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What are the 5 Main Vertebrate Groups?

Updated on September 17, 2012
Vertebrates include Amphibians, Reptiles, Birds, Mammals and Fish
Vertebrates include Amphibians, Reptiles, Birds, Mammals and Fish | Source

What Are Vertebrates?

One of the most interesting lessons I teach my high school students is on classification. It is fascinating seeing the students form an answer to the question "what is a fish?" or "what is a bird?" But before we can get down to what makes mammals, birds, reptiles, fish and amphibians different, we have to ask ourselves "what do they all have in common?"

Mammals, birds, reptiles, amphibians and fish are all members of the vertebrate phylum; but this begs the question:

"What are Vertebrates?"

Vertebrates are a group of animals that have backbones and spinal columns, that first appeared during the Cambrian Explosion around 525 million years ago. Vertebrates display the greatest difference in size of any group of organisms on Earth. Vertebrates range from frogs just a few millimetres long, to the mighty 33m blue whale! Despite the huge variety shown in this group, vertebrates comprise a mere 4% of all discovered animal species. This hub looks at the five major divisions of vertebrates, and what makes them unique.

The Vertebrate Groups

Name
Example
Key Features
Mammal
Polar Bear
Hair/Fur, Produce Milk
Bird
Ostrich
Feathers, beaks
Reptile
Alligator
Dry scales, leathery eggs
Amphibian
Axolotl
Moist, permeable skin, soft eggs
Fish
Great White Shark
Gills, wet scales
An overview of the distinguishing features of the five major vertebrate groups.

Pictures of Mammals

Click thumbnail to view full-size
Mammals give birth to live young, have a covering of hair or fur, are warm-blooded, and feed their young using mammary glands.Mammals are the largest animals on land and in the water...and are also some of the most charasmatic species - making them vital for worldwide conservation efforts.
Mammals give birth to live young, have a covering of hair or fur, are warm-blooded, and feed their young using mammary glands.
Mammals give birth to live young, have a covering of hair or fur, are warm-blooded, and feed their young using mammary glands. | Source
Mammals are the largest animals on land and in the water
Mammals are the largest animals on land and in the water | Source
...and are also some of the most charasmatic species - making them vital for worldwide conservation efforts.
...and are also some of the most charasmatic species - making them vital for worldwide conservation efforts. | Source

The Characteristics of Mammals

Mammals are possibly the most charasmatic of all of the vertebrates. Perhaps this is because we too are mammals, and feel a special affinity towards them. They are also (relatively) large, furry and cuddly - not many people call mammals creepy!. But what makes a mammal a mammal?

Mammals are named after mammary glands - a milk producing gland that all mammals use to feed their young. Additionally, mammals:

  • Have a covering of hair or fur;
  • Breathe air through lungs;
  • Maintain a constant internal temperature (homeotherms)*;
  • Undergo internal fertilisation and give birth to live young (are viviparous).

NB: Homeothermy is the correct scientific term for 'warm-blooded.'

Pictures of Reptiles

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Reptiles lay eggs with leathery shells, are covered in tough scales and are cold bloddedThey live both on land and in the sea......and many are venomous
Reptiles lay eggs with leathery shells, are covered in tough scales and are cold blodded
Reptiles lay eggs with leathery shells, are covered in tough scales and are cold blodded | Source
They live both on land and in the sea...
They live both on land and in the sea... | Source
...and many are venomous
...and many are venomous | Source

The Characteristics of Reptiles

Dinosaurs were the greatest creatures to roam our planet, both in terms of size and many people's affection. Sadly, it doesn't seem this affection has been granted to the dinosaurs descendents! Reptiles (the group to which dinosaurs belonged) are often thought of as creepy, scary or even - quite incorrectly - slimy and disgusting. Reptiles are actually covered in dry scaly skin that prevents water loss - a problem that prevented the amphibians from severing all ties to the water.

In addition to their dry, scaly, waterproof skin, reptiles:

  • Breathe air through lungs;
  • Have a temperature that varies with the environment (poikilotherms)*;
  • Undergo internal fertilisation;
  • Lay leathery-shelled eggs (are oviparous) on land.

NB: Poikilothermy is the correct scientific term for 'cold-blooded.'

