New User Special Price Expires in

Let's log you in.

Sign in with Facebook


Don't have a StudySoup account? Create one here!


Create a StudySoup account

Be part of our community, it's free to join!

Sign up with Facebook


Create your account
By creating an account you agree to StudySoup's terms and conditions and privacy policy

Already have a StudySoup account? Login here


Star Star Star Star Star
1 review
by: Crystal Florman

Evolution BIOL 1014

Crystal Florman
GPA 3.64

Preview These Notes for FREE

Get a free preview of these Notes, just enter your email below.

Unlock Preview
Unlock Preview

Preview these materials now for free

Why put in your email? Get access to more of this material and other relevant free materials for your school

View Preview

About this Document

Our class notes on Evolution. This is the first topic of the final exam.
Life: Continuity and Change
Dr. Kurt Pontasch
Class Notes
25 ?




Star Star Star Star Star
1 review
Star Star Star Star Star
"Almost no time left on the clock and my grade on the line. Where else would I go? Crystal has the best notes period!"
Maegan Senger

Popular in Life: Continuity and Change

Popular in Biology

This 7 page Class Notes was uploaded by Crystal Florman on Tuesday April 26, 2016. The Class Notes belongs to BIOL 1014 at University of Northern Iowa taught by Dr. Kurt Pontasch in Spring 2016. Since its upload, it has received 19 views. For similar materials see Life: Continuity and Change in Biology at University of Northern Iowa.


Reviews for Evolution

Star Star Star Star Star

Almost no time left on the clock and my grade on the line. Where else would I go? Crystal has the best notes period!

-Maegan Senger


Report this Material


What is Karma?


Karma is the currency of StudySoup.

You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!

