Natural Selection + Speciation Flashcards
What is Natural Selection
It is a situation where selection pressure(when genetic variations are successfully passed down on to the next generation of a species while decreasing the chances of others) results in selection/predation of some variants happens at the expense of others. Example of this population of mainly brown rabbits some are darker black so they stand out more and are more visible so they are predated on more.
Antibiotics
They are chemicals that kill bacteria without harming human tissue. The first one discovered was penicillin. Ideally an antibiotic will kill all the bacteria withing a population therefore mitigating any illnesses they may cause.
Resistant Bacteria
Variation can occur to make certain bacterium unsusceptible to the mechanism of action of the antibiotic and while the rest of the population dies out the resistant bacterium rapidly reproduces and results in an entire population of antibiotic resistant bacteria.
Volume of Antibiotics and Resistant Bacteria Relationship
in the absence of antibiotics the frequency of resistant bacteria remains low in the population. However when antibiotics are introduced the environment of the bacteria is changed and a selection pressure is now imposed. Individuals are better suited to this environment and make offspring with advantageous genes. Therefore, The more antibiotics are used the greater the selection pressure is exerted on the bacteria to develop a resistance.
Directional or Evolutionary selection
When a change in the environment occurs then the selection pressures would change. The alleles previously selected may no longer allow an advantage for survivability. Other alleles latent in the population that were insignificant before may now offer a better survival and would now be selected.
Evolution
When an environmental change or introduction of a new allele changes the genetically determined characteristics of generations to come. It is an incremental change in species of a long period of time.
Natural Selection in terms of Evolution
In each generation the best suites/best adapted survive and reproduce the species characteristics would change over long periods of time as the species becomes better suited to its envi. Therefore during significant environmental changes characteristics of the species would change to suit.
NS selects the most fir individuals especially in the face of changing environments and emergence of new alleles These changes happen incrementally over time which results in evolution.
Biological Species Concept
A group of organisms that share similar characteristics that can produce fertile offspring. The fact they can successfully interbreed with each other and not other organisms is the main defining aspect aka reproductive isolation
Limitation of the Biological Species Concept
It can only be applied to organisms tat reproduce sexually. It cannot be used to determine if asexual organisms belong to the same species or not
It cannot be applied to extinct organisms only studied as fossils/old bones/ skin
Phylogenetic (evolutionary) species concept
When organisms are very closely related in an evolutionary sense but differ phenotypically if they are geographically isolated they can be considered a separate species. This is done based on the Phylogenetic (evolutionary) species concept once the species can be differentiated and a common ancestor can be determined e.g monkeys and humans
