Selective breeding is when humans choose which animals or plants breed together. There are many reasons for this, ranging from useful to attractive.
Since the beginning of agriculture, farmers have been aware that breeding certain individuals will bring about desirable offspring. This is why we have crops that provide high food yields and different breeds of animals like dogs.
However, Gregor Mendel’s pea plant experiments carried out between 1856 and 1863, provided the foundation for our understanding of the scientific laws of inheritance. Mendel selectively bred pea plants to understand how different traits were passed onto offspring. These studies inform modern-day theories in selective breeding and genetics.
How does selective breeding differ from natural selection?
At a similar time to Mendel’s pea experiments, Charles Darwin and Alfred Russell Wallace presented their theory of evolution. Darwin discussed the process of selective breeding and how it has produced a change in species over time in his book On the Origin of Species, published in 1859.
- Darwin bred pigeons and selected mating pairs to generate certain traits in their offspring.
- Understanding selective breeding helped Darwin to formulate the theory of natural selection.
- Selection occurs in nature because the organisms better adapted to the environment are more likely to survive and reproduce.
What is the process of selective breeding?
- Choose the plants or animals from your existing stock that have the desired feature.
- Breed these with each other.
- Choose the best of the offspring and breed these together.
- Continue this process over several generations; eventually, all the offspring have the features you are looking for.
What are some examples of selective breeding in plants?
People have selected certain traits from the original brassica plant to create different foods we can eat. From kohlrabi to cauliflower, broccoli to kale, these tasty vegetables are all the outcome of selective breeding in plants.
Corn is a vital crop in many parts of the world. Selection of corn has been taking place for over 10.000 years! Yield has been increased by selecting more kernels. There are also varieties of corn that can survive in harsh climates, which is important in our changing world.
What are the benefits of selective breeding in plants?
Selective breeding can create new varieties of good crops. They may be bred for the following characteristics:
- Higher resistance to pests and disease – for instance, selective breeding can limit the number of crops that perish due to blight.
- Higher yield.
- Shorter time before harvest. More harvests mean more produce in a shorter amount of time.
- To allow plants to grow on lands not previously suitable for farming. For example, land can be unsuitable due to poor soil fertility.
- Selective breeding can increase the protein in crops which can help improve food production worldwide.
What are some problems with selective breeding?
The problem with selective breeding is a lack of variation. Selective breeding reduces the number of alleles (genetic differences) in a population. This leaves a population vulnerable to sudden changes in the environment and disease.
What are some problems with selective breeding in plants?
Crop Case Study: the banana
- Today’s bananas are a cultivar (type) called the Cavendish. Until the 1950s, however, the main variety of bananas grown was the Gros Michel, ‘Big Mike’ banana.
- Gros Michel bananas had thick peel and dense bunches, which made the banana easy to export and less prone to bruising.
- A fungal disease wiped out vast plantations of Gros Michel bananas in Central America in the 1950s, causing the swap to the Cavendish.
- In monoculture farming (fields planted with one type of crop), if one plant gets infected, the rest will likely also become infected.
Cavendish bananas are also susceptible to fungus, and the same could happen again. The spread of a fungus to other continents could have a globally devastating effect on the supply of this important crop.
The impact of climate change is leading to more extreme weather events, impacting pollinators, and shifting harvest times – or no harvest at all.
What is an example of selective breeding in animals?
Dogs
Based on the evidence, scientists agree that dogs were the first animal to be domesticated by humans. However, domesticated dogs have lived beside humans for at least 14,200 years – perhaps even longer!
Dogs have been selectively bred for their traits for centuries. This may include a dog being larger, smaller, stronger, or having a different fur color, depending on their environment and what they do with the people who care for them. This can benefit humans and dogs – for instance, if the dog has thick fur and lives in a cold place.
A pedigree dog is a puppy bred from parents of the same breed. Their parents will have been the same breed, and so on, back through the dogs’ genetic history. This lineage can be proven by registration with ‘The Pedigree Club,’ which records pedigree dogs in the country.
Selective breeding can lead to inbreeding. This is where animals have been mated with close relatives. This results in little variation in a population. As a result, the animals are more likely to have health problems caused by their genes or be more susceptible to certain diseases.
Breeds like French bulldogs and pugs, bred for squashed faces, suffer from breathing difficulties, eye ulcers, skin disorders, and other illnesses. Some problems are less obvious: bigger dogs like Labradors now have health problems because they have been bred to be larger, taller, and stronger. As a result, they may have joint issues and are more susceptible to cancer.
