It is a unifying theory that explains phenomena from cosmology to immunology. It is not speculation poorly grounded in imperfect fossil records, assumptions about leaps between major body plans, and extrapolations from poorly controlled experiments on populations. It is a theory subject to naturalistic testing. It isn't anti-religious and it doesn't claim that everything is random nor that there is necessarily no direction or purpose to life. B. Separate the various levels of evolution to avoid misconceptions.
Biological evolution is descent with modification.
The modification is heritable, which separates biological evolution from the evolution of non-living things. Microevolution is what happens in populations, between successive generations of organisms. Speciation is the separation of one lineage into two. Macroevolution describes the processes and patterns that take place between species and larger lineages of organisms and communities in their environments, which also change through time. The more we learn, the more concepts expand.