Zoology Exam 3

Phylum Chordata exhibit what characteristics?

• gill slits

• notochord

• nerve cord

• post-anal tail

• endostyle

Phylum Hemichordata exhibits what characteristics?

• gill slits

• analogous notochord

Subphylums in Phylum Chordata

• Urochordata

• Cephalochorda

• Vertebrata

Classes in Phylum Hemichordata

• Enteropneusta

• Pterobrachia

In Subphylum Vertebrata, jawless agnathans contain what classes?

• Class Myxini (“slimy fish”, hagfish)

• Class Cephalaspidomorphi (lampreys)

In Subphylum Vertebrata, jawed gnathostomes contain what classes?

• Class Chondrichthyes (cartilaginous fish)

• Class Osteichthyes (bony fish)

In Class Myxini and Cephalaspidomorphi, what happens to the 5 chordate characteristics?

• The Notochord is retained in adults

• Endostyle becomes a thyroid-like endocrine gland

• Has a post-anal tail and gill slits & dorsal hollow nerve cord across life stages

In Class Myxini and Cephalaspidomorphi, Respiratory gasses are
exchanged with the water at the site of the…

Gill sacs

Class Myxini exhibit sensory ____ around the mouth

Barbels

Class Myxini are called “slime eels” because…

They secrete slime from slime glands

Class Cephalaspidomorphi are anadromous, meaning…

They are born & grow in freshwater, migrate to the ocean to mature (parasitic life stage for
lamprey), and return to freshwater to spawn

How do organisms in Class Myxini and Cephalaspidomorphi get nutrients?

Class Myxini: Detrivores that absorb nutrients through skin and gills (no stomach)

Class Cephalaspidomorphi: Filter feeders in larval stage, parasites with simple digestive tract in adult stage

Do organisms in Class Myxini and Cephalaspidomorphi have jaws?

No, they are agnathans (jawless)

What kind of fins do organisms in Class Myxini and Cephalaspidomorphi have?

Class Myxini: No paired fins; one fleshy dorsal/caudal/ventral fin (similar to that of a lancelet)

Class Cephalaspidomorphi: No paired fins; fleshy dorsal fins that extend to form an adjoining caudal fin

Do organisms in Class Myxini and Cephalaspidomorphi have skulls? What are they made of?

Both possess a cartilaginous skull

Do organisms in Class Myxini and Cephalaspidomorphi have vertebral columns? What are they made of?

Class Myxini: some rudimentary vertebrae, but no true vertebral column

Class Caphalaspidomorphi: Cartilaginous vertebrae

Do organisms in Class Myxini and Cephalaspidomorphi have scales?

Neither possess scales, they are smooth bodied

Do organisms in Class Myxini and Cephalaspidomorphi have gill opercula?

No, they both possess gill pouches

What do gill arches do?

Function as support structures for gill filaments (high
surface area site of gas exchange)

Where did jaw bones evolve from?

The gill arches closest to the mouth

What is the adaptive value of a jaw?

• Enables more water to flow over the gills

•  Enables biting /ripping of prey

• Enables sucking

• Radiation of jaw shapes and forms to suit many niches

What are some structures that agnathans don’t have, but BOTH Chondrichthyes & Osteichthyes have?

• Jaws

  • Modified gill arches

  • Suspended from skull by
    ligaments

• Paired fins

  • Pectoral fins & pelvic fins

  • Evolved as stabilizers for
    swimming

What organisms are apart of Class Chondrichthyes?

Sharks, rays, skates and chimaeras

What are the 5 important characteristic of Class Chondrichtheys?

• they have paired fins & jaws

• Spiral intestinal valve

• Placoid scales - tough scales found on
  cartilaginous fishes

• 5 – 7 pairs of gill slits without opercula
  (except for chimeras, which are weird)

• Endoskeleton of cartilage

Some cartilaginous fish rely on ram ventilation, which is?

mouth is open and water is forced over the gills by forward movement of the whole animal

Many cartilaginous fish can breath through spiracles, which are?

a pair of round openings behind the eye. This allows them to breathe while motionless.

