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Questions and Answers
What exemplifies a derived character state in mammals?
What defines a sister group in evolutionary biology?
Which term refers to an organism that thrives in very specific situations?
What does the term 'benthic' refer to in marine biology?
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How does global diversity of marine fish vary across latitudes?
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What is the primary mode of respiration for slow-moving, benthic sharks?
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Which type of teeth are adapted for crushing mollusks?
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What is a characteristic feature of the ampullae of Lorenzini in sharks?
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Which feature of elasmobranchii is shared by all members?
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How are placoid scales advantageous for sharks?
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What unique reproductive feature do male sharks possess?
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What is the typical feeding behavior of chimera, a type of elasmobranchii?
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Which structure in sharks is modified from gill slits in some species?
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What factors contribute to the faster accumulation of species at high latitudes?
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Which freshwater river system is NOT mentioned as a major concentration area for species diversity?
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What feeding strategy do Hagfishes utilize?
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What principle explains why some species can be excluded from a niche?
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Which structure is characteristic of all Agnatha?
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What mechanism do Lampreys use to feed on their prey?
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Which feature is NOT associated with Chondrichthyes?
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How do coral reefs primarily affect fish populations?
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What is the main reason for the low number of species found near the poles?
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Which of the following characteristics is NOT found in all Agnatha?
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What characteristic distinguishes rays from skates?
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Which of the following features is present in both lungfishes and coelacanths?
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What adaptation do lungfishes exhibit to survive in dry conditions?
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What function do the barbels serve in sturgeons?
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Which characteristic is NOT associated with acipenseriformes?
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What type of scales do extant lungfishes possess?
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What is the primary benefit of cycloid scales found in eels?
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How do gars primarily breathe when underwater?
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What evolutionary significance is attributed to the diversity in scale types among fish?
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What is a unique feature of the Bowfins?
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What distinguishes the embryonic development of eels from that of other fish?
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Which of the following groups is characterized by the presence of a vestigial lung?
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What characteristic helps identify reedfishes among other fish?
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Which group of fish is known for lacking teeth on their jaws?
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What function does the Weberian apparatus serve in Ostariophysi fish?
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Which of the following adaptations is not associated with cave-adapted fish?
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How do anglerfishes attract their prey?
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Which type of swimming involves undulating the entire body and caudal fin?
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What unique feature do Characiformes fish possess that aids in identification?
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Which swim bladder adaptation allows some fish species to breathe air?
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Which fish family is known for its members that often exhibit complex behaviors, such as farming algae?
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What type of swimming mode is characterized by the use of flexible pectoral fins for propulsion?
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Which type of scale is described as having a flexible and comb-like edge that reduces drag?
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What is a key feature of the Siluriformes group of fish?
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Which fin structure allows fish to remain buoyant and is often modified in various species?
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What distinctive feature do Gobiiformes fish lack that affects their swimming behavior?
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Study Notes
Character States
- The original condition of a character is called the "primitive character state"
- A character whose state has changed from the primitive state is called a "derived character state"
- For example, the presence of hair is the primitive character state for all mammals. The absence of hair is a derived character state for one subclade - whales.
Clades and Taxa
- Clades are a group of organisms that share a common ancestor.
- A sister group is when two clades diverge from a single lineage and are the same age, but the two clades are not necessarily the same age.