Date Created: 04/26/16
Evolution  Variation and Selection A. Introduction  Two concepts are fundamental to the theory of evolution  Characteristics of living things change with time  That change is direct by natural selection  The change in characteristics is not in an individual over time- it’s in a population over time  Individuals can’t evolve  Evolution- the change in the genetic makeup of a population over time  Each individual in a population have a unique genotype  Genetic recombination is the total of all gene mixing that occurs during sexual reproduction  Sexual reproducing organisms tend to produce more offspring than necessary to maintain the population  Replace the parents  Geese live 10 years- raise 8 young per year  If everyone survived and reproduced there would be 19.5 million geese  Dramatic changes in the population because the death rate and the birth rate are equal  Although total numbness remain relatively constant- the genetic makeup of the population changes to be more adaptive to changes  Adaptation- occurs because death is not random- less fit organisms have higher death rates  The survivors, for the most part, are better suited to the environment they reproduce more and transmit more good genes to the next generation  Acquired characteristics- gained during a lifetime- learned behaviors, phenotypic changes due to the environment- not passed B. Theory of Natural Selection  It states that individuals with genes that make them better adaptive to their surroundings are more likely to have a higher survival rates and produce more offspring  First proposed by Charles Darwin in 1859  Wallace thought of it too  “On the Origin of Species by Means of Natural Selection or the Presentation or Favored Races in the Struggle of Life”  The struggle of life not only includes open conflict, but more often competition for resources that are in short supply  Natural Selection works by means of differential reproduction  Differential reproduction- organisms with genes that make them more fit to produce more offspring, therefore the favorable genes will become increasingly common in the population  Natural Selection gives Evolution a direction C. Gene Frequency Studies  Measure how often a certain gene turns up in the gametes of a certain population  Gene frequencies only change when there is a reason for change and then it is usually slow  Assume that alleles for earlobe type have the following frequencies in the human gene pool  FF- free earlobes- 60%  ff- attached earlobes- 40% o the frequencies will remain the same through each generation  Hardy- Weinberg’s Law  Gene frequencies remain the same if only 4 assumptions are met o Population is large enough so that chance alone or accidental deaths will not change gene frequencies  The population would have to be infinitely large to mathematically rule out chance  In reality if there is greater than 10,000 individuals no random change is likely- less than 100, random changes are likely  Chance can cause evolutionary change in small populations  Genetic Drifts- no direction- since it is not influenced by the relative adaptiveness in the change in allele frequency it results in what we can indeterminate evolution o Mutations must not occur  This condition is never met in any population, but they are not a major factor in changing gene frequencies  Since mutations are random the trend is often in a direction other than that which other factors are cousing the population to evolve lack of progress  Mutations provide “the raw material” for genetic variability and therefore evolution, but do not determine direction o There cannot be any immigration or emigration  Most populations experience at least some gene migration between populations- gene flow  Increase genetic variability in the population  However this condition for genetic equilibrium is sometimes met in nature- no gene flow o Reproduction must be totally random  more than just the mating process  also includes the many factors that contribute to the reproductive continuity of the population  ex: selection of a mate, physical efficiency of the mating process, frequency of mating process, fertility, number of offspring produced by each mating, survival of the offspring, offspring’s reproductive efficiency  for reproduction to be totally random all those factors must be random- seldom if ever happens  factors listed are almost always related to genotype  nonrandom reproduction is the universal rule  Nonrandom reproduction is the same thing as differential reproduction and natural selection  In all populations there are selection pressures acting to disturb the Hardy- Weinberg equilibrium o Selection pressures give direction to evolution o Complete equilibrium in a gene pool is not expected, therefore evolutionary change is a fundamental characteristic of all populations including humans  Speciation A. Geographic distribution of a species is known as its range  An organism can move to a new geographic region by:  Traveling under its own power  Be carried by storms and winds  Attach to other organisms or human transported objects  If the new area is suitable the species will establish a new colony and its range will expand  Many plants and animals we consider pests are what we call exotic species  Exotic Species- species introduced because of human activity  Become pests because there are no natural enemies or competitors in their new home B. How Species Originate  Sometimes a portion of the gene pool becomes separated from the rest of the gene pool by some geographic change  Geographic isolation  Geographic features hat cause geographic isolation are called geographic barriers  Following geographic isolation the group of isolated organisms will often experience different environmental conditions than the main population  These environmental differences act as natural selecting agents and causes differences in color, height, enzyme production, etc.  Over a long period of time these genetic differences result in regional populations known as subspecies  Speciation is the process of generating new species- it only occurs when gene flow between the 2 isolated populations does not occur even after the geographic barriers are removed  Speciation has 3 steps  Geographic isolation of part of the population o Allopatric populations don’t share the same range  Differences in selecting agents cause genetic differences  Genetic differences become so great that reproduction is impossible between the 2 groups o Even if they once again share the same range o Sympatric population- share the same range C. Maintaining Genetic Isolation  Once a new species is formed, the species must prevent mating across species lies  Mating between 2 different species are not successful because: o No offspring o Offspring would be infertile  Mechanisms that prevent interspecies mating are called:  Reproductive Isolation o Eco geographic isolation  Occurs when 2 populations become so specialized for different environmental conditions they can’t survive where the other lives o Habitat Isolation  Occurs when 2 sympatric species occupy different habitats within their common range, genetically determined preference for different habitats that isolates gene pools o Seasonal Isolation  Occurs when two sympatric species breeding during different seasons o Behavior Isolation  Occurs when behavioral genes are associated with successful courtship and mating ex: dancing fish and birds o Mechanical Isolation  Occurs when structural differences between two closely related species prevents mating  Genetic Isolating Mechanisms o Gamete Isolation  Occurs when two different species are able to mate, but the egg and the sperm will not form a zygote- no fertilization o Developmental Isolation  Occurs when mating and fertilization between two species are successful but the embryo doesn’t develop properly o Hybrid In Viability  Occurs when a hybrid resolving from interbreeding dies before reproducing or so malformed that it can’t reproduce o Hybrid Sterility  Occurs when a hybrid is healthy, but sterile o Selective Hybrid Elimination  Occurs when a hybrid is capable of reproducing, but they and their offspring are less fit and are eliminated from the population within a few generations, but if they are just as fit and sympatric they will soon form a new species  Usually several of these factors are in play at one time- most organisms rely on the first five  They prevent the mating rather than waste gametes with those that prevent birth or produce hybrids D. Polyploidy  So far we have only looked at speciation because of geographic isolation over many years  Plants can form new species by another method called Polyploidy  The number of chromosomes is increased  The increase of chromosome number is the result of abnormal cell division in which chromosomes do not separate properly either during mitosis or meiosis  Mitosis- is a plant increases its somatic cell chromosome number it may still be able to form normal gametes and reproduce with the parent population BUT  If it forms gametes with too many chromosomes it usually cannot reproduce with the parent population  The plant may produce asexually and produce a population of polyploidy plants- those plants can then reproduce sexually among themselves- new gene pool is formed E. Development of Evolutionary Thought  For centuries people believed that the various species of various plants and animals remained unchanged since their creation  Evolution occurs so slowly you usually can’t see it in your lifetime  Early 1700’s- people in France and England became interested in fossils and began to realize that many species were now extinct  Mid 1700’s- Buffon- proposed that animals might change over time- but didn’t come up with how they changed  1809-Lamarck- suggested a process by which evolution could occur- acquired characteristics could be passed on to offspring  Ex: giraffes started out with short necks- they constantly stretched their necks to get at food so they became slightly longer a lifetime, slightly longer necks were passed on to the offspring- necks got longer with each generation  He was wrong because acquired characteristics cannot be passed on  1858- Darwin and Wallace  Natural Selection by which evolution could occur  Made the following 5 assumptions o All organisms produce more offspring than survive o No two organisms are exactly alike o Among organisms there is a constant struggle for survival o Individuals with favorable characteristics are more likely to survive and produce more offspring o Favorable characteristics become more common in the species and unfavorable ones are lost  1900’s- Mendel’s work was rediscovered and explained how traits could be passed from generation from generation to generation F. Evolution above the Species Level  Tracing the evolutionary ancestry of an organism is difficult because many of the ancestors do not exist  Some organisms you can trace the fossil record, but that doesn’t tell us anything about the behavior, physiology or ecology of the organism  Have to use bits and pieces of evidence to trace the series of evolutionary steps leading to present day organisms  The incomplete fossil records is what creationists use to dispute the theory of evolution, but if evolution is defined as a change in the genetic makeup of a population overtime there is no doubt that it exists  With the fossil evidence, evolutionary trees are created which trace evolutionary changes over time  Most species do not survive into the present  At least 99% of all species that have ever existed are extinct  This basic pattern of evolution is called divergent evolution  Speciation events cause branches in the evolution of a group of organisms  There are other patterns as well  *** Adaptive radiation- characterized by the rapid increase in the number and kinds of closely related species o Occurs like an explosion of new species form one common ancestor o 2 ways it can work  An organism invades a previously unexplored environment  An organism evolves a new set of characteristics that allows it to displace organisms that previously occupied an environmental niche (habitat)  *** Convergent Evolution- occurs when organisms with widely different backgrounds develop similar characteristics G. Rate of Evolution  Can vary greatly- usually evolutionary time is measured in thousands of millions of years  Since natural selection is driven by the environment, rapid changes in the environment causes relatively rapid changes in the organisms present  ***Microevolution- the type described by Darwin- a slow progressive change  ***Macroevolution- whole groups of characteristics change at the same time- many new species appear and many old species become extinct  Much of the fossil records support this type  ***Punctuated Equilibrium- pattern of slow changes for millions of years followed by rapid evolution


