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” The first day of class should connect to the last day and every day in between!”

Refresh this page every time you arrive!                                                                                                                                                                                                                              This page changes and sometimes many times in the same day.  Its a fluid site. I post what I think we will do and then repost what we accomplish.  Homework posted is to be done at home and not completed days ahead of time.  What is posted ahead is subject to change and may not be updated. There is a sequence that needs to be followed. 

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a) To Introduce a structural way to investigate how “related” organisms are based on 

          morphology.

b) Morphology of skull of early human skulls discussion

c) Evolutionary relatedness – Diversity of Life, Unity of life – Decent with modification –           phylogenic tree and cladograms.     

 

From last nights video (#1): 

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 * Everyone can one more submission to the Monday nights form.

 

1. Review your Test 1 with the key below.  Everyone can earn points back on their test by doing the              following:  DO NOT LOSE YOUR TEST! YOU MUST RETURN IT TO earn 1 more point.

                                                                                                                                                                                                            Link to Test 1 Key:    https://www.dropbox.com/scl/fi/e7kx1o0xpb5e90p2jko5p/Test-1-Statistics-Experimental-Design-Mendelian-Genetics-Evolution-intro-Complete-Key-24-25-p.pdf?rlkey=3f5vauhaq4lirq72eesazsz6m&st=57g9bajn&dl=0    

   

 

a) Review your graded Test with the key..  Bring any questions to class Wednesday

 Please try to understand every question you got incorrect. Your next test will have similar topics. i is in best interest to review your mistakes.  

 

2. Please Read the connection notes below:

 

3. Please view the video below on Maize.

 

4. Please complete the form below the video.

 

 

Connections Notes:

 

So we have learned that there is overwhelming evidence that supports evolution through natural selection. We have seen that this change can be very quick and through careful work of the Grants in the Galapagos Islands, specifically on Daphne Major, we have seen that evolution in the finches beak depth can occur quickly in response to changing environmental conditions.  Remember that a drought on the island made significant changes in the beak depths in a very short time period. 

 

Notice that in 1977 there was a drought that caused a selective pressure for larger beak depths as only larger seeds were available after this drought. This trend was reversed in the 1980’s as the wet period introduced more smaller seed plants back to the island.

 

At the end of 1982, the Grants witnessed evolution again as a rainy period brought back the diversification of food, especially the small seeds.  So one piece of evidence of evolution is the evolution that we have witnessed first hand, with many thanks to the Grants!

 

Another piece of evidence of evolution, is in the morphology of organisms. That is the structures of organisms that tell a tale of their evolutionary decent.   Evolution is a process of decent with modification that occurs through natural selection as descendants face different environmental  conditions.  As a result  related species (species of organisms that evolved from one to another) can have underlying similarities yet function differently.  Similar structures from evolutionary related organisms is called Homology.

 

These are diagrams of the morphology of mammals who we have identified as being related by evolutionary decent in large part because of there homologous structures. These structures have different functions (flight in bats) or navigating water (in whales) yet structurally similar. Notice that all of these organisms have a big bone attached to smaller bones called phalanges (blue).

 

We have classified many organisms in terms of evolutionary descent mainly through morphology in concert with the fossil record.  Even before DNA mapping, scientists have been able to connect the pieces of evolution of organisms from morphology.  Since the advent of DNA sequencing (finding the actual code for genes to show evolutionary relationships) morphology has been found to be very accurate in determining these relationships as DNA data from organisms that are related morphologically are also related similarly in their genetic code.

 

Last night we investigated the evolutionary relationships of early hominids to consider how we evolved.  We used morphology (curved fingers, size and shape of skull, as well as the length of the arms to) to make judgements on the homology of our species with the older species. 

 

The evolution of homo sapiens has many theories. One of which states that the morphology of the early hominids resulted due to a change in diet.  Our current skulls are significantly larger than the skulls that you investigated last night due large part to a larger brain.  A larger brain requires an extreme amount of CONSTANT energy and that could only be achieved when our early ancestors could better control the availability of better nutrition.  Only when out early ancestors began hunting in coordinated large groups and using weapons did the nutrition improve dramatically. Some theorize that the our evolution to present day humans resulted very quickly like the finches in the Galapagos Islands when we learned how to throw, which lead to improved fitness from improved hunting techniques that lead to improved nutrition.

 

                                                                                                                                                                                                                             

 

Look at the homology of the skulls found in different parts in the world.  The age of these bones are determined through radioactive dating of surrounding material they were found in.  We will discuss this in class.

