Natural Selection

"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.

Actually, all the religious people believed God created this world, and put them on this world for a reason. They believed that they had purpose in life.

But when Charles Darwin came along and said that we're related to monkeys, people got very upset. BEcause if you question one part of the bible, you're questiong the entire bible, and that's what Darwin did.

After he released his book, people found it upsetting to know that we are here by chance, and that we don't actually have a purpose on earth.

but honestly, if that's teh case, then we should be happy we're here by chance and live it up while it lasts.

Natural selection leads to evolution by giving the organism that is best suited for the area to thrive. Thus those who not suited for the area die off and evolution moves forward.

Genetic drift has reduced the polymorphism of the cheetah population. The cheetahs probably underwent a "genetic bottleneck" a few thousand years ago, when the population was reduced to just a few individuals. Then as they reproduced, all surviving cheetah offspring were closely related.

The principles of natural selection are:

That life reproduces with variation.

That variant features are inherited by offspring.

That organisms always produce more offspring than can comfortably be sustained by the environment they inhabit.

That variant offspring therefore must compete for resources and mating opportunities.

That this competition results in the differential reproductive success of variants, and therefore in changing frequencies of variant traits in the population.

Camouflage is such a good adaption because it allows creatures of all kinds to 'hide in plain sight' from predators. One of the simplest examples of how this works is the dappled coat of the fawn (baby deer), necessary because the mother must leave the baby alone, hidden in the tall grass or bushes while she gets enough to eat. The dappling mimics the spots of sunlight passing between the tall grasses or leaves of the bushes. The fawn also sits very still as part of the deception because movement would attract the eye of a predator. The coloring and the ability to stay motionless are two very common forms of camouflage. Without these elements, far fewer baby deer would survive to maturity and continue the deer population.

Not all camouflage is for the purpose of hiding from predators; another form is designed to confuse predators, sometimes called 'dazzle camouflage'. Some examples of this type are zebra stripes, water birds like flamingos that flock in great numbers with bright feathers, and silvery fish who live in large schools (groups). The purpose of this adaption is when danger is detected, the large group will all move at once creating a flurry of stripes, flashing, or color that makes it difficult for a predator to pick out an individual to strike.

Another type of camouflage is designed to help predators be more successful. This type also uses coloring and the ability to remain motionless; some examples of this are lions, tigers, and snakes. Their ability to blend into their background and stay still allows them to wait without being noticed for the best moment to strike their prey. This helps that species to obtain food and survive.

Most species of bird, fish, or mammal have predators, and predators have the need to successfully catch prey. Each species has developed (evolved with) what works for them, allowing them to survive and produce the next generation of the species.

1. Overproduction - more offspring are born than survive

2. Genetic Variation - there is variation in the population

3. Struggle to Survive - organisms with suitable variations will survive and reproduce

4. Differential Reproduction - suitable variations are passed on to offspring

Genes are the medium by which inherited traits are passed on to offspring. It is inherited traits, and thus genes, that receive positive or negative selection.

Absolutely. We have "moderated" its effects some with our technology (especially in the last 100 years, but that is too short a period to make much difference) but you can't stop it.

Being hit and killed by a bus because of inattentiveness is as effective a means of selection as being killed and eaten by a predator because of inattentiveness was thousands of years ago.

Wegener proposed the continental drift theory, and provided scientific evidences for such, but couldn't explain the mechanism or processes behind the movement of continents. It wasn't until the mid-twentieth century with the discovery of the Mid-Atlantic Ridge that the processes causing plate movements began to be understood and led to the science of plate tectonics.

The europeans used Social Darwinism to justify their increase in emprie building with the justification that all creatures have and will still continue to evolve, and as such, there needed to be new accomodations met.

Volcanic eruptions, changes in earth's orbit, changes in the sun's intensity, and changes in ocean currents are some examples of what natural events affect climate.

Advantages:

* determines the fitness of an organism by direct application. * employs a wide range of criteria * provides for opportunism Disadvantages:

* involves a lot of chance. * some organisms escape the full range of possible criteria * is under employed in boom times, over-employed in lean times. * recessive traits 'hide' from the process. *

Natural selection is a direct product of the environment.

A couple of simple examples are:

In a cold environment the only plants and animals that will survive will be cold tolerant plants and animals.

In a forest of Bears the only animals to survive will be animals that are faster or bigger than Bears.

A sudden change in environmental conditions, such as an Ice Age, will see whole populations of some species disappear while only remnants of some species will survive.

Those remnants will display either cold tolerance or the ability to withstand the cold by other means ie: clothing or fire.

One part of the theory of evolution by natural selection is that only the best-adapted animals in a population survive.

Small changes add up over many generations.

Lets say you have two bunnies. One has a long tail, the other has short tail. The one with the long tail died because a predator was able to catch onto the long tail and eat it. Therefore, the long tailed bunny can't pass on the characteristic of a long tail and that trait is no longer seen in bunnies. However, the bunny with the short tail isn't caught by predators as easily, and as a result, passes on the trait of a short tail to its offspring. After a long amount of time, no bunnies will have long tails because all the bunnies with long tails were killed out, and as a result, can't pass on the characteristic of a long tail. Bunnies then evolve to always have short tails.

this is where the genes are mixed up, and it allows genes to be exchanged across chromosomes and randomizes the assortment of chromosomes to the offspring.

Previewing is important because it gives you some information about what you will be reading before you actually read the story.

according to Darwin's theory of evolution, species go through a natural selection over long periods of time. meaning that only the fittest of a species survive as it is the organisms of a species who are the most fit, that have the greater capability to hunt or gather food versus weaker organisms of that species who die out as the fitter organisms out-compete them for food or resources. for example, giraffes who have longer necks are considered to be more fit as they can more easily reach tall trees and gain access to food, as opposed to giraffes with shorter necks who can't reach enough food and therefore die out. it is considered natural selection as certain animals are "fitter" than others because of a mutation they have (like longer necks) that put them at an advantage.

Natural selection is the nonrandom survival and reproductive success of randomly varying organisms.

Evolution is the change in allele frequency over time in a population of organisms.

So, the individual naturally selected will leave more decedents in the population and his descendents will have the traits that made him survive and reproduce better and this will change the allele frequency of the population, the population's gene pool, and lead to evolution in this population.

Charles Darwin is credited with this theory in his book, The Origin Of Species. ---> Actually... Jean-Baptiste Pierre Antoine de Monet, Chevalier de la Marck (AKA Lamarck) was the first to propose the hypothesis that species change over time.

An organism with a charecteristic that is more helpful to its survival will be more likely to survive and breed than one without that characteristic.

External selection forces that make survival hard.

To get the fastest rate of evolution these forces should kill or disable 50% to 90% of the individuals in each generation before they are able to reproduce. But these forces should not kill so many as to make the species go extinct. In most cases these forces only kill or disable less than 10% of the individuals in each generation before they are able to reproduce.