Upload
baka
View
28
Download
1
Tags:
Embed Size (px)
DESCRIPTION
Introduction to Evolution. PHA Biology 9 Moretti / Dickson. EVOLUTION. Genetic changes in a species or population over time. Connecting Genetics and Evolution: Cystic Fibrosis Case Study. Figure 1. Chest Radiograph of CF Diffuse Interstitial Disease. - PowerPoint PPT Presentation
Citation preview
Figure 1. Chest Radiograph of CF Diffuse Interstitial Disease
Image: http://www.eradimaging.com/site/article.cfm?ID=327: Reprinted with permission from LearningRadiology.com. Case of the Week Archives—2003. Cystic Fibrosis. Available at: http://www.learningradiology.com/toc/tocsubsection/tocarchives2003.htm. Accessed January 28, 2008.11
Connecting Genetics and Evolution:Cystic Fibrosis Case Study
Agenda & Goals for Today: Share ideas from the Do Now
How does cystic fibrosis illustrate evolution? What causes evolution?
Notes Vocabulary – Define population, gene pool, and
fitness Levels of Evolution – Explain the difference
between micro and macro-evolution Natural Selection – Identify key principles of
natural selection Videos:
Evolution in Hummingbirds Evolution in Bacteria
** Announcement: Optional Challenge Questions **
Vocabulary Population
Group of individuals from the same species that live in the same area and interbreed
Gene Pool All the genes and all of their alleles in a population
Evolution (on a population scale) Any change in the proportions of alleles over time
(One allele becomes more common, another becomes less common)
Change in a population NOT change in an individual Fitness
How well a particular organism can survive and reproduce to pass on its genes to the next generation
Objectives for Class:• Use actual evidence to explain how the four principles of natural selection shape the evolution of
organisms
Large-scale, often over a very long time Branching of one species into two
species All species share a common ancestor
Example: Evolution of whales from four-legged land mammals
Macro-Evolution
Objectives for Class:• Use actual evidence to explain how the four principles of natural selection shape the evolution of
organisms
Micro-Evolution Small-scale Changes in a population’s gene pool over
time Caused by natural selection and/or
genetic drift
Example: CF allele becomes more common in European populations because it protects against tuberculosis
Micro-evolution leads to Macro-evolution
Objectives for Class:• Use actual evidence to explain how the four principles of natural selection shape the evolution of
organisms
How Does Natural Selection Happen?Video: Hummingbirds in Ecuador
What are some adaptations that these hummingbirds have?
As we watch the video: make a list of Principles of Natural Selectionhttp://www.pbs.org/wgbh/evolution/library/11/2/e_s_4.html
Objectives for Class:• Use actual evidence to explain how the four principles of natural selection shape the evolution of
organisms
Principles of Natural Selection Genetic variation between individuals
Due to mutation and gene shuffling (sexual reproduction)
More offspring are born than can survive Competition/struggle for limited resources Some individuals are more genetically “fit”
than others – they are better at surviving, reproducing, and passing on their genes
Result: Over many generations, the “fit” alleles become more common in the whole population because they are more helpful for surviving and reproducing.
SUMMARY: SURVIVAL & REPRODUCTION OF THE FITTEST
Examples of Natural Selection:Ex. 1: Long beaks become more common
in a hummingbird population because long beaks help get food
Ex. 2: Sickle cell anemia becomes more common in African populations because SCA protects against malaria
Ex. 3: CF becomes more common in Europeans because it protects against tuberculosis
Ex. 4: Some TB bacteria have evolved to resist antibiotics
Notes: SPECIES and SPECIATIONSpecies - A group of similar organisms Can breed with each other and
produce fertile offspringExamples: Human species (Homo sapiens) Horses and donkeys = two separate species
because their offspring (mules) aren’t fertile
Objectives for Class:• Explain the defining characteristics of a species• Describe the 2 steps of speciation
Speciation -
The formation of new species from a common ancestor
The gene pools of two populations must become separated Ex: The Galapagos Finches
Objectives for Class:• Explain the defining characteristics of a species• Describe the 2 steps of speciation
Two Main Steps of Speciation
1. Reproductive Isolation
2. Changes in the Gene Pool Gene Pools Diverge (become
different) Genetic Barriers to
Reproduction AriseObjectives for Class:• Explain the defining characteristics of a species• Describe the 2 steps of speciation
Reproductive IsolationOne population becomes separated and stops
breeding with the rest of the species1. Behavior:
Changes in courtship or other reproductive strategies
2. Geographic Geographic barrier splits population (i.e.:
river, mountain, body of water, etc.) Populations are separated and cannot
interbreed3. Temporal
Species reproduce at different times or have other behavior that becomes time sensitive (i.e.: feeding)
Objectives for Class:• Explain the defining characteristics of a species• Describe the 2 steps of speciation
Changes in the Gene PoolA. Gene Pools Diverge (become different):
The isolated populations become genetically different. The new environments or behaviors favor different
genetic traits (natural selection)
B. Genetic Barriers to Reproduction Arise
The two populations can no longer interbreed Due to genetic differences in habitat preference, mating
behavior, or physical compatibility
They are now two separate species!Objectives for Class:• Explain the defining characteristics of a species• Describe the 2 steps of speciation
Hybrid - The offspring of a mating between two
different species If a hybrid can’t have offspring, there are
still two separate species!
Reproductive Barriers That Maintain Separate Species
Before mating occurs Geographic barriers Ecological/habitat differences Temporal differences Behavioral/courtship differences Mechanical differences Chemical differences
Objectives for Class:• Explain the defining characteristics of a species• Describe the 2 steps of speciation
Reproductive Barriers That Maintain Separate Species
After mating occurs: Hybrid dies before birth Hybrid is weak and sickly Hybrid is sterile (can’t reproduce)
Objectives for Class:• Explain the defining characteristics of a species• Describe the 2 steps of speciation
Famous Hybrids that are strong but STERILE!