"Darwin's finches are an excellent example of the way in which species' gene pools have adapted in order for long term survival via their offspring." See http://www.Biology-online.org/2/11_natural_selection.htm.
Snow hare. Rabbits in the winter are easy prey (not much food, and a brown rabbit is a pretty easy thing to spot!). Rabbits that are white in the winter are hard to spot. Therefore hard to eat. Therefore they survive the winter to breed again in spring.
Brown rabbits are eaten and don't get a chance to breed in spring in northern climates. White rabbits survive in the winter and breed again. Low population/high population....natural selection!
One classic but hypothetical example is Daisyworld. In this hypothetical model, we envision a planet inhabited by a single species of life, a single population of daisies. These come in two variants: black daisies and white. The colour is a trait that is passed on genetically to offspring. In the model, that star at which the planet revolves is variant, increasing or decreasing in intensity, changing the amount of light/heat the planet is exposed to. Black daisies will absorb more sunlight, increasing temperatures at the planet surface, while white daisies reflect more sunlight, cooling the planet. Theoretically, increasing temperatures should make things uncomfortable for the black daisies, who heat up faster because of their colour, relative to the white daisies, so that when solar luminosity increases, white daisies gain a reproductive advantage over the black daisies.
A similar example but from real life is the evolution of the peppered moth during and after the industrial revolution. Initially, lighter moths and darker moths were in equilibrium, but as the industrial revolution caused soot to stain the surfaces on which moths frequently settle, and predators could more easily distinguish the lighter moths against the darkening surfaces, darker moths gained a reproductive advantage, as they more often survived predation.
Two more recent findings are:
Herrel, 2008, Rapid large-scale evolutionary divergence in morphology and performance associated with exploitation of a different dietary resource.
This paper describes how in a few short decades a population of lizards transported to a different environment gained different morphological features by adapting to its new habitat.
Rolshausen, 2009, Contemporary evolution of reproductive isolation and phenotypic divergence in sympatry along a migratory divide.
This paper describes how the interaction between migratory flocks and human settlements is causing a speciation event to occur between flocks that migrate along routes including cities, and those migrating away from cities.
Yes
Yes.
Some individual organisms are better equipped to live and reproduce in their environment than others. If what makes them better equipped is heritable, their offspring will be more numerous and will tend to inherit the same traits or qualities themselves. The opposite will happen to those poorly equipped. They will have fewer or no offspring, and their negative traits will tend to disappear from the population as time goes on. These two tendencies are called positive (natural) selection and negative (natural) selection respectively. Natural selection is always relative to the environment. What is advantageous in one environment may not be so in another, and what is disadvantageous (deleterious) in one environment may not be so in another.
Natural selection is limited by the ability of the population to produce variation. This in turn is limited by the amount of mutation a lineage can survive. Too many mutations, and the effect becomes detrimental. Too few, and the population may not be able to adapt fast enough to changing circumstances and go extinct.
Without variation natural selection would have nothing to select from that would confer survivability and reproductive success. on the organisms being selected against the organisms conspecifics and the immediate environment. Mutation and sexual recombination provide the main sources of this variation that is needed to make selection work. Mutation is the variation presented that causes the real adaptive change that can lead to speciation.
"Natural selection is the process by which heritable traits that make it more likely for an organism to survive and successfully reproduce become more common in a population over successive generations. It is a key mechanism of evolution." - Wikipedia.orgThey key words in this statement in which describe Natural Selection is: Successive Generations. Meaning more than one, or even a few generations. Therefor your time in which an evolutionary trait takes to develop depends on two main factors: The type of Organism that you are studying, and the environment in which it lives. If there are less "X" factors then the Organism will be able to advance much more quickly.
Natural selection does work on preexisting variations in a population. This is how the population was shaped to be the way that they currently are or were.
Yes.
No. Natural selection requires reproductive variation to work on. Besides reproductive variation and natural selection, there are various forces, biochemical as well as population dynamical, that affect the allelic composition of a population.
Natural selection acts on the genotype, but indirectly, through the phenotype.
Natural selection creates a stronger species that is able to live longer and produce more. It continues to work because after a few generations, the traits will become common in the population.
Natural selection creates a stronger species that is able to live longer and produce more. It continues to work because after a few generations, the traits will become common in the population.
Things that produce differing replicas of themselves. The most common example of this is life.
Natural selection can only work on genetic variation that already exists. So mutation comes first, then natural selection.
This is backward, natural selection works on genotype not phenotype.
Natural selection reduces the number of fertile offspring an organism may raise.
Natural selection creates a stronger species that is able to live longer and produce more. It continues to work because after a few generations, the traits will become common in the population.
because he created the natural selection