- Taxa is a term for any group of organisms:
- Species
- Genus
- Family
Terms
- Adaptation - a specialized feature that helps an organism survive in its environment
- Specialist - an organism that thrives only in very specific environments
- Generalist - an organism that can survive and thrive in a variety of environments
- Benthic - organisms that live on the substrate or bottom
- Pelagic - organisms that live in the open water column
Global Diversity of Marine Fish
- More species at low latitudes (near the equator)
- Stable conditions with no seasonality
- More food available due to warm waters and high productivity
- More space for organisms to live and specialize
- Species accumulate faster at high latitudes (near poles)
- Unstable conditions with seasonality
- Fewer species due to difficult living conditions
- Competitive exclusion principle: dominant species may restrict the diversity of other species in an area
- Coastal areas can be particularly diverse
- Coral reefs provide shelter from predators and are a rich source of food
Global Diversity of Freshwater Fish
- Mostly concentrated near the equator focusing on large landmasses with large, warm river systems
- Amazon and La Plata Rivers (South America)
- Congo River (Africa)
- Mekong and Yangtze Rivers (Asia)
- Mississippi River (North America)
Agnatha: Jawless Fishes
- Primitive vertebrates that originated in the Cambrian period
-
Myxiniformes (Hagfishes)
- Vestigial eye
- 4 pairs of sensory tentacles
- Mouth with rasping tongue and keratin teeth
- Mucus gland pores
- 12 external gill slits (paired)
- Slime defense mechanism releases mucin vesicles and skeins of fibrous thread
-
Petromyzontiformes (Lampreys)
- Eye
- Oral disk with keratin teeth and rasping tongue
- 7 external gill slits (paired)
- Anterior and posterior dorsal fins
- Caudal fin
Chondrichthyes: Cartilaginous Fishes
- Consist of ratfish/chimeras, rays, and sharks
- Maintain buoyancy with a large oil-filled liver and a heterocercal caudal fin.
- Gill openings are independent and physically separate but connected to the esophagus, making them more efficient than pouched gills.
- Respiration modes:
- Slow-moving, benthic sharks actively pump water across gills with their mouths
- Spiracle pulls water in and across gills
- Ram ventilation: forward movement passively forces water across the gills
-
Placoid Scales:
- Present in all species
- Dermal denticles made of dentine and enameloid
- Lightweight, highly protective and reduce drag
-
Teeth:
- Made of calcium phosphate
- Smooth or serrated
- Replaced throughout life
-
Ampullae of Lorenzini:
- Electroreceptors that detect electric fields
- Gel-filled pores throughout the body connected to sensory cells
-
Synapomorphies:
- Cartilaginous skeleton
- Chondrocranium lacks sutures
- Unsegmented soft fin rays
- Teeth not fused to jaws
- Males have claspers for internal fertilization
-
Chimeroidea (Ratfish/Chimeras:
- Gill cover over 4 gill slits
- Live at depths from 80-2600m
- Scavengers or invertivores
- Upper jaw fused to the chondrocranium
- Males have cephalic claspers
-
Elasmobranchii:
- Includes Selachii (sharks) and Batoidea (rays and skates)
- Oldest fossil teeth from 418 Mya
Selachii: Sharks
- Pelvic fins usually not anchored to the skeleton by the pelvic girdle.
- Soft fin rays unsegmented
Batoidea: Skates and Rays
- Anatomy: Skates vs Rays
- Rays are live-bearing (viviporous)
- Skates are egg-laying (oviparous)
- Skates have a prominent dorsal fin
- Rays only have a very reduced dorsal fin
- Rays are kite-shaped with ship-like tails
- Skates have fleshy tails
- Skeletal Anatomy
- Skeleton is cartilaginous
- Pelvic girdle is fused to the vertebral column, which is a derived feature for Chondrichthyes
- Scapular girdle is present
Sarcopterygii: Lobe-finned Fishes
- Consist of Dipnoi (lungfish), Actinistia (coelacanths) and Polypteriformes (reedfish)
-
Dipnoi (Lungfishes)
- Cosmoid scales (extinct)
- Cycloid scales (extant)
- Distribution of extant species is due to the breakup of the supercontinent Gondwana.
