Phylum Chordata

PHYLUM CHORDATA

Animals under this phylum are referred to as chordates or vertebrates

Characteristic features of this phylum (vertebrata)

  1. The body is composed of head, trunk and usually a tail
  2. They have two limbs for locomotion
  3. They have an endoskeleton composed of bones and cartilage
  4. They have a bilateral symmetry
  5. Possess kidneys as organs of excretion
  6. They have a hollow dorsal nerve cord

 

THE PHYLUM CHORDATA INCLUDES THE FOLLOWING FIVE MAIN CLASSES.

Class : – Pisces

Class:   – Aves

Class:   – Amphibia

Class : – Reptilia

Class:   – Mammalia

 

CLASS PISCES- THE FISHES

Examples Tilapia, Silver fish, Nile perch etc.

CHARACTERISTIC FEATURES OF FISH

  1. They live in water only i.e aquatic animals.
  2. Have gills for gaseous exchange or breathing
  3. The body is covered with dermal scales for protection of skin.
  4. Have fins for stability and movement in water.
  5. Possess a lateral line for detecting directional flow of water current.
  6. Do not maintain a steady body temperature i.e is poikilothermic animals.
  7. Have eyes without eyelids.
  8. Lack an external and middle ear but have an inner ear.
  9. Have a swim bladder for bouyancy.
  10. They show no or little parental care to their young ones.

Drawing showing parts of fish

 fish diagram

CLASS AMPHIBIA – THE AMPHIBIANS

Examples of amphibians – Toads, Frogs, Salamanders

 CHARACTERISTIC FEATURES OF AMPHIBIANS

  1. They live both on land and in water. Adults return to water to breed.
  2. Lay eggs in water where they are fertilised externally.
    3.       Have a soft, moist and warty skin without scales.
  3. Have four limbs for locomotion. Hind limbs have webbed toes which help in swimming.
  4. They undergo metamorphosis in their development.
  5. They are poikilothermic animals i.e. they cannot maintain a constant body temperature
  6. Use lungs, skin, and buccal cavity for breathing. Tadpoles use gills for gaseous exchange
  7. They have no external ear but have an ear drum located around the surfaces of the head
  8. They do not take care of their eggs and young ones
  9. They have a three cambered heart

 

Diagram of toad (page 49 fig 4.11 B tropical biology)

 

 

Difference between a frog and a toad

Frog Toad
Live in moist places near ponds Live in dry shady
Body is smooth and shiny Body is dry and warty
Poisonous glands absent Poisonous glands present
Have teeth on upper jaw No teeth at all
Mostly active during the day Mostly active at night

 

CLASS REPTILIA – The Reptiles:

Examples of reptiles: Lizards, Snakes, Turtles, Crocodiles, Alligators

CHARACTERISTIC FEATURES OF REPTILES

  1. Majority live on land.
  2. Have a dry skin covered with horny scales.
  3. Use lungs for breathing
  4. Lay yolky eggs which are fertilised internally.
  5. Have two pairs of legs for locomotion except for the case of snakes
  6. They are poikilothermic animals
  7. They have teeth that look alike i.e. are hormodonts
  8. They have four chambered heart

Adaptations of life on land

  1. They have scales to prevent water lose
  2. They have lungs that enable them to breath effectively
  3. Ty lay eggs with shells to prevent them from drying
  4. Their excreta is in form of uric acid to retain water in the body

 

CLASS AVES- THE BIRDS

Examples of birds: Owls, Eagles, Ostriches, Kiwi, Emu, Doves, Pied crow, Weaver birds, Parrots

 

CHARACTERISTIC FEATURES OF BIRDS:

  1. They are terrestrial animals i.e. live on land.
  2. Breathe by means of lungs which are connected to air Sacs.
  3. Body is covered with feathers.
  4. Fore limbs are modified into wings for flight.
  5. Have two feet covered with scales.
  6. Lay eggs after being fertilised internally. These eggs contain a lot of Yolk and albumen within a shell.
  7. Have beaks and lack teeth. This represents a mouth.
  8. Have hollow bones.
  9. Have no external ear lobes.

1 o.    Have the ability to keep their body temperature constant i.e. are homoiothermic animals.

11.    They show much parental care to their eggs and young ones.

 

CLASS MAMMALIA, THE MAMMALS

Examples of Mammals: Spiny ant eater, Kangaroo, Mole, Rat, Zebra, Cow, Pig, Whale, Cat, man, etc

 

CHARACTERISTICS OF MAMMALS

  1. They are mainly terrestrial; except a few mammals
  2. Body is covered with hair or fur
  3. Use lungs for breathing or gas exchange.
  4. They have external earlobes
  5. Have different types of teeth namely- incisors, canines, premolars, and molars. They are termed as heterodonts
  6. Carry out internal fertilization
  7. They show much parental care to their young ones
  8. They are homoeothermic animals
  9. They have sweat glands found in the body

 

 

2 responses to “Phylum Chordata

  1. thank you 🙂

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