Contents
Genetic Manipulation (selection)
Genetic modification of organisms has been occurring through human manipulation since the beginning of agriculture. Humans selectively bred crops and livestock to propagate desirable traits in a process termed artificial selection. The original grass that gave rise to domesticated corn called teosinte hardly resembles what we think of when imagining modern maize.
![Maize-teosinte](https://upload.wikimedia.org/wikipedia/commons/thumb/c/cb/Maize-teosinte.jpg/512px-Maize-teosinte.jpg)
Teosinte, the progenitor of maize. Corn came about due to selective breeding. Credit: John Doebley (CC-BY)
Variation: Crop domestication
Selective breeding can yield a variety of features even within the same species. Below is selection of vegetables of the species Brassica oleracea that have been developed into different varieties over the course of agricultural history.
![Starr 070730-7852 Brassica oleracea var. capitata](https://upload.wikimedia.org/wikipedia/commons/thumb/e/ec/Starr_070730-7852_Brassica_oleracea_var._capitata.jpg/256px-Starr_070730-7852_Brassica_oleracea_var._capitata.jpg)
Cabbage: Brassica oleracea var. capitata Credit: Forest & Kim Starr (CC-BY 3.0)
![Brocoli 02](https://upload.wikimedia.org/wikipedia/commons/thumb/4/4a/Brocoli_02.jpg/256px-Brocoli_02.jpg)
Broccoli: Brassica oleracea var. italica Credit: Coyau (CC-BY-SA 3.0)
![Chou-rave 01](https://upload.wikimedia.org/wikipedia/commons/thumb/d/de/Chou-rave_01.jpg/256px-Chou-rave_01.jpg)
Kohlrabi: Brassica oleracea var. gongylodes Coyau (CC-BY-SA 3.0)
![Romanesco Brassica oleracea Richard Bartz](https://upload.wikimedia.org/wikipedia/commons/thumb/b/b5/Romanesco_Brassica_oleracea_Richard_Bartz.jpg/256px-Romanesco_Brassica_oleracea_Richard_Bartz.jpg)
Romanesco: Brassica oleracea var. botrytis Credit: Richard Bartz (CC-BY-SA 2.5)
Variation: Animal domestication
![Dog morphological variation](https://upload.wikimedia.org/wikipedia/commons/thumb/6/69/Dog_morphological_variation.png/512px-Dog_morphological_variation.png)
Credit: Mary Bloom, American Kennel Club (CC-BY-SA 4.0)
![Collage of Nine Dogs](https://upload.wikimedia.org/wikipedia/commons/thumb/d/d9/Collage_of_Nine_Dogs.jpg/512px-Collage_of_Nine_Dogs.jpg)
Companion animals like dogs underwent thousands of years of domestication and selection for traits that were desirable for different circumstances. A high degree of morphological diversity exists between dog breeds and their ancestral grey wolf progenitor.
Genetic Manipulation (engineered)
Artificial selection takes multiple generations over a long period of time. With the advent of recombinant DNA and biotechnology, scientists can now genetically modify organisms through introduction of foreign genes to provide desirable characteristics within one generation. This process does not require traits to naturally arise in a species.
![Zebrafish](https://upload.wikimedia.org/wikipedia/commons/thumb/a/ac/Zebrafisch.jpg/512px-Zebrafisch.jpg)
GloFish are transgenic zebra fish (Danio rerio) expressing variants of GFP. Bottom features a wild-type fish. Credit: Azul (CC-BY)
![The perks of working for a pet company... I brought home a GloFish tank and a bunch of fish! Yes these fish actually glow under black light. #GloFish #Tetra #Fish #Aquarium](https://farm9.staticflickr.com/8583/16230167703_74dffa67db_z.jpg)
Black tetra (Gymnocorymbus ternetzi) GloFish Credit: https://www.flickr.com/photos/fergy08/ (CC-BY 2.0)