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Understanding Evolution: Principles, Mechanisms, and Applications, Lecture notes of Biology

Howard UniversityBiology

An overview of the theory of evolution, its key concepts such as alleles, mutations, natural selection, and genetic drift, and its applications in various fields. It also discusses the evidence supporting the theory and the role of influential figures like Jean-Baptiste Lamarck and Charles Darwin.

Typology: Lecture notes

2021/2022

Uploaded on 05/31/2022

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Processes of Evolution
What is Evolution?
- Evolution is a change in the genetic composition of populations over time
Theory
- A cohesive set of principles, ideas, and facts that have been well tested over time
by scientists and have stood up to intense scrutiny and testing.
Hypothesis
- A testable prediction. Many hypotheses must be tested before the theory can be
established.
Evolutionary Theory
- Is a set of ideas used to understand the mechanisms of evolutionary change
- This theory is supposed with many lines of evidence and has stood up to more than
a century of intense scrutiny and hypothesis tested (attempts to falsify)
Evolutionary theory has many useful applications
- Understanding treating and preventing diseases
- Developing better crops and industrial process
- Understanding the diversification of life and how species interact
- Making predictions about the biological world
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Download Understanding Evolution: Principles, Mechanisms, and Applications and more Lecture notes Biology in PDF only on Docsity!

Processes of Evolution What is Evolution?

  • Evolution is a change in the genetic composition of populations over time Theory
  • A cohesive set of principles, ideas, and facts that have been well tested over time by scientists and have stood up to intense scrutiny and testing. Hypothesis
  • A testable prediction. Many hypotheses must be tested before the theory can be established. Evolutionary Theory
  • Is a set of ideas used to understand the mechanisms of evolutionary change
  • This theory is supposed with many lines of evidence and has stood up to more than a century of intense scrutiny and hypothesis tested (attempts to falsify) Evolutionary theory has many useful applications
  • Understanding treating and preventing diseases
  • Developing better crops and industrial process
  • Understanding the diversification of life and how species interact
  • Making predictions about the biological world

Evidence for evolution

  • All life on earth share similarities in their genetics and anatomy that can be used to reconstruct their evolutionary history
  • The fossil record establishes a timeline for evolutionary historical events
  • We can observe evolution in the laboratory and in nature Jean- Baptiste Lamarck
  • proposed that species changes over time but wrong about the mechanism Charles Darwin and Alfred Russell Wallace proposed that
  • Species change over time
  • All species share a common ancestor
  • Species have diverged gradually Terminology ● Allele- a copy of a gene ● Mutation- adds new alleles to the gene pool ● Allele frequency- the proportion of an allele in the gene pool ● Genotype frequency- the proportion of each genotype in the population Calculation of these frequencies is used to measure evolutionary change

Jan 24 Natural selection? Survival of the fittest Four requirements ( postulates )

  1. Individuals vary
  2. This variation is heritable ( at least partially) EX: Height
  3. Not all individuals survive & reproduce equally
    • Survive- long enough
  4. The difference in survival and reproduction are linked to the variation and postulate # Adaptation: a trait that increases the chance that a given individual will survive and reproduce, increasing the frequency of the trait in the next generation Positive selection: selection for a beneficial change (rare) Purifying selection: selection against deleterious changes (common) What are the mechanisms of evolutionary change?

● Nature Selection Mutation ● Gene flow ● Genetic drift ● Nonrandom mating

  1. If mutations occur during the production of gametes (reproductive cells), they can be passed to the next generation. Mutation : is the origin of genetic variation. Mutations are random with respect to the needs of an organism ● most are neutral (no effect on phenotype at all, or an inconsequential effect) ● some are harmful ● few are beneficial Gene flow is a result of the migration of individuals between populations. ● New individuals can add alleles to the gene pool or change allele frequencies. Genetic Drift results from random changes in allele frequencies ● Very strong in small populations

Jan 26 Genetic Drift results from random changes in allele frequencies ● Very strong in small populations Population bottleneck: if a population is reduced to only a small number of individuals, genetic drift will reduce genetic variation in the population A colonizing population is unlikely to have all the alleles present in the whole population

  • This is called a founder effect (equivalent to a population bottleneck) In large populations, genetic drift can influence frequencies of alleles that do not affect survival and reproduction
  • This is where the term “drift” comes from (allele frequencies drifting up and down randomly) Nonrandom mating occurs when individuals choose mates with particular phenotypes, instead of just choosing at random
  • EX: self-fertilization is common in plants
  • If individuals choose the same genotype as themselves, homozygote frequencies will increase

The frequency of a is typically represented by “q” If p is the frequency of allele A And q is the frequency of allele a, p+q= q= 1-p p=1-q In this system, there would be three genotypes: AA, Aa, and aa.

  • Genetic structure of a population: allele frequencies at each locus and genotype frequencies.
  • How the genetic structure of the population changes over time is a measure of evolutionary change