Evolutionary trends are either progressive or retrogressive. During progressive evolution new structures are created whereas in retrogressive evolution the existing structures are reduced or eliminated.
Generally the evolutionary trend is the development of more complex forms from simpler organisms. This is called progressive evolution. Sometimes simpler forms originate from more complex forms due to adaptation to the particular requirement. This is called retrogressive evolution.
- Natural Selection - Irreversibility - Species Sorting.
A pattern of evolution in which direction of change is persistent over an appreciable span of time.
Adaptation for stronger shells.
Perhaps the most significant evolutionary trend among the metazoan invertebrate phyla is that of cephalization. This term refers to the development of a head, containing a brain. Another process called segmentation allowed animals to develop distinct body parts, such as legs, wings and feelers.
Orthoselection :A primary selective pressure of a directional kind, which results in a self-perpetuating evolutionary trend. Species selection, via the effect hypothesis, has been advanced as an alternative explanation for such trends.
1. The size of the brain relative to the whole body increases in certain evolutionary lines.2. Increased specialization of function.3. The increasing sophistication and complexity of the forebrain.
evolutionary changes in organisms
macroevolution .........novanet
Adaptation for stronger shells.
macroevolution .........novanet
Direct Development vs Indirect Development.
Air-breathing animals do not return to breathing water.
Secular trends in new childhood epidemics, insights from evolutionary medicine.
Misidentification of Cope's Rule - Functional or Physical Boundaries - Signor-Lipps Effect
Cladograms tell you which animals are the closet in relationship, which are the farthest, what characteristics the animals have in common, what characteristics they would need to have in order to be closely related to them, and the number of shared characteristics between the animals.
a natural system of classification is that system of classification in which the organism is classified on the basis of their vegitative characters which are permanent and do not change with the envoirment this system of classification avoids the grouping of hetereogeneous and un related groups of organisms according to this sytem plants are classified on the basis of evolutionary trends while as animals are classified on basis of both evolutionary and phylogenetic trends........junaid
a natural system of classification is that system of classification in which the organism is classified on the basis of their vegitative characters which are permanent and do not change with the envoirment this system of classification avoids the grouping of hetereogeneous and un related groups of organisms according to this sytem plants are classified on the basis of evolutionary trends while as animals are classified on basis of both evolutionary and phylogenetic trends........junaid
a natural system of classification is that system of classification in which the organism is classified on the basis of their vegitative characters which are permanent and do not change with the envoirment this system of classification avoids the grouping of hetereogeneous and un related groups of organisms according to this sytem plants are classified on the basis of evolutionary trends while as animals are classified on basis of both evolutionary and phylogenetic trends........junaid
a natural system of classification is that system of classification in which the organism is classified on the basis of their vegitative characters which are permanent and do not change with the envoirment this system of classification avoids the grouping of hetereogeneous and un related groups of organisms according to this sytem plants are classified on the basis of evolutionary trends while as animals are classified on basis of both evolutionary and phylogenetic trends........junaid