mrmurraysci.weebly.com · Web viewBiology 11: Processes of Evolution Unit Learning Goals C5 Describe the five agents of evolutionary change: mutation, genetic drift, gene flow, non-random

Biology 11: Processes of Evolution

Name: _________________________

1

Biology 11: Processes of EvolutionUnit Learning Goals

C5 Describe the five agents of evolutionary change: mutation, genetic

drift, gene flow, non-random mating, and natural selection (pp 264-265)

(pp 268-275)

C6 Understand the concept of speciation (macroevolution)

C7 Compare gradual change model with the punctuated equilibrium

model of evolution

Part A: Darwin’s Theory of Evolution

-Darwin’s 5-year voyage on the Beagle provided him with many pieces of evidence to demonstrate that Evolution has occurred.

-Darwin’s Theory of Evolution by Natural Selection is his explanation for how organisms have adapted to their environment.

-Darwin was influenced by his observations of Artificial Selection. Examine the diagrams right and explain this concept.

________________________________________________

________________________________________________

________________________________________________

-What are some other examples of artificial selection?

________________________________________________

________________________________________________

________________________________________________

________________________________________________

________________________________________________

2

-The diagram right illustrates Darwin’s idea of natural selection, except that he did not know about alleles.

-Lamarck, a French naturalist (1744-1829), proposed that Giraffe’s long necks evolved because they were needed. How would Darwin have explained this?

_______________________________________________

_______________________________________________

_______________________________________________

_______________________________________________

_______________________________________________

_______________________________________________

_______________________________________________

_______________________________________________

_______________________________________________

_______________________________________________

_______________________________________________

_______________________________________________

_______________________________________________

-How does natural selection differ from artificial selection?

_________________________________________________

_________________________________________________

_________________________________________________

_________________________________________________

_________________________________________________

_________________________________________________

_________________________________________________

-Pesticide application to agricultural fields is an example of how humans can inadvertently cause natural selection to occur. This reveals three things about natural selection:

a) Natural selection is an editing and not a creative process.

b) Natural selection is time and space specific.

3

c) Evolutionary change can occur in a short time span.

Part B: Genetics and The Modern Theory of Evolution

-Since Darwin, many additions have been made to the Theory of Evolution

by means of Natural Selection. Genetics, in particular, has been incredibly

important in explaining how natural selection operates.

-Below are some important terms and ideas we have to know about before

we look further into the Modern Theory of Evolution:

a) A population is a ____________________________________________

____________________________________________________________

b) Alleles are _________________________________________________

c) What does it mean for an individual to be homozygous for a trait? And heterozygous?

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

d) How are genotypes different from phenotypes?

_______________________________________________________________

_______________________________________________________________

_____________________________________________________________________________________

_____________________________________________________________________________________

e) Examine the diagram below. What is the gene pool and allele frequency of a population?

_____________________________________________________________________________________

4

_____________________________________________________________________________________

f) Microevolution is a___________________________________________________________________

Part C: Hardy-Weinberg Equilibrium

-Since Darwin’s time, scientists have studied how populations evolve, and they have extended his ideas to include other processes, besides natural selection, that can cause populations to evolve.

-The Hardy-Weinberg Equilibrium states that the frequency of alleles in a gene pool will remain constant over time unless five agents of microevolution are present:

1. Mutations

-Mutations are changes in the arrangements of nucleotides in DNA.

-Where must mutations occur if they are to affect a population’s genetic variability?

_________________________________________________

_________________________________________________

_________________________________________________

_________________________________________________

_________________________________________________

-Remember that mutations can be harmful, neutral or helpful.

2. Genetic Drift

-Examine the diagram right. How is genetic drift different from natural selection?

_____________________________________________________________________________________

_____________________________________________________________________________________

_____________________________________________________________________________________

_____________________________________________________________________________________

-Would the impact of genetic drift be felt more in a small population or a large population?

_____________________________________________________________________________________

-There are several different types of Genetic Drift:

a) Bottle Neck Effect

-The Bottle Neck Effect is a type of genetic drift where the population size is dramatically reduced by a natural disaster.

