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TRANSCRIPT
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Chordates, Fishes & Amphibians
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Chordates● Chordate- members of the phylum Chordata
● Must have 4 characteristics at some stage in life● Dorsal hollow nerve cord● Notochord- long supporting rod that runs through body just
below nerve cord● Pharyngeal pouches- paired structures in throat region● Tail that extends beyond the anus
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● Most chordates are vertebrates● They have vertebrae- individual segments that make up the
backbone & encloses the spinal cord
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Fishes● Aquatic vertebrates that (for the most part)have:● Paired fins- for movement● Scales- for protection● Gills- for gas exchange
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● Feeding● Every mode of feeding found in the fishes● Some may vary feeding depending upon what is available● Have specialized fingerlike pouches called pyloric ceca that
secrete digestive enzymes & absorb nutrients
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● Respiration● Most use gills that are made up
of filaments
● Filaments provide large surface area for exchange of oxygen & carbon dioxide
● Bring water into mouth and move it over the gill filaments and out the gill slits
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● Circulation● Closed circulatory system
● Blood is pumped from heart to the gills (where it gets oxygen) and then to the rest of the body and back to the heart
● Most fishes have a 4-part heart, with TWO chambers● Atrium- blood enters and flows to the ventricle● Ventricle- pumps blood into bulbus arteriosis
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● 2 chambers: atrium & ventricle
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● Response● Well-developed ● Brain has several parts
● Olfactory lobe- smell● Cerebrum- voluntary activities● Optic lobe- vision● Cerebellum- body movements● Medulla oblongata- functioning of internal organs
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● Lateral line system- allows fishes to detect gentle currents & vibrations
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● Movement● Alternately contract paired muscles on either side of
backbone● This creates backward force on the surrounding water & when
fins move, it propels the fish forward
● Many bone fishes have a swim bladder that adjusts their buoyancy b/c their tissue is more dense than the water
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● Reproduction● Eggs are fertilized either internal or external, depending on
the species● Oviparous- eggs hatch outside the mother’s body● Ovoviparous- eggs remain in the mother after fertilization &
are “born alive” using yolk for nutrients while developing● Viviparous- embryos remain in mothers body and get
nutrients from mother
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Excretion● Rid themselves of nitrogenous wastes in form of ammonia
● Some wastes diffuse through gills
● Kidneys remove wastes from the blood
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Groups of Fishes● Jawless fishes (Class Agnatha)- have no true teeth or jaws
● Lampreys & hagfishes
● Cartilagenous fishes (Class Chondrichthyes)- skeleton made of cartilage- no bones!● Sharks, rays● Have many rows of teeth● Have toothlike scales covering skin to make it rough
● Bony fishes (Class Osteichthyes)- skeleton made of bone● Ray-finned fishes have slender bony spines connected to fins● Flounder, bass, catfish, angelfish
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Amphibians● Amphibian means double life- meaning live both in water
and on land● Lives in water as a larva● Lives on land as an adult● Breathes with lungs as an adult● Has moist skin that contains mucus glands● Lacks scales and claws
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● Feeding● Tadpoles are filter feeders or herbivores● Adults are carnivorous● At end of digestive tract is large muscular cavity called cloaca
which is where digestive wastes, urine, eggs/sperm leave the body
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● Respiration● Gas exchange occurs through skin and gills in the larval stage● In adults, the gills are replaced by lungs
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● Circulation● Double-loop
● First loop carries oxygen-poor blood from heart to the lungs and skin & takes oxygen-rich blood from the lungs and skin back to the heart
● Second loop transports oxygen-rich blood from heart to rest of the body and oxygen-poor blood from body back to the heart.
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Amphibian heart has 3 chambers
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● Excretion● Kidneys filter wastes from the blood● Urine travels through waste to ureters & out the cloaca
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● Reproduction● Eggs are laid in water, so can keep moist● In frogs, the male will squeeze a female & she will release
eggs which he then fertilizes- Externally
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● Movement● Larvae move like fishes● Most adults have 4 limbs use legs to move
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● Response● Well-developed nervous system, similar to the fish● Have a nictitating membrane covering the eye to keep it
moist on land and protect it under water● Hear through a tympanic membrane located on each side of
the head
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Groups of Amphibians● Salamanders (order Urodela)● Have long tails● Carnivores at all stages● Include salamanders & newts
● Frogs & Toads (order Anura)● Jump● Frogs have long legs, toad legs are shorter● Frogs are generally aquatic, toads are terrestrial● Both lack tails
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● Caecilians (order Apoda)● Legless animals● Many have scales