Mcdonald Publishing MC-P197 Vertebrates Poster Set
Mcdonald Publishing MC-P197 Vertebrates Poster Set

A collection of four posters detailing the vertebrate groups - great for a youngster's wall!

 

Pictures of Birds

Click thumbnail to view full-size
Birds have beaks and feathers, are warm-blooded, and lay hard shelled eggs.The hollow bones and lightweight feathers allow some birds to hover or even fly backwards - like this Black-Chinned Hummingbird.But feathers don't guarantee flight!
Birds have beaks and feathers, are warm-blooded, and lay hard shelled eggs.
Birds have beaks and feathers, are warm-blooded, and lay hard shelled eggs. | Source
The hollow bones and lightweight feathers allow some birds to hover or even fly backwards - like this Black-Chinned Hummingbird.
The hollow bones and lightweight feathers allow some birds to hover or even fly backwards - like this Black-Chinned Hummingbird. | Source
But feathers don't guarantee flight!
But feathers don't guarantee flight! | Source

The Characteristics of Birds

Man has been fascinated by the flight of birds for thousands of years. In fact, the obsession with flapping flight probably set back the invention of the airplane by decades, if not centuries! Although not all birds can fly, all birds share the same set of adaptations:

All birds:

  • Have a hard beak;
  • Have feathers;
  • Breathe air through lungs;
  • Undergo internal fertilisation;
  • Lay hard-shelled eggs (oviparous) in nests on land;
  • Maintain a constant internal temperature (homeothermic).

Pictures of Fish

Click thumbnail to view full-size
Fish absorb oxygen from the water through gills, are covered in scales and lay soft shelled eggs. They live in both marine and freshwater environments.Wierdly, sharks and rays are classified as vertebrates, even though they don't have a backbone.
Fish absorb oxygen from the water through gills, are covered in scales and lay soft shelled eggs. They live in both marine and freshwater environments.
Fish absorb oxygen from the water through gills, are covered in scales and lay soft shelled eggs. They live in both marine and freshwater environments. | Source
Wierdly, sharks and rays are classified as vertebrates, even though they don't have a backbone.
Wierdly, sharks and rays are classified as vertebrates, even though they don't have a backbone. | Source

The Characteristics of Fish

Fish spend their entire lives in water and are exquisitely adapted to this lifestyle.

Fish:

  • Absorb oxygen from the water through gills;
  • Have fins for swimming;
  • Undergo external fertilisation;
  • Lay soft shelled eggs (oviparous) in water;
  • (Most) Have an internal temperature that varies with the environment (Poikilothermic).

There are several exceptions to these rules. Sharks, for example, give birth to live young and practice internal fertilisation. In fact, sharks lack a true backbone as their skeleton is made of cartilage and not bone.

Pictures of Amphibians

Click thumbnail to view full-size
Amphibians have slimy skin and must return to water to breed. They lay soft shelled eggs and are cold-bloodedAmphibians can be beautiful......or less than beautiful!
Amphibians have slimy skin and must return to water to breed. They lay soft shelled eggs and are cold-blooded
Amphibians have slimy skin and must return to water to breed. They lay soft shelled eggs and are cold-blooded | Source
Amphibians can be beautiful...
Amphibians can be beautiful... | Source
...or less than beautiful!
...or less than beautiful! | Source

The Characteristics of Amphibians

Amphibians were the first group of vertebrates to leave the water and walk on dry land. They even managed to grow to huge sizes before the dinosaurs took over the world. There are three types of extant amphibian - frogs and toads, salamanders and caecilians.

Many amphibians undergo a metamorphosis from a juvenile stage to an adult stage, with the adult stage adapted to life outside of water. One of the greatest differences between these stages is how the animal breathes. When juvenile, amphibians use gills to 'breathe' in water; when adult, amphibians lose their gills and develop lungs, although most can absorb some oxygen from water through their porous skin.

Amphibians:

  • Breathe air through lungs (when adult);
  • Have moist, porous skin;
  • Undergo external fertilisation;
  • Lay soft-shelled, gelatinous eggs in water;
  • Have an internal temperature that varies with the environment (Poikilothermic).

Interviews with Animal Groups

What is your favourite vertebrate group?

