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Selective Breeding vs. Natural Selection
Selective Breeding
vs.
Natural Selection
7.11C identify some changes in genetic traits that have occurred over several generations through natural selection and selective breeding such as the Galapagos Medium Ground Finch (Geospiza fortis) or domestic animals.
Natural Selection &
Selective Breeding Goal:
• I can explain natural selection in
my own words.
• I can explain selective breeding in
my own words.
• I can provide examples of natural
selection & selective breeding.
Natural Selection
The process by which some individuals
are better ADAPTED to their
environment and are more likely to
SURVIVE and reproduce than other
members of the same species.
◦ Variation of a trait
◦ Competition
◦ Over production
1. Variation in
traits.
For example, some
beetles are green
and some are
brown.
What is needed for natural
selection to occur?
2. Overproduction.
Most species
produce far more
offspring than can
possibly survive.
Why?
3. There is
competition. The members of a
species must compete
with one another to
survive because food,
space, and other
resources are limited.
End result:
Since the brown beetles
live longer, they have more
offspring. The brown
coloration becomes more
common in the population.
If this process continues,
eventually, all individuals in
the population will be
brown.
Natural Selection Example: Peppered Moth
Can you see the moths?
Example: Peppered Moths
Manchester, England 1845.
The trunks of the trees in the forest were light grayish-green due to the presence of lichens.
Most of the peppered moths in the area were light colored with dark spots.
Manchester, England from 1845 to 1890
As the industrial revolution progressed, the
tree trunks became covered with soot and
turned dark.
Over a period of 45 years, the dark variety of
the peppered moth became more common.
Natural Selection Example:
Galapagos Ground Finch In the 1850’s
Charles
Darwin
observed
finches on the
islands for 5
years
Galapagos Ground Finch Cont.
Darwin discovered that there were many variations
of one kind of bird, the finch. (difference in form of
the same species)
He noticed that there were finches with large beaks
on some islands and finches with small beaks on
other islands
NATURAL SELECTION
Discuss and be ready to share:
• Define natural selection in
your own words.
• Describe some examples of
natural selection discussed
today.
• Come up with your own
examples of natural selection.
the process of selecting or choosing specific
plants or animals to breed for particular
desirable genetic traits
typically, strains which are selectively bred are
domesticated, and the breeding is sometimes
done by a professional breeder
Selective Breeding
Natural Selection vs. Selective Breeding
Natural Selection Selective Breeding
Change in genetic traits over time because of environmental factors
The mating of parent organisms by humans to produce desired traits in the next generation
• Organisms that are alive longer, have the
opportunity to reproduce;
• The more organisms that have a trait, the more
likely it will be passed on to the next generation
Domestic Animals
Various animals that have been tamed and
made fit for a human environment.
SELECTIVE BREEDING
Summary: Human Influence on characteristics and behavior.
Domestic Animals
◦ Ex: Chickens, Dogs, Cows
Plants:
◦ Ex: Corn, Brasilica, Fruit hybrids
Cows are breed for particular traits…
◦ Dairy cow for milk production
◦ Raised as livestock for meat
◦ Strength for pulling a plow, no horns for safety, manure
for fertilizer
Why breed plants? higher-yielding (make more/bigger fruit)
resistant to pests and diseases
drought-resistant or regionally adapted to different
environments and growing conditions
Domestication of plants is an artificial selection
process conducted by humans to produce plants
that have more desirable traits than wild plants
Undesirable: dependent on artificial environments for
their continued existence (will not survive on own).
Selective Breeding
Selective breeding can also bring about
bad or undesirable traits
Some breeds of dogs are
selectively bred for their
aggressiveness, however, this
sometimes produces dogs are
too aggressive an cannot be
controlled.
Below is a picture of a horse (left) and donkey
(right) and a mule (bottom). When a horse is
bred with a donkey a mule is produced. A
mule has the strength of a horse and the sure
footedness (balance) of a donkey.
Undesirable traits
• Stubborn
• Sterile – cannot
reproduce
Make a T chart
Natural Selection Selective Breeding
Selective Breeding or Natural
Selection …you decide Cabbage Varieties Leafy Sea Dragon
Selective Breeding or Natural
Selection …you decide Cabbage Varieties Leafy Sea Dragon
NATURAL
SELECTION
SELECTIVE
BREEDING
Selective Breeding or Natural
Selection …you decide
Bengal Cat Tesonite (Corn)
Selective Breeding or Natural
Selection …you decide
Bengal Cat Tesonite (Corn)
SELECTIVE
BREEDING
SELECTIVE
BREEDING
Selective Breeding or Natural
Selection …you decide
Liger
Puggle
Selective Breeding or Natural
Selection …you decide
Liger Puggle
SELECTIVE
BREEDING
SELECTIVE
BREEDING
Selective Breeding or Natural
Selection …you decide
Eyes that rotate in all directions
zebra
Selective Breeding or Natural
Selection …you decide
Eyes that rotate in all directions
zebra
NATURAL
SELECTION
NATURAL
SELECTION
