Natural and Artificial Selection Flashcards Preview

OCR Biology F215 > Natural and Artificial Selection > Flashcards

Flashcards in Natural and Artificial Selection Deck (8)
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0
Q

What is natural selection?

A
  • Organisms best adapted to their environments are more likely to survive to reproductive age, passing on their favourable characteristics via alleles to their offspring.
  • ENVIRONMENT does the selecting.
  • Mechanism for evolution
1
Q

What is artificial selection?

A
  • Humans select the organisms with useful characteristics.
  • Humans allow those with useful characteristics to breed and prevent the ones without the characteristics from breeding.
  • Humans have a significant effect upon the evolution of these populations/species.
2
Q

What traits are selected for when breeding a modern dairy cow?

A
  • Docility (easy to handle).
  • High yield of meat.
  • High yield of milk.
  • Ability to survive in the environment.
3
Q

Describe the steps used to produce the modern dairy cow by artificial selection.

A
  • Females are selected according to their performance (high milk yield is desirable).
  • Males are selected by testing the performance of their female offspring.
  • A suitable bull is selected and its sperm can be collected and stored.
  • The sperm can be delivered by ARTIFICIAL SECTION to a large number of suitable females.
  • Offspring can then be tested, and over a number of generations the milk yield per cow can be increased.
4
Q

What traits are selected for when breeding bread wheat?

A
  • Resistance to fungal infections.
  • High protein content.
  • Straw (stem) stiffness.
  • Resistance to lodging (stem bending in wind).
  • Increased yield.
5
Q

Describe the steps used to produce bread wheat by artificial selection

A
  • Einkorn wheat crossed naturally with wild grass to produce a hybrid, this hybrid was sterile but became fertile after a chromosome mutation to produce wild emmer wheat.
  • This caused a rise in farmers growing cultivated emmer wheat.
  • The cultivated emmer wheat was then bred with other species to produce HYBRIDS which were sterile as they possessed an uneven number of chromosomes, so could not pair during meiosis.
  • Chromosome mutation of the STERILE HYBRID led to a doubling in the number of chromosomes making the hybrid fertile, this hybrid was known as spelt wheat.
  • Further gene mutation and selection over generations has left to modern bread wheat!
6
Q

What are the similarities between artificial and natural selection?

A
  • they both change the allele frequencies in the nest generation - the alleles that code for the desirable characteristic will become more common in the next generation
  • both may make use of random mutations when they occur - if a random mutation produces an allele that gives a desirable phenotype it will selected for in the next generation
7
Q

What are the differences between artificial and natural selection?

A
  • in natural selection the organisms that reproduce are selected by the environment but in artificial selection this is carried out by humans
  • artificial selection aims for a predetermined result but in natural selection the result is unpredictable
  • natural selection makes the species better adapted to the environment but artificial selection makes the species more useful to humans