Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
ADAPTATION
How Populations Evolve
An example of n...
© 2015 Pearson Education, Inc.
Big Ideas
Darwin’s Theory
of Evolution
The Evolution of
Populations
Mechanisms of
Microevol...
DEFINITIONS
Preadaptation:
In a population, the presence of traits or versions of traits in some individuals
that allow th...
DEFINITIONS, continued
Microevolution:
The changes in a population’s gene pool over one or more generations
Speciation:
Th...
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Mutation and sexual recombination generate
variat...
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Sexual recombination
– Generates variation by shu...
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Diploidy and balancing selection variation
• Dipl...
Heterozygote advantage? For a lethal version of a gene?
Sickle Cell Anemia
confers a survival
advantage on
carriers!
So, in areas where
malaria is common,
people are actually
bet...
Gene pool = the total collection of genes & their alleles in
a population at any one time
Diversity (Variation) = individu...
Mechanism that results in the diversity of life on Earth:
Mutations in gametes can generate new alleles that become
“fixed...
Natural selection sca example ss
Natural selection sca example ss
Natural selection sca example ss
Natural selection sca example ss
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Natural selection sca example ss

Sickle Cell Anemia as an example of selection
Published on: Mar 3, 2016
Published in: Education      
Source: www.slideshare.net


Transcripts - Natural selection sca example ss

  • 1. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings ADAPTATION How Populations Evolve An example of natural selection and microevolution favoring the allele for SCA Biology 100
  • 2. © 2015 Pearson Education, Inc. Big Ideas Darwin’s Theory of Evolution The Evolution of Populations Mechanisms of Microevolution
  • 3. DEFINITIONS Preadaptation: In a population, the presence of traits or versions of traits in some individuals that allow them to reproduce when their environment changes. Adaptation In a changing environment, the frequency of phenotypes (characteristics) of the individuals in a population shift to reflect the individuals who reproduce most efficiently. Fitness = relative ability to reproduce Gene pool = all the genes and their alleles carried by all the individuals In a population Microevolution  Speciation  Macroevolution
  • 4. DEFINITIONS, continued Microevolution: The changes in a population’s gene pool over one or more generations Speciation: The generation of a new species from another. Macroevolution = changes in taxonomic groups, genus or higher (family, order, class, kingdom) Gene pool = all the genes and their alleles carried by all the individuals In a population Mutation = any change in the nucleotide base sequence of a nucleic acid. If it occurs in a gene of a gamete, it can potentially generate a new allele that could be passed onto offspring and fixed into the population’s gene pool. Microevolution  Speciation  Macroevolution
  • 5. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Mutation and sexual recombination generate variation • Mutations, or changes in the nucleotide sequence of DNA can create new alleles • Diploidy, two sets of genes in an organism’s cells, allows for more varied phenotypes between individuals in a population
  • 6. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Sexual recombination – Generates variation by shuffling alleles during meiosis A1 A2A1 A3 A1 A1 A2 A3 A2 A1 A3 and XParents Meiosis Gametes Fertilization Offspring, with new combinations of alleles
  • 7. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Diploidy and balancing selection variation • Diploidy preserves variation – By “hiding” recessive alleles • Balanced polymorphism – May result from the heterozygote advantage or frequency-dependent selection
  • 8. Heterozygote advantage? For a lethal version of a gene?
  • 9. Sickle Cell Anemia confers a survival advantage on carriers! So, in areas where malaria is common, people are actually better-off having one SCA allele & one normal hemoglobin alleles, rather than two normal hemoglobin alleles.
  • 10. Gene pool = the total collection of genes & their alleles in a population at any one time Diversity (Variation) = individuals each carry different alleles, so that no two individuals are exactly alike. No two individuals have identical phenotypes. Preadaptated population = a population that has individuals with the phenotypes that will allow them to survive and reproduce in a new environment Adaptation = inherited changes in a population that allow survival and reproduction in a changed environment Microevolution = a change in the relative frequencies of alleles in a gene pool over one or more generations
  • 11. Mechanism that results in the diversity of life on Earth: Mutations in gametes can generate new alleles that become “fixed” in the population once the individuals inheriting the new alleles pass them to more and more offspring. Sexual reproduction maintains diploidy. Diploidy contributes to phenotypic variation in the population. Diploid individuals can carry alleles that may or may not be expressed as a trait (dominant/recessive relationships), or that can combine in heterozygotes to generate novel phenotypes (red/white results in pink, IA /IB results in AB blood). Variation preadapts the population to survive & reproduce if the environment changes and natural selection occurs. If living systems couldn’t adapt, life probably wouldn’t exist.