OBSTACLES TO TRANSITION FROM WATER TO LAND

1- Weight-bearing: Sea-dwelling creatures have no problem in bearing their own weight in the sea. However, most land-dwelling creatures consume 40 percent of their energy just in carrying their bodies around. The fish’s bones are not linked to the backbone. Therefore they can’t take on a load-bearing function. Land-dwelling creatures' bones, in contrast, are directly connected to the backbone. For this reason, the claim that these fins slowly developed into feet is unfounded.

 2- Heat retention: Land-dwelling creatures possess a physical mechanism that can withstand great temperature changes. A living organism with a body system regulated according to the constant temperature of the sea would need to acquire a protective system to ensure minimum harm from the temperature changes on land. It is preposterous to claim that fish acquired such a system by random mutations as soon as they stepped onto land.

 3- Water: Essential to metabolism, water needs to be used economically due to its relative scarcity on land. For instance, the skin has to be able to permit a certain amount of water loss, while also preventing excessive evaporation. That is why land-dwelling creatures experience thirst, something that sea-dwelling creatures do not do. For this reason, the skin of sea-dwelling animals is not suitable for a nonaquatic habitat.

 4- Kidneys: Sea-dwelling organisms discharge waste materials, especially ammonia, by means of their aquatic environment: In freshwater fish, most of the nitrogenous wastes (including large amounts of ammonia, NH3) leave by diffusion out of the gills. The kidney is mostly a device for maintaining water balance in the animal, rather than an organ of excretion. Therefore, in order for the passage from water to land to have occurred, living things without a kidney would have had to develop a kidney system all at once.

 5- Respiratory system: Fish "breathe" by taking in oxygen dissolved in water that they pass through their gills. They cannot live more than a few minutes out of water. In order to survive on land, they would have to acquire a perfect lung system all of a sudden.

-    The Impasse of transition from Land to Air 

-    There are various structural differences between birds and reptiles, one of which concerns bone structure. Due to their bulky natures, dinosaurs-the ancestors of birds according to evolutionists-had thick, solid bones. Birds, in contrast, whether living or extinct, have hollow bones that are very light, as they must be in order for flight to take place. Reptiles have the slowest metabolic structure in the animal kingdom. Birds, on the other hand, are at the opposite end of the metabolic spectrum. For instance, the body temperature of a sparrow can rise to as much as 48°C due to its fast metabolism. On the other hand, reptiles lack the ability to regulate their body temperature. Instead, they expose their bodies to sunlight in order to warm up. Put simply, reptiles consume the least energy of all animals and birds the most. In land-dwelling creatures, air flow is bidirectional. Upon inhaling, the air travels through the passages in the lungs (bronchial tubes), ending in tiny air sacs (alveoli). The exchange of oxygen and carbon dioxide takes place here. Then, upon exhaling, this used air makes its way back and finds its way out of the lung by the same route.eptiles have a diaphragm-type respiratory system, whereas birds have an abdominal air sac system instead of a diaphragm.

John Ruben, an acknowledged authority in the field of respiratory physiology, observes in the following passage:The earliest stages in the derivation of the avian abdominal air sac system from a diaphragm-ventilating ancestor would have necessitated selection for a diaphragmatic hernia in taxa transitional between theropods and birds. Such a debilitating condition would have immediately compromised the entire pulmonary ventilatory apparatus and seems unlikely to have been of any selective advantage.

Reptile bodies are covered with scales, and those of birds with feathers. The hypothesis that bird feathers evolved from reptile scales is completely unfounded, and is indeed disproved by the fossil record, as the evolutionary paleontologist Barbara Stahl admits: How [feathers] arose initially, presumably from reptiles scales, defies analysis... It seems, from the complex construction of feathers, that their evolution from reptilian scales would have required an immense period of time and involved a series of intermediate structures. So far, the fossil record does not bear out that supposition.

Larry Martin, a specialist on ancient birds from the University of Kansas, also opposes the theory that birds are descended from dinosaurs. Discussing the contradiction that evolution falls into on the subject, he states:

To tell you the truth, if I had to support the dinosaur origin of birds with those characters, I'd be embarrassed every time I had to get up and talk about it.

-    The Impasse of Evolution of Reptile to Mammal 

-    Mammals are warm-blooded animals (this means they can generate their own heat and maintain it at a steady level), they give live birth, they suckle their young, and their bodies are covered in fur or hair. Reptiles, on the other hand, are cold-blooded (i.e., they cannot generate heat, and their body temperature changes according to the external temperature), they lay eggs, they do not suckle their young, and their bodies are covered in scales.Mammal jaws consist of only one mandibular bone containing the teeth. In reptiles, there are three little bones on both sides of the mandible. 

-    All mammals have three bones in their middle ear (hammer, anvil, and stirrup). Reptiles have but a single bone in the middle ear. Furthermore, when mammals suddenly made their appearance, they were already very different from each other. Such dissimilar animals as bats, horses, mice, and whales are all mammals, and they all emerged during the same geological period. Establishing an evolutionary relationship among them is impossible even by the broadest stretch of the imagination. The evolutionist zoologist R. Eric Lombard makes this point in an article that appeared in the leading journal Evolution:

-    Those searching for specific information useful in constructing phylogenies of mammalian taxa will be disappointed.

Roger Lewin, 

"The transition to the first mammal, ... is still an enigma."