Mechanisms for Evolution

Natural Selection Darwin found on his journey that certain animals were better suited for their environments than other animals Darwin found that some of these animals were better suited to survival than others

Natural Selection Darwin believed that certain animals were better suited to survival and that helped them live and have offspring Those animals that lived and had offspring would be the ones that you see in the world This idea was called natural selection

Natural Selection Natural selection can only happen when one organism has an increased chance to spread its genes The probability that an organism will pass on its genes to the next generation is referred to as fitness

Natural Selection An organism that has an increase in fitness have a larger chance of passing on their genes An organism that has a decrease in fitness has a smaller chance of passing on their genes

Overproduction There are also several other things that Darwin noticed during his travels that helped form his opinion of natural selection One of the things he noticed was the number of offspring that were produced

Overproduction Most animals can produce more offspring than can survive to maturity This means that some of the offspring will die when they are young The offspring that will die are ones that will not be passing their genes on in the gene pool

Overproduction The idea that some offspring do not survive to maturity and cannot contribute their combination of genes is called overproduction Examples of this would be wild octopus More octopus are produced each year than can survive

Adaptation Some of the variations help an organism survive in an environment These variations tend to become more frequent in a population The more frequent that trait is in a population, the better chance that population will survive

Adaptation A trait that makes an individual more likely to survive in an environment is called an adaptation Something like thick fur in a cold environment is a successful adaptation Something like thick fur in a warm environment is not a successful adaptation

Adaptation Remember an adaptation is a something that is passed down from the parents Adaptations are not something that is spontaneous or planned by the organism

Genetic Variation Darwin also noticed that within a population there are a difference in traits The difference in traits creates a full range of traits within a species This is easy to observe in any population

Genetic Variation The range of traits within a population helps determine how natural selection proceeds Natural selection tends to select for certain traits and have certain other traits die out The range in traits is called genetic variation

Genetic Variation The range in traits allows for a species to survive if some traits are not variable If deer with large antlers are hunted and killed easier, there will be deer that have small antlers that would survive If there were no variation among deer, none would survive

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Artificial Selection What is the process that Darwin proposed is the driving force behind evolution? Natural selection is a process that occurs in the natural world This means that no human can interfere

Artificial Selection Sometimes humans tamper with natural selection This can be seen most often in dogs Humans tend to want dogs with certain desirable traits They breed dogs together that have these traits

Artificial Selection Artificial selection is the process of humans selecting individual traits to give to the next generation It is the only way that we could have gotten one of these from one of these

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