What is Concurrent (or cocurrent) gas exchange?

• blood & water flow in the same direction (ancestral state)

• max PO2 in the blood is the PO2 in the water leaving the gills

What is Countercurrent gas exchange?

• blood & water flow in opposite directions (derived state)

• max PO2 in the blood is MUCH HIGHER than the PO2 in the water leaving
  the gills

All fish will gills use countercurrent gas exchange at the site of the gills!

What type of circulation do Class Chondrichthyes have?

Closed circulatory system with 2 chamber heart

What do some species in Class Chondrichtheys have to protect their eyes while feeding?

nictitating membranes

What is the lateral line system used by Class Chondrichtheys?

A series of pores & canals lined with cells called neuromasts specialized to detect vibrations

What is the Ampullae of Lorenzini in Class Chondrichtheys?

A sensory organs in the head that detect electrical charges (≤0.5m away), important in detecting prey

How do Class Chondrichtheys achieve neutral buoyancy?

They use their large oil-rich livers

How do cartilaginous fish reduce water loss?

They retain urea in the blood, the amount of which is controlled by the kidneys. Excess salts excreted by kidneys, intestines and rectal gland (sometimes called a “salt gland”). This allows them to absorb water through the gills to prevent dehydration.

Some cartilaginous fish are called “euryhaline”, meaning?

They are found primarily in estuarine environments were salinity changes regularly

Class Chondrichtheys exhibit what type of reproduction?

They are dioecious (2 different sexes) with internal fertilization. Males have claspers and females have cloacas. Some species are oviparous or “egg laying”. Some are viviparous meaning the give live birth. Some exhibit Ovoviviparity or “yolk sac
viviparity”, and others exhibit Placental viviparity

In Class Chondrichtheys, what is oophagy?

Embryos eating eggs while still in the uterus.

What is Intrauterine cannibalism?

When the largest embryo eats the other embryos

Why is it so important that cartilaginous fish are conserved?

• Low fecundity: few offspring produced each cycle

• Long gestation: time embryos spend developing

• Slow growth

• No parental care

In Class Chondrichtheys Subclass Elasmobranchii, what type of body do organisms have?

A fusiform body (can swim fast), and a well-developed, often heterocercal tail

What are the common names of the organism in Class Chondrichtheys, Subclass Holocephali?

Chimeras, ratfishes, elephant fishes, ghost sharks

What is the overall importance of cartilaginous fishes?

• Top predators in many environments

• Keystone species in many ecosystems

  • disproportionately large effects on their biotic environment relative to their own biomass

  • their removal could cause whole ecosystems to collapse

• Cultural value

• Ecotourism

What are Class Osteichtheys general characteristics?

• Have a skull and vertebrae made of bone

• Have jaws

• Paired fins

• Have hardened operculum (gill cover)

• Have a swim bladder: gas-filled sac for buoyancy and/or respiration

In Class Osteichtheys, the size of intestines vary depending on prey type:

• Predators have short, straight intestines

• Herbivores and detritivores have long, coiled intestines

Most bony fishes have a circulatory system very similar to that of the cartilaginous fishes:

• 2-chambered heart pumps deoxygenated blood

• Singular closed circuit going to gills then rest of body and back to heart

In Class Osteichtheys, gill structure is similar to cartilaginous fishes:

• Gills on each side covered by an operculum

• Gill arch provides support in the gills

• Gill rakers project the inner surface of the gill

• Gill filaments trail behind the gill arch

Organisms in Class Osteichtheys have gills with filaments containing lamellae or…

Rows of thin plates or disks which contain capillaries. blood in these capillaries flows in the opposite direction as the water passing over them (counter-current gas exchange)

How do fish in Class Osteichtheys achieve buoyancy?

