Transcript CHAPTER 16 NOTES

CHAPTER 16 NOTES
GENETICS & EVOLUTION
 Gene pool – consists of all the genes that are
present in a population
 Relative frequency – the number of times that
an allele occurs in a gene pool
– Ex. In a mouse population, the dominant
allele for black fur may appear 40% and
the recessive allele for brown fur may
appear 60%
 In genetic terms, evolution is any change in
the relative frequency of alleles in a
population
GENETIC VARIATION
2 Main Sources of Genetic
Variation:
1. Mutations – change in a
sequence of DNA
2. Gene shuffling that results from
sexual reproduction
DEFINITIONS
 Species – interbreeding populations
of organisms that can produce fertile
offspring
 Speciation – formation of a new
species
 Reproductive Isolation – when
members of two populations cannot
interbreed and produce fertile
offspring
How do organisms become
isolated?
 1. Behavioral isolation – when 2
populations are capable of
interbreeding but have differences in
courtship rituals or other
reproductive strategies that involve
behavior
 2. Geographic isolation – when 2
populations are separated by
geographic barriers such as rivers,
mountains or bodies of water
Speciation in Darwin’s Finches
 Darwin found over a dozen different species
of finches on the Galapagos Islands that all
evolved from a common ancestor
 How?
 A few finches (original species) flew or were
blown to one of the Galapagos Islands
 Then some birds migrated to neighboring
islands and because the environments were
different they adapted to their own
environments and became separate species
DARWIN’S FINCHES
Darwin’s Finches are an example
of adaptive radiation
Adaptive radiation is when a
single species has evolved into
diverse forms that live in
different ways