Exam 2 BZ 214

What two groups make up Chondrichthyes

Elasmobranchi (sharks skates and rays) and Holocephali (chimaeras)

When did sharks originate?

The late Ordovician Period (>450 mya)

Derived characteristics of Chondrichthyes

cartilaginous skeleton, 5-7 gill slits, placoid scales, spiracle, enlarged olfactory capsules, pronounces (overhanging) snout, mechanism for tooth replacement, claspers in males and internal fertilization.

What are placoid scales homologous with?

teeth because they share the same mesoderm origin.

How many radiations in cartilaginous fish have there been?

3 but only one persists to today.

What traits did early elasmobranchs from the first radiation have?

large fins, keel so possibly fast open water swimmers, triangular pelvic and pectoral fins (stationary hydrofoil), terminal mouth, amphistylic jaw suspension, internal fertilization, caudal fin supported by fin rays.

When did the first radiation of Chondrichthyes take place?

From the Ordovician to the Triassic

When did the the second radiation of Chondrichthyes take place?

Carboniferous and extinct by late cretaceous 250 mya to 190 mya

What are the major changes associated with the second radiation?

more developed subterminal mouth, articulations in the internal supports of the paired fins, the internal skeleton has moveable parts and is more flexible, more pronounced heterocercal tail.

What is different about the paired fins in the second radiation?

They could rotate and change shape allowing for more control of movement.

How did the teeth look of Elasmobranchs in the second radiation and how did this best support them?

Heterodont so teeth with slashing teeth up front and crushing teeth in the back which allowed them to expand their diets.

What kind of jaw suspension did Elasmobranchs in the second radiation have?

amphystilic

What did the caudal fins of Elasmobranchs in the second radiation look like?

Larger upper lobe which made it stiffer and allowed for more forward thrust.

What did the caudal fins of Elasmobranchs in the first radiation look like?

Notochord in the upper lobe but largely supported by fin rays.

What did teeth in the first radiation of Elasmobranchs look like?

They had three cusps with a larger middle one. These teeth were replaced often and developed from a tooth whorl.

What type of jaw suspension did Elasmobranchs of the first radiation have?

amphistylic

What were the characteristics of the pectoral and pelvic fins in Elasmobranchs of the first radiation?

Triangular and broadly attached to body (stationary hydrofoil) so they could not move it to change position.

What feature did Elasmobranchs of the first radiation have in regards to their lifestyle?

A keel (at base of tail) that indiciates, fast open water swimming.

Did early elasmobranchs have small or large fins?

large

When did the third major radiation take place?

Early triassic - modern day (Cretaceous)

What kind of jaw suspension do Elasmobranchs of the third radiation have?

Hyostylic allows for jaw to be protruded forward.

What kind of scales were present in the third radiation?

placoid scales which make the skin feel rough but reduce drag.

What happened to the notochord during the third radiation?

It was replaced by a cartilaginous centra that calcify and neural and heal arches that protect the spinal cord.

Do sharks have a swim bladder?

No

How do sharks regulate buoyancy?

oily liver, fin placement, high blood urea concentration and light cartilaginous skeleton.

How did the sensory system change in the third radiation?

It became more developed and they receive enough info to be equal to tetrapods.

What is amphistylic jaw suspension?

upper jaw is braced against the cranium and is also supported by the hyomandibular

What is hyostylic jaw suspenion?

A type of jaw suspension seen in most fishes, in which the upper jaw is not directly connected to the cranium.

What are the four parts of sharks sensory systems?

Mechanoreception, Electroreception, Chemoreception, Vision

What is the order in which sharks use their senses when approaching prey?

Chemoreception → Mechanoreception → Visual → Electroreception

What does chemoreception allow sharks to do?

detect chemicals like blood in the water

How does mechanoreception work and what does mechanoreception allow a shark to do?

Neuromast cell receptors throughout the head of the shark (part of the lateral line system), plus detect vibrations in the inner ear. These allow the shark to key in on erratic movement and track prey.

How does a sharks vision work and what does it allow them to do?

Highly developed with the presence of a septum lucid that increases sensitivity in dim light can cover this to reduce sensitivity in bright light. They can cover the eye with a membrane during the final attack.

True or false, sharks can protect their eyes?

True! They have a membrane that covered eye during the final attack.

What is electroreception?

It is done through ampullae of Lorenzini receptors that allow the shark to detect prey by the electrical signals given off by the preys muscle contractions.

What kind of fertilization do sharks have?

Internal via claspers (in males)

True or False Elasmobranchs have only one form of parental investment?

False! Elasmobranchs have nearly ever type of paternal investment.

What happens if you flip a shark onto its back?

It goes into a coma like state which could be to help mating process (requires direct contact).

Why do different sharks have different teeth shapes?

Different food choices.

What kind of endotherms are sharks?

regional endotherms, so they keep some parts of their bodies warmer than the environment. Heat generated by muscles is kept in muscles which allows for higher muscle activity than prey.

What does the tooth whorl do in sharks?

It continuously replaces teeth, they must have the minerals to make teeth and this is energetically expensive.

What is a subterminal mouth and where do we see it?

It is seen in modern day sharks and allows the upper jaw to protrude out to get sensory organs out of the way.

What has happened through the three major radiations?

Sharks have adapted more advantageous body plans.

What is included in Elasmobranchi?

sharks, skates and rays.

What is included in Holocephali

chmaeras

How are skates different from rays?

Skates have a thick tail and are oviparous while rays have a thin tail and are viviparous.

What is leichotropy?

When the yolk provides nutrients for the developing embryo.

What is Matrotrophy?

Female reproductive tract provides energy for developing embryo.

What kinds of reproduction do most Elasmobranchs have?

oviparity and viviparity.

