuit is called the_________.In birds, blood only goes to the_________to gain oxygen.

double circuit; heart; lungs/skin; heart; pulmocutaneous circuit; lungs blood travels from the heart to the lungs/skin and back to the heart to become oxygenated and it is then pumped out to the body and goes back to the heart

In addition to the ability to capture prey more effectively, what other benefit did jaws provide?

enhanced gas exchange in gills

Teeth are thought to be an exaptation of what structure?

epidermal scales

What characteristics of closed circulatory systems enable some animals to become very large?

equal and regulated distribution of nutrients and gases increase pressure and flow rates of blood Remember that closed systems have both a pump and different sizes of tubes. Larger pumps that are connected to increasing smaller tubes as the blood moves away from the pump allow the maintenance of pressure. (Pressure increases as the tube gets smaller and smaller)

Craniates are the first group of animals where we see the evolution of a head containing sensory organs.

false

What types of circulatory systems are found among invertebrate animals?

gastrovascular circulation open circulation simple diffusion closed circulation

What traits do the Osteichthyes share?

hey have paired fins they have ossified skeletons they have swim bladders

There a four shared features of Chordates. Match the feature with the appropriate characteristic or function.

in invertebrate chordates can be involved in filtering food from water ingest through the mouth: pharyngeal slits found between the digestive tract and nerve cord: notochord in some embryos this develops into the central nervous system: dorsal hollow nerve cord

There a four shared features of Chordates. Match the feature with the appropriate characteristic or function.

in jawed fish this provides support for the jaw: pharyngeal slits is derived from the ectoderm: dorsal hollow nerve cord provides skeletal support: notochord

Which of the three embryonic tissue layers gives rise to the circulatory system?

mesoderm

What is the key limitation of an amphibian circulatory system?

mixing of oxygenated and de-oxygenated blood in the heart

Which of the following are part of an open circulatory system?

ostia hemocoel hemolymph heart In open circulatory systems, the heart(s) pump hemolymph into the body cavity (hemocoel). The hemolymph is then taked up through ostia to be reoxygenated and recirculated.

What are the advantages of a cranium and vertebrae?

protection of brain and support for the body

In what type of blood flow is the blood directed through the lungs and back to the heart?

pulmonary circulation

Diffusion is the primary source of gas exchange for what groups of animals?

sponges (Porifera) jellyfish (Cnidaria)

Which of the following is true of open circulatory systems?

the hemolymph bathes the tissues and organs directly they have a highly efficient pump (true heart) they generally operate under low pressure

How is the amphibian circulation system is unique from other closed systems?

there is no septum between the atrium and ventricle the pulmonary circuit includes the skin *Reptiles have a three chambered heart, a partial septum, and do not use their skin to oxygenate their blood*

What traits do the Chondrichthyes share?

they have cartilaginous skeletons they have paired fins they are all jawed fish

All chordates have three germ layers (are triploblastic) and are deuterostomes.

true

In insects the circulatory system is NOT responsible for delivering oxygen to tissues.

true

Mixing of blood with interstitial (body) fluids occurs in both open systems and in closed systems with two and three chambered hearts.

true

The four chambered hearts of birds and mammals evolved from a common ancestor with a four chambered heart.

true

The vertebrate skeleton evolved initially as a structure made out of unmineralized cartilage.

true

Invertebrates with open circulatory systems have_______that have_________muscles and are capable of producing_______pumping forces.

true hearts; striated; strong Open circulatory systems still need a good pumping systems to move the blood (hemolymph).

In adult vertebrates the______ replaces the _______

vertebral column; notochord