Pre Test Info for the Second Midterm

This graph plots the rate of photosynthesis as a function of the concentration of carbon dioxide in a growth chamber where scientists were able to hold all variables constant while varying the CO2 concentration.

                                                 ***********************************

  

This graph plots the relationship between photosynthetic rate and the density of sugar cane plants in a series of field experiments that varied the plant density.

                                           *************************************

This graph plots how heart rate (shown in the pink line- the one on top) and the cellular lactate concentration depended on cycling speed.

Plant Diversity

Here is a link to a powerpoint presentation about plant diversity.

Do not worry about the life cycles.  focus on understanding the major evolutionary advances that have occurred during plant evolution.

http://www.slideshare.net/secret/DBv71wnKTH1YBN

Factors Limiting the Rate of Photosynthesis

The graph above shows how the rate of photosynthesis is affected by irradiance (light level) and the concentration of carbon dioxide.

The rate of photosynthesis can be limited by a variety of environmental factors including

1) light
2) concentration of carbon dioxide
3) water
4) soil nutrients

Which factor most limits photosynthesis varies between environments.

Light- Can directly limit the rate of photosythesis by limiting the rate at which ATP and NADPH are produced.

Carbon dioxide- can directly limit the rate of photosynthesis by limiting the rate at which the Calvin Cyle takes place.

Water- can indirectly limit the rate of photosynthesis. When plants are water stressed they close their stomata (long before the concentration of water in the cell becomes too low for water to supply electrons to P680). Thus, the rate of photosynthesis is water stressed plants is directly limited by the amount of carbon dioxide in the leaf.

Soil Nutrients- Sometimes the rate limiting step in photosynthesis is the rate at which carbon dioxide + RuBP ==> PGA. This reaction is catalyzed by the enzyme RuBP carboxylase. Increasing the amount of RuBP carboxlyase in the cell can increase the rate at which this reaction occurs. Fertilizing plants with nitrogen will increase the amount of RuBP Carboxylase produced by the plant.

Expected Learning Outcomes

By the end of this class a fully engaged student should be able to

- discuss the factors that can directly or indirectly limit the rates of photosynthesis
- discuss how the most limiting factors should vary between environments
- discuss how the activities of farmers such as irrigation and fertilization can increase photosynthetic rates
- interpret the graph at the top of the post (irradiance measures light intensity and the three lines represent different concentrations of carbon dioxide)
- explain what why the graph shows that shape

Why Aren't Plants Black?

If I was hired as an engineer to design a machine whose job was to convert light energy into chemical energy I probably would not choose to use a green pigment. Instead, I would choose to use a black pigment because black pigments would absorb more energy because they would absorb all wavelengths of light. If you look at a field of plants you will notice that they are green (OK this doesn't work too well around Lubbock in the winter)and we have learned that chlorophyll, a green pigment, is the dominant photosynthetic pigment. What is going on?

Here is one theory about why chlorophyll is the dominant photosynthetic pigment in plants today. Early on there were photosynthetic bacteria with purple pigments (purple is a combination of red and violet). These aquatic bacteria had a very simple sort of cyclic electron flow that was able to convert light energy into energy in ATP (they didn't have non-cyclic flow or the Calvin Cycle).

Origin of chlorophyll- The purple pigment absorbed all wavelengths of light except for the reds and violets. Thus, any bacteria using purple pigments that lived deeper in the water than the purple bacteria on the surface would have no light to use because it had all been absorbed by the surface bacteris (exploitative competition). Because red and violet wavelengths pass through to deeper water, bacteria that contained a pigment that was able to absorb these wavelengths would be able to coexist with the purple bacteria. This was the origin of chlorophyll.

Competition purple and green photosynthetic pigments. Over time there was competition between organisms with purple photosynthetic pigments and green photosynthetic pigments. Obviously, the green photosynthetic pigments won this competition because chlorophyll is the dominant photosynthetic pigment today (there are still examples of photosynthetic bacteria with purple pigments, but they are limited to very harsh environments). Interestingly, chlorophyll came to dominate, not because it was a better at absorbing light energy, but rather because the cyclic flow machinery associated with chlorophyll was more efficient at producing ATP than the machinery associated with the purple pigment was. Thus, it is an evolutionary accident that modern plants are green.