• Physoclistous fish do it by adding dissolved O2 collected from the water (from the blood into the swim-bladder). These fish lack a pneumatic duct and regulate the volume of the swim bladder by excreting gas from the blood into the bladder

• Physostomous fish can do this but can also gulp air at the surface to fill the swim bladder. They control how much gas enters the swim bladder via a “gas gland", which secretes lactic acid and causes localized high acidity in the blood; forcing hemoglobin to release oxygen. To reduce volume of gas, they open a muscular valve called an “ovale”, in the swim bladder that is adjacent to a capillary bed; O2 diffuses into the blood.

How do bony fishes smell, taste, see, and hear?

• They have 2 nares (nostrils) that open into chambers lined with sensory pads called olfactory rosette

• They have taste buds on the tongue, lips, mouth, and if present, barbels

• Nocturnal fish have larger eyes and pupils than diurnal fish

• Their ears have 2 fluid-filled sacs lined with hairs; within the lower part of each sac are otoliths (ear bones) that vibrate, stimulating hair cells with mechanoreceptors at the base

How do bony fish feel and orient themselves?

• Otoliths used for orientation

• Like cartilaginous fish, they have lateral lines to detect vibrations

How do marine bony fish osmoregulate?

They drink large amounts of sea water and produce highly concentrated urine. They actively (using ATP) pump out excess salts via kidneys, intestines, and gills.

How do marine bony fish osmoregulate?

They produce large amounts of very dilute urine; pumping excess water out of their body. They have special salt-absorbing cells in the gills actively (using ATP) transfering salt from the water to the blood, replacing salt lost via diffusion.

Some organisms in Class Osteichtheys are sequential hermaphrodites, specifically exhibiting protandry and protogyny, meaning…

• Protandry is the chronological
  change from male to female;
  anemone fish

• Protogyny is the chronological
  change from female to male; wrasse

Some organisms in Class Osteichtheys, Subclass Actinopterygii exhibit visual defenses such as…

• Cryptic coloration: blending in with the environment

• Disruptive coloration: uses colorful stripes, bars, spots to break up their outline to confuse predators

• Countershading: a distinctive color pattern found in open water fishes (and other organisms) used as camouflage. Ventral side is silver or white, dorsal is dark (ex. tuna)

Unique characteristic of Class Osteichtheys, Subclass Actinopterygii:

• paired and median fins are both very flexible

• Muscles controlling fin movement are within the body (not in the fin itself)

• Fins consist of membranes of skin stretched between long, dermal rays or spines.

• Fin rays are soft. segmented and branching

• Spines are hard, pointy, stuff and non-segmented

Most organisms in Class Osteichtheys, Subclass Actinopterygii have homocercal tails, meaning:

The upper and lower lobes of the caudal fin are roughly the same size

Certain primitive lineages of ray-finned fish have non-overlapping, ___ scales that have a diamond shape

Ganoid

Most actinopterygian species (ray-finned fishes) have a type of overlapping scales:

• Cycloid scales - smooth overlapping scales

• Ctenoid scales - tiny spines exposed on the edge of the scales, overlapping

What are the unique features of Class Osteichtheys, Subclass sarcopterygians?

• Fleshly fins with muscles &
  bones inside of them

  • Paired fins have skeletal elements
    homologous to tetrapod forelimb

•  Diphycercal tails

• Highly modified swim bladders

• Cosmoid scales

In Class Osteichtheys, Subclass Sarcopterygii, scales are cosmoid, meaning?

Thin enamel outer layer produced in the epidermis
– Thick inner bone layer produced by the dermis
– Early tetrapods (fossils) appear to have this scale type

Which Subclass contains fish thought to be the ancestors of all tetrapods?

Subclass Sarcopterygii

What are some challenges early tetrapods faced? What are some advantages they were afforded in terrestrial environments?

Challenges:

• Lower fluid density

• Constant risk of drying out through skin or eggs

• Air tempurature fluctuations

Benefits:

• Oxygen density is higher

• Easier to keep a body temperature separate from air temp than from water temp.

