- Slides: 14
Natural Selection & Artificial Selection
Natural Selection VS Artificial Selection Natural Selection: Artificial Selection: Process by which organisms that are best suited to their environment survive and reproduce most successfully. Method of breeding that allows only those organisms with desired characteristics to produce the next generation. Favourable traits become more common and less favorable traits become less common in following generations. Deliberate breeding results in desired traits in plants and animals
Natural Selection Example White coloured VS Dark Coloured Pepper Moths during the Industrial Revolution Manchester, England from 1845 to 1890. Before the industrial revolution, the trunks of the trees in the forest around Manchester were light grayish-green due to the presence of lichens.
Natural Selection Example The Industrial Revolution
Natural Selection Example Most of the peppered moths in the area were light colored with dark spots. As the industrial revolution progressed, the tree trunks became covered with soot and turned dark. Over a period of 45 years, the dark variety of the peppered moth became more common. Why?
Natural Selection Example Survival of the strongest? Survival of the fittest! Fitness: an organism's ability to survive and reproduce in a particular environment. Darker moths were better hidden from predators and survived in greater numbers Able to pass their now favorable trait on and continue to increase in numbers.
Natural Selection Individuals in a species show a wide range of variation because of differences in their genes Genes that allow individuals to survive are then passed on to their offspring Individuals poorly adapted are less likely to survive, reproduce, and pass on their genes
Natural Selection 1850’s: Charles Darwin described how organisms might change over time. 5 years of observations on the islands. Established that all species have descended over time from a common ancestor Theory of evolution resulted from a process that he called natural selection
Natural Selection in Horses Early Horse (Eohippus) Modern Horses (Equus) Lived 55 -60 million years ago Began to develop 2 million years ago Lived in forests and ate leaves About the size of a fox As a result of changes in the global climate, lived in grasslands and ate grass 4 toes to walk on soft forest floor Developed long legs and one toe (hoof) to help the horse run faster from predators and longer teeth to eat the grass
Artificial Selection Domestic Animals: Chickens, Dogs, Cows, Horses Plants: Corn, Wheat, Fruit hybrids
Artificial Selection Steps: 1. Decide which characteristics are important 2. Choose parents that show these characteristics 3. Select the best offspring from parents to breed the next generation 4. Repeat the process continuously
Domestic Dogs come in lots of different varieties, or breeds They may be different colors and sizes, but they are all still dogs. They are all still the same species.
Artificial Selection in Plants Florists and flower producers can use artificial selection to create blends of colors, different color patterns, and even leaf coloring patterns on their stems to get the desired results Create new hybrids of crops and fruit Corn can be bred to be larger and thicker in the cobs to increase grain yield from a single plant Broccoflower (a cross between broccoli and cauliflower) Tangelo (the hybrid of a tangerine and a grapefruit)