Black Plants

It would be possible for modern plants to be black if they had enough accessory pigments to allow them to absorb all wavelengths of light. In fact, some red algae that live deep below the surface where light levels are low are basically black. Because the amount of light is not the factor that limits the rate of photosynthesis in most terrestrial plants, it is not worth the cost of producing extra accessory pigments. However, deep in the ocean where light levels are low, plants benefit from being able to absorb all wavelengths of light so deep marine algae have invested in extra accessory pigments.

Expected Learning Outcomes

By the end of this course a fully engaged student should be able to

- discuss why terrestrial plants to not invest in the accessory pigments required to make them black

Leaf Structure

Lecture Video: http://mediacast.ttu.edu/Mediasite/Play/c952faeba33546d3b8910e6e1bbf716c1d?catalog=4dc7289a-d3e0-4ae5-8fdc-5b86c027a06b




In most plants, leaves are the major sites of photosynthesis. Thus, we can think of leaves as "photosynthesis machines" and use our knowledge of natural selection to try to understand aspects of leaf structure.

Further Reading

http://micro.magnet.fsu.edu/cells/leaftissue/leaftissue.html

Expected Learning Outcomes

By the end of this course a fully engaged student should be able to

- discuss important differences between animals and plants in gas uptake
- diagram the cross section of a leaf
- discuss the characteristics and purpose of the cuticle, stomata, spongy mesophyl cells, and the palisade cells.
- explain the adaptive basis of leaf structure

Photosynthesis- Light Independent Reactions

Lecture Video- http://mediacast.ttu.edu/Mediasite/Play/842d916401044c20a370989776ea66631d?catalog=4dc7289a-d3e0-4ae5-8fdc-5b86c027a06b


Photosythesis takes place in two steps. In the first step, known as the light dependent reactions, light energy is converted into chemical energy held in the bonds of ATP and NADPH.

Expected Learning Outcomes

By the end of this course a fully engaged student should be able to

- list the parts of a photosystem
- discuss the function of a photosystem
- describe where the light dependent reactions of photosythesis occur and discuss why these reactions occur in this location
- describe cyclc electron flow, be able to explain both the energetic result and what chemcical changes occur
- describe non-cyclic electron flow, be able to explain both the energetic result and what chemical changes occur
- describe the cause and the result of chemiosmosis
- answer the question- "why doesn't photosynthesis stop after the production of ATP and NADPH in the light dependent reactions

Further Reading

A simple introduction to the process of photosynthesis
Photosynthesis- http://www.eoearth.org/article/Photosynthesis

Here is a link to some fairly detailed info about photosynthesis (it contains some very good diagrams).
http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookPS.html

Powerpoint Presentation

Here is the powerpoint presentation that I will use in class.

http://www.slideshare.net/MarkMcGinley/photosynthesis-light-dependent-reactions

Further Viewing

These videos contain animations that might help you to understand what is happening in the light dependent reactions. I encourage you to watch each of these videos.

1) This video has some great animations of what is going on in the light dependent reactions.

http://www.youtube.com/watch?v=hj_WKgnL6MI

2) This is a video of a woman with a very southern accent talking about photosyntheis with some decent animations.

http://www.youtube.com/watch?v=RFl25vSElaE&feature=related

3)Another explanation of light dependent reactions.

http://www.youtube.com/watch?v=BK_cjd6Evcw

Introduction to Photosynthesis

Lecture Video- http://mediacast.ttu.edu/Mediasite/Play/842d916401044c20a370989776ea66631d?catalog=4dc7289a-d3e0-4ae5-8fdc-5b86c027a06b


Photosythesis takes place in two steps. In the first step, known as the light dependent reactions, light energy is converted into chemical energy held in the bonds of ATP and NADPH.

