Catastrophism is the theory that the Earth has largely been shaped by sudden, short-lived, violent events, possibly worldwide in scope. This is in contrast to uniformitarianism (sometimes described as gradualism), in which slow incremental changes, such as erosion, created all the Earth's geological features.
Gradualism, from the Latin gradus ("step"), is a hypothesis, a theory or a tenet assuming that change comes about gradually or that variation is gradual in nature and happens over time as opposed to in large steps. Uniformitarianism, incrementalism, and reformism are similar concepts.
uniformitarianism. ... This is known as uniformitarianism: the idea that Earth has always changed in uniform ways and that the present is the key to the past. The principle of uniformitarianism is essential to understanding Earth's history
Homologous structures are structures that are similar in related organisms because they were inherited from a common ancestor. These structures may or may not have the same function in the descendants. Figure below shows the hands of several different mammals. They all have the same basic pattern of bones.
Analogous structures are structures that are similar in unrelated organisms. The structures are similar because they evolved to do the same job, not because they were inherited from a common ancestor. For example, the wings of bats and birds, shown in Figure below, look similar on the outside.
Vestigial structures are various cells, tissues, and organs in a body which no longer serve a function. A vestigial structure can arise due to a mutation in the genome.
Variation, in biology, any difference between cells, individual organisms, or groups of organisms of any species caused either by genetic differences (genotypic variation) or by the effect of environmental factors on the expression of the genetic potentials
Adaptation is the physical or behavioural characteristic of an organism that helps an organism to survive better in the surrounding environment.ā Living things are adapted to the habitat they live in. This is because they have special features that help them to survive.
In biology, evolution is the change in the characteristics of a species over several generations and relies on the process of natural selection. The theory of evolution is based on the idea that all species? are related and gradually change over time.
Natural selection is the process through which populations of living organisms adapt and change. ... Natural selection can lead to speciation, where one species gives rise to a new and distinctly different species. It is one of the processes that drives evolution and helps to explain the diversity of life on Earth.
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