https://www.youtube.com/watch?feature=player_embedded&v=yRZZpk_9k8E
Friday, October 31, 2014
Lionfish
Lionfish
Distribution of Lionfish
http://lionfish.gcfi.org/manual/InvasiveLionfishGuide_GCFI_SpecialPublicationSeries_Number1_2012.pdf
Articles
NOAA_ Why are lionfish a growing problem in the Atlantic Ocean?
http://oceanservice.noaa.gov/facts/lionfish.html
Lionfish. National Invasive Species Information Center. USDA
http://www.invasivespeciesinfo.gov/aquatics/lionfish.shtml
Invasion of the lionfish. Smithsonian.com
http://www.smithsonianmag.com/science-nature/invasion-of-the-lionfish-131647135/
Lionfish invasion is threatening the Atlantic Ocean
http://www.upi.com/Science_News/2013/10/21/Lionfish-invasion-is-threatening-the-Atlantic-Ocean/9321382363683/
Lionfish infestation in Atlantic Ocean a growing epidemic. CNN October 19, 2013
Invasive lionfish: a guide to control and management
http://lionfish.gcfi.org/manual/InvasiveLionfishGuide_GCFI_SpecialPublicationSeries_Number1_2012.pdf
Persistent hunting can help win the war on lionfish.
Videos
Lionfish Population Has Scientists Worried- 2008
https://www.youtube.com/watch?v=Ar0CX8dj948
TED talk- Mark Hixon (Marine Biologist)
http://hixon.science.oregonstate.edu/content/highlight-lionfish-invasion
All you can eat lionfish
Feral Hogs
A plague of pigs in Texas. Smithsonian.com
http://www.smithsonianmag.com/science-nature/a-plague-of-pigs-in-texas-73769069/
Feral hogs in Texas. Texas Cooperative Extension
http://icwdm.org/publications/pdf/feral%20pig/txferalhogs.pdf
Texas losing war on feral hogs. Houston Chronicle. July 2013/
http://www.chron.com/sports/outdoors/article/Texas-losing-war-on-feral-hogs-4685490.php
Can wild pigs ravaging the US be stopped? Scientific American. October 21, 2014
http://www.scientificamerican.com/article/can-wild-pigs-ravaging-the-u-s-be-stopped/
Videos
Killer Aliens: Feral Hogs
http://www.animalplanet.com/tv-shows/other/videos/killer-aliens-feral-hogs.htm
Wild hogs impacting Texas agriculture- American's Heartland.
https://www.youtube.com/watch?v=m3KSMSrJQGk
Feral pigs in Australia
https://www.youtube.com/watch?v=bNSngI9ttgo
Cost of Invasive Species
Environmental and economic costs of vertebrate species invasions into the United States. David Pmental. 2007
http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1037&context=nwrcinvasive
Wednesday, October 29, 2014
Interesting Recent Articles About Human Population Growth
Population Controls Will Not Solve Environmental Issues. BBC. Oct. 27, 2014
http://www.bbc.com/news/science-environment-29788754
It's Not A Small World Afterall: World Population Will Soar
http://www.bbc.com/news/science-environment-29788754
World Population Stabilization Unlikely This Century. Science October 2014
http://www.sciencemag.org/content/346/6206/234.abstract
Invasive Species
Invasive species are an important threat to biodiversity and can be very costly to humans.
Further Reading
1) Invasive Species- http://www.eoearth.org/article/Invasive_species
2) Marine Invasive species - http://www.eoearth.org/article/Marine_invasive_species
3) Aquatic Invasive Species- http://www.eoearth.org/article/Aquatic_invasive_species
4) Invasion Fact Sheet- http://www.eoearth.org/article/Invasion_fact_sheet
Powerpoint Presentation
Invasive Species Slideshow- http://www.slideshare.net/secret/bL1TCLiLtoH5Np
Expected Learning Outcomes
By the end of this course a fully engaged student should be able to
- discuss threats caused by invasive species
- discuss strategies to exclude or eliminate invasive species
- discuss some invasive species in Texas
- discuss factors that allow species to invade new communities
Friday, October 17, 2014
Human Population Growth
I have spent a lot of time telling you that exponential growth is an unrealistic model of population growth. Interestingly, human populations have experienced exponential-like growth. How can this be?
What makes humans different from other species?
In other species per capita birth rates and per capita deaths rates are density dependent. However, as human populations have increased there has been no corresponding decline in per capita birth rates or increase in per capita death rates. What makes humans different from other species?
Humans have the ability to alter their environment so that they can avoid the density dependent effects on birth and death rates. 1) Humans have increased food production by improvements in agriculture (e.g., irrigation, fertilization, mechanized farming, genetically improved crops). 2) Humans have been able to decrease death rates by improvements in medicine and public health (things as simple as not pooping in the water you drink helps a lot!). 3) Humans have elimnated most human predators (ocassionally, someone gets killed by a shark or a mountain lion).