See results

Comments

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    • profile image

      samyah 3 weeks ago

      i love it

    • profile image

      jalylah 3 weeks ago

      so mammals really and only 9 on reptiles

    • profile image

      kaleigh 2 months ago

      lol love it

    • profile image

      Charles 12 months ago

      I LOVE IT!

    • profile image

      shasha 2 years ago

      its very good for kids and my son loves it

    • profile image

      ashin 2 years ago

      nice also lovely

    • profile image

      Oliver 2 years ago

      I fond it exa leant and fun keep it up

    • profile image

      mervin apostol 3 years ago

      my crush is_________________________________

    • profile image

      Aminallover 3 years ago

      Hello how do I reference this? What is the name of the author and year?

    • vibesites profile image

      vibesites 5 years ago from United States

      Very interesting and absolutely educational, and recommended for students and little kids who are interested in biology. :)

    • Marcy Goodfleisch profile image

      Marcy Goodfleisch 5 years ago from Planet Earth

      Very nice hub, and so instructional for kids! I love the photos you included here!

      Voted up!

    • TFScientist profile image
      Author

      Rhys Baker 5 years ago from Peterborough, UK

      Yeah..I tried finding out some more and struggled. How I wish I had my uni papers access again.

      I have a first class degree in Biology with a specialism in Toxicology and Cell Biology and a Teaching Certificate in Secondary Science.

      I was arguing with my dept. head about the tongue map - she was adamant there were discrete regions until I showed her the changes. It actually makes sense. If you put something sour on the tip of your tongue, it tastes sour; if you put something sweet on the tip of your tongue it tastes sweet. I have no clue what unami is... :)

    • Lwelch profile image

      Lena Welch 5 years ago from USA

      I would agree with you on that one. I think the only reason I learned it was that my professor did a dissertation on birds. Finding the pages for you was hard. I had to look up monophyletic groups and birds and birds and cladistics.

      A lot of education in the classroom is slow. A few weeks ago I learned that the taste bud maps were incorrect and they have known since 1974 - and it is still in classrooms!

      What is your degree background?

    • TFScientist profile image
      Author

      Rhys Baker 5 years ago from Peterborough, UK

      More to the point it shows how far education lags behind these discoveries - it seems the reclassification of reptilian occurred in 2004. This wasn't mentioned in my degree lectures, even as late as 2010!

      It doesn't seem that this classification change is going to filter down below uni study as the change is so technical that birds and reptiles remain as two essentially separate groups only linked by a common ancestor that therefore requires both descendants to be recognised in the same Clade. It also seems to defy common sense for the traits that I previously listed. But you are right - it is fascinating...if highly technical!

    • Lwelch profile image

      Lena Welch 5 years ago from USA

      Aww the computer booted my edited comment with the easier to read article: http://www.ucmp.berkeley.edu/diapsids/avians.html

    • Lwelch profile image

      Lena Welch 5 years ago from USA

      Here is a great page explaining the phylogeny of animals. It shows the cladograms with birds as a type of reptile and explains why current thinking is placing birds with crocodiles.

      http://biology.unm.edu/ccouncil/Biology_203/Summar...

      Here is another one:

      http://www.uwlax.edu/biology/Zoo-Lab/Lab-10/Reptil...

      It is interesting to look at and really shows how much our views in science are still changing, even in areas that were once thought to be fairly absolute. Thus we get avian and non-avian reptiles.

    • TFScientist profile image
      Author

      Rhys Baker 5 years ago from Peterborough, UK

      It would surprise me if birds were considered reptiles due to huge differences between them (birds are homeothermic, lay hard shelled eggs, have no teeth, possess a beak and are covered in feathers not scales) iamaware that research is revealing that they are much closer related to dinosaurs than we ever thought. But this doesn't make them reptiles. Scales, leathery eggs and polikilothermy would make them reptiles.

    • Nettlemere profile image

      Nettlemere 5 years ago from Burnley, Lancashire, UK

      I can't vote for my favourite I like them all. Great hub though, ideal for biology classes and general interest.

    • Lwelch profile image

      Lena Welch 5 years ago from USA

      Interesting article as I just did this in Bio 175. Did you know that birds are now considered reptiles?