Expected Learning Outcomes

By the end of this course a fully engaged student should be able to

- list the parts of a photosystem
- discuss the function of a photosystem
- describe where the light dependent reactions of photosythesis occur and discuss why these reactions occur in this location
- describe cyclc electron flow, be able to explain both the energetic result and what chemcical changes occur
- describe non-cyclic electron flow, be able to explain both the energetic result and what chemical changes occur
- describe the cause and the result of chemiosmosis
- answer the question- "why doesn't photosynthesis stop after the production of ATP and NADPH in the light dependent reactions

Further Reading

A simple introduction to the process of photosynthesis
Photosynthesis- http://www.eoearth.org/article/Photosynthesis

Here is a link to some fairly detailed info about photosynthesis (it contains some very good diagrams).
http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookPS.html

Powerpoint Presentation

Here is the powerpoint presentation that I will use in class.

http://www.slideshare.net/MarkMcGinley/photosynthesis-light-dependent-reactions

Further Viewing

These videos contain animations that might help you to understand what is happening in the light dependent reactions. I encourage you to watch each of these videos.

1) This video has some great animations of what is going on in the light dependent reactions.

http://www.youtube.com/watch?v=hj_WKgnL6MI

2) This is a video of a woman with a very southern accent talking about photosyntheis with some decent animations.

http://www.youtube.com/watch?v=RFl25vSElaE&feature=related

3)Another explanation of light dependent reactions.

http://www.youtube.com/watch?v=BK_cjd6Evcw

Introduction to Energetics

Lecture Video: http://mediacast.ttu.edu/Mediasite/Play/dfea523e65f54ad2af1a25fda81bd2f91d?catalog=4dc7289a-d3e0-4ae5-8fdc-5b86c027a06b


In order to understand the two important energetic processes taking place in living organims (photosynthesis and cellular respiration) it is useful to understand some basics of energetics.From a physics perspective, energy is required to do work. Because this is a biology class, we will focus on biological work. The three main types of biological work are (1) active transport, (2) biosynthesis, and (3) movement. The key point for this class is to realize that organisms require energy to do the biological work required to keep them alive.

Energetic processes follow the laws of physics. The two most important laws of physics that relate to energy are the First and Second Laws of Thermodynamics.

First Law of Thermodynamics

The total amount of energy in the universe is constant. Energy can not be created and existing energy can not be destroyed. Energy can only undergo conversion from one form to another.

Biological relevance- No living organisms are capable of creating their own energy so they must get it from another source.

Second Law of Thermodynamics

Left to itself, any system undergoes energy conversion to less organized form. Each time this happens some energy becomes so disorganized that it is no longer available to do work.

Entropy is a measure of the amount of energy that is so disorganized so that it can no longer do work. A simpler way of stating the Second Law of Thermodynamics is that entropy increases over time.

What does it mean when energy becomes disorganized? Another term for "organized energy" is "concentrated energy". Energy is only able to do work when it is concentrated enough to power a particular process.

Apparent Problem

The Second Law of Thermodynamics states that entropy should increase over time, yet life contains highly concentrated energy. How can this be?? They key phrase in the definition is "left to itself". It turns out that energetically, the earth is not left to itself; the earth receives a constant input of energy from the sun and it is this energy that is used to fight entropy.

Light

Light energy from the sun reaches the earth. Light is part of the electromagnetic spectrum. Different portions of the electromagnetic spectrum vary in their wave lengths. Forms of electromagnetic energy with shorter wavelengths (e.g., x rays and gamma rays) contain more energy than forms of energy with longer wave lengths (e.g, radio waves). Interestingly, light falls within the middle of the spectrum with wavelengths from about 400 - 700 nm. Different wavelengths of light have different colors. Ranging from the longest to the shortest wavelengths the colors are red, orange, yellow, blue, green, indigo, violet (some people remember this using ROY G BIV).

As you might recall from your physics class, light has characteristics of waves and of particles. Light energy is "packaged" in units known as photons and the amount of energy in a photon depends of the wavelength of that light.

Fusion reactions on the sun convert nuclear energy in to electromagnetic energy. The electromagnetic energy travels through outer space until reaches the earth. Unfortunately, we,and all other organisms can not directly use light energy to do biological work. Instead light energy must be converted into potential energy stored in the chemical bonds of molecules. This potential (stored) energy can then be used to power biological work.