 

Tonights homework is about another way that we were able to have a CONSTANT supply of energy to our larger brains and that is to cultivate plants.  This ability to grow crops came much later than the ability to hunt effectively in larger groups with weapons.  It was a significant development because it allowed humans to gather in larger communities in more permanent residences as they were became less nomadic and less dependent on hunting for all there nutrition. One important plant that is vital to sustain our current society and one that was has been cultivated for over 8000 years in North and South America is maize or corn.

                                                                                                                                                                                                                                                                                                                    https://digfir-published.macmillanusa.com/

3 ____________________________________________________________________________________                  Jump to: Wednesday Homework / top      10/7 – Wednesday – A Day – 4/5A ,7/8A 

a) Evolutionary relatedness – Diversity of Life, Unity of life – Decent with modification                – phylogenic tree and cladograms.                                                                 

 

b) To differentiate between Divergent vs Convergent evolution

 

c) To identify analogous and homologous structures

 

    

Period  4/5, 7/8:

 

1. Short Test 1 Review- FRQ review – test corrections – Due Friday

 

2.  Evolution presentation – Morphology, homologous and  structures, analogous  convergent & divergent evolution

 

3. Review/complete the classwork cladogram from yesterday.

 

Cladogram Classwork 2122.pdf
View Download   

 

Cladogram Classwork 2122 Key p.pdf
View Download

 

3. Reviewed last night amazing form.                                                                                                                          

How AMAIZING was that video!  So the ancestor to corn has been right under our noses all along but because of the mutations in only few genes that happen to be regulatory genes (switches) the 2 organisms are phenotypically very different!  Can you see why I am teaching you about chromosomes with evolution and now introducing more genetics into our discussion?  All these concepts are intertwined.  Can you guess the next major unit we will start?

 

So what is homologous in Maize in corn?  What homologous structure do they both have?

                        

4. Classwork: Minions

Evolution 1 – Cladograms of Minions.pdf
View Download

                                                                                                                                                                                                                                                                                                                                                                                                                                                                            

Today’s notes:

 

 Divergent Evolution – species sharing a recent common ancestor due to homologous structures descend with new modifications or traits.

 

homologous structures – similar structures that may produce different traits between evolutionary related species. Example: Hand of a human (mammal) and a flipper of a whale (mammal). 

 

 Convergent Evolution – species that DO NOT share a recent common ancestor due to having analogous structures that develop similar traits due to being exposed to similar selective pressures.

 

analogous structures –  dissimilar structures that provide the similar traits between species that are not closely evolutionary related. Example: The wing of a bat (mammal) and the wing of bird. 

 

Phylogenic Trees and cladograms

 

Phylogenetic trees of the  finches in the Galapagos islands:

Evolutionary relationships of the 13 species. Logic suggests that new species developed from older species and  that this decent occurred with modification or better decent with newer modifications.

 

Notice the current existing species are located to the right.  The more you move to the left the more time has passed or older the species.  Notice the length of the branch (x-axis) denotes the increased age of the species, meaning it will have greater differences in characteristics or more mutations (due to longer time period).  Also Note the node, the point that illustrates the place in the diagram that reveals when speciation has occurred (reproductive isolation).  A clade is group of species that are related more closely because they share a common ancestor.                                        

Notice arrow above that points to the Node or common ancestor to all the birds that flew from South America.  

 

Cladograms are diagrams that are very similar to phylogenic trees that show common ancestry between species but are written a bit diffrently.  Cladograms tend to be hypothesis of how organisms are related by morphology, archeology, or genetic mapping.  

 

Classic Divergent Evolution:

Cladograms are built using many forms of data. In this case morphological data is used to construct this hypothesis of  how these organisms are most closely related. Time in these diagrams is the Y – axis so unlike the diagram above, as you move higher and right the species becomes younger or evolved later than the organisms that are lower and to the left. Notice that these diagram also have Nodes or places that illustrate common ancestors. In Cladograms, often the new characteristic in written where it first develops. Notice that the human all the characteristics listed and thus is the last to evolve while the Lamprey has the least of the characteristics and thus evolved much earlier in time.

Some cladograms are written this way:

 

Combining Phylogentic tree and cladograms:

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Hardy – Weinberg Basics (NOTES) – 

 

Known as the Hardy-Weinberg Principle or the Hardy-Weinberg Equilibrium.

This principle is used to study microevolution – the change in the gene or allele frequencies in a population from one generation to the next.  Specifically microevolution studies if ONE type of allele is changing in frequency from one generation to the next.  Remember that evolution is “decent with modification” through NEW alleles that are selected for based on environmental pressures that develop through mutations.  Mutations are rare and occur slowly through time and thus evolution is a very slow process when it comes to developing NEW alleles in organisms that have long life spans.  MicroEvolution however can occur from one generation to the next if we can exam the frequency (how often) the expressed characteristic (allele) from a single gene changes.  

