Lessons Divided by Standard EOC D.1.D Discuss Darwin’s principle of survival of the fittest and explain what Darwin meant by natural selection.

Natural Selection and Survival of the Fittest The two terms are synonymous! Natural selection: the process by which individuals that are better adapted to their environment survive and reproduce more successfully than less well adapted individuals. Survival of the Fittest: an organism that is ‘fit’ for the environment will survive and reproduce with greater frequency than one that is less fit. Individual variations make an organism more or less fit in the current environment.

Variation or Adaptation and Fitness Either variation or adaptation could make an organism ‘fit’ for the environment. The term variation refers to individual variations in a population of a single species. The term adaptation refers to characteristics possessed by all organisms of a population that make them ‘fit’ for the environment. One species could be considered better adapted to a particular environment than another species.

Variations and Adaptatioons Could Be: Physical (Controlled by Genes) Speed, Camouflage, Claws, Quills, etc. Behavioral Solitary, Herds, Packs, Mating Rituals,etc.

Darwin Formulated His Theory of Natural Selection By Being Aware of Farming and Breeding Practices Darwin noticed how easily people could manipulate the characteristics of domesticated plants and animals. Artificial Selection- aka Selective Breeding - human breeders choose those variations that they prefer in their stock.

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Darwin had abandoned the idea that species were perfect and unchanging Darwin had abandoned the idea that species were perfect and unchanging. (Immutable) He reasoned that ‘mother nature’ could select for traits ‘she’ wanted as easily as humans.

Another definition. Natural Selection- the process by which nature picks and chooses the organisms with the best variations aka Survival of the Fittest.

Peppered Moth

Peppered Moth When newly industrialized parts of Britain became polluted in the nineteenth century, smoke killed lichens growing on trees and blackened their bark. Pale coloured moths which had been well camouflaged before when they rested on tree trunks became very conspicuous and were eaten by birds. Rare dark moths, which had been conspicuous before, were now well camouflaged in the black background. As birds switched from eating mainly dark moths to mainly pale moths, the most common moth color changed from pale to dark. Natural selection had caused a change in the British moth population. The moths had evolved.

Peppered Moth In recent years, the burning of cleaner fuels and the advent of Clean Air laws has changed the countryside even in industrial areas, and the sootiness that prevailed during the 19th century is all but gone from urban England. Coincidentally, the prevalance of the darker form has declined dramatically. In fact, some biologists suggest that the dark forms will be all but extinct within a few decades.

The concept of evolution is important in medicine and agriculture! Consider this example of pesticide resistance. Have you heard of MRSA? Antibiotic resistance? .

Natural Selection Occurs Due to 4 Truths about LIfe Overproduction – many species produce more offspring that can possibly survive Genetic Variation exists among members of the same species/population There is a Struggle for Existence! Some organisms are more successful at surviving and reproducing.

1. Overproduction – producing more offspring than will ever survive Frog Eggs Maple Seeds Turtle Eggs The giant panda has a low birth rate but even under conditions of intense parental care not all offspring survive.

Genetic Variation – different individuals have different traits Genetic Variation – different individuals have different traits. Some traits provide an advantage to survival and reproduction. EX: better camouflage in frogs, stronger or faster lions

3. Struggle for Existence – only the most fit survive, competition can be intense for resources, or mates or space This zebra was slower than the others in the herd. Perhaps it was sick. A white rabbit is easy to see but, a grey one would be harder to see.

4. Differential Survival and Reproductive Success.

Darwin's Theory Restated Individual Organisms In Nature Differ From One Another. Some Of This Variation Is Inherited Organisms In Nature Produce More Offspring Than Can Survive, And Many Of These Offspring Do Not Reproduce. copyright cmassengale

Darwin's Theory Restated Because So Many Organisms Are Produced, Members Of Each Species Must Compete For Limited Resources Because Each Organism Is Unique, Each Has Different Advantages & Disadvantages In The Struggle For Existence copyright cmassengale

Darwin's Theory Restated Individuals Best Suited To Their Environment Survive & Reproduce Successfully – Passing Their Traits To Their Offspring. Species Change Over Time. Over Long Periods, Natural Selection Causes Changes That May Eventually Lead To New Species copyright cmassengale

Darwin's Theory Restated Species Alive Today Have Descended With Modifications From Species That Lived In The Past All Organisms On Earth Are United Into A Single Tree Of Life By Common Descent copyright cmassengale