Fishes. <*-[-[-[-<<

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  • fish and other vertebrates at some time development notochard, a hollow dorsal nerve cord + pharyngeal slits.
  • replaced by backbone (vertebral column) encloses + protects nerve cord.
  • two sets of paired appendages, closed circulatory system with ventral heart, gills/lungs for breathing.
  • definition: Aquatic vertebrate that characterized by scales, fins, and pharyngeal gills.
  • some do not have scales.
  • many difference - 4 living classes of vertebrates make up group animals.
  • soooo many fishes, living :) and extinct :(.
  • 3 main groups 1. jaw-less fish 2. sharks + relatives 3. bony fishes.
  • (shark +relative) = cartilaginous fishes --> skeletons soft, flexible.
  • cartilage > bone.

Evolution.

  • primitive living vertebrates.(first to evolve, characteristics of ancestors, not inferior to other verbs)
  • first fish/vertebrate -->odd-looking + jaw-less = bony planks covered body.
  • ocean - - Cambrian period -->540 million years ago.
  • over 100 million, retained basic armored jaw-less body plan.
  • Ordovician +Silurian periods --> under went major transformation, adaptive radiation.
  • groups emerged --> jaw-less fish with little armor, other jaw-less armored, variety of forms.
  • extinct by Devonian period --> 350 million years ago.
  • Jaw-less = limited small particles of food, filter feeders, suck like vacuum.
  • Jaws = plants, animals and defend with a bite.
  • Early Jawed + paired pectoral(anterior) + pelvic(posterior) =fins.
  • fins give control in water.
  • fins + girdle --> forelimbs and shoulder bones -->hind limbs and hip bones.
  • jawed fish disappeared left behind 2 classes
  • Cartilaginous (sharks and rays)
  • bony fish = 97% of fish.

Form and Function

Feeding.

  • herbivores, carnivores, parasites, filter feeders, detritus
  • single fish - several modes, depending on availability.
  • carp - eat everything, algae, water plants, worms and mollusks., arthropods, dead fish and detritus.
  • Great white sharks, tuna and Barracuda = carnivores.
  • Pencil Catfish - parasites. lay eggs in gills of larger fish.
  • male in certain Angler fish - attach to female obtain nutrients from her blood.
  • Lamprey Larvae and Manta Rays - filter feeders along with Whale Shark (largest fish 18.5 meters)
  • Saw fish kill and stun prey slashing into school of fish with long snout covered with sharp teeth.
  • Parrot fish - teeth fused beak bites off chunk living coral + additional teeth in throat grind chunks into sand.
  • Archer fish - shoots down prey with drops of water.
  • Angler fish- worm like, lighted lures --> entice prey,.
  • enormous jaws swallowing prey larger than themselves.
  • strong blunt teeth --> crush clam and mollusks shells.
  • Don't Really Chew Food. -->tear into conveniently sized chunks, and swallow whole.
  • mouth --> esophagus --> stomach. partially broken down.
  • processed in finger-like pouches -->pyloric. stomach + intestine meet.
  • digestive enzymes + absorb nutrients.
  • intestine liver + pancreas added to food.
  • waste out anus.
  • intestines adapted meet nutritional needs.
  • herbivores have longer intestine than carnivores (more time to break down, plants harder to break down)
  • Lamprey/Cartilaginous --> spirals around intestine to help absorb more nutrients.

Respiration.

  • gills located either side of pharynx.
  • contain capillaries --> exchange of oxygen CO2.
  • breathe - pumping H2O through mouth > gill filaments out through slits.
  • almost all bony fish --> single opening - water exhaled - beneath protective gill cover.
  • Skates + Rays breathe on ocean floor, although mouth located underneath body. inhale water special openings on upper surface of body.
  • lung fish, gars, Siamese fighting --> oxygen-poor water, bodies of water dry up (special organs--> absorb oxygen from air)
  • swim bladder (air-breathing) gas-filled sac lies top of body cavity beneath backbone.
  • regulate buoyancy - lesser greater depths.
  • some die if cannot get to surface for air.

Internal Transport.

  • closed circulatory system, heart pumps blood all over.
  • atrium + ventricle --> blood body collects atrium --> pumps to ventricle.
  • Ventricle --> aorta --> fine capillary, net of gills = gas exchange.
  • Gills --> body tissues + internal organs - leave muscles + organs. collects in veins --> thin walled sac --> sinus Venous and then back =to Atrium.

Excretion.

  • form of ammonia, some through gills, by kidneys (excretory organs --> tubules - filter nitrogenous waste from blood and concentrate)
  • control amount of water in body.
  • salt water - lose water osmosis, kidneys marine fish concentrate nitrogenous waste - return as much h2o possible
  • freshwater fish kidneys pump lots dilute urine.
  • control kidney function. (salmon)

Response.

