The central ideas of evolution are that life has a history that has changed over time and different species share common ancestors. Living things are adapted over time to their environmental situations through genetic variation and natural selection. The fossil record provides snapshots of the past that, when assembled, illustrate a landscape of evolutionary change over time.
Unit Essential Question(s):
How do we use the theory of evolution to learn about the history of the Earth?
Discuss how to date, evolution is the only well-supported scientific explanation for life's diversity.
Recognize that scientists do not debate whether evolution (descent with modification) took place, but they do argue how it took place.
Identify the mechanisms for evolutionary change: mutation, migration, genetic drift and natural selection.
Explain how random changes in an organisms DNA is known as a mutation. Some mutations are beneficial, some are harmful and some have no impact at all. A single mutation can impact the evolution of a species however, in most cases the evolutionary change is caused by an accumulation of mutations.
Discuss how when members of the same species with different traits breed, then frequency of those different traits will increase throughout the population. This in known as migration.
Explore how when a random event occurs to a population it can impact the passing of traits onto the next generation. These changes from one generation to another that occur as a result of these random events are known as genetic drift.
LEQ: Number 2
Explore the key principles of natural selection
Variations exist among individuals.
Organisms produce more offspring than the environment can support.
Differential reproduction occurs where individuals with beneficial traits have a better chance to successfully reproduce.
There is heredity. Beneficial traits are passed on to offspring and eventually over time the beneficial traits will become common in the population
LEQ: Number 3
Discuss how the presence of geographical barriers such as rivers, mountains, canyons, desserts as well as man made barriers such as highways and dams can cause some populations to be split and seperated from other members of their species. Explain that over time as mutations occur within the seperated populations evolutionary changes can occur.
Emphasis that over time as the populations continue to change they become seperate species.
Give examples of these type of evolutionary change including european ground squirrels.
LEQ: Number 4
HOTS: Error analysis could be used to demonstrate the ET LEQ.
Discuss how without genetic variation, some of the basic mechanisms of evolutionary change cannot operate.
Recognize that variation exists among individuals within species.
Recognize that variation is an inherited trait that makes an individual different from the other members of it's species.
Describe how mutations cause variations to occur within a population.
Explain how any variations which makes an organism better suited to survive is known as an adaptation. One example of an adaptation is camoflauge.
LEQ: Number 2
Explain the role that the environment plays on natrual selection. Discuss how environmental changes can lead to changes within a species.
Discuss how variations which offer an advantage for survival will usually cause a population to increase but variations which decreases a species survival chance will cause a population to decrease
Explain that when organisms are competing for resources, if one has an adaptation that will allow it to obtain those resources easier that it will eventually lose the battle for resources. This will force the losing species to either move to a new environment or it may become extinct.
LEQ: Number 3
Explain how changes in the environmental conditions can influence the adaptations which some organisms have made in order to survive in that area.
Discuss how variations that may have originally been a disadvantage may become an advantage if the environmental conditions in an are change.
Use the peppered moths of England as an example of a species that has evolved due to changing environment.
Explain that when a species is not able to adapt to an environmental change the organism must either move to a new area where they can compete for resources or the species will become extinct.
LEQ: Number 4
HOTS: Deductive reasoning or constructing support could be used to demonstrate the ET LEQ.
Explain how a fossil is the remains, imprint or traces of an organisms that once lived on the Earth. Fossils are found in sedimentary rocks and offer us clues as to past life forms and ecosystems on the Earth. Be sure to explain that the fossil record is incomplete due to the fact that conditions have to be perfect in order for fossilization to occur. Sometimes the dead organism is not covered with sediments quickly, or sedimentation does not occur in that habitat, the organism is soft bodied or geological events (weathering, erosion, rock cycle) occur over very long periods of time before the fossil is discovered.
Discuss how scientists have found fossils of the ancestors of modern day organisms and that by examining these fossils scientists are able to see how those species have changed over time into their present forms.
Describe how scientists have used the traits observed in fossils to add them to the Linnean classification system and that based on the fossil record, scientists believe that 99% of all the species that have ever existed on the Earth are now extinct.
LEQ: Number 2
HOTS: Constructing support or deductive reasoning could be used to demonstrate the ET LEQ.