Unit 4

• Gene


  A segment of DNA that codes for a particular trait
• Allele


  A different version of the same gene
• Alleles


  • Inherited from each parent
  • Can be dominant or recessive
  • Offspring only inherited two alleles for each gene, one from each parent
• Mutation and sexual reproduction


  1. Mutation (happens randomly)

  2. Sexual reproduction (each parent contributes half of their genetic material to the offspring)
• Mutation and sexual reproduction


  Source of variation
• Mutations introduce new alleles by chance, increasing genetic variation, upon which natural selection acts, guiding the evolution of species
• Gene frequency


  Which gene do you see the most in the population? / Which gets more passed along?
• High fitness


  Organism possesses traits or characteristics that allow it to thrive, reproduce successfully, and pass on its genes to future generations
• Evolution


  A change in the gene (DNA) over time or changes in the frequency of alleles within a population over time
• Evolution


  • Applied to population
  • Led to diversity
• Factors that lead to evolution


  • The potential for a species to increase in number
  • The genetic variation of individuals in a species due to mutation and sexual reproduction
  • Competition for an environment's limited supply of the resources that individuals need in order to survive and reproduce
  • The ensuing proliferation of those organisms that are better able to survive and reproduce in that environment
• Natural selection


  The process through which species adapt to their environments in order to survive. Individuals with advantageous traits are more likely to survive and reproduce, passing on their genes to the next generation
• Genetic variation


  Genetic variation occurs within a population due to differences in alleles (versions of genes) among individuals
• Intraspecific competition


  Competition within the same species
• Interspecific competition


  Competition between members of different species
• Competition and variation

  Lead to differential reproductive success through the process of natural selection
• Competition selects for individuals with advantageous traits, while variation ensures a diverse range of traits. Those with advantageous traits are more likely to survive, reproduce, and pass on their genes, leading to evolutionary change over time
• Differential reproduction


  Individuals with certain advantageous traits are more likely to survive and pass on to the offspring
• Heritable traits


  Passed on genetically from parents to offspring (e.g. eye color, height, and certain diseases)
• Inherited variation


  Differences in traits that are passed down from parents to offspring. Offspring will have similar traits to parents but not exactly
• Inherited variation is influenced by mutation, natural selection, environmental factors, learned behaviors, cultural practice
• Adaptation


  Population changes over time through which organisms develop traits that better suit them to the environment to enhance chances of survival and reproduction
• Gene pool


  All the genes and alleles are present in the population / all the possible allele in the population
• Natural selection can influence an individual's chance to survive and reproduce but cannot change an individual's gene
• Populations, not individuals, can evolve or change over time because evolution involves changes in the genetic inheritance of a group of organisms overtime
• Individuals retain the same gene and cannot change their gene for a favorable set whenever they feel like it
• A population's gene pool includes all the genes of every individual in that population, while a gene pool for a single gene only focuses on the different alleles of that specific gene present in the population
• Speciation


  Creation of new species through natural selection
• Evolution is not the same as speciation. Speciation is a result of evolution. Evolution mostly deals with how populations become adapted to their environment, but not how this adaption leads to speciation. For speciation to occur, barriers for the gene flow between populations have to evolve
• Requirements for two populations to evolve into separate species


  • Isolation
  • Genetic divergence - genetic differences between populations of the same species