What Happens When a Photon of Light Hits a Molecule?

Three things can happen when a photon of light hits a molecule- (1) the light can be transmitted (passed through), (2) the light can be reflected, or (3) the photon of light can be absorbed.

When a molecule absorbs a photon of light energy, the electromagnetic energy of light excites an electron in the molecule to a higher energy level (thus, giving the electron potential energy). The excited electron almost immediately falls back to resting stage and the potential energy in the electron is converted into heat (a form of electromagnetic energy) which is released to the atmosphere.

Pigments

When we think of pigments, we think of color. What determines an objects color? The color of an object depends on the wavelengths of light that are reflected back to our eyes. Thus, when you see red you are seeing the red wavelengths that have been reflected from the object that you are looking at. What happens to the other wavelength? They have been absorbed.

Different molecules absorb and reflect different wavelengths of light. A pigment is defined as a molecule that absorbs particular wavelengths of light. What is important to remember is that the color of a pigment is the color of light it reflects.

Absorption Spectrum

An absorption spectrum is a graph that plots how much light energy is absorbed (y-axis, usually measured as intensity or as a percentage) versus the wavelength of the ligh (x-axis, measured in nm). Take a look at the absorption spectrum shown below. You can see that this pigment absorbs mostly green wavelengths and reflects the red and violet wavelengths. When the red and violet wavelengths reach your eye it would appear to you as purple.

Can you draw the absorption spectrum for a red, green and blue pigment?



Lecture Video- http://mediacast.ttu.edu/Mediasite/Play/dfea523e65f54ad2af1a25fda81bd2f91d?catalog=4dc7289a-d3e0-4ae5-8fdc-5b86c027a06b

Expected Learning Outcomes

By the end of the course a fully engaged student should be able to

- give examples of biological work
- list different forms of energy, give examples of the different forms, and give examples of energy conversions
- define the First and Second Laws of Thermodynamics and discuss why these laws are important for biologists
- discuss electromagnetic energy, including the wavelengths associated with different forms of electromagnetic energy and the relationship between wavelength and energy
- define a photon
- discuss the three things that can happen when a photon of light hits a molecule
- define a pigment
- draw and interpret an absorption spectrum

Further Reading

Electromagnetic radiation- http://www.eoearth.org/article/Electromagnetic_radiation

Global Carbon Cycle and Global Climate Change

Most of the slides from the global climate change portion of this presentation came from Katharine Hayhoe's website (she is a professor in the Tech Political Science Dept and the link to her website is listed on the presentation).

Global Carbon Cycle and Global Climate Change
http://www.slideshare.net/secret/C6iDTujQlIh73C

Further Reading

Climate Change FAQ- http://www.eoearth.org/article/Climate_change_FAQs

Causes of Climate Change- http://www.eoearth.org/article/Causes_of_climate_change

Global Warming- http://www.eoearth.org/article/Global_warming

Economics of Climate Change- http://www.eoearth.org/article/Economics_of_climate_change

Mauna Loa Curve- http://www.eoearth.org/article/Mauna_Loa_curve

Expected Learning Outcomes

By the end of this course a fully engaged student should be able to

- identify the major reservoirs of carbon

- discuss the two most important biological processes that result in a movement of carbon from one reservoir to another

- discuss the three ways that human activity has altered the global carbon cycle

- explain the Mauna Loa Curve

- discuss why climate scientists have concluded that global temperatures have increased

- discuss why climate scientists have concluded that this increase in temperature is most likely caused by humans

- discuss some potential consequences of global climate change

Ecosystem Ecology

Ecosystem ecologists focus on the flow of energy and the cycling of nutrients through the ecosystem.

