Selective Breeding

by kartikayguptalivecouk (student)

GCSE Science

Selective Breeding in Plants and Animals

Selective Breeding in Plants

Desired Characteristics plants are bred for:

Decorative plants are selectively bred for colour.
Food plants are selectively bred for better yield.
Most plants are selectively bred to be hardier.
Most plants are selectively bred for resistance against disease.
Some plants are selectively bred for fragrance.
Some plants are selectively bred for texture and taste.

Breeding for Characteristics

The definition of selective breeding is:

The breeder would breed two adults that have the desired characteristic, then he would keep on breeding the younger generations, choosing the offspring with the strongest sense of that characteristic and thus as the generations get further and further the characteristic being breed for would become stronger.

Selective breeding can also allow the combination of two adults feature for example if you wanted an orange coloured plant you could breed a red and a yellow coloured plant to get the genes to have a co - dominant relationship.

Selective Breeding in Plants (notes)

In farming the farmers need to make the most profit that is possible so they breed the plants to get offspring that give a very high yield. To breed the plants they must put them in controlled conditions to stop any contamination from any other pollen. Then the plants are pollinated by the farmers using a brush to ensure that the right plants are pollinated.

The ways they can increase the yield is by selectively breeding the plant so that the piece we eat for example the carrot will grow very big. We could decrease the size of the part we don’t eat so more growth happens in the part we eat,

Breed it so it grows faster and lastly improve the looks of the crop so it is more desirable.

Selective plant breeding can cause problems as when selectively breeding it can also create different characteristic that are undesired for example like a miracle rice it may need lots of nutrients to grow thus is impossible for some to grow thus useless.

B5b.1a The process of selective breeding

Questions (pg. 337)

TOP

Some characteristics can be breed for in selective breeding as they are coded for by genes thus can be manipulated.

So characteristics don’t depend on genes so won’t be effected by selective breeding.

To increase crop yield we can either, increase the part we eat so that it has more weight and thus can be sold for more, reduce the part we don’t eat so that the energy that would of gone into that it used for the part we do eat and also make the crop faster growing so that we get more ...

This is a preview of the whole essay

Questions (pg. 337)

TOP

Some characteristics can be breed for in selective breeding as they are coded for by genes thus can be manipulated.

So characteristics don’t depend on genes so won’t be effected by selective breeding.

To increase crop yield we can either, increase the part we eat so that it has more weight and thus can be sold for more, reduce the part we don’t eat so that the energy that would of gone into that it used for the part we do eat and also make the crop faster growing so that we get more mass in a short period of time.
If we increase eth part we eat of the crop in size it will increase the crop yield as when growing the crop we would get more mass for one seed thus the yield would be much higher. By reducing the part we don’t eat in size it will increase the part we do eat in size thus it will give more mass per drop thus more yield. If it grows faster in a period of time we can grow more crops after harvesting the first set thus the crops will be higher in number so higher yield.
The reason plants are grown in horticulture is because they are trying to get more attractive plants as plants can get boring so to keep people interest they produce more types and shapes

BOTTOM

When you sexually reproduce something for selective breeding there are only the alleles of the specific mother and father so there are only limited characteristics that can be inherited as they have the desired traits, while in the wild there is any chance of a plant fertilising another plant so the possibilities are endless about the alleles.
It is useful as it means that there is more chance of the desired trait to be passed down as there is little genetic variation so it doesn’t get any other variation due to other alleles.
The problem with the narrow selective breeding as there may be a mutual problem that at first isn’t noticed by the scientists such a reduced resistant to a specific disease and by narrowly breeding you are making the allele more dominant so if the crop is released it could be a flop due to this.
Yes these plants should be kept as they may have desired characteristics that we will need later in time for example there may be a disease that is killing all of the plants and one of the older crops that aren’t as efficient in growing have that specific resistance thus are able to be grown and selectively breed with the plants so they get the resilience from the specific disease.