- Burrowing mechanism to survive during dry periods
- Aestivation: A period dormancy during drought periods
- Lungfishes can survive up to 5 years during aestivation
-
Cranial Anatomy:
- Ceratohyal (floor of mouth)
- Clavicle (part of pectoral girdle)
- Cranial rib (an accessory structure associated with their lung) are involved in breathing and feeding
-
Scales:
- Cosmoid scales (extinct lungfishes)
- Benefit: durable and provide defense against predators
- Drawback: poor flexibility
- Cycloid scales (extant lungfishes)
- Benefit: flexibility
- Drawback: Limited defense against predators
- Cosmoid scales (extinct lungfishes)
-
Actinistia (Coelacanths):
- Vestigial lung derived from the swim bladder
- Filled with fat, rather than air, and is likely an adaption for buoyancy at great depths
- Cosmoid scales: likely derived from the fusion of placoid scales
-
Polypteriformes (Reedfishes): ~360 Mya
- Juveniles have external gills, resorbed over time
- Respire using lungs, but cannot extract sufficient oxygen from water
- Must periodically surface and gulp air
-
Spiracular breathing:
- Respire through two spiracles on the top of the head
- Air can pass through spiracles into the mouth
- If habitat is desiccating, they can make short over-land excursions
Acipenseriformes: Sturgeons and Paddlefishes
-
Acipenseridae (Sturgeons): ~350 Mya
- 28 species
- Lack scales, possess five lateral rows of bony plates called scutes
- Four barbels (sensory organs in front of mouth)
- Lack teeth
- Skeleton is largely made of cartilage; many bones do not fully ossify
- Commercially harvested for their eggs
-
Polyodontidae (Paddlefish): ~350 Mya
- 8 species; only 2 extant
-
Rostrum (paddle) has 2 functions:
- Provide lift and stability while filter-feeding
- Counteract the drag created by the lower jaw that drops below the body
- Lack teeth
- Lack scales
- Ampullae of Lorenzini present
Amiiformes (Bowfins): ~250 Mya
- Only 2 species
- Very old lineage
- Vascularized swim bladder can function as a lung
- Protruding tube-like nostrils
- Single-layered cycloid scales
Lepisosteiformes (Gars): ~250 Mya
- 7 extant species
- Vascularized swim bladder can function as a lung (similar to Bowfins)
-
Ganoid scales:
- Rhomboid shape
- 3 layers
- Inner bony plate
- Middle layer of osteodentin
- Outer layer of ganoine
- Largely non-overlapping
- Inflexible and tough
- Benefit: durable and defense against predators
- Drawback: poor flexibility
Actinopterygii: Ray-finned Fishes
-
Elopiformes (Tarpon):
- 2 species
- Cycloid scales
- Can live in marine and brackish water
- Obligate air breathers: need to have access to the surface
- Likely a unique origin from that in lungfish, reedfish, sturgeons, paddlefish, bowfins, and gars
-
Anguilliformes (eels):
- True eels
-
Scales:
- Freshwater: small, soft, cycloid scales embedded in their epidermis
- Marine: lack scales, produce mucus for protection
-
Freshwater eels are derived from marine ancestors
- Lacking scales is viable in marine environments, but not freshwater
-
Fins
- Freshwater: pectoral fins and continuous dorsal, caudal, and anal fins
- Marine: continuous dorsal, caudal, and anal fins### Osteoglossiformes
- “Bony Tongues,” about 245 species
- Mostly freshwater
- Cycloid scales, most teeth on tongue and roof of mouth
Ostariophysi
- More than 11,000 species, all freshwater except Antarctica
-
Weberian apparatus:
- Minute bones connecting inner ear to swim bladder
- Amplify sound waves by resonating through swim bladder
- Provides enhanced ability to sense vibrations and hear
Cypriniformes
- About 4,500 species, cycloid scales
- Lack teeth on jaws, lack stomachs, many have barbels (whiskers)
Characiformes
- About 2,200 species, well-developed teeth
- Adipose fin: tiny fin by caudal fin, distinct character
Gymnotiformes
- About 240 species
- Lack pelvic and dorsal fins, possess electric organs
- Electric organs produce weak electric fields for navigation
- Electric eels can stun prey
Siluriformes
- More than 3,800 species, majority freshwater
- Adipose fin present
- Usually negatively buoyant, reduced swim bladder, large bony skull
- Lack scales, produce mucus; some have dermal plates