Further Readings

Ecosystems- http://www.eoearth.org/article/Ecosystem

Ecological energetics- http://www.eoearth.org/article/Ecological_energetics

Nitrogen cycle- http://www.eoearth.org/article/Nitrogen_cycle

Expected Learning Outcomes

By the end of this course a fully engaged student should be able to

- diagram and discuss the flow of energy through an ecosystem
- diagram, discuss the causes of, and discuss some of the implications of the enegy pyramid
- diagram nitrogen cycle within an ecosystem
- discuss the factors that influence the rate of flow from dead bodies to the soil and discuss the implications of differences in this rate

Community Ecology: The Portal Experiment

Lecture Video- http://mediacast.ttu.edu/Mediasite/Play/7feddd71db3e46eaa48d3bd62f4b50e71d?catalog=4dc7289a-d3e0-4ae5-8fdc-5b86c027a06b


Here are some photos from the research site in Portal, Arizona. For more information about the research project at Portal you can look at their website at
http://portal.weecology.org/

Expected Learning Outcomes

By the end of this course a fully engaged student should be able to

- distinguish between direct and indirect, positive and negative effects
- describe the experimental design that Dr. Brown and his colleagues used to study exploitative competition between desert rats and rodents
-discuss why and how the outcome of studies of interactions between organisms can vary over time
- discuss the way that the ecological community responded when they learned the importance of long term studies
- discuss how indirect interactions lead to one of my favorite phrases "the world is complicated"

Community Ecology

Required Readings

Community Ecology- http://www.eoearth.org/article/Community_ecology

Competition- http://www.eoearth.org/article/Competition

Interspecific Competition- http://www.eoearth.org/article/Interspecific_competition

Exploitative Competition- http://www.eoearth.org/article/Exploitative_competition

Predation- http://www.eoearth.org/article/Predation

Mutualism- http://www.eoearth.org/article/Mutualism

Expected Learning Outcomes

By the end of this course a fully engaged student should be able to

- define competition, exploitative competition and interference competition

- identify and explain examples of exploitative and interference competition from a variety of environments

- define predation (narrow and broad sense), herbivory, and parasitms

- identify and explain examples of predation, herbivory, and parasitism from a variety of environments

- identify examples of morphological and behavioral adaptations that animals have to help capture their food

- identify examples of morphological, biochemical, or behavioral adaptations that animals have to protect them from predators

- identify and explain examples of mutualisms from a variety of habitats


Past Test Questions (answers at bottom of post)

In the southeastern United States, a weedy plant called Kudzu has caused a great deal of problems. Because Kudzu has such high growth rates it is able to rapidly overgrow buildings and other plants.

1. Which of the following would best describe the ecological relationship between Kudzu and a species of pine tree that is commonly overgrown by Kudzu?
(a) mutualism
(b) parasitism
(c) exploitative competition
(d) herbivory
(e) none of the above

Answer- 1. c

Human Population Growth

Lecture Video: http://mediacast.ttu.edu/Mediasite/Play/52d8d4c10b014322accd92829c7c5c991d?catalog=4dc7289a-d3e0-4ae5-8fdc-5b86c027a06b


I have spent a lot of time trying to convince 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

The section on Human Population Growth in your textbook is quite good.

Also see the article "Human Population Explosion" from the EoE.
http://www.eoearth.org/article/Human_population_explosion

Both of these contain a good discussion of the "demographic transition".

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

Powerpoint Presentation

http://www.slideshare.net/MarkMcGinley/human-population-growth-16369173

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.

Past  MC Test Questions (answers at bottom of post)

1. In developing countries, why have per capita birth rates not decreased as human populations have increased in size?
(a) because we have increased rates of food production
(b) because of the improvements in education of women
(c) because of improvements in medical care
(d) a and c
(e) a, b, and c

2. Why do some people consider the high growth rates of human populations in developing countries to be of concern?
(a) because many people are born into conditions that do not provide them enough food
(b) because many people are born into conditions without clean water and adequate sanitation
(c) because increasing population sizes have led to increasing habitat destruction
(d) a, b, and c
(e) none of the above

answers- 1.d, 2.d

Population Biology 3- Logistic Growth

Lecture Video- http://mediacast.ttu.edu/Mediasite/Play/83f60ff04a32459896329229dc3cc5fd1d?catalog=4dc7289a-d3e0-4ae5-8fdc-5b86c027a06b


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 attemtp to think about population growth in the real world, we attempted to examine how per capitat birth rates and per capitat 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 exmaines 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. These real world situations are much harder to understand than the simple "idealized" populations that I am talking about in BIOL 1404. You can take an Advanced Population Biology course if you want to learn more about how to apply these models to the "real real world".

