Monday, March 8, 2010

Artificial Selection in Plants and Animals

Artificial selection is a type of selection in which the individuals of a species are chosen to ensure the presence or absence of certain traits. This selection is usually repeated in successive generations until those attributes approach in the descendents of offspring. Artifical selection is known as selective breeding or unnatural selection. It is a great principle to farmers and breeders because they can use it to change the traits of their plants and animals. This can satisfy their needs and makes their lives easier. Artificial selection is commonly used to produce new breeds from the variable offspring of hybrid crosses. It can be accelerated by techniques such as plant tissue culture and the artificial insemination of livestock. Artificial selection can greatly affect the lives of farmers and breeders when they choose the desirable traits for their plants and/or animals such as disease resistance and high crop yield in plants, and high production and new desirable traits in animals.

When an organism undergoes an advantageous change that is passed to successive generations, it is known as natural selection. Artificial selection was utilized by Charles Darwin to be contrasted with natural selection in which differential reproduction of organisms with certain traits is attributed to improved survival or reproductive ability (“Darwinian fitness”).

Using artificial selection, farmers and breeders choose desirable traits for their plants mainly the ones that are disease-resistant and high crop yield. Plant breeders start off with variable hybrid plants and then apply selection to produce new crops, trees, and flowers with desirable traits. Plants without any desirable trait is less likely to survive as they do not have fertilizers and pesticides. In fact, they will eventually evolutes.

The domestication of plants began with wheat, peas, and olives and dramatically increased the amount of food produced, which helped support human production growth. The seeds from wild plants were actively collected, planted and cultivated. As food was harvested, seeds from best plants were selected for the planting of subsequent crops.

Farmers have cultivated numerous crops from the wild mustard by artificially selecting them for certain attributes.

Source: http://evolution.berkeley.edu/evolibrary/article/_0_0/evo_30

These vegetables were cultivated from wild mustard. This evolution came through artificial selection.

Source: http://www.gly.uga.edu/railsback/1122/Brassica2.jpeg

The dramatic results of artificial selection that can be seen in Brassica; six different vegetables – kale, Brussels sprouts, broccoli, kohlrabi, cabbage, and cauliflower. They all have the sea cabbage, Brassica oleracea as their single common ancestor.

Ontario has a large agricultural sector which produces a wide range of foods. Among Ontario’s most valuable food crops are vegetables such as tomatoes, carrots, onions, and potatoes; grains such as wheat, oats, and barley; corn (mostly for use as livestock feed); canola (for oil); soybeans; and fruits such as apples, pears, peaches, grapes, and strawberries.

Over many years of artificial selection, the frequency of desirable gene variants increases in the population.

Source: http://evolution.berkeley.edu/evolibrary/news/070201_corn

This process has produced all of the major crop plants from their wild ancestors. By figuring this out, scientists are discovering clues about how to improve crops to change human needs. Most importantly, they would like to find out which gene variants were favored by ancient people (which genes were the targets of selection).

Using artificial selection, these plants have improved by quality. The one of the left was before artificial selection was used and the one on the right was after artificial selection.
 
 




Wild sunflowers Domestic sunflowers 






Wild tomatoes Domestic tomatoes
 
 
 
 





Teosinte plants Corn plants

Source: http://evolution.berkeley.edu/evolibrary/news/070201_corn

With artificial selection in plants, plants can greatly improve by quality. Through artificial selection, the plants with the desired traits of each generation were selected to reproduce, creating the next generation. This was used by a technique (plant tissue culture) in which selected plants can be cloned and grown directly into new plants. These plants can cultivate vegetables, which are beneficial for farmers because they can sell it and make good money.

With artificial selection, animal characteristics can be changed by using a technique (artificial insemination of livestock). Farmers and breeders can change the characteristics of their animals by selecting for reproduction those individuals with the most desirable qualities such as speed in racehorses, milk production in cows, trail scenting in dogs.
 

Pigs are artificially selected to produce the largest amount of meat.

