Download Changes In Populations

Changes In Populations
The Gene Pool
•
•
•
•
Population – a group of organisms of the same species living together in a given area
Gene pool – the alleles for every gene present in a population at any one time
Allele frequency – the frequency with which a particular gene variant is found in a population
To calculate allele frequency for a gene
• Number of each allele divided by total number of alleles
Phenotype
Number of Plants Genotype Number of Alleles
r r
r
Red flowers
25
CC
50 C
r
y
y
y
Orange flowers
50
CC
Yellow flowers
25
CC
Total: 100
r
50 C and 50 C
y
y
50 C
Total: 200
• Variation exists within a population
• Ex) Different colors of wildflowers
• Variation exists between populations of same species
• Ex) Different allele frequencies of wildflower colors
Changes to Gene Pools
• Genetic mutations introduce variation into a gene pool
• Ex) White coloring is a mutation of Bengal tiger coloring
• Outside forces can change gene pools
• Ex) Bird species preying on green caterpillars alters
allele frequency in caterpillar population
• Events affecting the success of certain alleles being passed on to
the next generation is called natural selection
Biology 9.1 – Changes In Populations