Twine TimePage 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)