Part II: Evolution, Natural selection and Mutations

To-Do Date: Mar 29 at 9:30am

In order to understand the origin of new diseases like Covid-19, we need to understand evolution, natural selection and mutations. Let's start with evolution

Evolution

This is a term that means ''change'' in our daily language, but for biologists means 

"change in the gene pool of a population over generations''. 

This video does a good job of explaining that idea.    You want to focus on the following study guide questions as  you watch the video

2. What is evolution? What is a gene? What is a gene pool? What reshuffles genetic information from generation to generation? What is evolution in terms of frequency of genes? What are 5 different mechanisms that can lead to evolution? Which of these introduces new genes? Which of these leads to adaptations? What is an adaptation?  What is natural selection in terms of genes, variations and adaptation to environment?

 

 

 

 

Natural Selection 

Let's delve deeper into natural selection as a mechanism of evolution. Natural selection can be defined 

'as a difference in the survival and reproduction of individuals in a population'  

I can think of this as ''Nature'' or the environment selecting which individuals do better than others and therefore survive and reproduce. There are three conditions necessary for natural selection to occur.  You will want to focus on the following study guide question 

3. What is natural selection? Why does their need to be variability in the population for natural selection to occur?Why does that variability need to be heritable? Why does their need to be difference in reproductive success? How does the environment determine which traits are most favorable?

Watch this short video to learn about the three ingredients necessary for natural selection Links to an external site.

Natural Selection Simulator

Visit this Natural Selection simulation site: Natural Selection (Links to an external site.)    Here is their introduction

This simulation can be used to study the effect of environment on natural selection. A predator eats a prey organism with two possible phenotypes; brown and gray. You will play the part of the predator. "Eat" as many prey as you can in the time available by clicking on them. You can choose from three different environments. Select the environment, then click "Run Simulation" to start.

At the beginning on the simulation the prey population is a roughly even split of brown and gray. The simulation starts with 50 prey organisms and each is randomly assigned a phenotype, with a 50% of the organism being either color. After the simulation has run, you will be given the starting and ending percentages for gray and brown individuals in the prey population.

Bring this information to Class (This will be worth 10 points) - We will use this in lab next week. 

      •  Hypothesis: What is your hypothesis about the change in the mouse population over time? (remember this will include a ''because'' statement)
      • Prediction: What do you predict will happen to gene pool of the mouse population on the grassland, mountain rock and desert sand? 
      • Gather evidence:  You will perform this game simulation  3times, once for each  environment. For each round:
        • Pick an environment under "select the environment." Then click "run simulation."
        • Use your mouse to click on as many prey animals as possible. 
        • Record the starting and ending percentages for each color prey in this Google Sheet. Links to an external site. 
      • We will analyze the data in class. 

Sources of Genetic Variation

There are two main sources of genetic variation that we have examined: sexual reproduction and mutations. Sexual reproduction reshuffles genetic traits and is very important when talking about the evolution of eukaryotes. But viruses and bacteria are much more influenced by mutations.  Therefore we are going to focus on this as a source of variation.

I've borrowed a video from one of my fellow Bio 16 instructors, Riva Bruenn, since she does such a good job with the topic.    You will want to focus on the following study guide question 

4. How do mutations affect the genetic variation of a virus?  What are mutations? How does the mutation in the DNA affect the RNA? How do these  mutations affect the protein? What mutations will have the greatest impact on protein amino acid sequence? The least  impact? What is the relation between mutations and protein shape, folding and function?  How does the environment affect the impact of a mutation on the organism?  How do mutations happen in day to day life of cells? Why are mutations random? 

 

 

 

Next we will look at Evolution, Natural Selection and Mutations in some case studies.