1. 25.2 Part II. The Cladogram of Animals

2. The Cladogram of animals
The features of animal body plans provide information for building a cladogram of animals
The animal cladogram presents our current understanding of relationships among the animal phyla
Animals are defined by the adult body plans and patterns of embryological development

3. The blue boxes represent important traits that have evolved over time

4. Difference Between Phyla
The animal cladogram represents the sequence in which important body plan features evolved
Every phylum has a unique combination of ancient traits inherited from its ancestors and new traits found only in that particular phylum
Remember just because an animal has a more complicated body system does not mean it can function better than an animal with a more simple body system
Any system found in living animals are able to function well enough to enable those animals to survive and reproduce
Example: Monkey brains are much more complicated than a fish brain, but fish brains work well enough to enable fish to survive

5. Changes within Phyla: Themes and Variations
Within each phylum different groups represent different variations on the basic body plan themes that have evolved over time
For example: Both wings and arms evolved through changes in the standard vertebrate forelimb
Many land vertebrates typically have four limbs
In birds the front limbs have evolved into wings
In primates the front limbs have evolved into arms

6. Evolutionary Experiments
Each phylum’s body plan can be viewed as an evolutionary experiment in which a particular set of body structures perform essential functions
Fossil records of each phylum marks the beginning of the experiment
The very first versions of most major body plans were developed hundreds of millions of years ago
Ever since a phylum’s body plan was first developed each phylum’s evolutionary history has shown variations in its body plan to adapt to changing environments
If the variation in body plan allowed the phylum to reproduce and survive than the phylum still exists
If the variation in body plan hasn’t functioned well enough over time then the phylum or particular groups within the phylum become EXTINCT