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Section 6.1 Evidence of a Changing Earth
You Know: Visit the Royal Tyrrell Museum
Royal Tyrrell Museum
Activity: Finding Fossils and Famous Footprints
Did Humans Evolve? Is Evolution Still Happening?
a Fossil & Laetoli Footprints
Mini Investigation: Variations on a Theme
The forelimbs of different vertebrates are well adapted to serve specific functions. However, hypothesizing the potential adaptive advantages of such homologous features are not always easy. Explore the bill shapes of six different bird species. Choose four species that are living and two that are extinct.
Web Activity: Were Neanderthals Humans?
For many years, paleontologists disagreed over the classification of Neanderthal. Although they were shorter and heavier than modern humans, their fossil remains are very similar to other recent hominids that have been classified as archaic H. sapiens . Many paleontologists suggested Neanderthal, be classified as a subspecies of humans (i.e., as H. sapiens neanderthalensis ), while others concluded they should be placed in a separate species (i.e., as H. neanderthalensis ). Fossil evidence does not provide much information concerning mating patterns and other reproductive isolating mechanisms between very similar populations. However, in the late 1990s, several different samples of mitochondrial DNA were actually extracted from well-preserved Neanderthal fossils, amplified, using polymerase chain reaction, and sequenced.
. Compare an actual Neanderthal mtDNA sequence to that of modern humans.
(a) How does the mitochondrial DNA of humans compare with chimpanzees?
(b) How many base-pair differences are typically found between the mtDNA of any two distantly related people?
(c) How many base pairs could be sequenced in the Neanderthal mtDNA?
How many differences were detected between the Neanderthal sequence
and that of a modern human?
Hominids: Mitochondrial DNA
6. New Zealand scientist David Lambert collected DNA samples from 7000-year-old nesting grounds of the Adelie penguin in Antarctica. He collected wonderfully preserved DNA samples from ancient frozen bones in layers of ice directly beneath the present day nesting colonies. What does Lambert's evidence suggest about the rate of evolutionary change in this species of penguin?
Penguins Yield Evolution Clue
and Evolutionary Biology
Section 6.3 The Making of a Theory-Accounting for the Evidence
Activity: Simulating Natural Selection-Evolution in Action
In 1848, near Manchester, the first appearance of a melanic (almost black) form of peppered moth was recorded. By the late 1800s, much of the lichen was dead and the trees, rocks, and other hard surfaces were covered in dark soot. By the 1920s, the moth population was almost entirely of melanic individuals. Scientists suspected that the melanic moths had gained a selective advantage.
Biologist H.B.D. Kettlewell formed and tested a hypothesis that the observed evolutionary change in the colouration of the peppered moth throughout the 1800s was a result of changes in the environment ( Figure 1 ).
Biologist Laurence Cook has reported that, since 1975, the prevalence of melanic moths around Manchester has decreased significantly and lighter coloured moths are making a dramatic comeback. Tree bark is becoming lighter again; however, during the study, lighter-coloured lichens that supposedly camouflage the moths did not seem to be more common and the moths were seldom seen on trees.
Follow the links below to animations that model how environmental changes can affect individuals of a species of various colours. Think about how this model supports or refutes Kettlewell's theory.
You Know: Darwin's Writings
Voyage of the Beagle
Section 6.4 Questions
7. Some prions that cause diseases such as bovine spongiform encephalopathy (mad-cow disease) and the inherited form of human spongiform encephalopathy ( Creudtzfeldt-Jacob disease) result from single genetic mutations. Research the genetics of these diseases and explain how they are transmitted. Suggest why they are not eliminated by natural selection.
This CBC News article explains Mad Cow disease, how it is transmitted, as well as explaining the significance of prion disease identification.
8. Research Richard Dawkin's theory about "selfish genes." Prepare arguments for a class debate on his theory.
Defence of Selfish Genes
Activity: Testing a Theory-Lactose Intolerance and Evolution
People with lactose intolerance may suffer from nausea, cramps, gas, and diarrhea after consuming foods-dairy products, in particular-that contain lactose. The severity of symptoms varies from individual to individual and depends, in part, on the amount of lactose ingested.
For this task, you and two other students will investigate lactose intolerance and tolerance. Review the components of this task and decide as a team which of you will complete which one of the two parts (I or II). Each member is responsible for completing and submitting his or her assigned task, along with a report that includes responses to the Analysis questions. Each team member should be familiar with all the other members' reports. Present your survey and other plans for your procedures to your teacher for approval before carrying them out. Following completion of the procedure and analysis, you will be asked to review one of your team member's reports, and you will submit your report to a team member for peer review.
As a team, find answers to the following questions:
(a) What is the incidence of lactose intolerance in human populations?
(b) What gene(s) are responsible for the regulation and production of the lactase enzyme?
(c) What role has natural selection and mutation played in the evolution and prevalence of lactose tolerance and intolerance?
What technology and methods are currently used to diagnose, avoid,
and or manage lactose intolerance?
Part I: The Genetics and Prevalence of Lactose Tolerance and Intolerance
1. In this investigation, your goal is to obtain a crude lower estimate of the incidence of lactose intolerance in your school or community. Conduct a survey of at least 40 students and/or adults in your school or community.
After completing your survey, generate some hypotheses regarding
the incidence of lactose intolerance in the total population of surveyed
II: Natural Selection and Lactose Intolerance
Intolerance is Normal!
Milk Makes You Sick
(g) What might be the selective advantages of not producing lactase as an adult?
(h) Other than humans, would adult mammals ever suffer from the symptoms of lactose intolerance? Explain.
(i) Would you expect lactose intolerance to be an ancestral or a derived condition? Explain.
(j) What change in the environment and/or human behaviour would create a selective advantage for those individuals who continued to produce lactase as adults?
When and where did humans begin to domesticate cattle, camels, and
goats? When and where did humans begin using milk as a source of animal
protein? How is this information significant?
III: Options and Opportunities in the Control and Treatment of Lactose
Therapy in a Liquid
(m) What products have humans used as alternatives to milk to avoid or reduce the incidence of lactose intolerance? Explain how the lactose is removed or reduced in these products.
(n) What is Lactaid? Design and conduct a simple experiment to demonstrate how this product functions. Explain how people with lactose intolerance could use the product.
How might recent discoveries in genetics be used to develop new diagnostic
tools for detecting lactose intolerance?
Chapter 6 Review
A simulation showing how natural selection achieves better results for adaptability than random chance by using a target sentence and mutations to arrive at a result. Requires Java
A fun simulation that demonstrates the ability of evolutionary techniques to solve enormous problems rapidly by finding a goal phrase through mutations and adaptation. Requires Java
A demonstration of natural selection used in Richard Dawkins' book The Blind Watchmaker. He uses the example of a child typing Shakespeare to illustrate how natural selection can produce unlikely results. Requires Java.
Unit 20B Performance Task-The Sixth Extinction
A Canadian site which outlines past mass extinctions and their causes.
Will the Sixth Extinction Affect the Evolution of Species?
Five Worst Extinctions in Earth's History
Geographic - The Sixth Extinction
One Creature Drives So Many To Extinction
Sixth Extinction is Already Here
Modern Mass Extinction?
of Live - Video Clip
Current Mass Extinction
of Influenza A Viruses Between Animals and People
Eradicating the Scourge