What are 4 sarcopterygian “pre-adaptations” enabling the evolution of life on land?

• Air filled cavity

  • vascularized swim bladder/lung

• Modified heart

  • pumped de-oxygenated and oxygenated blood

  • some had reduced mixing of oxygenated and deoxygenated blood

• Internal nares (connecting to respiratory system)

  • predecessor to tetrapod nostrils

• Bony and muscular elements within the paired fins

  • predecessors to support-providing limbs

  • Homologous bones: humerus, radius, and ulna

What are the morphological changes observable in early tetrapods?

• Skull had fewer/lighter bones

• Forelimbs were more weight bearing

• More developed wrist bones and digits

• Increasingly important lungs

• Head could turn from side to side and nod forward and back with the appearance of the atlas (1st cervical vertebra)

• Pelvic and pectoral girdles enlarged and attach to the vertebral column for better weight bearing

• Eyes move to the front/top of head; vision becomes adapted to air, not water

What are some extinct genus’s of early tetrapods?

• Acanthostega

• Ichthyostega

What is the difference between Mullerian and Batesian mimicry?

• Mullerian: Two or more chemically defended species evolve to look alike

• Batesian: Non-defended animal is protected by looking like a defended one

How do amphibians feed?

• Most are carnivores as adults

  • Tadpoles usually herbivorous or filter feed

• From the mouth, prey pass through the esophagus, stomach, small intestines, large intestines, then to the cloaca.

How do amphibians respirate?

• Gas exchange occurs at 4 different sites:

  • Pulmonary respiration (via lungs)

  • Cutaneous respiration (via skin)

  • Buccal respiration (via mouth)

  • Gills

What kind of circulation do amphibians exhibit?

They have a 3 chambered heart with 2 complete circuits of blood flow.

What are some conservation threats that amphibians face? Why are so many species endangered?

• They are vulnerable to both aquatic and terrestrial pollution

• Skin is thin, moist and permeable to many chemicals

• Greatly impacted by human activities and change in climate; resulting in habitat loss and extinctions

• Amphibian pandemic - a fungal pathogen called chytrid fungus

Describe the characteristics, natural histories,
reproduction, and development of Class Amphibia, Order Gymnophiona

• “naked snake”

• Caecilians

• Smooth slimy skin

• Internal fertilization

• Some are oviparous, most are viviparous

• Young feed on mothers fatty tissue after birth

Where are the centers of diversity for the three orders of amphibians listed and what biomes do they occupy?

Gymnophiona: tropical rainforests of South America, Africa, SE Asia.

Urodela: North America (especially Appalachian region).

Anura: worldwide (except Antarctica), greatest diversity in the tropics

What amphibian order is the most speciose?

Anura (frogs and toads)

How do caecilians move?

• Internal concertina motion – alternate contraction and extension of body sections against soil resistance.

• Can also move like snakes using external concertina motion.

• Efficient underground burrowers.

What adaptations do anurans have that enable them to jump many times their own body length?

• Long, muscular hindlegs with elongated pelvic girdle.

• Fused radius/ulna and tibia/fibula for strength.

• Rigid vertebral column and shock-absorbing forelimbs.

• Elastic connective tissue stores and releases energy.

Describe the characteristics, natural histories,
reproduction, and development of Class Amphibia, Order Urodela?

• Salamanders

• Urodela means “with tail”

• Head-trunk tail body plan

• Rely on chemical communication to find a mate

• Fertilization is usually internal

• Exhibit Paedomorphosis (the evolution of an adult form that resembles the juvenile form)

Describe the characteristics, natural histories,
reproduction, and development of Class Amphibia, Order Anura?

• Frogs and Toads

• Fused head-trunk and no tail

• External fertilization (amplexus).

