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Introduction to Evolution (BIL 107)
"Nothing in biology makes sense except in the light of evolution."
-- Theodosius Dobzhansky
But before we begin, a quick poll.
Is it a trick question with a trick answer?
(no, not really.)
An informal poll: Which is the most highly evolved species?
EVOLUTION is defined as change over time.
ORGANIC EVOLUTION is the genetic (and phenotypic) change of living
organisms over time.
We are the products of our ancestors' choices.
Another poll, this one with three parts.
Now the big question...why?
Common Misconceptions About Evolution
There are those who actively seek to discredit the idea of evolution by distorting or misrepresenting the mechanisms and theories presented by scientists.
But sometimes there are just simple misunderstandings. Here are just a few.
MISCONCEPTION: Evolution is "only a theory".
Organic evolution is not a theory at all. It is a process by which living organisms change from one generation to the next. The only thing theoretical about evolution is how it happens.
MISCONCEPTION: Evolution describes the origin of life on earth.
Evolution is not the process by which life originated. It is the process by which life has changed since its origin. The origin of life and the evolution of life are two separate concepts.
MISCONCEPTION: Evolutionary theory implies that life evolved, and is evolving, by chance.
While random processes (genetic drift) do contribute to evolution, natural selection is a non-random process that can result in evolution happening in a particular "direction" (i.e., creating populations of organisms that are adapted to a particular environment).
MISCONCEPTION: Evolution is progress: evolving organisms are getting better.
Evolution is a process, and it has no value system. Populations change, but how does one define "better"? Organisms evolve to fit their environments, which means diversity of form and function. But there is no one form or function that is superior to all others.
MISCONCEPTION: Individual organisms evolve during their lifetimes.
Individuals adapt as they live and age. Only populations of organisms evolve, from one generation to the next.
MISCONCEPTION: Evolution always occurs gradually, over very long periods of time.
Relatively small genetic changes can sometimes result in major phenotypic changes. If these are passed to the next generation, they can magnify (especially if they are adaptive), and major evolutionary modifications can occur relatively rapidly.
MISCONCEPTION: Our species is no longer evolving.
Genetic drift and natural selection are alive and well in Homo sapiens populations. Pathogens, parasites, and other environmental factors all can affect individuals, and sometimes they can cause differential reproduction among individuals of different genotype.
MISCONCEPTION: Because evolution is slow, humans cannot influence it.
Humans are influencing evolution as we speak. For example, our activities that produce pollution and climate change are driving evolution of species that can reproduce quickly enough to evolve in response. Others may simply go extinct, if they cannot cope with the relatively rapid changes wrought by humans.
Here are some more common misconceptions about evolution.
So join me on a 14-week tour of the Marvels of Evolution.
You won't see the world the same way when we're through.