Buy Material

Are you sure you want to buy this material for

25 Karma

Buy Material

BOOM! Enjoy Your Free Notes!

We've added these Notes to your profile, click here to view them now.


You're already Subscribed!

Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'

Why people love StudySoup

Steve Martinelli UC Los Angeles

"There's no way I would have passed my Organic Chemistry class this semester without the notes and study guides I got from StudySoup."

Janice Dongeun University of Washington

"I used the money I made selling my notes & study guides to pay for spring break in Olympia, Washington...which was Sweet!"

Bentley McCaw University of Florida

"I was shooting for a perfect 4.0 GPA this semester. Having StudySoup as a study aid was critical to helping me achieve my goal...and I nailed it!"


"Their 'Elite Notetakers' are making over $1,200/month in sales by creating high quality content that helps their classmates in a time of need."

Become an Elite Notetaker and start selling your notes online!

Refund Policy


All subscriptions to StudySoup are paid in full at the time of subscribing. To change your credit card information or to cancel your subscription, go to "Edit Settings". All credit card information will be available there. If you should decide to cancel your subscription, it will continue to be valid until the next payment period, as all payments for the current period were made in advance. For special circumstances, please email


StudySoup has more than 1 million course-specific study resources to help students study smarter. If you’re having trouble finding what you’re looking for, our customer support team can help you find what you need! Feel free to contact them here:

Recurring Subscriptions: If you have canceled your recurring subscription on the day of renewal and have not downloaded any documents, you may request a refund by submitting an email to

Satisfaction Guarantee: If you’re not satisfied with your subscription, you can contact us for further help. Contact must be made within 3 business days of your subscription purchase and your refund request will be subject for review.

Please Note: Refunds can never be provided more than 30 days after the initial purchase date regardless of your activity on the site.