Classification and Evolutionary Relationships
Why scientists classify organisms
Classification helps scientists understand how living things are related.
By grouping organisms with similar features, we can trace their evolutionary history.
Vertebrates
Vertebrates are animals that have:
A vertebral column (backbone)
A skull protecting the brain
Jaws, usually with teeth
Examples include mammals, birds, reptiles, amphibians, and fish.
Evidence from limb structure
Different vertebrates use their front limbs for different jobs:
Grasping
Flying
Running
Swimming
Even though the functions are different, the basic bone structure is the same.
Common limb pattern
All these vertebrates have:
One upper bone → Humerus
Two lower bones → Radius and Ulna
A group of wrist bones
Five groups of bones forming the hand and fingers(some are missing or reduced in birds)
This same structure is called a homologous structure.
What this tells us about evolution
If animals were not related, it would be strange for them to have such similar bones.
The best explanation is that:
They all came from a common ancestor
Over time, the limb changed slightly in each group to suit different needs
This supports the theory of evolution.