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
-how population size changes over time in logistic growth when the initial population size is much smaller than the carrying capacity
-how the population size changes over time in logistic growth when the initial population size is much larger than the carrying capacity
-how population growth rate changes over time in logistic growth when the initial population size is much smaller than the carrying capacity
-how the population growth rate changes over time in logistic growth when the initial population size is much larger than the carrying capacity
-how the per capita growth rate varies over time in logistic growth
-how the population 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

Fun With Graphs- Exponential Growth

Take a look at this before Monday as well.

How do I know which graph to draw?

1) In the population ecology portion of this course we will be discussing two models of population growth- exponential growth and logistic growth. Thus, you need to know which growth model you are describing before you know which graph to draw.

2) You can't draw a graph until you know what the axes are.

Hopefully, this is a review, but it is probably worth talking about. The x-axis (the horizontal axis) is known as the independent variable. The y-axis (the vertical axis) is the dependent variable. Changing the value of the independent variable results in a change in the dependent variable. Id DOES matter which variable goes on which axis so try to get it right.

In population ecology there will be two main independent variables that we are interested in studying. Because we are interested in patterns of population growth, we will often want to observe how variables change over time. Time is always the independent variable, so it always goes on the x-axis. Sometimes we are interested in how parameters depend on population size. In this case, population size is always the independent variable.

Powerpoint Presentation

This powerpoint presentation "Fun With Graphs: Exponential Growth" reviews the graphs you are expected to be able to draw, understand, and interpret that relate to exponential growth.

http://www.slideshare.net/secret/mavlOD8flFs67G

NOTE:

Any graphs that contain the incorrect axes will be considered to be completely wrong on all exams and assignments!!

Population Biology 2. Exponential Growth

We may start examining this material on Monday Feb 2nd so please look it over before then.

Lecture Video- http://mediacast.ttu.edu/Mediasite/Play/b8c64d66f62a4747b7983398113f0b391d?catalog=4dc7289a-d3e0-4ae5-8fdc-5b86c027a06b


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 then take a look at the blog post entitled "How Did I Know What the Exponential Growth Curve Looked Like?".

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 the population growth rate depends on the population size

d) how per capita growth rate changes over time in exponential growth

e) how per capita growth rate depends on population size

- explain why exponential growth is an unrealistic pattern of growth for most species

- define and explain the carrying capacity

Population Biology. 1. Basic Parameters

We may have time to start this topic on Monday February 2nd so it would help if you take a look at this before then.

Lecture Video: http://mediacast.ttu.edu/Mediasite/Play/20ade8c97b0b40af8eaab29ae07eee6f1d?catalog=4dc7289a-d3e0-4ae5-8fdc-5b86c027a06b

IMPORTANT NOTE!!!
For the next several lectures we will be using math and graphs to help us explore population ecology. From my experience teaching this topic in the past, many of you will experience some difficulties with this material because you are not confident when dealing with math and graphs.

Rather than introducing the concepts to you in lecture and then having you work on activities to help you master the material out of class, this year I would like to "flip the class". This year I would like for you to study the material before coming to class so that we can use the class time to answer your questions and to help you master the material.

Assignment- Before Wed December 30th, I expect that you will have read the following post and are able to meet all of the expected learning outcomes listed below. If you have not mastered the material in this blog, then you will find that you will be hopelessly lost in the lectures that follow!!

Expected Learning Outcomes

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?

2. List the equation/equations for calculating the following parameters
a) b
b) the population growth rate
c) r

Sexual Selection

This is the material that we will discuss on Monday February 2nd.

Lecture Videos to Watch- http://mediacast.ttu.edu/Mediasite/Play/46946a59e6fe4dfda9dcec19246d2acf1d?catalog=4dc7289a-d3e0-4ae5-8fdc-5b86c027a06b

I think that sexual selection is one of the most interesting topics in all of biology. First, studying this topic helps to illustrate that natural selection is much more than "survival of the fittest". Second, many of the traits produced by sexual selection are particularly weird and wonderful. Finally, I think that it is fun to use what we have learned about mate choice in animals to helping us to understand human behavior.

