Consider the following groups of animals

1. Protozoans – single-celled organisms such as amoebas and paramecia.

2. Annelids – earthworms, leeches.

3. Echinoderms – starfish, sea urchins, sea cucumbers.

4. Mollusks – snails, octopi, squid, snails

5. Arthropods – insects, spiders, crustaceans such as shrimp, crabs, lobsters.

6. Fishes – tilapia, sharks

7. Amphibians – frogs, toads

8. Reptiles – lizards, crocodiles

9. Birds – parrots, eagles

10. Mammals – goats, cows
All the ten different groups of animals listed above have DIFFERENT BODY PLANS.

A body plan simply describes how different parts (or systems) of an organism are assembled to form the entire SHAPE and SIZE of the organism.

A body of an organism usually consists of many vital systems which are structurally and functionally linked together[/b]such that it is impossible for some of these vital systems to be absent without affecting the viability of the organism.


According to the theory of evolution, all the different life forms on earth descended from a [b]single common ancestor through slight modifications brought about by mutations and natural selection acting together over a long period of time .


Therefore, if this theory of gradual evolution through common descent is true, then one body plan of an animal has to be evolved gradually from another body plan.

But the gradual evolution of one body plan into another body plan would face two serious problems:

1. Problem of mutations in the developmental genes which are universally accepted to be extremely disadvantageous.


2. Problem of constructing a series of reasonable intermediate organisms.


Now let me explain these two problems one after the other.

THE FIRST PROBLEM:

Changing from one body plan to another is a MORPHOLOGICAL change which can only be effected by mutations in the developmental genes (i:e the genes that control the development of embryo from a single fertilized egg).

All examples of evolution (like virus antibiotic resistance and peppered moth evolution) usually cited by evolutionists are mere BIOCHEMICAL changes which are brought about by mutations in the structural genes. But structural genes tend to have little effect on the development of a body plan. Simply changing a protein here and there by mutations in the structural genes cannot change the entire body plan.


For a body plan to morphologically change from old one to a new one, mutations in the developmental genes are not only require but necessary. But as agreed by all scientists, mutations in the developmental genes are extremely disadvantageous because the developing embryo is very sensitive to early developmental mutations
.
Wallace Arthur, a staunch evolutionist, wrote:

"Those genes that control early developmental processes are involved in the establishment of the basic body plan. Mutations in these genes will usually be extremely disadvantageous, and it is conceivable that they are always so."


In fact, Wikipedia submits as follows;

" The development of a fertilized egg into an adult is a complex and delicate process of interaction between genes and the environment that must be carried out precisely and if there is any alteration in the usual process caused by the absence of a necessary gene or the presence of a different one, it can arrest the normal development.... "

But it is this very mutations in the developmental genes that is required for one body plan to evolve into another body plan. This simply shows that evolution of one body plan into another body plan by developmental gene mutations is impossible.


However, evolutionists for decades have been studying mutations in the structural genes which can only deal with how organisms survive as they are (microevolution), and it doesn’t tell us how they got to be the way they are (macroevolution).


THE SECOND PROBLEM:
Another serious problem facing the gradual evolution of old body plan into a new body plan is how the series of reasonable intermediate organisms can be constructed throughout

Along the way, functional organisms must pass through the stage of intermediate forms. But even the functionality of these intermediate organisms transforming from one body plan into another has long puzzled even the most dedicated evolutionists.

For example, S. J. Gould, the late Harvard paleontologist, asked;

"But how can a series of reasonable intermediates be constructed (during the transformation of the old body plan into a new body plan) ?"

In other words, a stage must be reached ( may be half-way) when the significant parts of the old body plan would have been disappeared while the new body plan would be yet to complete. But, at this very stage, the viability of such an intermediate organism would be zero because there is no way for the remnants of the old body plan to harmonize perfectly with the rudiments of the new body plan.


When one vital system (like circulatory system) in the old body plan has to be enlarged and modified for effective functioning and perfect incorporation into the new body plan, many other vital systems ( like respiratory system, nervous system, etc) in the old body plan have to be simultaneously enlarged and modified in the required proportion for perfect harmony to take place


As you can see, all these intelligent and simultaneous adjustments must take place in a single generation if the new body plan must survive to exist.


But if "gradual evolution through slight modifications over many generations that has no purpose and direction" is the rule of the game, then how is it going to be possible to achieve all these intelligent and simultaneous adjustments in a single generation ?


If properly understood, these two problems are enough as theoretical evidence to prove that gradual evolution of new body plan from old body plan is impossible.


The practical evidence that confirmed this theoretical evidence is the existence of CAMBRIAN EXPLOSION, a term used to describe the relatively short period in the fossil records when almost major animal phyla with different body plans suddenly appeared without any traces of preceding intermediate organisms.


Berkeley University’s Professor Philip Johnson describes the open inconsistency between the theory of gradual evolution and the fact of Cambrian explosion by saying,

"'Darwinist theory assumes that a species develops within “a triangle of increasingly expanding diversification.” According to this, life began from the first living organism or primitive animal species, diversified increasingly and gave rise to higher categories of biological classification. But animals fossils show us that this triangle actually stands upside-down: Phyla existed all together from the first moment, their numbers declining subsequently.'”


As Philip Johnson has said, rather than phyla developing gradually, all phyla appeared at once and the same time, with some of them later becoming extinct. And all these very different life forms appearing suddenly means they were created rather than evolved.