Chapter 11 Diversity Within Species
Today’s Outcome
Outcome 13: The student should demonstrate an understanding of how population genetics,
natural selection and evolution relate to each other.
Today’s Objectives
• Define and distinguish among population, species and subspecies.
• Provide supportive evidence that two organisms belong to the same species.
• Define gene pool and explain how the number of alleles in the gene pool differs from the
number of alleles and individual can possess.
• Define gene frequency, recognize gene frequency statistics, and calculate the frequency
of an allele in a population.
• List five factors that can cause a change in gene frequency and explain how these factors
influence gene frequency.
• List factors contributing to the process of speciation
Why Diversity?
Diversity is a hallmark of life. Diversity is essential to survival in a changing world.
In biological terms differences that are favorable are maintained, those that are not helpful are
weeded out.
Key Concepts
- organisms with similar characteristics that naturally interbreed and produce
fertile offspring.
Species share genes – gene flow occurs naturally
Species have specific chromosome number
Hybrid viability determines degree of separation
- all members of a single species in a given area.
Gene pool - all genes within a population
Gene frequency - proportion of “A” vs. “a” in a population.
Calculate the proportion of each allele in the mice population in text:
Gene Pools for 3 different traits
long tail (T)
=
short tail (t)
=
=
=
Brown color (B)
White/albino(b)
=
=
=
=
Size-large (S)
size-small (s)
=
=
=
=
We’re talking gene pools
Breeds, races, strains, varieties = sub groups within a species
Subspecies differ in gene frequency and differences tend to cluster due to environment
Gene Pool Differences in Gene Frequency
Where would one expect to find the highest gene frequency for light skin, freckles and red hair?
Where would one expect to find the highest gene frequency for dark skin and thick nappy hair?
Where would one expect to find the highest gene frequency for thick padding around eyes, a
small stout body and thick straight dark hair?
Natural Selection
What are some of the factors that have shaped human genetic variation?
•
•
•
•
Climate - especially hair texture, skin color, body shape
Disease - resistance factors
Food - adaptations for nutrition
Sex/Mates - adaptations for attracting mates
Population Genetics
Population
Frequency of lactose intolerance
Asians
95%
Native Americans
75%
Hispanics
60%
African Americans
50%
Caucasians
20%
Population
Basques (Western Europe)
Central Europe
China
U.S. Whites
U.S. Blacks
Native
Rh+
Rh- ( no Rh protein on RBC’s)
Many gene frequency differences represent the selective pressure exerted by disease. Example:
Micro vs. Macro Evolution
The pope declares that there is no reason to dispute microevolution and the process of natural
selection. Some fundamental/dogmatic religions have a problem aligning the idea of
macroevolution with their doctrine but virtually all religions acknowledge natural selection and
microevolution. Most individuals and many clergy haven’t kept up with the current position of
their religion.
Open ended questions
• What is diversity?
• What is race?
• What does human nature have to do with our perception of race/ethnicity?
• What does biology have to do with it?
Genes and Race/Ethnicity
From a biological point of view diversity is a good thing, an important thing and sometimes an
essential factor in surivival. Certain genes are more valuable in a given environment. Human
variation has been shaped by natural selection for over 100,000 years.
Genes and Race/Ethnicity
Populations can be differentiated by recognizable variations in gene frequencies.
Roughly speaking, race is the part of one person’s variation on the theme of humanity created by
the interplay of geography and inheritance.
Race simply reflects Variations in the frequency of genes for:
• melanin production
• hair color and texture
• stature
• facial features
• ability to produce lactase
• blood types
• resistance to disease
• and many, many others
•
Eugenics
“good genes”
movement to improve the human gene pool
Positive Eugenics Negative Eugenics Eugenics Policies and the Sterilization of mental defectives was common until the 1960’s
Statement of Policy
Sec. 1. It is hereby declared to be the policy of the state to prevent the procreation and increase in
number of feebleminded and insane persons, idiots, imbeciles, moral degenerates and sexual
perverts, likely to become a menace to society or wards of the state.
Eugenics Movement
1907 Indiana first state to pass involuntary sterilization laws (criminals & insane)
1924 Immigration act limits entry of “idiots, imbeciles, feebleminded, etc.”
1927 Buck vs. Bell compulsory sterilization of mentally retarded
1930’s Nazi Germany’s negative eugenics
1956 Many state eugenics laws repelled
1965 Immigration restrictions lifted
1980 California’s Center for Germinal Choice instituted
1994 The Bell Curve published