Transcript Presentation: Artificial and Natural Selection

LG 2 Artificial and Natural
Selection
Genetic Variation
Genes –
Traits –
Parents to Offspring –
Artificial Selection
Nature’s Variations –
Natural Selection
Environmental Factors –
Struggle for Existence –
Fitness –
Adaptations –
Populations –
UNIT V
EVOLUTION
Learning Goal 2
Describe the effects of environmental
factors on artificial and natural
selection.
• Dogs were the first animals to be
domesticated by humans. DNA studies
show that they are most closely related
to modern wolves. The first
archeological evidence of domestic
dogs was found at a site in Germany
that was about 16,000 years old. More
recent DNA evidence shows that dogs
and wolves may have split as long as
135,000 years ago
Genetic Variation
• Genes –
• Members of a
population do not
have identical
genes.
• Traits –
• Because genes are
not identical,
members of a
population exhibit
different genetic
traits.
• Parents to Offspring
– Genes for traits
are passed from
parents to offspring.
Artificial Selection
• Nature’s Variations –
Nature’s variations are
selected by humans to
produce desirable traits in
offspring.
• Plants – Larger fruits, better
taste, drought resistance,
pest resistance.
• Can become very different
from the wild ancestor, for
example broccoli,
cauliflower, cabbage,
brussel sprouts are all
descended from the same
ancestral plant.
• Animals – Bred for leaner
meat, more milk, size
• Plant and animal breeding
has been going on for so
long that modern
domesticated plants and
animals are very different
from their ancestors.
• People realized that if
humans can bring about
such changes that a similar
process could occur
naturally.
Natural Selection
• Environmental Factors –
Natures’ variations are
selected by environmental
factors.
• Struggle for Existence –
Comes about due to
competition in organisms’
struggle for existence.
• Fitness – An organism’s
fitness is defined as its
ability to survive and
reproduce in its
environment.
• Adaptations – Fitness
results from adaptations,
inherited characteristics that
increase an organisms’
chance for survival.
• Populations - Natural
selection can only be
observed in populations not
individuals and results in
changes in inherited
characteristics over time.