- “Armored” have dermal plates or plates derived from vertebral processes
- Sound production by flicking pectoral fins
- Barbels (whiskers) up to 4 pairs: nasal, maxilla, and 2 pair on dentary
- Some breathe air:
- Gulp air into modified swim bladder
- Diffuse air through modified gill arches
- Gulp air into the modified stomach/digestive tract
Esociformes
- About 10 species
-
Esocidae (pikes):
- 7 species
- North America, Western Europe, Siberia
- Sportfish and top predators
-
Umbridae (mud minnows):
- 3 species
- Mississippi River Basin and eastern US
- Live in stagnant, low-oxygen waters (marshes, ditches, swamps)
Salmoniformes
- Food and sport fish, adipose fin present
Percopsiformes
- Chologaster: swamp fish live near the surface
- Forbesichthys: spring cavefish live in intermittent surface
- Typhlichthys: southern cavefish live in sub-surface
-
Cave adaptations:
- De-pigmentation: loss of selection for visual signaling, colors are expensive to make
- Eye-loss: expensive structures, require vitamins, limited utility in dark
- Elaboration of the lateral line system: mechanosensory (vibrations) and chemosensory (smell) function
- Flattening of head: possible increase in mouth size and sensory receptor surface area
Acanthomorpha
- Hollow, unsegmented spines along anterior dorsal and anal fin: can be extended for defense, retracted to reduce drag
- Well-developed snout cartilage allows for upper jaw protrusion
- Mostly ctenoid scales: outer bony layer, inner fibrous collagen layer with small spines
- Highly flexible for mobility
- Comb-like edge creates turbulence that reduces drag
- Less protection than placoid, cosmoid, or ganoid scales
Holocentriformes
- Nocturnal, marine, large eyes
- Reddish color provides camouflage in dim light
Batrachoidiformes
- Marine, toadfish
Gobiiformes
- 90% marine, small burrowing species
- Lack swim bladder, actively swim to prevent sinking
Scombriformes
- Marine, mostly pelagic active swimmers
- Fastest swimmers, large predators
Syngnathiformes
- Marine, mimic seaweed and coral
- Males become pregnant and carry young
- Loss of fins: pelvic, sometimes caudal fin
- Seahorses have prehensile tails for grasping, slow swimmers
Synbranchiformes
- Freshwater, labyrinth organ:
- Vascularized area within branchial arch (gill arch)
- Diffuses inhaled oxygen into blood
- Survive on land if moist
Carangiformes
- Mostly large, laterally compressed, silvery fishes
- Remoras have specialized dorsal fin that forms a suction cup
- Attached to sharks, whales, turtles, tuna, swordfish
- Commensalism: attachment to host for travel
Pleuronectiformes
- Mostly marine, exhibit eye migration during development
- Ovalentaria: produce adhesive eggs
Pomacentridae
- Farm plots of algae
- Longfin Damselfish has a mutualistic relationship with Mysidium integrum
- Clownfish have mutualistic relationships with anemones
Polycentridae
- Leaf fishes, mimic dead leaves, ambush predator
Cichlidae
- About 1,700 species, East African Great Lakes, significant paradox
- Distributed throughout Africa, Americas, India, and Madagascar
- Freshwater
Perciformes
-
Triglidae (sea robins):
- Marine, possess sensory organs on pectoral fins
- Used to sift through substrate for food
-
Percide (perches and darters):
- Large-bodied predators: walleye and perches (sport and food fish)
- Dramatic transition to small bodies: darters
- Darters lack swim bladders, strictly benthic
- Centrarchidae (sunfishes and black basses)
Labriformes
- Wrasses (more than 400 species) and parrotfishes (about 90 species)
- Wrasses and parrotfishes associate with coral reefs
- Parrotfishes are a sub-clade of wrasses
- Parrotfish teeth are fused into a “beak” for grazing on coral
Lophiiformes
- Mass is mostly head and jaws, large mouths
- Lure used to attract prey: frogfish lures mimic invertebrates, anglerfish lures emit light
- Illicium (rod/stalk): modified dorsal spine controlled by muscles
- Esca (bait/lure): luminescent organ housing symbiotic bacteria
Tetraodontiformes
- Many fins lost or functionally lost, clavus: a pseudocaudal fin acts as a rudder
Fish Swimming Modes
-
Body-Caudal Fin (BCF) Swimming:
-
