Download Evolution by Natural Selection

Cardinal Notes
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Topic/Objective:
Evolution by Natural Selection
Name:
Class: Biology
Date:
Essential Question(s):
1. What conditions need to be present for natural selection to occur? (underline in red)
2. How does natural selection lead to a population changing over time? (underline in blue)
Evolution by Natural Selection Questions/Connections:
Evolution: ​ process of change over time
Natural Selection:​ mechanism of how evolution occurs: ​the process in which
organisms better adapted to their environment tend to survive and produce more
offspring Charles Darwin ● First to propose how evolution works, by natural selection ● At 22, Darwin went on a five year trip around the world on the ship, the HMS Beagle (began in Britain) ○ As the ship’s naturalist, he made observations of organisms in South America and the Galapagos Islands. Fun fact: the main mission of the HMS Beagle was to chart the South
American coastline.
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"​It is not the strongest of the species that survive, nor the most intelligent, but the one
most responsive to change.​" - Charles Darwin
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● On the voyage they stopped at the Galapagos Islands. ○ Darwin found 14 different species of finches on the different islands. Darwin believed they evolved from a common ancestor because there is only one type of finch on the mainland. ○ The differences between the species of finch were associated with the different food they ate. ○ Darwin concluded that the variation in the beaks of the original population allowed for natural selection to occur on the different islands (the finches that were most fit for a particular island were more likely to survive and reproduce). ○ Over many generations, the finches separated into different species of finch. Each species adapted to the particular environment of the island. ● Darwin wrote the book, “Origin of the Species” Conditions that need to be present for natural selection to occur: 1. Genetic Variation​: Variation within genes (traits) that can be passed from parent to offspring. Ex: some beetles are dark and some are light. 2. Competition:​ Not all organisms can survive because of limited food, predators, disease, shelter, hunting, etc. Ex: dark beetles are more likely to get eaten by bird. a. The factor that has a negative impact on the population of a species is called a ​stressor. In the picture to the right the stressor would be the bird (predator) 3. Fitness​:​ Organisms with the most beneficial trait are more likely to survive and reproduce. By reproducing the beneficial trait will be passed on to the offspring through genes. ​Fitness depends upon the environment. a. In the picture to the right, the light beetles were more fit for the environment because they were better able to blend in and therefore not get eaten by the bird. End Result The more beneficial trait will make the organism more likely to survive. An organism that survives is more likely to reproduce and pass on the beneficial trait. If this process continues, eventually, all the organisms in a population will have the same adaptation. Right page 3
Survival of the fittest. NOTE: Fitness does not mean the fastest, strongest, or biggest. NOTE: For natural selection to happen, genetic variation has to already EXIST in the population. (variation occurs from ​random mutations or from meiosis) Summary: __________________________________________________________________________
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