introduction

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Introduction

Two concepts are fundamental to evolution:

The characteristics of living things change with time

That change is directed by natural selection

The change in characteristics is not in an individual during its lifetime

Instead, it’s in the population over time

Evolution

the change in the genetic makeup of a population over time

Each individual in a population has a unique genotype because the gametes used in fertilization were unique

Variability is due to mutations and meiosis (crossing over and independent assortment)

Genetic Recombination

The sum of all gene mixing that occurs during sexual reproduction

Another important concept is that sexually reproducing organisms tend to produce far more offspring than is necessary to maintain the population, to replace the parents

Geese live ten years and they raise 8 young per year

If the parents and all offspring survived and reproduced at that rate, there would be over 19 and a half million from only 2 parents

Dramatic increases in population size do not occur because the death rate equals the reproductive rate

Although total numbers remain fairly constant, the genetic makeup of the population changes in ways that allows the population to adapt to environmental changes

This occurs because death is not random, the strong survive

For the most part, survivors are better fit for the environment and therefore reproduce more and transfer more of their “good genes” to the next generation

Acquired Characteristics

Characteristics gained during a lifetime that are not passed on to the next generation

Ex. learned behaviors and phenotypic changes in an individual