Evolution Test - 29

The first small dinosaurs appeared during Triassic period (225 million years ago) of Mesozoic era. This makes option D incorrect as dinosaurs did not appear 500 million years ago. 

Trilobites were the dominant species during the Cambrian Period, 540 to 490 million years ago. They are a fossil group of extinct marine arthropods that form the class Trilobita. They finally disappeared in the mass extinction at the end of the Permian about 250 million years ago. 

Convergent evolution is the process whereby organisms not closely related (not monophyletic), independently evolve similar traits as a result of having to adapt to similar environments or ecological niches. Wings of mosquito, bats, birds are examples of convergent evolution as these organisms not closely related (not monophyletic), independently evolve similar traits as a result of having to adapt to similar environments. Thus, option A is correct.
Divergent evolution is the accumulation of differences between groups, which can lead to the formation of new species, usually a result of diffusion of the same species to different and isolated environments which blocks the gene flow among the distinct populations allowing differentiated fixation of characteristics through genetic drift and natural selection. 
Parallel evolution is the evolution of geographically separated groups in such a way that they show morphological resemblances. 
Adaptation is the evolutionary process whereby a population becomes better suited to its habitat. 

Convergent evolution is the process, whereby organisms not closely related, independently evolve similar traits as a result of having to adapt to similar environments or ecological niches. Thus, option B is correct.
Evolutionary convergence does not explains development of dissimilar characteristics in closely related groups, development of characteristics by random mating and replacement of common characteristics in different groups. 

Archaeopteryx is considered by many to be the first bird or a connecting link between the reptiles and the birds. It is actually intermediate between the present birds and the predatory dinosaurs. This is the bird which belongs to the Jurassic period which was present about 150 million years ago. 

Cretaceous period of the mesozoic era was the last phase. It was considered as the longest phase of the mesozoic era. It was also known as the age of reptiles. In this era, the mammals arose from the reptiles. The transition from reptile to mammal were the evolution of warm-bloodedness, of molar occlusion, of the three-ossicle middle ear, of hair, and of mammary glands. 

Darwin's finches are known for their diverse beak shapes and structures. This arises due to different feeding habit and habitat and is an example of adaptive radiation. Adaptive radiation refers to the diversification of organisms from their ancestral species due to change in habitat, feeding habit etc.

In evolutionary biology, adaptive radiation is a process in which organisms diversify rapidly into a multitude of new forms, particularly when a change in the environment makes new resources available, creates new challenges and opens environmental niches. Thus, option D is correct.
Adaptive convergence is a form of evolution in which two unrelated (or distantly related) species evolve very similar forms due to similar selective pressures.  Thus, option C is wrong.
Genetic drift or allelic drift is the change in the frequency of a gene variant (allele) in a population due to random sampling. Thus, option B is wrong.
Speciation is the evolutionary process by which new biological species arise. Thus, option A is wrong.

The structures which are similar in their morphology, anatomy, genetics and embryology but dissimilar in their function are called as homologous organs. Many mammals have similar limb structures. The flipper of a whale, the wing of a bat, and the leg of a cat are all very similar to the human arm.