Source:http://library.thinkquest.org/C0118084/Gene/Genetic_variation/artificialselection.htm  

Source: http://www.windows.ucar.edu/tour/link=/cool_stuff/tour_evolution_7.html&br=gr

This picture shows how selecting for different traits of breeding has caused different dog breeds to have distinctive characteristics. (Dog breeds from left to right: top row- Alaskan Malamute, Basset Hound, Llasa Apsa; middle row- Beagle puppy, Shar Pei, Chow; bottom row- Pekinese, Tibetan Terrier, Pug.)

Breeding a male horse with excellent racing qualities with a healthy female horse so that the offspring will have the desired traits such as the racing qualities. Hens could be artificially selected to produce more eggs and cows can be artificially selected for a high milk production.

Advantages of Artificial Selection

  • It creates new desirable traits for plants and animals.
  • Animals can produce a lot of products (ex. pigs produce meat, hens produce eggs, and cows produce milk).
  • Farmers and breeders can attract a lot of consumers by selling their plants and the products produced by animals in their new desirable trait.
  • Artificial selection rules out weakness and disability.

    Disadvantages of Artificial Selection
  • If there is an environmental factor occurring on plants and animals that were domesticated through artificial selection, there will be a higher possibility of extinction.
  • With artificial selection, the society will be highly competitive.
  • This is very expensive so only wealthy farmers and breeders can afford it.
  • It is not according to God’s plan of creation.
  • It is inhumane so it can cause mutations or produce new problems.

In artificial selection, plants and animals can have their traits changed.to satisfy the needs of humans. Personally, I find artificial selection similar to genetic screening in designer babies that I did in my Unit 5 blog based on its facts, advantages, and disadvantages. The advantages of artificial selection include creating new desirable traits for plants and animals, animals producing a lot of products, farmers and breeders making good money, and also it gets rid of weakness and disability. Artificial selection gives farmers and breeders an opportunity to change the traits of their plants and animals. Based on my images that I showed about artificial selection in plants, they improved by quality and charcateristics such as disease-resistant and high crop yield. Animals can produce a lot of products. Pigs and produce the largest amount of meat and hens can produce a lot of eggs. There can be high milk production in cows and high speed in racehorses. On the other hand, there are disadvantages for artificial selection. From what I have learned from Unit 2 SBI 3U1, biodiversity is important to ensure survival. So if we completely create plants and animals with desirable traits and an environmental factors occurs, there will be a higher possibility of extinction but if there are different plants and animals with different traits, it will not affect the entire population so the resistant ones will reproduce and pass the genes and create a greater biodiversity. Artificial selection is very expensive so only wealthy farmers and breeders can afford it. It is not according to God’s plan of creation. It is God who created plants and animals and have given them traits so farmers and breeders cannot make any preferences. As I find that there are more disadvantages than advantages for artificial selection and there are severe consequences, artificial selection should not be used in plants and animals.

Resources

2 comments:

  1. Hi John, thanks for the informative and interesting blog! I would have phrases some things differently, and some phrases I didn't quite understand, but overall it was a good blog. I don't agree though that artificial selection should not be used at all, because in our current situation, society has a dependence on artificial selection, and the food that it produces. An alternative to stopping it completely is to use it more thoughtfully and responsibly. I found it odd that you have more evidence supporting artificial selection in your blog than evidence against, so I don't know where you got your opinion from. There is no denying the numerous strong points of artificial selection, like the ones you have described quite well in this blog,and that is why we can't stop it completely. You have not really given any of it's weak points though, but they are numerous as well. I disagree that it is not God's plan for creation, because if it wasn't, wouldn't he stop it? I believe it is part of God's plan, because everything happens for a reason and is part of God's plan.

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  2. Wow. I found your blog entry very informative, you explained the process of selective breeding in a very detailed and orderly way. YOu showed me in a way that selective breeding was sort of like a "forced evolution". Although I do agree with Anil, you did'nt really touch base with the negative points of artificial selection as much as you did with its positive points. Selective breeding has many negative effects, like negative traits and weaknesses being passed down each generation because of the lack of variety which you explained briefly in the end.

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