Question

how does body organization complexity relate to body shape/size and physiological exchange with the environment?

Answer 1

In the process of organic evolution, the organisms developed from unicellular level to multi cellular level.

Unicellular organisms perform all basic functions of life. The physiological exchange with the environment in the unicellular organisms occurs by the process of simple diffusion, because the entire surface of their cell is in direct contact with the environment.

In the multicellular organisms, there are four levels of body organization. They are :

1. Cellular, 2. Tissue level, 3.Organ level, and 5. Organ system level.

Generally with the increase in the complexity of the organism, the body size of the organism also increases. Large body size gives various advantages like :

Ability to tolerate the environmental changes, which is not that easily possible with the small size

Able to avoid the predators,

Able to acquire the food easily

Metabolically becoming efficient

But there are certain disadvantages also with the large body size. They are:

With the increase in the body size, the surface area of the out side of the organism body increases at a slower rate than the increase in the body volume.

The processes that could occur by simple diffusion cannot occur in the large sized organisms.

So, in large sized organisms, at many places, the parts and their surfaces have foldings so as to increase the surface area for the efficient carrying out of metabolic activities.

Internal transport systems are developed in the large sized organisms, so as carry out many of the physiological life processes effectively and to have effective physiological exchange with the environment.

With the increase in the body complexity, the shape also gets changed. The body symmetry gets changed from radial to Bilateral.

The organisms with the radial symmetry can interact with the environment from all the sides of the organisms.

Having Bilateral symmetry has given the major evolutionary advance to the organisms as it is well suited for forward movement in the organisms.