Adj natural selection
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Transcript of Adj natural selection
Evolution by Natural
SelectionHour 2, 2-23-2011
Learning Targets for Evolution
8.1 I can define evolution and use the definition to predict where modern
organisms have come from.
8.2 I can recognize that evolution requires a long period of time to occur.
8.3 I can compare artificial selection to natural selection and am able to
identify each from examples.
8.4 I can identify the two major sources of variation in organisms that
reproduce sexually.
8.5 I can explain why genetic variation within a population is essential for
change over time.
8.6 I can list examples of challenges that organisms face in their struggle
for existence.
8.7 I can explain why organisms compete with one another in order to
survive.
8.8 I can define the term adaptation.
Learning Targets Continued… 8.9 I can predict what will happen when organism’s adaptations are more suited to
their environment.
8.10 I can describe the difference between an individual and a population and state
which is affected by evolution.
8.11 I can differentiate between the concept of an adaptation and the process of
evolution.
8.12 I can predict how an adaptation will change in frequency within the population
over time.
8.13. I can use graphical data to describe how the frequency of a particular trait will
change in response to different natural selection pressures.
8.14 I can explain convergence in terms of how unrelated species respond to similar
environmental pressures.
8.15 I can use the process of natural selection to explain how divergence and
adaptive radiation lead to diverse populations from one common ancestor.
8.16 I can use co-evolution to explain what will happen to two organisms that are
closely connected to each other
Why should we study evolution?
Important TermsEvolution Artificial selectionNatural selectionVariationCompetitionAdaptationConvergence
Divergence Adaptive
radiation Co-evolution Theory
What is a Theory? Theory- a well-substantiated
explanation of some aspect of the natural world that can incorporate facts, laws, inferences, and tested hypotheses
Law- a descriptive generalization about how some aspect of the natural world behaves under stated circumstances and that carries the weight of scientific evidence
Fact-an observation that has been repeatedly confirmed
Hypothesis- a testable statement about the natural world
Belief- a psychological state in which a person holds a premise (or statement) to be true.
Evolution by Natural Selection is a theory
Evolution (or change in organisms over time) is a scientific theory; it is a well-substantiated explanation of an aspect of the natural world that incorporates facts (observable phenomena) such as virus and bacterial adaptations, inferences (geological processes have always been happening at a constant rate in the history of the Earth), and tested hypotheses (evolutionary relationships echoed in DNA analysis).
Age of the Earth Earth is about 4.5
billion years old Geologists
confirmed this approximate date through determining the age of rock formations and the time it would take for them to form
Why does it matter how old the Earth is?
Time is important: If weathering and other geological
processes have been happening at the same rate for a very long time (or always) then the Earth must be several billion years old to account for the formations.
Other ways we know: Chemical analysis of ice cores radio active fluorine
Evolution Change in organisms over
time
These changes are seen in populations not in individuals
Charles Darwin On the Origin of Species in 1859. Darwin supplied evidence that
evolution has occurred. He also explained his ideas about how (mechanism) evolution occurs.
Darwin’s theory was based on artificial selection. In artificial selection, nature provided the variation, and humans selected those variations that they found useful.
For example, animal breeders used only the largest hogs, fastest horses, or cows that produced the most milk for breeding.
Artificial Selection
Variation in traits exists
Breeder selects favorable traits in organism
Breeder mates animals with the favorable traits more than other organisms
Desired traits become more common in population
Natural Selection
Variation in traits exists
Nature “selects” favorable traits in organism because some of these trait give a reproductive or survival advantage
Organisms with favorable traits survive better and have more offspring
Traits that give a reproductive/survival advantage become more common in population
Why do both forms of selection require
variation?
Sources of variation
Genetic Shuffling in Anaphase I of meiosis
Mutation to DNA passed down to offspring (very rare!)
What is competition?
Competition Competition is a struggle for limited
resources in which there can only be one or a few “winners”
On Earth we have a finite number of resources; there are many more organisms than resources.
A struggle for survival results, the organisms that get the resources will live and pass on their genes to the next generation.
Besides limited resources; what are some other challenges organisms must face to survive and reproduce?
Adaptations Traits that
provide some type of advantage to organisms in the struggle for survival are called adaptations.
There are recognizable patterns to the way organisms adapt
Predict what will happen to a bunny population with a
brown fur mutation in an equatorial environment.
Convergence
Unrelated species respond to environmental pressures with similar functional adaptations
Divergence Humans DID
NOT come from apes, rather both species had a common ancestor long ago
IDA
Draw a diagram of how scientist would
describe the relationship between
Ida, humans and apes.
Adaptive Radiation
Adaptive radiation is the pattern of adaptation that isolates a species into two separate lineages
Co-Evolution Co-evolution is
when a species directly influences the evolution of another species and both populations evolve in parallel.