Transcript Selective breeding—The selection of certain seeds or

Selective breeding—The selection of certain
seeds or animals for reproduction so that
the next generation has the same desirable
traits.
• To take advantage of hybrid vigor.
• Hybrid vigor – desirable characteristics that give the
organisms a competitive edge over the parent
organism.
– Example: A disease-resistant plant or a chicken that grows
larger than its parents.
•What is Natural Selection?
• Organisms and species that survive
and reproduce are the sole ancestors to
the next generation. Those that fail to
reproduce will not continue.
• This is selection happening natural
rather than due to human intrusion.
•What is Selective Breeding?
• The selection of certain seeds
or animals for reproduction so
that the next generation has the
same desirable traits.
• This selection happens because
humans choose (or breed) only
what they select. It is not natural.
• The continued breeding of individuals with similar
characteristics in order to maintain the desired
characteristics of a line of organisms.
• Inbreeding Depression: The increased chance that a
cross between two individuals will bring together
two recessive alleles for a genetic defect.
– Example: Deafness in Dalmatians
• Loss of variety in the population
• Can amplify undesired traits unintentionally
– Example: German Shepherd Dogs with hip problems.
• Diseases and pests can become resistant
– Example: Due to selection and overuse of pesticides many
pests and crop diseases have evolved and developed
resistance rendering the pesticides useless.
• It is VERY important to maintain natural populations of
organisms as a source of genes or a Gene Pool.
• Natural populations are
diverse enough to withstand
changes in the environment. If
there is a change in
environmental conditions,
some part of the population
will have the genetic make up
to survive and pass on their
genes which will allow the
population to survive.
• Irish Potato Famine (1845-1852)
– New potato plants arise from pieces of the parent plant,
not as a result of reproduction.
– Ireland planted mostly the “Lumper” variety of potato, so
the entire crop was ONE potato (No diversity).
– The entire crop was victim to a rot causing fungus which
destroyed potatoes, and left one million people to starve.
• The results of selective breeding are all around us, from our
pets to our food.
• Without selective breeding, we wouldn’t have an amazing
variety of dogs. We also wouldn’t have broccoli, cauliflower,
cabbages, kale, or Brussels sprouts—which all were derived
from a single wild mustard plant.
• Now YOU the budding new scientists can take advantage of
our understanding of genetic principles to produce healthy
plants and animals by using selective breeding tactics.
• Click the link to practice selective breeding
and create your own “designer dog!”.
– http://pbskids.org/dragonflytv/games/game_dog
breeding.html