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Analogous Structures
Analogous Structures
Each of these creatures to the right have wings even though they are distantly related. These animals developed similar structures independently so that they can fly.
Artificial selection
Artificial selection is an evolutionary process in which humans select for or against particular features in organisms.
For example, when a farmer breeds only the most muscular creatures, each generation becomes meatier. Consider Belgian blue cattle. They have been bred for their meat.
Convergent Evolution
Convergent Evolution
Convergent evolution occurs when different species occupy similar ecological niches and adapt in similar ways in response to similar selective pressures.
The animals shown at the right have developed similar shapes independently. Streamlined bodies work best in water environments!
Traits that arise through convergent evolution are referred to as 'analogous structures'.
They are contrasted with 'homologous structures', which have a common origin.
These animals have analogous structures.
Homologous Structures
Homologous Structures
In contrast to convergent evolution where similar traits develop independently, homologous structures develop from a common ancestor.
Mutation
Mutation
An accidental change in a gene can be either helpful, harmful, or neutral. Mutations can be caused by random mistakes, radiation, chemicals, or by infections agents. DNA mutations result in genetic variation within a species.
Natural Selection
Natural Selection
Natural selection is a mechanism of evolution. Organisms that are more adapted to their environment are more likely to survive and pass on their genes. This process causes species to change and diverge over time.
Population
Population
A group of the same species occupying a particular geographic region. The picture to the left shows the range of the black bear population.
Reproductive Fitness
Reproductive Fitness
A creature is deemed "Fit" if it reproduces.
Scientific Theory
Scientific Theory
•A very detailed explanation based on facts.
•Repeatedly confirmed by science.
•Not a guess or a hunch!
Variation
Variation
Darwin noticed that species usually have a great deal of variation.
Mutations are the ultimate source of genetic variation. Genetic variation refers to diversity in gene frequencies as well as differences between individuals or within populations. Sexual reproduction and genetic drift contribute to variation as well. Variation is variety.
Variation increases the chances that better individuals will survive - ultimately preserving the species.
Vestigial Organ
Vestigial Organ
Vestigial organs are organs, tissues or cells in a body which are no longer used in current life forms. In the case of whales, they have vestigial pelvic bones; whale ancestors used to live on land.
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