  • well developed nervous system around brain.
  • brain-clearly visible.
  • anterior parts = olfactory bulb connected by stalks --> 2 lobes --> cerebrum (sense of smell + taking care or young + exploring)
  • Optic Lobes process information from eyes.
  • cerebellum - coordinated body movements.
  • Medulla - control many internal organ functions and maintain balance.
  • cartilaginous + bony --> spinal cord enclosed + protected by vertebral column.
  • well developed eyes, color vision.
  • only active at night/ cloudy water large eyes. - big pupils gather light.
  • color not so great, can see in dark as well as cats.
  • extraordinary sense of taste + smell. (chemo-receptors)
  • salmon distinguishing odor of own stream + others.
  • sharks can detect drop of blood in 115 liters of sea water.
  • ears inside head, don't hear well. -->detect gentle currents, and vibrations.
  • lateral lines - detect other fish (located down sides of body)
  • electric eels, catfish, and sharks - detect electricity.
  • shark.. 1 millionth of volt (less charge than an animal makes)
  • electric eels/catfish produce strong electrical field around bodies - produce jolt up to 650 volts. (stun/kill/discourage prey)

Reproduction.

  • separate male and females. born male change into female.
  • few hermaphrodites.
  • oviparous = lay eggs, external fertilization (sharks+rays- lay fertilized eggs)
  • some Cod don't take care of their young,
  • hundred - millions of eggs --> few offspring survive.
  • Siamese fish - build nest of bubbles, and twigs around eggs.
  • Chichilds and Catfish - hold eggs in mouth.
  • male seahorse carries babies in pouch until ready to hatch.
  • these guys lay less eggs, because more will survive.
  • guppies develop inside mom (nourished food in yolk sac) and they swim on their own. (ovuviviparous)
  • viviparous/ truly live-bearing --> sharks nourished by mums body.
  • mating "rituals"
  • guppy male dance up and down in front of female.
  • Chichilds beautiful colors + build elaborate nests.
  • stickleback build nests and drive away males, and dance for passing females.

Jaw-less Fishes.

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  • two classes --> lampreys + hag-fishes.
  • developed heavily boned ancestors, but have no bones themselves.
  • snake like bodies - notochord (supported)

Lampreys.

  • filter feeder + larvae + parasites.
  • head taken up by circular sucking dish, round jaw-less center.
  • adults attach to fish (whales + porpoises_ scrape skin away with large teeth + strong rasping tongue.
  • suck up tissues + body fluids.
  • rarely kill host --> leave weak + large open wound easily infected.

Hag-fishes

  • most primitive vertebrate alive today.
  • pinkish grey bodies 4-6 tentacles around mouth.
  • lack eyes, light-detecting regions around body.
  • dead, dying fish, toothed tongue crape hole (food)
  • secrete slime, 6 hearts and possess open circulatory
  • regularly tie themselves in half-knots.

Sharks + Relatives.

  • Chondrichthyes --> sharks, rays, skates, saw fish.
  • endoskeleton = cartilage.
  • tooth like scales covering skin. (sharkskin = sandpaper)
  • 225 sharks - large curved tails, torpedo shape bodies, round snouts, mouth underneath.
  • 3000 teeth in lifetime
  • not all attack people. (more people killed by lighting than sharks)
  • some filter feed, or flat teeth to crush shells.
  • Rays + skates live on floor. = flat squished sharks. minimum 1 meter --> 7 meter.

Bony Fishes.

  • osteichthyes. 40% vertebrates.
  • 15,000 --> 40,000 alive today.
  • almost all ray-finned fishes ( guppies, groupers, salmon eyes)
  • ray-fin = tiny bony spines/rays -->thin layer skin from fins.
  • stone fish, scorpion fish, lion fish fin rays --> poison spines.
  • flying fish - leap water + glide winglike pectoral fins.
  • mud-skippers - lot of time out of water. (suction cup)
  • trigger fish - wedge through tiny places - fold fins.
  • 7 living species not ray-finned
  • 6 lungfish - Australia + Africa + south America - flooded rainy + baked dry
  • water available - eliminate carbon dioxide - gulp air into sac.
  • dry season - burrow in mud + enter dormant state.
  • single species of coelacanth, latimeria.
  • - few bones in fin bases. walk on base with fins, like legs.
  • - thoguht to be extinct with the dinosaurs, until fisherman caught one in 1938.
  • closest ancestors of all land vertebrates.

Where Have The Fish Gone ?

  • good source of protein, delicious and healthful.
  • don't eat fish? most chicken sold today, ate ground up fish.
  • used to , house servants signed contract stating they wouldn't have to eat "trash fish" salmon three times a week.
  • Now salmon and Halibut = expensive.
  • Pollution + development - fouled water habitats.
  • increasing demand for fish.

Fish in the World.

  • fish help control population of organisms they eat.
  • mosquito fish - ponds and lakes, eat large amount of insects, and larvae.
  • grass carp + cichlids keep waterways clear of plant growth.
  • pretty colors and exotic forms.