Where is human population growth occuring?
The rates of human population growth are not the same in all regions. Today, human populations are increasing in size much faster in developing countries (e.g., Mexico, other countries in Central America, Africa, and Southeast Asia) than they are in developed countries (e.g, USA, Canda, Western Europe). The figure at the top of this post shows the patterns of population growth in developed and developing nations.
Thus we see that populations are increasing most rapidly in the countries that are least able to deal with a rapidly increasing population. See "Population Challenges-The Basics" that can be downloaded from the Population Institute's website.
http://www.populationinstitute.org/population-issues/index.php
Human Population Growth Problem?
There is a great deal of debate about whether increasing human populations are a problem or not, and if they are what should be done about it. Unfortunately, we don't have time to discuss this issue in very much detail in class. My personal opinion is that we have too many people consuming too many resources and the last thing that we need are billions more people living on the planet. This is an issue that I am always intersted in talking more about if you would like to chat.
Further Reading
"Human Population Explostion" from the EoE.
http://www.eoearth.org/article/Human_population_explosion
Website
World Population Clock (and other interesting info)
http://www.worldometers.info/population/
Really Cool Video
Here is a link to a YouTube video on "World Population" The first minute and a half or so is a little boring, so you can skip over it if you wish. However, I think the animation showing when and where human population growth has been occuring is really cool.
http://www.youtube.com/watch?v=4BbkQiQyaYc
Expected Learning Outcomes
By the end of this course a fully engaged student should be able to
- describe patterns of human population growth in developed and developing nations
- discuss some reasons why the pattern of population growth in humans is so different from that in other species
- describe the demographic transition
- discuss their own personal view of human population growth.
Thursday, October 16, 2014
Monday, October 13, 2014
Population Biology III: Logistic Growth
We are trying to develop a mathematical model that helps us to understand patterns of population growth. So far our first attempt, the exponential growth model, did not help us to understand population growth (for reasons that I hope that you understand by now).
The "Real" world
In our attempt to think about population growth in the real world, we attempted to examine how per capita birth rates and per capita death rates should vary as population size varies. The model that describes this pattern of growth is known as the logistic growth model. It is important to realize that although this model is much more realistic, and therefore useful to us, than the exponential growth model, the logistic growth model still only examines what I call "the theoretical real world". That is, this model applies to our ideas about how populations should generally behave and do not thus relate directly to studying the population sizes of white tailed deer in central Texas or parrot fish on a coral reef in Fiji.
Logistic Growth
We have discussed why, in the real world, r should decrease as population sizes increase. If this is the case then there is a population size at which the per capita birth rate equals the per capita death rate. We call this population size the carrying capacity.
1) When populations are smaller than the carrying capacity we expect them to increase in size until they reach the carrying capacity.
2) When populations are larger than carrying capacity we espect them to decrease in size untile they reach the carrying capacity.
3) When the population size equals the carrying capacity we expect no change in the size of the population.
The logistic growth equation is a mathematical equation developed by biologists to describe patterns of population growth consistent with the ideas above. Before focusing on the biological isights that we can gain from the logistic growth model (the real purpose of everything we have been doing) it is important to really understand patterns of logistic growth. Hopefully, this powerpoint presentation will help you understand these patterns better.
Powerpoint Presentation
Click here for a powerpoint presentation entitled "Fun With Graphs- Logistic Growth"
http://www.slideshare.net/secret/gyB3cjnSplLw41
NOTE: THERE IS AN ERROR ON SLIDE 16 OF THIS PRESENTATION!!!
The title of the graph on slide 16 should read "Logistic Growth: dN/dt vs t (Not N), N initially << k"
The x-axis of the graph is TIME (please ignore the values of K on the x-axis because K does not belong on the time axis). The shape of the graph is correct. Make sure you change the x-axis to Time rather than Population Size.
Expected Learning Outcomes
By the end of this course a fully engaged students should be able to
- define the carrying capacity
- draw, and interpret the following graphs associated with logistic growth
a) how population size changes over time in logistic growth when the initial population size is much smaller than the carrying capacity
b) how population growth rate changes over time in logistic growth when the initial population size is much smaller than the carrying capacity
c) how the per capita growth rate varies over time in logistic growth
- discuss the causes for the shape of the s-curve (this answer will need to include a discussion of both math and biology)
- discuss the factors that regulate population size, be able to distinguish between density dependent and density independent factors that regulate population growth and give examples
Population Biology II: Exponential Growth
From the first lesson on Population Ecology we learned that the population growth rate (dN/dt) can be calculated as the product of the per capita growth rate (r) and the population size (N).
dN/dt = rN
This is the fundamental equation describing population growth and this equation is always true.
