http://grist.org/news/if-youre-27-or-younger-youve-never-experienced-a-colder-than-average-month/
Saturday, November 17, 2012
Wednesday, November 14, 2012
Monday, November 5, 2012
The Physical Environment
Introduction
The physical environment can have a profound influence on ecology at a variety of levels. For example, the physical environment can act as a strong selective presssure to produce adaptations or can influence the rates of nutrient cycling through an ecosystem. For our simple purposes here, the two most important components of the physical environment are temperature and precipitation. I suggest that we can predict a lot about what is going on ecologically in an environment if we know something about temperature and precipitation patterns.
From watching the nightly news we all know how difficult it is for the local weatherperson to accurately predict what the weather is going to be like tomorrow. Fortunately, it is much easier to understand broad patterns of variation in temperature and precipitation.
Temperature
The dominant global temperature pattern is that it tends to get cooler as you move away from the poles. The cause of this is relatively simple. Because the earth is so far from the sun, the light rays hitting the earth are basically paralell to each other. Because of the curvature of the earth, sunlight hitting the earth near the equator falls over a smaller area than sunlight hitting near the poles. Because the same amount of light energy is hitting a smaller area near the equator, the concentration of energy/area is greater near the equator than the pole thus resulting in higher temperatures.
Elevation is another factor that influences global temperatures. Because there is less insulating atmosphere above areas of high elevation temperatures tend to decrease as you go up in elevation.
Large bodies of water can mediate temperature variations. For example, seasonal and daily variation in temperatures are much lower in areas near the ocean (maritime climates) than they are in areas far from the ocean (continental climates).
Global temperature patterns can also be affected by patterns of ocean circulation. For example, the west coast of continents are often cooled by cool water flowing from the poles to the tropics while the east coasts of continents can be warmed by warmer water from the tropics to the poles (e.g., the Gulf Stream). If you have ever been to the beach in southern California you surely noticed how cold the water was; east coast beaches at similar latitudes have much warmer water.
Precipitation
In order to understand global precipitation patterns you need to understand global patterns of atmospheric circulation. Hopefully, after studying the article on atmospheric circulation you will be able to explain-
1. why there tends to be high precipitation in tropical regions and
2. why precipitation tends to be low at 30 degrees North and South of the equator.
Patterns of precipitation can also be influenced by the presence of mountains. As air masses containing moisture hit a mountain they are forced upward. Because rising air cools and cool air
holds less moisture, precipitation occurs on the windward side of mountains. Once the air mass has passed over the mountain in falls to lower elevations and gets warmer. Because most of the moisture has been lost as precipitation on the windward side of the mountain and the warmer air holds more moisture there is very little precipitation on the leward side of the mountain resulting in a "rainshadow desert".
Let's think about Lubbock!
Let's see if we can use our newfound understanding of some of the factors influencing temperature and precipitation to make predictions about what the climate should be like in Lubbock. What information do we need about the geographic location of Lubbock to help us understand the climate? First, we need to know the latitude; Lubbock is located approximately 33 degrees north. Second we need to know something about the proximity to the ocean. As an old beach boy, I can guarantee you that we are a long, long way from the ocean in Lubbock. Third, where is Lubbock in relation to mountains? Lubbock is located to the east of the southern extension of the Rockies.
Why is all of this important?
1. What can we learn from the latitude of 33 degrees North? This latitude is still close enough to the equator to be warm so we expect relatively high temperatures. Because Lubbock lies near the 30 degree zone of low precipitation we would predict relatively low precipitation. At 30 degrees North we would predict that Lubbock would receive predominately winds from the west.
2. From the continental location of Lubbock we would predict fairly extreme daily and seasonal fluctuations of temperatures.
3. Because Lubbock lies in the Westerlies most of the precipitation that is arriving in Lubbock comes from the Pacific Ocean. Because these winds have passed over the Rockies we would predict that Lubbock would lie in a rainshadow, again causing low precipitation.