Selective breeding in animals

Desired characteristic for animals are:

High yield for example a sheep that produces a lot of wool and a cow that creates lots of milk.
Efficiency in creating matter, for example an animal is better if it needs less feed to make the same 1kg of protein and meat.
Better qualities of yield for example in sheep stronger wool or in a pig nicer tasting food.
Resistance from disease as its better if more animals survive overall.
Appearance for example dogs are selectively breed for better coats
Fitness levels as animals like horses are used for racing so having two fast horse will give an fast offspring

Selective breeding in animals (notes)

Humans have controlled and domesticated animals for hundreds of years, the reasons for are food, materials and aides to life. The humans would breed their best animals to get the best offspring. By doing this the farmers have made the animals much more efficient so that the ways that they grow are much faster allowing more profit and yield. The different bred have different advantages so cross breeds are created which mixes the desired characteristics to get the super animal.

For example when breeding fish for pets, there is a lot of selective breeding to get a good breed.

The half-moon Siamese fish is very hardy and lives a much longer life, while the full moon Siamese fighting fish is much more visually pleasing to look at so cross breeds are developed for perfect fish.

Selectively breeding in chickens

The patterns show that both chickens are at similar sizes at day one, the meat chicken being slightly bigger and once we get to 45 days the meat chicken completely overtakes the layer chicken to to around 4 times the weight as it is 2400 grams while the layer is around 600 grams.
The students kept the chicken to make the test fair as it showed it wasn’t any conditions that affected the growth of the chickens as they were in the same place.
The meat chicken has been selectively bred to use its energy to creating body mass, while the layer is bred to use all its energy laying eggs.
No because they were both fed the same food and if there were chemicals it would affect the layer chickens as well.
A) The advantages of selectively breeding the grown meat chickens is that the farmer will make more profit as they are able to convert more of the energy into meat mass.

B) The advantages of breeding the layer chicken is that it uses its energy to create more eggs and lay them.

He could breed the meat chicken and layer chicken as they would give much bigger chickens and because they are layer chickens they will give lots of eggs thus they will lay much bigger eggs.

P339 Qu 1 – 3

You chose the male and female animals that have the desired characteristics. Then you breed them, you repeat this process with other organisms with desired characteristics. You keep on doing this until your characteristic is see able in the organism.
A) if you increase the muscle the yield is increased as muscle is what we eat. B) If there is resistance of disease they won’t die as much so more animals survive so there is more yield. C) If the animal is docile it is much easier to give the optimum conditions for best growth as you are able to get close and give them the needs they need.
We can’t breed one sheep with all the needs as there are clashing alleles that override each other that give desired characteristics, so they are specific so they can be breed for one use only.

End of topic questions p. 341 Qu 1- 4

1)A) Characteristics that are helpful such as higher yield can be done by selective breeding
B) Characteristics that are undesired can appear that were dormant such as poison or toxicity; an example can be plants that selectively breed change the ph. of the soil so it can’t be used again. Secondly if you selectively breed a plant you can get a plant with reduced resilience thus the plant actually has fewer yields as more die.
2) She would first of all breed both plants to get red plants that are red and big or red and small, white and big, white and small. Then using the big and red and white and red and small you will get a red and medium, then you breed the red and big repeatedly to get the red to a bigger size until it’s a red big plants.
3) a) the sheep have adapted to the hot weather thus have less wool, to get more wool they buy the sheep from Europe which have more wool so they can selectively breed one with more yield thus profit.
B) The European and Australian sheep breeds wont be ready for the climate so they could die out and so to stop this they breed them with the Indian sheep that are already resilient to the conditions.
C) The farmer first breeds the first generation together than he chooses the offspring with the required characteristics and breeds them. Then he repeats this process to refine the specific characteristic thus he will breed the animals successfully.
4) a) we could do a D.N.A test, if the genetics are mostly similar then they are the same breed.
B) A black goldfish could have arisen from a mutation
C) The reason they have been bred is because g goldfish are a pet so to get nicer varieties the fish breeders get better colours so they are the best breeders so really for competition.