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.

Why are we learning about this? Living organisms are dependent on the environment and other species for their survival. Because we are all part of a giant food web, changes in one part of the web can have a big impact on other parts of the web. When one food source disappears, a predator will have to find another food source in order to survive.

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

Selected by Nature vs. Selected by Humans IN OTHER WORDS… Natural Selection Selective Breeding Process of selection whereby favorable traits become more common and less favorable traits become less common in following generations. A form of artificial selection whereby deliberate breeding results in desired traits in plants and animals Selected by Nature vs. Selected by Humans

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: Decide which characteristics are important Choose parents that show these characteristics Select the best offspring from parents to breed the next generation Repeat the process continuously

Domestic Animals

Selective Breeding of Horses Ancient Wild Horses Help Unlock Past Aug. 23, 2011 — An international team of researchers has used ancient DNA to produce compelling evidence that the lack of genetic diversity in modern stallions is the result of the “domestication” process. 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

Selective Breeding of Farm Animals Chickens - bred for eggs or meat The chickens on the left are egg-laying hens. They have been selectively bred to lay lots of eggs, but they grow at a normal rate. Most are still kept in battery cages, though this system is to be banned in 2012. The chickens on the right are broiler chickens. They have been bred for meat. They grow twice as quickly and are usually slaughtered at six weeks old. Most meat chickens are kept intensively in large sheds. You can click on the link to read more about these chickens. http://www.ciwf.org.uk/includes/documents/cm_docs/2008/s/science_worksheets_selective_breeding.pdf

Hybrid Fruits Nectarcots Pluots Peacotums a peach/apricot/plum hybrid. The mellow-tasting fruit has the texture of a peach, but tastes like a blend of plum and apricot.