5

-What consequence has this had for Prairie Chickens?

_________________________________________________________

_________________________________________________________

_________________________________________________________

_________________________________________________________

_________________________________________________________

-Pingelap Island is another example of this, where the rate of colourblindness is much higher than other populations due to a bottleneck event. This resulted in the recessive alleles for this disorder being present at a higher frequency in the post-disaster gene pool.

b) Founder Effect

-Differences in the gene pool of a small colony compared to the original population.

-How will the colony size affect how closely it resembles the original population genetically?

_______________________________________________________

_______________________________________________________

-Tristan da Cunha is an example of this, where 15 British people founded the colony and 1 had the recessive allele for progressive blindness. By the 1960s, the rate of occurrence was 10x that of the rate found in the original population.

3. Gene Flow

-Is the movement of genes in and out of a population.

-How could this occur?

_______________________________________________________

_______________________________________________________

-What is the over-all effect of gene flow?

_______________________________________________________

_______________________________________________________

6

4. Non-Random Mating

-What characteristics do organisms usually look for in choosing a mate?

___________________________________________________

___________________________________________________

___________________________________________________

___________________________________________________

5. Natural Selection

-Natural selection is the survival of the fittest, where the best adapted organism will survive and reproduce at a higher rate. This means that it will pass its genes onto the next generation at a higher rate.

Part D: Natural Selection

-In your own words, explain why natural selection is the only mechanism that consistently leads to adaptive evolution. Section 13.2 in your text will be helpful in doing so.

_____________________________________________________________________________________

_____________________________________________________________________________________

_____________________________________________________________________________________

_____________________________________________________________________________________

_____________________________________________________________________________________

_____________________________________________________________________________________

_____________________________________________________________________________________

-Three types of natural selection alter the genetic variation of a population’s gene pool:

1. Stabilizing Selection

-The intermediate group (clutch size) has the highest rate of survival and reproduction.

2. Directional Selection

-Over many generations, one of the phenotypes has the highest rate of survival and reproduction.

7

3. Disruptive (or Diversifying) Selection

-Under what conditions might this type of natural selection occur?

____________________________________________

____________________________________________

____________________________________________

____________________________________________

Part E: Speciation and Macro-Evolution

-Why are donkeys and horses not considered the same species?

-Members of the same species produce fertile, viable offspring.

1. Types of Reproductive Isolation

-There are several pre-zygotic and post-zygotic barriers that prevented organisms from reproducing together:

8

2. Types of Speciation

-What is the difference between Allopatric and Sympatric speciation?

_____________________________________________

_____________________________________________

_____________________________________________

_____________________________________________

-What cannot occur between populations undergoing these two types of speciation?

_____________________________________________

-What type of speciation are the chipmunks below showing?

*Explore this idea further by examining the allopatric speciation of lizards animation.

3. Hybrid Production

-Examine the diagram right. What does it indicate about the two toad population? Are they one species or two?

__________________________________

__________________________________

__________________________________

__________________________________

__________________________________

__________________________________

9

-Populations undergoing speciation can have three possible results depending on the strength of reproductive barriers:

4. Adaptive Radiation

-What is adaptive radiation?

______________________________________

______________________________________

______________________________________

______________________________________

______________________________________

______________________________________

______________________________________

______________________________________

______________________________________

______________________________________

______________________________________

______________________________________

-Molecular analysis indicates that the species of Hawaiian depicted are all descended through allopatric and sympatric speciation from an ancestral tarweed that arrived 5 million years ago from North America.

5. Models of Evolutionary Change

10

-Examine the two models of evolutionary change depicted right. How are they different from each other?

-Gradualism:

______________________________________________

______________________________________________

______________________________________________

-Punctuated Equilibrium:

______________________________________________

______________________________________________

______________________________________________

Part F: Test Your Understanding

-Is evolution goal oriented?

_____________________________________________________________________________________

-Try the concept map below:

11