 

If there is micro evolution than an allele will have a change in its frequency. Frequency is how often that allele exists in a population.  If an allele exists less often (in subsequent populations) the normal distribution for alleles of a single gene will move toward another allele of the same gene that is increasing and establish a new normal distribution.  This is called Direction Selection.

 

When a new normal distribution is established we can “see” this by physical measurements. For example: The Finches significant beak length increases in the Galapagos Islands during a drought.  But with microevolution we can investigate the changes in subsequent populations without “seeing” significant changes that we can physically measure. We can identify the beginning of a shift from the old normal distribution to the new normal distribution with microevolution.

Looking back at out Peppered Moths we can see that the allele for dark wings (melonics) increased with as the melonics were selected for due to the dark colored soot that collected on their natural habitat, which increased their fitness over the light colored moths that were now more susceptible to predators.  Natural selection caused a new normal distribution to occur.  We normally identify evolution AFTER a new normal distribution has been established. With microevolution we can identify exactly when a selective pressure STARTS a change in the frequency of the available alleles for a single gene.

Would we want know if allele frequencies are starting to change if certain alleles are responsible for a disease?

 

How do we know when there is a change in how often an allele in expressed in a population?  Well we have to work from a Null position!  We need to know what to expect if there is no evolution!  This is where Hardy-Weinberg comes in.

 

Mendelian genetics was being argued against in the early 1900’s as some suggested that if Mendelian genetics were true then the dominant allele would eventually “dominate” the population.  The next generation should have more dominant traits than the previous generation yet the frequency of dominant alleles seemed to stay constant from one generation to the next.  It took the work of a mathematician, G.H. Hardy in 1908, to solve the problem and he did so very reluctantly as he though his work was just too simple.  He was taken back how other biologist thought his work was so brilliant. Hardy with a simply derived formula demonstrated that allele frequency will stay constant unless other forces are at play.

 

A German physician,  Wilhelm Weinberg independently also derived the equation in 1908 and thus we call the principle of constant (no change, Null) allele frequencies the Hardy-Weinberg Principle.

 

The forces that can change the allele frequency and thus indicate evolution is occurring are:

 

    1.  Small populations can cause genetic drift or change in allele frequency do to chance events.

         When will a flipping a coin give us frequencies of heads or tails that approximate .5 ?  

         Only in large number of flips. So only in large population size will the chromosome segregate in meiosis in      

         frequencies that approximate 0.5 .  How many small families have all girls or boys if the probabilities to 

         have a boy or girl is about .5?

 

    2.  Selective mating can cause a change in allele frequency if only the males that have certain allele will mate.

          This will cause in increase in fitness of certain males with certain alleles. In our human population we may  

          select who we settle down with but as a population we are not eliminating all males that are tall!!!  

 

    3.   There are mutations occurring.  This would cause new alleles to appear or render old alleles useless for   

           their current application (recessive alleles). The latter would increase the number the recessive allele  

           frequency.  Mutations that occur naturally do so very very infrequently that the chance of themm occuring is  

           very low.  Remember Maize had 4 mutations in about 9,000 years!

 

    4.   There is gene flow in and out of population. If there are individuals of other stable populations that   

            migrate into or out of the population being studied there will be change in allele frequency as other             

            populations are subjected to different selective pressures and thus have different allele frequencies. We call  

            this Gene Flow. If peppered moths that lived closer to the factories in the cities migrated to another area   

            was isolated from factories that population would have an increase in the dark colored wings.

 

    5.    There is Natural Selection Occurring. There is a selective pressure that increases the fitness of   

             individuals that have a certain allele.  In our modern times, especially with modern medicine, people with  

             many illnesses or alleles that would be unfavorable in the “wild” are not selected against anymore.  In the wild it would                    be disadvantageous to be near sighted as we would not have glasses to help us hunt or protect ourselves from predators.  But                if I am not mistaken people who wear glasses have the same fitness as those who do not.

 

So Hardy – Weinberg Principle (Equilibrium) is a formula that predicts the frequencies of alleles in the the next generation, which will be the same as the previous generation, if there is

 

                                                                 1.  Large populations

                                                                 2.  No selective mating

                                                                 3.  No mutations

                                                                 4.  No gene flow

                                                                 5.  No Natural Selection                                                                                                                      

In our modern society these 5 conditions are essentially met and the allele frequency is expected to stay the same.

If there is microevolution occurring  the Hardy – Weinberg formula will act as a baseline to judge against.  

 

We need accurate data from our population to measure against this baseline.  For example what is the current frequency of individuals that have hemophilia (a autosomal recessive disorder)?  

 

What should it be if there is no evolution ——–> Hardy – Weinberg calculations