How did we do. If anyone has ever been in Lubbock (especially in the spring time) you would know that the wind almost always blows in from the west. Temperatures are relatively warm but there is fairly large seasonal and daily variations in temperature. Lubbock has a semi-arid climate and receives on average about 18 inches of precipitation per year. Thus, with just a little bit of knowlege about the factors that influence global patterns of temperature and precipitation we were able to fairly accurately the climate in Lubbock. Thus, I would expect that organisms native to Lubbock should be well adapted to the low precipitation, continental climate of the region (the short grass prairie was the dominant vegetation type presettlement).
See use these patterns to understand climate in your town (note climate patterns in Texas are complicated in central and eastern Texas becasue of the influence of air masses coming up from the Gulf). Compare the temperature and precipitation of your town with that if very divergent locations around the globe.
Further Reading
If you would like some more detailed information about factors affecting climate and the atmosphere you can check out the Atmosphere Chapter in Michael Pidwirny's online Physical Geography textbook http://www.physicalgeography.net/fundamentals/contents.html.
Powerpoint Presentation
Click here to see the powerpoint presentation "Factors Influencing the Physical Environment".
http://www.slideshare.net/secret/EaVq4nm5KuSsBI
Expected Learning Outcomes
At the end of this course a fully engaged student should be able to
- describe global patterns of variation in temperature and precipitation and be able to explain the causes of these patterns
- for any location in the world, use your knowledge of the factors that affect global patterns to preict the local climate
Natural Selection
An understanding of the process of natural selection helps us to understand the amazing diversity of life on the earth.
Expected Learning Outcomes
By the end of the course a fully engaged students should be able to
1) define the process of natural selection
2) distinguish between the patterns of stabilizing, disruptive, and directional selection and provide examples of each pattern
3) describe how the process of natural selection has produced a trait that is an adaptation to a particular environmental condition.
4) explain why organisms are not expected to be perfectly adapted to their environments
5) discuss the conditions that would cause natural selection to stop
6) explain why natural selection is expected to produce selfish traits
Readings
Natural selection http://www.eoearth.org/article/Natural_selection
Here is a link to a website from UC Berkeley-
http://evolution.berkeley.edu/evolibrary/article/evo_25
Friday, October 26, 2012
Midterm Exam
Hello Everyone,
Here is a copy of the Midterm Exam. Note that on question #4 that you should answer two of the three choices. The essay questions are intentionally "broad" (you might say "vague") to allow you the greatest flexibility when answering the question. If you have questions about this exam then please feel free to contact me via email.
Remember, you may use your notes or any other source of info to answer these questions. Please do not work with anyone else. Good luck! You can turn a hard copy of the exam in at the beginning of class on Monday.
1. (20 points)
What is the outcome in the following scenario involving
competition for resources between two species competing for two limiting
resources? Be sure to show how you
determined your answer.
Species A is more limited by the level of R1 than Species B
and Species B is more limited by the level of R2 than Species A. Species A consumers more R1 than it does R2
and Species B consumes more R2 than it does R1.
2. (10 points)
Draw the graph that shows how the population growth rate
varies over time in logistic growth when the initial population size is much
smaller than the carrying capacity.
3. (10 points)
Diagram the Energy Pyramid.
Briefly discuss why the diagram has this shape.
4. (60 points)
Answer only two of the following questions
a) Compare and contrast the equilibrium and non-equilibrium
approach to studying community structure.
Choose one of the approaches and show how it can be used to help understand one environmental issue that has arisen as
the result of human alteration of the environment in some way.
b) Discuss an example in which human alteration of an
ecosystem process (i.e., energy flow, nutrient cycling) has produced an environmental
problem. What could be done to help
solve this problem?
c) The World is Complicated!!! Discuss as this relates to
this class.
Wednesday, October 24, 2012
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.
Population Biology 3. 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
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