What is oviparity?

Eggs hatch in the oviduct and young feed on the yolk

What is viviparity?

young are born alive and are mini adults.

What does a yolk sac placenta do?

Passes on nutrients directly from the bloodstream of the mother to the bloodstream of the embryo.

Do Elasmobranchs produce few or many eggs?

few because eggs have large yolks.

Where are eggs deposited in oviparous forms?

in a sac that gets tangled up with algae , hatching can take months.

What kind of lifecycle do skates and rays have?

benthic so they undulate fins and chill on the sea floor

Do any elasmobranchs exhibit sexual dimorphism?

yes, skates and rays, females are larger than males (males must change teeth to grab females during breeding season)

How are Holocephali different from Elasmobranchs?

a single external gill opening, no spiracle, holostylic jaw suspension, no scales in adults, no stomach, no enamel, clasper is on head in males.

What is included in Holocephali?

ratfish and chimaeras

When did Holocpehali appear?

Jurassic

Where do holocephali live?

deep water.

What form of reproduction do holocephali do?

internal fertilization via claspers with oviparous (eggs laid in horny shell).

What does ovoviviparity mean?

Elasmobranchs that the eggs hatch in oviduct, young feed on yolk and energy from mom and they’re born alive.

What are some different ecological groups of Chondrichthyes?

coastal and open water

Where can the greatest diversity of sharks be found?

continental and insular shelves.

Is the open ocean a good habitat for sharks?

no, due to large space and low productivity compared to the continental shelf waters.

Are tiger sharks, whale sharks and basking sharks coastal or pelagic?

coastal, some can also be benthic.

Is the Greenland shark coastal or pelagic?

Pelagic

What are the ancestors of tetrapods and how?

Lobe finned fish, because the bones that extend into the lobes are homologous with bones in the legs of tetrapods.

What is the most likely explanation for the evolution of early tetrapods?

Predation on terrestrial invertebrates allowed the early tetrapods to exploit abundant food resources.

Did adults or juveniles of early tetrapods make the transition to land and why?

Juveniles because they were light and mobile enough to move about on land in pursuit of prey.

Does warm water have high or low oxygen content?

low, hypoxic water existed because gas solubility is inversely related to temperature. High temperature and little water movement led to low oxygen content and made organisms look to land.

How did the movement of the continents aid in the transition to land?

It exposed more shallow coastline leading to more interactions with land.

When organisms transitioned to land were outside temperatures high or low?

Still high but with a high oxygen content.

Did early vertebrates eat plants or other things?

Vertebrates cannot digest plant material without the aid of bacteria in their gut so they likely hunted insects early on.

What are three advantages to the invasion of land?

1. new food resources 2. Avoidance of aquatic predators and competitors 3. Oxygen is abundant

What did abundant oxygen on land lead to?

Higher metabolic rates since air is easier to move than water and breathing in water costed more energy.

What are three disadvantages to transition to land?

1. Water becomes a limiting factor in distribution (desiccation, respiration, reproduction) basically it is easier to dehydrate in air since now there is limited water. 2. Water provides good support even though its more difficult to move through air requires gravity and you must support your own body weight now. 3. Water has a high heat capacity and is very thermally stable so now you must find your own ways to keep heat in.

What happened to the bones and musculature of early tetrapods

They had to become bigger and thicker to support their own body weight which resulted in an increased metabolism and nutrient intake.

How did increased musculature and bone change how early tetrapods and amphibians move?

Pulled limbs underneath them allowing for independent movement of limbs.

How did early tetrapods and amphibians move?

Like how a fish swims without being able to independently move neck.

How did animals adapt to the drastic temperature changes that occurred on land?

Increased thermoregulation (endothermy), perspire when too much heat and release it by panting or sweating.

What are the costs of endothermy?

High metabolic rates because it takes a lot of energy to keep heat in, must hunt constantly to gain enough nutrients to support this, must put on more fat when they’re cold.

What is one benefit of endothermy?

They can hunt at any time regardless of environment or temperature.

What is happening to your proteins when you overheat?

They denature

What happens to a whale when its breached?

They have to feel their own body weight for the first time which puts a lot of pressure on internal organs and they are very well insulated so cook in their own skin.

What is a major difference between bone and cartilage?

Bone is vascularized which makes it a living tissue. It can receive direct blood flow.

Which is stronger, bones or cartilage?

Neither one is stronger than the other, is bone were stronger than sharks would be unable to bite through us.

What is the primary role of bone?

It provides support and movement via attachments for soft tissues and muscles.

What does bone protect?

vital organs

Does bone play a role in any major bodily processes?

yes! it aids in metabolism of minerals like calcium and phosphorus and is a site for red marrow which produces blood cells.

What are the two basic structural types of bone?

company and spongy

What does compact bone form?

The outer shell of all bones and the shafts in long bones.

What does sponges bone form?

The inside of bones and fills irregular ones. it is also found at the expanded heads of long bones.

What is the organic component of bone and what does it do?

collagen, gives strength.

What does bone formation begin with?

A blastema, embryonic mesenchymal cells that differentiate into tissue (muscle, cartilage or bone).

What do the blastema cells develop into?

Fibroblasts or osteoblasts.

What forms bone cells and what forms collagen cells?

Fibroblasts form collagen, osteoblasts form bone.

What forms the membrane bone?

Osteoblasts and fibroblasts together.

What is Intramembranous ossification?

Membrane bone formation

What takes place in in intramembranous bone formation?

increased vascularity, proliferation of mesenchymal cells, osteoblasts lay down osteoid, some osteoblasts become trapped as osteocytes, osteoid calcifies to become spicules of spongy bone, compact bone formed.