Describe the Order Aura, Family Ranidae

• True frogs

• Long legs, webbed feet, smooth skin

• Aquatic or near water; global (except Antatrica)

Describe the Order Aura, Family Hylidae

• Tree frogs

• Adhesive toe pads, forward-facing eyes

• Aboreal or semi-aquatic; terrestrial habitats

Describe the Order Aura, Family Bufonidae

• Toads

• Dry, warty skin; toothless; paratoid glands secrete toxins

• Widespread; arid to rainforest biomes (e.g., cane toad invasive in Australia)

What type of skull did the most recent common ancestor of all living amniotes probably have?

anapsid

How many pairs of temporal openings are in the skulls of the following animals?

• Dinosaur: Diapsid skull

• Chicken: Diapsid skull

• Human: Synapsid skull

• Snake: Diapsid skull

• Turtle: Anapsid skull

Birds are modern descendants of which group of dinosaurs?

Theropods (meat-eating dinosaurs)

What type of nitrogenous waste do the following animals excrete?

• Terrestrial adult amphibians: Urea

• Aquatic juvenile amphibians: Ammonia

• Non-avian reptiles: Uric acid

• Fish: Ammonia

Non-avian reptiles are ectotherms?

True

How many heart chambers do the following animals in the following taxa have?

• Class Osteichtheys (excluding lungfish): 2

• Class Amphibia: 3

• Class Reptilia, Order Crocodilia: 4

• Class Reptilia (excluding crocodilians): 3

• Class Chondrichtheys: 2

Match the correct fish class or classes to the following traits

• Some fish in this class have a heterocercal tail (caudal fin): Chondrichtheys

• Spiral-shaped intestinal valve that causes them to produce corkscrew-shaped poop: Chondrichtheys

• Gill openings without true oppercula: Myxini, Cephalaspidomorphi, and Chondrichtheys

• Jawless fish with slime glands: Myxini

• Dead whale-eating fish with sensory barbels: Myxini

• Jaws: Chondrichtheys and Osteichtheys

• Jawless ectoparasites of other fish: Cephalaspidomorphi

• Fish without scales: Myxini and Cephalaspidomorphi

• Use an air-filled or oil-filled swim bladder to achieve neutral buoyancy: Osteichtheys

• Have ganoid, cycloid, ctenoid, or cosmoid scales: Osteichtheys

• Use a fatty liver to achieve neutral buoyancy: Chondrichtheys

• Fish with skulls: Myxini, Cephalaspidomorphi, Chondrichtheys and Osteichtheys

• Use gill sacs for respiration: Myxini and Cephalaspidomorphi

• Have a skeleton with a true vertebral column: Cephalaspidomorphi, Chondrichtheys, and Osteichtheys

• This class has placoid scales: Chondrichtheys

• Fish with paired fins:Chondrichtheys and Osteichtheys

Which of the following are elasmobranchs?

Skates, shark, sawfish, and stingray

What agnathan structure is homologous to the jaw of a gnathostome?

Gill arch

What is the adaptive value of paired fins?

Provides increased stability in the water

What is true of fish in class Chondrichtheys?

• They have structures called ampullae of Lorenzini in their heads that allow them to detect electrical signals

• In salty environments they retain high amounts urea in their blood

• They have 5 to 7 pairs of gill slits (except for chimeras)

• Intrauterine oophagy and cannibalism is common, at least among sharks

Amphibians that can move via internal concertina belong to what order?

Gymnophiona

Which of the following classes contains animals that use lateral lines to sense vibrations in the water?

Osteichtheys, Amphibia, and Chondrichtheys

Which order of amphibians has a enter of diversity outside of the tropics?

Urodela

Which amphibian order is the most speciose?

Anura

What is the adaptive value of countershading?

Crypsis

Match the correct amphibian family to each of the following common names

Newts: Order Urodela

True frogs: Order Anura, family Ranidae

Salamanders: Order Urodela

Toads: Order Anura, family Bufonidae

Tree frogs: Oder Anura, family Hylidae

Caecilians: Order Gymnophiona

What are the snyapomorphis of amniotes?

• amniotic eggs

• desiccation-resistant skin

• rib ventilation