Download BIO 370 1 Introduction to Evolutionary Biology I. What is Evolution

BIO 370
1
Introduction to Evolutionary Biology
I. What is Evolution?
A. Evolution –Latin - evolvere, “to unfold, or unroll” To reveal or manifest hidden potentialities.
B. Evolution in the broadest sense means change.
1. The term evolution is usually applied to not to an individual, but to a population, or to a system.
2. An evolving system is ordinarily one in which there is descent of entities – one generation after
another. Moreover, the characteristics of one generation differ across generations.
C. Thus evolution in the broad sense (but not broadest) is descent with modification, and often, with
diversification.
D. Descent with modification.
1. In all such systems, there are populations, or groups.
2. There is variation in a characteristic among the members of that population.
3. There is hereditary similarity between parent and offspring entities.
4. Over many generations, there may be changes in the proportion of individuals with different
characteristics within populations.
5. This constitutes descent with modification.
E. Descent with diversification.
1. Populations may become subdivided so that several populations are derived from a common
ancestral population.
2. If the populations differ in their proportion of the possible variants, then the populations
diverge, or diversity.
F. Biological evolution holds that characteristics of one generation are passed on to the other, by the
hereditary transmission of characteristics, (i.e. genetically based on DNA, or in a few cases, RNA).
1. Biological evolution depends upon two fundamental processes.
a) chance (random variation in the survival and reproduction of a variant) and
b) natural selection – consistent, nonrandom differences among variants in their survival
rates or reproductive rates. The sorting process.
2. The end result of natural selection is adaptation - A trait that increases the ability of an
individual to survive or reproduce compared to individuals without the trait. [Freeman and
Herron]
3. Biological (or organic) evolution is thus change in the properties of populations of organisms,
or groups of such populations over the course of generations.
G. What is not Evolution?
1. The development of an individual of the course of its lifetime. This is known as ontogeny.
2. Change in an ecosystem.
BIO 370
2
II. Why is Evolutionary Biology Important?
Aside from helping us understand the world around us, evolutionary biology has some useful
applications.
A. Health Sciences.
B. Agriculture.
Perhaps the field that has reaped the greatest benefits from evolution, and suffered the worst
problems at the greatest cost.
1) Our vegetable crops and domestic animals are all the product of artificial selection.
2) An important extension of selective breeding is the backcrossing of a crop species with
individuals of the wild strain for the benefits of resistance to insects or fungi.
3) Genetic engineering in agriculture.
C. Natural Products
1) Taq polymerase
D. Conservation and environmental management.
1) Evolutionary principles tell us how to :
Reduce the likelihood of genetic deterioration (through inbreeding depression) in small,
endangered populations.
How to measure the genetic diversity of small populations.
How to genetically distinguish species from races of a species and whether it is pure enough to
preserve.
E. Understanding the biological world around us.
1) Nothing in biology makes sense except in the light of evolution.”
Theodosius Dobzhansky