Transcript PPT - Contact Ms. Bosse

• Breeding organisms with specific traits in
order to produce offspring with ideal traits is
called artificial selection.
(Intentional breeding for certain traits)
Who have we
studied that
bred organisms
through
artificial
selection?
A Goldendoodle
(Golden retriever/ Poodle)
Mendel and the pea
plants
Darwin and Natural Selection
• Charles Darwin (1809- 1882)
He was an English scientist and it took him years
to develop his theory of natural selection.
• He began in 1831 at age 22 when he took a job as a naturalist
on the English ship HMS Beagle, which sailed around the world
on a five-year scientific journey.
Darwin and Natural Selection
• As the ship’s naturalist, Darwin studied and collected
biological and fossil specimens at every port along the
route.
• The specimens were quite diverse, but he became
curious about possible relationships among species
because of similarities he saw.
Darwin and Natural Selection
• One of the things Darwin
observed is that in nature,
the traits of individuals vary
in populations.
• Then these variations are
then passed to offspring.
• Darwin hypothesized that there was a force in nature
that picked which traits are better for survival in a
species.
Darwin and Natural Selection
• On the Galápagos Islands, Darwin studied many
species of animals and plants that are unique to the
islands but similar to species on the mainland.
• These observations led Darwin to consider the possibility that
species can change over time, especially if exposed to different
environments where they must adapt to different things.
Darwin and Natural Selection
• He also observed that individuals struggle to compete
in changing environmental conditions.
• What do individuals compete for?
• Only some individuals survive the competition and live
to produce offspring.
Darwin and Natural Selection
• Natural selection is the idea that organisms with
favorable/beneficial traits survive, reproduce, and pass
those traits to the next generation.
• Organisms without these variations/traits are less
likely to survive and reproduce.
Darwin and Natural Selection
• Darwin proposed that natural selection explains
how species change over time….
• He had four ideas to explain how natural
selection works.
1.In nature, organisms
produce more offspring
than can survive.
Darwin and Natural Selection
2. In any population, individuals have variations.
• For example, color, size, and speed.
Darwin and Natural Selection
3. Individuals with certain useful variations are the ones
that survive in their environment, passing those
variations to the next generation.
•
Whereas individuals without those variations would
not survive to reproduce.
Darwin and Natural Selection
4. Over time, offspring with the FAVORABLE variations
make up most of the population.
•
The allele for the unfavorable variation may
eventually cease to exist.
Why do you think more and more bad bacteria
(like the kind that cause sinus infections) are becoming
resistant to anti-biotics?
How do you think natural
selection will affect this species
of moth?
(both the same species, just
have variations)
Question 1
What is the difference between artificial and
natural selection?
Natural Selection:
Nature’s way of making sure the
best traits live on….
“Survival of the fittest”
ADAPTATIONS
• Recall that an adaptation is any variation that aids an
organism’s chances of survival in its environment.
• Examples are:
Thorns on plants
Special colorings for an organism
Enhanced night vision
ADAPTATIONS
• Some other structural adaptations are subtle.
• Mimicry is a structural adaptation that enables one
species to resemble another species.
• In one form of mimicry, a harmless species has
adaptations that result in a physical resemblance to a
harmful species.
ADAPTATIONS
• Another subtle adaptation is camouflage, an
adaptation that enables species to blend with their
surroundings.
• Because well-camouflaged organisms are
not easily found by predators, they survive to
reproduce.