Natural Selection vs. Selective Breeding Environmental and Human Influences Natural selection and selective breeding can both produce changes in animals and plants. The difference between the two is that natural selection occurs in nature, but selective breeding only occurs when humans intervene.

Natural Selection vs. Selective Breeding 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. Natural Selection vs. Selective Breeding

Natural Selection Selective Breeding Selected by nature Selected by humans

Natural Selection Example: White Colored vs Dark Colored Peppered 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 Darwin’s Finches Selection Individuals have high genetic diversity Best fit genes get passed down Poor genes = less likely to survive

Galapagos Finches

Natural Selection and Horses

Early Horse (Eohippus) • lived 55-60 million years ago • lived in forests and ate leaves • about the size of a fox • 4 toes to walk on soft forest floor Modern Horses (Equus) • began to develop 2 million years ago • as a result of changes in the global climate, lived in grasslands and ate grass • developed long legs and one toe (hoof) to help the horse run faster from predators and longer teeth to eat the grass

Selective breeding Domestic Animals Plants: Human Influence on characteristics and behavior. Domestic Animals Ex: Chickens, Dogs, Cows, Horses Plants: Ex: Corn, Wheat, Fruit hybrids

These are the steps in selective breeding: Identify desirable characteristics Choose parents w/ these characteristics Select the best offspring from parents to breed the next generation Repeat 1-3 continuously

Domestic Animals

Selective Breeding of Horses Horses were first domesticated for transportation, agricultural work and warfare Today they are also bred for racing and companionship

Different varieties of dog have been produced over many generations by selective breeding. For example, pedigree dogs come in lots of different varieties, called breeds of dog. They may be different colors and sizes, but they are all still dogs. They are all still the same species. Different breeds of dogs http://www.bbc.co.uk/bitesize/ks3/science/organisms_behaviour_healt h/variation_classification/revision/5/ (click on the link and read about selective breeding of cows and other examples of selective breeding)

Cows-bred for meat or milk The picture above shows a dairy cow. She has been bred for milk. She has been selectively bred to produce enough milk for ten calves, but her calf is removed from her shortly after birth. Most cows are only milked twice a day. It may have to carry over 20 liters of milk. Many cows go lame through carrying all this milk. The cow above has been selectively bred for meat. She produces enough milk to feed one calf. Her calf will milk her six times per day. She only needs a small udder.

Aberdeen Angus bull - bred for beef Friesan cow - dairy breed