Anguilliform swimming (eels):
- Swimming with most of the body and caudal fin
- High maneuverability and flexibility
- Slow speed, low hydrodynamic efficiency
- Swimming interrupted by periods of inactivity
- Cylindrical and elongate body, pointed head, paired fins reduced or absent
-
Carangiform swimming (jacks):
- Swim with posterior body region and caudal fin
- Intermediate maneuverability, flexibility, and hydrodynamic efficiency
- Slow-medium speed; near-constant swimming
- Laterally compressed
- Narrow in front of tail, rounded or blunt head, pointed fins
-
Thunniform swimming (tunas):
- Swim with caudal fin
- Intermediate body flexibility
- Low maneuverability, high hydrodynamic efficiency
- Constant medium-to-high speed swimming
- Laterally compressed, narrow in front of tail, pointed head, pointed fins
-
Ostraciform swimming (boxfishes):
- Swim with caudal fin
- Very little body flexibility
- High maneuverability, very slow speed, low hydrodynamic efficiency
- Large pectoral fins used for steering
- Other fins reduced or vestigial
-
Anguilliform swimming (eels):
-
Median-Paired Fin (MPF) Swimming:
-
Labriform swimming (wrasses):
- Swim with pectoral fins
- Intermediate body flexibility
- Intermediate maneuverability, slow speed
- Intermediate hydrodynamic efficiency
- Swimming in bursts
- Laterally compressed, long, tapered pectoral fins
-
Rajiform swimming (rays):
- Swim with pectoral fins, low body flexibility
- Low maneuverability, slow speed, high stability
- Low-to-high hydrodynamic efficiency
- Dorso-ventrally compressed, expanded pectoral fins
- Benthic species have dorsally positioned eyes
-
Gymnotiform swimming (knife fish):
- Swim with anal fin
- Low body flexibility, high maneuverability, slow speed
- Anal fin expanded along the body
- Laterally compressed
-
Amiiform swimming (bowfin):
- Swim with dorsal fin
- Low body flexibility, high maneuverability, slow speed
- Elongate, tubular shape
-
Balistiform swimming (triggerfish):
- Swim with dorsal and anal fin
- Low body flexibility, high maneuverability, slow speed
- Tapered head and body (triggerfish and pufferfish)
- Laterally compressed (triggerfish)
- Rounded body (pufferfish)
-
Labriform swimming (wrasses):
Caudal Fin Types
-
Protocercal:
- Undifferentiated, symmetrical
- Lampreys and hagfishes
-
Heterocercal:
- Unequal-lobed (upper larger), asymmetrical
- Passively generated some lift
- Sharks and sturgeons
-
Hypocercal:
- Asymmetrical: bottom larger
- Uncommon
- Flying fish: passive drag to keep from drifting
-
Homocercal:
- Symmetrical, most common
- Most variable in shape
- Tunas and wrasses
- Sub-types:
- Rounded (sunfishes)
- Truncate (darters)
- Lunate (tunas)
-
Hemihomocercal:
- Asymmetrical (without lobes), abbreviated homocercal
- Bowfin and gar
Locomotion
- Most species use their pectoral fins to some degree:
- Carangiform/thunniform: use long stiff pectoral fins for steering at moderate-to-high speeds
- Ostraciform/balistiform: use flexible pectoral fins to supplement dorsal and anal fins for propulsion
- Some species rarely use their caudal fin, but will in certain situations:
- Labriform/amiiform swimmers: use tail to generate a burst of propulsion
- Anguilliform swimmers: usually benthic, often complex habitat
- Carangiform/thunniform swimmers: pelagic, open water away from structures
- Ostraciform swimmers: coral reefs, but not necessarily benthic
- Labriform swimmers: coral reefs, rarely benthic
- Rajiform swimmers:
- Undulating pelvic fins: benthic, simple or moderately complex, often sandy areas (many species burrow)
- Oscillating pelvic fins: pelagic, open water
- Gymnotiform swimmers: complex habitat, but not benthic
- Amiiform swimmers: variable habitat, complex or simple
- Balistiform swimmers: complex habitat
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Description
Test your knowledge on elasmobranchii, including sharks and their unique characteristics. This quiz covers various aspects of their biology, including respiratory systems, feeding behaviors, and adaptations. Dive into the fascinating world of marine life and understand the diversity of species across different environments.