Lecture 14 - Amphibians / Gnathostomata

Question 1

What are the classes and subclass of Superclass: Gnathostomata

Answer 1

• Class: Chondrichthyes (cartilagenous fish)
• Class: Osteichthyes (bony fish)
  -Subclass: Actinopterygii (ray-finned fish)

Question 2

What are the divisions of Superclass: Gnathostomata

Answer 2

• Sub-division: Teleostei (modern bony fish)
• Infradivision: Enteleostei (higher teleosts)

Question 3

What are the order and super order Superclass: Gnathostomata

Answer 3

• Superorder: Acantopterygii (spiny-rayed fish)
• Order: Perciformes

Question 4

What are the subclasses of Class: Chondrichthyes

Answer 4

• Subclass: Elasmobranchi
• Superorder: Batoidea (skates and rays)
• Superorder: Selachii (sharks)

Question 5

Explain Class: Chondrichthyes

Answer 5

• Skeleton of cartilage
• Placoid scales; teeth modified placoids
• Fusiform (spindle shaped) body

-Sense organs well developed

• Some predators; some filter feeders

Examples: Carcharadon carcharias (great white), C. taurus (ragged-tooth)

Question 6

Explain Superclass: Gnathostomata

Answer 6

• Skeleton bony
• Skin with mucous glands and embedded scales
• Four types of scales – cycloid (smooth edged), ctenoid (rough edged), lanceolate (sharp, long margins) and rhomboid (non-overlapping)
• Fins both paired and median
• Mouth terminal
• Respiration by gills
• Swim bladder often present
• Two-chambered heart
• Ten pairs of cranial nerves

Question 7

Explain Class: Osteichthyes

Answer 7

• Ray-finned fish
• Internal bony skeleton
• Scales of bone
• Gills covered by operculum
• Swim bladder present
• Feeding habits diverse: facultative filter feeders (sardine/pilchard)- pump water into their mouth
• Other filter feeders swim with their mouth open
• Opportunist feeders (trout and hake )- has different food sources. They are also often described as generalist predators
• Predators (yellowtail, snoek)

Question 8

Explain sea horses

Answer 8

• Males bear the offspring
• Female produces eggs, deposits it into male brood pouch
• He releases sperm to fertilize the eggs
• 2 to 4 weeks and he will give birth to hundreds of baby seahorses
• They receive no parental care

Question 9

Explain Class Amphibia

Answer 9

• Normally tetrapods
• Adult normally have lungs
• Metamorphosis
• Mostly moist, smooth skins
• Heart – 3-chambers; closed circulation
• External water source for fertilization generally
• Ectothermic

Question 10

Explain Evolution of amphibians from lobe finned fishes

Answer 10

• Lobe finned fish of Devonian are ancestral to amphibians
• Lobe finned fish- consist of 6 species of lungfish & 1specie of coelacanth.
• Lobe finned fish have fleshy fins and live in stagnant ponds or ponds that dry up. (in Africa, South America and Australia)
• They have lungs –breathe air

Question 11

Explain Two hypotheses describe evolution of amphibians from lobe‑finned fishes

Answer 11

• Lobe‑finned fishes that could move from pond‑to‑pond had an advantage over those that could not.
• The supply of food on land and the absence of predators promoted adaptation to land.

    - Lobe finned fish diversified during carboniferous

Question 12

Class: Amphibia eggs and metamorphosis

Answer 12

• Generally, amphibian eggs are protected by a coat of jelly but not by a shell. They are not amniotic egg
• The young hatch into aquatic larvae with gills (tadpoles).
• The aquatic larvae usually undergo metamorphosis to develop into a terrestrial adult.

Question 13

Explain tetrapods

Answer 13

• All animals studied from this point on are tetrapods (have four limbs).
• Land animals use limbs to support their body since the air is less buoyant than water.
• About 4,200 species of amphibians belong to class Amphibia.
• The first amphibians diversified during the Carboniferous Period which is known as the Age of the Amphibians.

Question 14

What are the subclasses of Class: Amphibia

Answer 14

• Urodela
• Apoda
• Anura

Question 15

Explain Subclass : Apoda

Answer 15

• Apoda means without legs
• Legless, often sightless
• Worm-shaped body form (earthworm like)
• Caecilians are legless; most burrow in soil and feed on worms, etc.
• Reproduction involves a return to the water; “amphibian” refers to this need to return to water from land.
• They shed eggs into the water for external fertilization.

Question 16

Explain Urodela

Answer 16

• With tail
• Newts and salamanders are included in this subclass.
• They have a long body and tail, and two pairs of legs
• Retain postanal tail of larva
• Some retain external gills of larva (= neoteny)
• They lay eggs on land or in water;
• Their S-shaped locomotion is similar to fish movements.
• Salamanders and newts are carnivorous, feeding on insects, snails, etc.
• Salamanders practice internal fertilization.
• Salamanders can regrow entire limbs and regenerate parts of major organs, an ability that relies on their immune systems.

Question 17

Explain Anura

Answer 17

• Without tail
• Anura includes Frogs and toads
• Frogs and toads are tailless as adults; the hind limbs are specialized for jumping.
• Frogs and toads have the head and trunk fused; frogs live near or in fresh water while toads live in damp places away from water.
• Frogs have smooth skin while toads have a bumpy skin

Question 18

Explain frogs and lungs

Answer 18

• Barbourula kalimantanensis defies evolutionary convention
• They inhabit cold fast-flowing rivers of Borneo rainforests
• Breathes entirely through skin and lacks lungs.
• Cold water contains more oxygen, thus skin breathing is an advantage
• Two spp. of salamander and caecelians also lack lungs

Question 19

Explain the lifecycle of a frog

Answer 19

• Eggs
• Tadpole
• Tadpole ( 4 legs )
• Froglet
• Adult Frog