Natural Selection: The Mechanism of Evolution What is Evolution? •
Evolution is a _________________ in a population of organisms over ________. •
This is often referred to as “_______________________________________________” o
Each species comes from other _________________ changing over ___________. History of Evolution •
________________ is considered the father of evolution. o
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Alfred ______________________ is also a ttributed to the Theory of Evolution. Darwin noticed the ________________ in the Galapagos islands were ____________________ but had _______________________ for their environment. Darwin’s Theory of Evolution •
_____________ change over time. o
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Species living today ____________ from those in the p ast. All organisms share __________________ ancestors with other organisms. o
Far enough back in time, any pair of organisms shares a ____________________________________. Natural Selection •
Natural selection -­‐ individuals ______________ suited to their environment _________________ and _________________________. •
Natural S election is ________ evolution happens. •
Natural selection acts on the ___________________________. o
Individuals with ________________________ phenotypes for their environment are more likely to _______________________ and _____________________ (passing on these b eneficial __________). •
Eventually, _________________________ traits may b e wiped out of the population. o
Leaving only the _____________________ traits. Requirements of Natural Selection •
In order for evolution by natural s election to occur five things must be present: 1. _______________________ if offspring. 2. Every organism must ___________________ to survive. 3. ___________________ within a species. 4. Variations allow members of a species to ____________________ and _____________________ b etter than others. 5. These variations must b e ________________________. Overproduction of Offspring •
Populations have _________ offspring each year than ____________________ can support. o
Example: In a litter of rabbits only one or two may survive to reproductive a ge. Struggle for Survival •
Members of a species _____________ regularly to obtain food, living space, and other necessities of life. Variation within a Species •
There are ___________________ a mong members of a species. o
Example: Gerbils have different fur colors. Some Variations are Beneficial for the Environment •
If an organism has a trait that h elps it ________________, it is more likely to survive and ___________________. o
A faster cheetah is more likely to catch a gazelle and s urvive. 
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The cheetah can gather enough food for ________________ a nd its _____________________. Survival of the Fittest o
Individuals that are more _______________ to their environment __________________ and successfully ________________________. 
Biological Fitness: refers to an individual’s capabilities to _____________ AND _____________________. •
Fitness does n ot refer to how ______________________ fit an organism is. Beneficial Variations must b e Inheritable •
If more of the organisms with the _________________ trait survive, then in the following generations, more and more of the population have that ________________. o
Example: If faster cheetahs will b e able to catch food and survive and reproduce. The s lower ones will die b efore b eing able to reproduce. 
____________________ the p opulation only contains ______________ cheetahs. Hare Example A population of hares are living in a cold, snowy, polar region. About 1 of each liter survives to adulthood where it can reproduce. The polar region has a limited a mount of food that a ll a nimals compete for. The rabbits eat mainly vegetation that is frozen over in the winter, so they must eat enough during the short spring months to survive. Snow covers the ground 8 out of 12 of the months, and the hare is the main food source for larger predators like foxes and wolves. The hares range in coat coloration. Some hares are white and some hares a re brown. Pick out the evidence within this scenario that fits each requirement of natural selection. 1. Overproduction of offspring _________________________________________________________________________________________ _________________________________________________________________________________________ _________________________________________________________________________________________ 2. Every organism must s truggle to survive _________________________________________________________________________________________ _________________________________________________________________________________________ _________________________________________________________________________________________ 3. Variation within a species _________________________________________________________________________________________
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_________________________________________________________________________________________ 4. Variations allow members of a species to survive and reproduce b etter than others _________________________________________________________________________________________
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_________________________________________________________________________________________ 5. These variations must b e inheritable _________________________________________________________________________________________
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_________________________________________________________________________________________ Predict what will happen over time using what you know about natural selection. _______________________________________________________________________________________________ _______________________________________________________________________________________________ _______________________________________________________________________________________________ _______________________________________________________________________________________________