If we want to use this equation to analyze how population sizes change over time, then it makes sense to start by examining the simplest formulation of this equation which occurs when the per capita growth rate is constant. The equation dN/dt = rN when r is constant is known as the exponential growth equation and this equation describes a patter on growth known as exponential growth.
The graph plotting how population size changes over time is shown in the Exponential Growth article. This graph shows an exponential growth curve (sometimes known as the "j-curve"). If you have questions about why the graph has this shape let me know and I will try to explain it more thoroughly.
It is important that you are able to look at this graph and determine all of the information held in the graph. The exponential growth curve allows us to discuss how two parameters change over time- 1) the population size (shown by the x-axis) and 2) the population growth rate (shown by the slope of the line). I find that it is easier to discuss only one parameter at a time so let's start with the population size.
1) Over time, the population size increases (we know this because the line has a positive slope).
Now let's think about the population growth rate.
2) Over time, the population growth rate increases (we know this becasue the line gets steeper over time.
3) Over time, the rate at which the population growth rate increases over time, increases over time (we know this because the slope increases faster and faster over time).
Thus, if populations are growing exponentially then they keep increasing in size at an ever faster rate forever and ever.
Now try this-
Can you draw the following graphs?
1) plot how the population growth rate varies over time.
(hint- we have alredy described what this pattern will look like using words- just turn these words into pictures).
2) plot how the population growth rate depends on population size.
(hint- this graph is a little trickier, but we do have an equation that relates the two variables)
3) plot how the per capita growth rate varies over time.
(hint- think about what the basic assumption we made aboiut exponential growth)
4) plot how the per capita growth rate
(see the hint from number 3)
Exponential Growth is Unrealistic
Because population sizes keep increasing at ever faster rates for ever, exponential growth does not seem to be an accurate description of population growth in most animals, plants, and microbes. If this is an unrealistic model then why did I teach it to you? I started with exponential growth becasue it is the simplest model of population growth and scientists always like to describe the world using the simplest models that they can.
Obviously, in this case we have started with a model that is too simple to realistically describe the world. What is wrong with the exponential growth model? The fundamental assumption we made about exponential growth is that the per capita growth rate is constant. This must not be a realistic assumtpion.
It is important that you understand, and are able to explain, both the mathematical reasons and biological reasons that exponential growth is an unreasonable model of population growth. I tried to explain biologically why exponential growth is unrealistic in the "Exponential Growth" article and the attached Powerpoint presentation so take a look at those.
Suggested Readings
Here are some articles you should look at from the Encyclopedia of the Earth. I wrote these so they are brilliant!!!
Population Ecology http://www.eoearth.org/article/Population_ecology
Exponential Growth http://www.eoearth.org/article/Exponential_growth
Logistic Growth http://www.eoearth.org/article/Logistic_growth
Carrying Capacity http://www.eoearth.org/article/Carrying_capacity
Intraspecific Competition http://www.eoearth.org/article/Intraspecific_competition
Powerpoint Presentation
Click here for the Powerpoint presentation "Why is Exponential Growth Unrealistic?"
http://www.slideshare.net/secret/IDPugQtl2wvONv
Expected Learning Outcomes
By the end of this course a fully engaged student should be able to
- draw and interpret the following graphs associate with exponential growth
a) how population size change over time in exponential growth
b) how population growth rate varies over time in exponential growth
c) how per capita growth rate changes over time in exponential growth
e) how per capita growth rate depends on population size in exponential growth
- explain why exponential growth is an unrealistic pattern of growth for most species
- define and explain the carrying capacity
Population Biology 1- Basic Parameters
By the end of this course, a fully engaged student should be able to
- define b, d, r, B, D, dN/dt.
- identify and use the proper units associated with each parameter
- use the correct algebraic equations to calculate each of these parameters
- be equally comfortable referring to these concepts verbally or via their algebraic symbols.
Basic Parameters of Population Ecology
Here is a brief introduction to some of the important parameters that we will need to understand to be able to study population ecology. For each of the parameters it is important that you know (1) the name of the parameter, (2) the algebraic symbol used to represent the parameter, (3) the units of measurement for the parameter, (4) how to calculate the parameter, and (5) how to describe (in words) what a particular value of that parameter means.
It is probably easiest for me to introduce these concepts using an example.
Imagine that in a population of 100 elephants that in one year 10 elephants are born and 5 elephants die.
1) Population Size (N) units- individuals. Measures the number of individuals in a population.
N = 100 individuals
In this population of elephants, there are 100 individuals.
2) Population Birth Rate (B) units- number of births per time. Measures the number of births per time that occur in a population.
B = 10 births/year
In this population, each year there are 10 births.
