Genbio finals module 7

• Biological diversity - the number and the kinds of organisms living on earth at a particular time. How organisms arose and how they are all related are some of the interesting questions relating to life's diversity.
• The evolutionary theory is the scientific explanation of the diversity of life.
• Evolution or change over time, is the process of how present-day organisms have descended from ancient ones.
• A theory is well-supported, testable explanation of a natural phenomenon.
• Natural Selection - A key factor for an organism to thrive and reproduce depends on how well-suited the organism is to the environment. Also a process by which organisms survive in the environment.
• Fitness - the ability of an individual to survive and reproduce in a specific environment.
• For an individual to be fit in an environment, it has to successfully adapt to it.
• Natural selection:

  • Individuals that are not suited to the environment either die or live with few offspring.
  • Individuals with characteristics that are very suited to the environment survive and reproduce successfully.
  • Overtime, this results in changes in the inherited characteristics of a population.
• Two principle of natural selection:

  • Descent with modification
  • Principle of common descent
• Descent with modification - wherein species descend through generations with several changes over time. This principle also implies that organisms are related to one another.
• Principle with common descent - which means that all organisms share common ancestry.
• Types of natural selection:

  • Directional selection
  • Stabilizing selection
  • Disruptive or diversifying selection
• Directional selection - happens when a change in the environment causes a change in the observable spectrum of phenotypes. Organisms with a phenotype that is well-suited to their current environment are more likely to survive.
• Stabilizing selection - occurs when intermediate phenotypes are more likely to survive in the environment.
• Disruptive or diversifying selection - occurs when extreme phenotypes are more likely to adapt to the environment.
• Nonrandom mating

  • also contributes to the population change from one generation the next.
  • Described as the selected probability of mating with another individual in the population.
  • May take two forms, namely, inbreeding and outbreeding.
• Inbreeding

  • is when individuals are more likely to mate with their close relatives than with distant relatives.
  • individuals choose their mates based on their genetic history.
  • This type of breeding is common, and it results in change in genotype frequencies, although the frequencies of alleles in the population remain unchanged.
• Inbreeding depression - a condition with higher chance of inheriting disease conditions caused by harmful recessive genes. May lower the population's ability to survive and reproduce.
• Outbreeding - or assortative mating, happens when individuals select distant relatives than close relatives as their partners. Individuals with similar phenotypes are more likely to mate.
• Genetic drift - caused by unpredictable changes in allele frequencies due to small population sizes. A certain allele can be passed on to numerous offspring by chance.
• Population bottleneck

  • occurs when a sudden sharp decline in the population (such as volcanic eruptions) results in a drastic reduction of the total genetic diversity of the original population.
  • The decrease in the number of individuals brought about by the changes in nature.
• Founder effect

  • happens when there is a loss of genetic variation because of the migration of a small subgroup in a population.
• Mutation - the change in the structure of a gene cause by alternations in the DNA sequence of an organism.
• Different types of mutations:

  • Substitution
  • Insertion
  • Deletion
  • Frameshift
• Substitution - which occurs when the genetic codon has one altered nitrogenous base.
• Substitution may cause the following:

  • changes in the protein structure because the alteration of the codon cause a change in the amino acid produced.
  • silent mutation, wherein an altered nitrogenous base still produces a codon that encodes for the same amino acid.
  • change an amino-acid producing codon into a STOP codon, causing a formation of an incomplete protein.
• Insertion - which is characterized by the addition of an extra set of base pairs to the genetic material.
• Deletion - occurs when a set of base pairs in the genetic material is omitted.
• Insertions and deletions in the genetic material cause another type of mutation called frameshift.
• Frameshift - happens when the information is no longer parsed correctly, resulting in the production of useless proteins.
• Mutations can either be neutral or beneficial.
• Neutral mutation - affects the organism's phenotype but has no impact on its survival or reproduction.
• Beneficial mutation - affects the phenotype of organisms, resulting in an increase in their chances of survival or reproduction.
• Recombination - simply a rearrangement of genes. This process naturally occurs during the crossing over stage in meiosis, where there is an exchange of DNA between homologous chromosomes.
• Gene flow - also known as Migration. This happens when there is transfer of genes from the gene pool of one population to another.
• Two types of migration:

  • Emigration
  • Immigration
• Emigration

  • Happens when organisms leave their habitat or area.
• Immigration

  • Happens when organisms enter another habitat and live in it. Invade a particular area.
• Both immigration and emigration affect the number of alleles that are present in the population.
• Artificial Selection - nature provides the variation among different organisms so that humans can select the variations that are useful to them.