Unit 3 Notes Evolution and Adaptations

Selective Pressure  Selective Pressures are the factors that cause young plants and animals in nature to fail to survive  Examples of these include predators, parasites, drought, lack of food, and temperature extremes.  Some organisms are better equipped to survive, by having genetic variations that provide protection  Examples of these include traits that allow the organism to blend in with its surroundings, making it easier to be hidden from predators

Selective Pressure  Other organisms that are lacking these traits generally end up being the predator’s dinner  Some organisms have genetic traits that may actually cause further harm to the organism  Examples of this include if the organisms’ genes slow it down or cause its exterior coloring to make it apparent with its background

Natural Selection  When specific traits are favored to assist in an organisms’ survival is known as natural selection  Charles Darwin and Alfred Russell Wallace discovered the concepts of natural selection.  When organisms are modified over many generations this is called biological evolution

Adaptations to the Environment  Selective Pressures are constantly being exerted on populations, causing the gene pool of the population to be tested  Fitness is the ability of an organism to adapt for survival and reproduction based on the selective pressures being exerted on the organism

Limits of Change 1. Adaptation – the population of survivors may gradually adapt to the new condition through natural selection 2. Migration – the surviving population may migrate and find an area where conditions are suitable 3. Extinction – failing the first two possibilities, extinction is inevitable

Adaptations  In order for a population to successfully adapt to the environmental conditions, they need to have some individuals that possess the alleles (variations of genes or new combinations of genes) required to survive in the new conditions.  This is not the only requirement – the population must have enough organisms within it that possess the alleles in order to reproduce and carry on the population

Keys to Survival  There are four keys to survival for a population 1. Geographical Distribution 2. Specialization to a given habitat or food supply 3. Genetic Variation within the gene pool of the species 4. The reproductive rate relative to the rate of environmental change

Keys to Survival  Less vulnerable species to be affected by changes in these keys are r-strategists  More vulnerable species to be affected by changes in these keys are K-strategists  Most organisms fall in between both of these

Genetic Change  Genetic change or adaptations occur over generations  An organism does not adapt within its lifetime genetically

Evolution of Species  After all of the adaptations that occur over MANY generations the “final” product may be so different from the initial population that started the process that it is considered a new species  There is also a process where two or more species are developed from one individual species

Two Species From One  Reproductive Isolation  When the original population separates into smaller populations that do not interbreed with one another  Separated Subpopulations exposed to different selective pressures  As the populations are adapted to these pressures they begin to become so different that they are no longer considered the same species

Darwin’s Finches  Charles Darwin discovered a variation of species of finches in the Galapagos Island  What he observed was that the different finches had specific physical characteristics  The physical characteristics that each species has determines its feeding habits, making them different species.