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Twine Time
Page 320
Entry Task
• Explain what evolution means.
Include the following words in your
description: adaptation, population,
natural selection, selective pressure,
variation, species
• Explain why some species become
extinct.
Entry Task
• Evolution provides an explanation for how species
change across time. Natural Selection is the
mechanism for evolution. Evolution only occurs
when there are variations in a population and
when there are selective pressures acting on those
variations. Selective pressures cause individuals
with beneficial characteristics (adaptations) to
survive and cause individuals without the
adaptations to die off. Across time, more
individuals with the adaptations survive and
reproduce. As more of the population has the
adaptation, eventually the population can be
recognized as a distinct species.
Entry Task
• Explain why some species become
extinct.
• Species become extinct when the entire
population of individuals is no longer
able to survive in its environment. If
the environment of a species changes
and the species doesn’t possess
characteristics or adaptations that
would help it survive, the species will
become extinct.
Twine Time
• New header/thread: “Twine Time”
• Learning Target: I can appreciate the
immense expanse of time in Earth’s
history by building a timeline to scale
and interpreting the biotic and abiotic
events placed on the timeline.
• Update your table of contents
Twine Time
•Key idea: we’re going to build a
timeline to represent the history
of the earth, and we’re going to
place events on the timeline
when they occurred. Try to
identify any patterns in the
events and placement of them.
Twine Time
•Abiotic: Nonliving. The abiotic
factors of the environment
include light, temperature, and
atmospheric gases.
•Biotic: having to do with life or
living organisms.
Twine Time
• P&P #1: You should have 35 event
cards in your packet.
• P&P#2: Sort the cards into two piles:
biotic events (biological events) and
abiotic events
• P&P #3: Order each set of cards in
the order you think they occurred.
• Call me when you think you have the
correct order.
Twine Time
•Order the events in the order
you think they occurred.
•Answer P&P #6 – which biotic
and abiotic event occurred
closest to the middle of earth’s
history (about 2.3 BYA)?
Twine Time
•Complete #7-9.
•You must show your
calculations in your
notebook!
•Let me know when your
timeline is complete.
Twine Time
•Answer all P&P questions
•Read/Notes “Ongoing
Research” p. 324-325
•Answer R&C #1-3 p. 323
P&P #11a
• What patterns do you see in the placement of
events on the timeline?
• More events occur near the present than the past
• Very few events are given for the first 3 billion
years of Earth’s history
• The biological events tend to be grouped together
• Plants appeared first, then animals
• One or more biotic events occur after an abiotic
event
R&C #2
• Look at the events that represented
changes in Earth’s surface or atmosphere.
Compare the location of these events on
the timeline with the events showing the
appearance of different plant and animal
life. How are they related?
• In general, changes in Earth’s environment
are followed by changes in the types of
plants and animals on Earth.
R&C #3
• Explain how the process of natural selection and evolution might lead to the
appearance of new species.
• Evolution is a change in the characteristics of
organisms over time. Natural selection is the
mechanism that drives evolution. These processes
cause advantageous characteristics to be passed on to
more and more individuals in a population.
Eventually, a large portion of a population might have
more advantageous characteristics that makes these
individuals distinct from the original population.
When these individuals have changed to the point
that they can no longer interbreed with the original
population, they are considered a new species.
Ongoing Research…
• What were the Grants studying?
• What was the variation that they were interested in?
• What was the selective pressure that was occurring?
• This is an example of microevolution: the change in
the frequency of characteristics (genetic traits)
within a population.
• Contrast this with macroevolution: change in
characteristics at the species level or higher (e.g.,
formation of new species)