3) Population Death Rate (D) units- number of deaths per time. Measures the number of deaths per time that occur in a population.
D = 5 deaths/year
In this population, each year there are 5 deaths.
4) Population Growth Rate (dN/dt) units- number of idividuals per time. Measures the rate of change of the population size.
dN/dt = B - D
dN/dt = 10 births/year - 5 deaths/year = 5 individuals/year
In this population, the population size increases by 5 individuals each year.
5) Per Capita Birth Rate (b) units- births per time per individual. Measures the number of births per time averaged across all members of the population.
b = B/N
b = (10 births/year)/100 individuals = 0.10 births/year/individual
In this population, each year 0.10 babies are born for each individual in the population.
6) Per Capita Death Rate (d) units - deaths per time per individual. Measures the number of deaths per time averaged across all members of the population.
d = D/N
d = (5 deaths/year)/100 individuals = 0.05 deaths/year/individual
In this population, each year 0.005 individuals die for each individual in the population.
7) Per Capita Growth Rate (r) units = individuals/time/individual. Measure the rate of change in population size averaged across all individuals. The per capita growth rate can be calcuated two ways.
a) r = b - d
r = 0.10 births/year/individual - 0.05 deaths/year/individual = 0.05 ind/year/ind
b) r = (dN/dt)/N
r = (5 individuals/year)/100 individuals = 0.05 individuals/year/individual
In this population, each year 0.05 individuals are added for each individual in the population.
Practice Problem
1. In a population of 50 tigers, in one year 10 tigers are born and 20 tigers die. What is B, D, dN/dt, b, d, r?
Writing Assignment #2
Use what you have learned about the ecology of Yellowstone National Park to introduce an intelligent friend/family member to my favorite statement about ecology- "the world is complicated".
3 pages max (you may add an additional page for references)
Rough draft due- Friday October 17
Workshop Papers- Monday Octoer 20th
Final Draft Due- Monday October 27th
Fire and Wolves in Yellowstone National Park
Powerpoint Presentation
http://www.slideshare.net/MarkMcGinley/fires-wolves-yellowstone
Expected Learning Outcomes
By the end of this course a fully engaged student should be able to
1) Discuss the importance of indirect interactions in communities.
2) Define a trophic cascade and differentiate between top down and bottom up regulation.
3) Discuss the effect of the 1988.
4) Discuss the effect of the reintroduction of wolves to Yellowstone National Park
Friday, October 3, 2014
Disturbance Ecology
The approach that community ecologists use to understand patterns of biodiversity depends on whether they think that communities are full (i.e., member of communities is limited by biotic interactions such as competition and predation) or whether communities are not full. The "equilibrial approach" to understanding community structure assumes that community membership is limited by competition. Thus, to understand the number of species in a community it will be necessary to understand the number of potential distinct niches. The "non-equilibrial approach" assumes that some procese or processes (such as predation or disturbance) have limited competitive exclusion.Disturbance Ecology
Ecological disturbances are one example of a process that can limit competitive exclusion. If a disturbance disrupts population growth of a superior competitor, then the population size of the superior competitor may not get large enough to competitively exclude other species.
Powerpoint Presentation
http://www.slideshare.net/secret/GH30nvAxRaF4P
Further Reading
1) Here is a link to a chapter entitled - The response of animals to disturbance and their roles in patch generation. that Mike Willig and I wrote for a book Ecosystems of Disturbed Ground. The first portion of this chapter talks about our view of disturbance the second discusses some of my research in Texas.
http://hydrodictyon.eeb.uconn.edu/people/willig/Willig_pdf/094.Willig&McGinley.1999.pdf
2) The Fire Ecology Factsheet- http://www.eoearth.org/article/Fire_ecology_fact_sheet
Expected Learning Outcomes
By the end of this course a fully engaged student should be able to
- define disturbance
- list examples of disturbances
- distinguish between a disturbance and a disaster
- discuss the characteristics of a disturbance regime
- discuss some adaptations of organisms to disturbances
- discuss why disturbances are natural parts of many ecosystems
- discuss the intermediate disturbance hypothesis
Free Learning: Tilman's Model of Competition for Two Limiting Resources
In case you are interested in seeing how the model of competition for one limiting resource can be extended to a model of competition for 2 limited resources.
Slideshow
http://www.slideshare.net/MarkMcGinley/tilmans-model-of-competition-for-two-resources
Expected Learning Outcomes
By the end of this course a fully engaged student should be able to
1)define ZNGI, consumption vector, supply vector, resource supply point
2)determine the outcome of competition when provided with information about ZNGIs, consumption vectors, and resource supply point.
3) distinguish between a stable and unstable equilibrium and be able to discuss why stable equilibria are particularly important outcomes from these models.
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