The image shows the changes of beak shape in the Galapagos finch to suit the different food sources available on different islands in the archipelago. Natural selection has caused one species to evolve into different, distinct species. 5.2 Natural selection adapted from:

5.2 Essential idea: The diversity of life has evolved and continues to evolve by natural selection.

History of Evolutionary Thoughts

Lamarck’s Theory of Evolution Jean-Baptiste Lamarck, 1809 one of first scientists to understand that change occurs over time stated that changes are adaptations to environment acquired in an organism’s lifetime said acquired changes were passed to offspring

Lamarck’s Theory of Evolution Idea called Law of Use and Disuse If a body part were used, it got stronger If body part NOT used, it deteriorated

Lamarck’s Theory of Evolution Inheritance of Acquired Characteristics proposed that by selective use or disuse of organs, organisms acquired or lost certain traits during their lifetime these traits could then be passed on to their offspring over time this led to new species

Lamarck’s Theory of Evolution

Lamarck’s Mistakes Lamarck did not know how traits were inherited (Traits are passed through genes !) genes are NOT changed by activities in life change through mutation occurs before an organism is born

Charles Darwin British naturalist In 1858, Darwin and Wallace independently proposed the idea of evolution by natural selection If they both had the idea, then why is only Darwin really remembered???

Charles Darwin On theOrigin of Species by Means of Natural Selection Darwin published On the Origin of Species by Means of Natural Selection the following year

Charles Darwin ( ) archaeopteryx.html Archaeopteryx is one of the most important fossils ever found. Thought to be a transitional form between birds and reptiles. For more information on his life go to:

5.2.U1 Natural selection can only occur if there is variation among members of the same species. The harlequin ladybird (Harmonia axyridis) is highly variable in appearance, with over 100 different color forms reported worldwide. The implication of variation is that some individuals will be more suited to particular conditions and hence more likely to survive.

5.2.U1 Natural selection can only occur if there is variation among members of the same species. Natural selection favors traits that help an organism to survive If all organisms are identical, then they all have the same chances of surviving and reproducing and therefore natural selection cannot happen So why is variation important? -Genetic variation in a population allows some individuals to survive should the environment change -We have learned the importance of genetic variation in our crops from history: Irish Potato Famine griculture_02

5.2.U2 Mutation, meiosis and sexual reproduction cause variation between individuals in a species.

5.2.U3 Adaptations are characteristics that make an individual suited to its environment and way of life.

5.2.U4 Species tend to produce more offspring than the environment can support. images/Guardian/Weather/WeatherWatch/2013/3/29/ /Female-Frog-and-Frogspawn-008.jpg Why don’t they all survive???

5.2.U5 Individuals that are better adapted tend to survive and produce more offspring while the less well adapted tend to die or produce fewer offspring.

5.2.U6 Individuals that reproduce pass on characteristics to their offspring. Allele frequency changes Gene frequency = the number of times an allele appears in a gene pool compared to other alleles

5.2.U6 Individuals that reproduce pass on characteristics to their offspring. n.b. only heritable characteristics, those with a genetic basis, can be passed on to offspring. Children can inherit the nose shape of their parents, but not a nose job. Allele frequency changes Gene frequency = the number of times an allele appears in a gene pool compared to other alleles

5.2.U7 Natural selection increases the frequency of characteristics that make individuals better adapted and decreases the frequency of other characteristics leading to changes within the species. Alleles* that encode for well adapted characteristics increase in frequency whilst those that encode for ill adapted characteristics decrease. Allele frequency changes Gene frequency = the number of times an allele appears in a gene pool compared to other alleles

Summary: Darwin’s Theory of Natural Selection 1. Populations produce more offspring than can possibly survive. (overproduction) 2. Individuals in a population vary extensively from each other, mostly due to inheritance. (variation) 3. Struggle to survive: individuals whose inherited characteristics best fit to environment leave more offspring than less fit. (survival of the fittest) 4. Unequal ability of individuals to survive and reproduce leads to gradual change in population. (adaptation) 5. Favorable characteristics accumulate over generations – (descent with modification). PBS: How does evolution really work? VIDEO CLIP:

5.2.A2 Evolution of antibiotic resistance in bacteria.

ntibiotics/antibiotics_fla.html VIDEO CLIP (stop at 5:15):

Useful background information to (Darwin’s) Galapagos ground finches Darwin’s Finches: Adaptive Radiation One of Darwin’s most famous examples was the evolution of the Galapagos finches. He noticed that the finches on a set of neighboring islands were all closely related, yet separate species. He deduced that they had come from a single population of finches on the mainland and had probably been blown to their new habitats by a storm. Each habitat had different selection pressures, so over millions of years, the finches adapted to suit their own islands. Eventually, they became separate species. This is known as adaptive radiation.

5.2.A1 Changes in beaks of finches on Daphne Major. Variation: there is a difference in the size and shape of beaks Medium ground finch : Evolution in action Beak shape and size in Geospiza fortis Endemic to the Galapagos Islands Habitats are arid lowland forests and shrub land. Generally feeds on seeds, but will also feed on insects and the fruit of cacti.

5.2.A1 Changes in beaks of finches on Daphne Major. Medium ground finch : Evolution in action st Environmental change: 1974 to 1977 drought (La Niña) conditions were experienced on Daphne Major as a consequence there was a shortage in smaller sized seeds 2 nd Environmental change: 1983 heavy and frequent rains (El Niño event) were experienced on Daphne Major as a consequence there was an abundance of smaller sized seeds Deduce the results from the graphs Variation: there is a difference in the size and shape of beaks Beak shape and size in Geospiza fortis