Expected Learning Outcomes

By the end of this course a fully engaged student should be able to

- discuss the critical difference between males and females and discuss how this difference influences differences in behavior and morphology between species.

- discuss why sexual selection is just a subset of natural selection

- discus why females should be choosier about who they mate with than males

- discuss why males often compete with other males to fertilize eggs of females

- compare and contrast male-male competition in species with internal fertilization and species with external fertilization

- describe the studies used by scientists to see if females are capable of choosing the best males

- discuss how females can determine which is the best male

- discuss why the variation in female reproductive success is much less than the variation in male reproductive success

- discuss how you would use sexual selection to help you understand human behavior

Past Exam Questions (answers at the bottom of the post)

1. Why are females choosier than males about who they mate with?
(a) female gametes are much more expensive than male gametes
(b) male gametes are much more expensive than female gametes
(c) in some species, males are larger than females
(d) in some species, males compete to mate with the female
(e) c and d

2. Why should females prefer to mate with the oldest males?
(a) because they can pass on good mating genes to their daughters
(b) because they can pass on good survival genes to their sons
(c) because the can pass on good survival genes to their daughters
(d) a and c
(e) b and c

3. Why might females sometimes cause male-male competition to occur?
(a) to assure that she mates with the oldest male
(b) to assure that she mates with the most symmetric male
(c) the male who wins the fight is likely to have “good genes”

(d) a and c

(e) a, b, and c

Further Reading

Here is a link to a website that a student sent to me  called "The 30 Strangest Animal Mating Habits" http://www.neatorama.com/2007/04/30/30-strangest-animal-mating-habits/

Take a look at this and see if you can relate what the animals are doing to some of the theories that we have talked about in class.

Here is a link to a youtube video showing the mating display of lyrebirds. I was lucky enough to see a lyrebird doing its mating display when I was a kid living in Australia. There was a professional nature photographer who had been hiking around the bush for a couple of weeks waiting to see the display and he was pissed that my Dad and I were able to see the display after spending only about an hour in the woods. What do you think is going on with the lyrebirds?

http://www.youtube.com/watch?v=VjE0Kdfos4Y

Here is a link to the Powerpoint Presentation I prepared for this topic.

http://www.slideshare.net/secret/CG2HHvtrLA1KwL

Answers. 1. a, 2. e, 3. c

Here is a link to an interesting article that I  discovered on an ex-student's Facebook page. Biology is Cool!!!!!

Male spider snaps off own genitals inside female to fertilise her remotely, while being eaten.

http://blogs.discovermagazine.com/notrocketscience/2012/02/01/male-spider-snaps-off-own-genitals-inside-female-to-fertilise-her-remotely-while-being-eaten/

The Evolution of Antibiotic Resistance

I think that the evolution of antibiotic resistance is an interesting and important issue. Below I has listed the expected learning outcomes for this topic in BIOL 1404. Because this topic has widespread medical relevance I have included a lot of additional readings and a powerpoint presentation that I developed for another class last semester. This info is not required, but is only intended to provide more info to interested students.

Expected Learning Outcomes

By the end of the course a fully engaged students should be able to

- discuss the causes of the development of antibiotic resistance

- discuss what we have learned from ecology and evolutionary biology about potentila problems associated with antibiotic use

- discuss what we have learned from evolutionary biology that should help us fight microbial diseases more effectively

Past Exam Questions (answers at the bottom of the post)

In the 1950s, Japanese physicians began to notice that some hospital patients suffering from bacterial dysentery, which produces severe diarrhea, did not respond to antibiotics that had generally been effective in the past.

1. In order for the result described above to have occurred, which of the following must have been true in the population of dysentery-causing bacteria?
(a) there was variation in the susceptibility of the bacteria to antibiotics
(b) antibiotic resistance was heritable
(c) bacteria that were more resistant to antibiotics had higher survival rates than less resistant bacteria
(d) a, b, and c
(e) neither a, b, or c was true


2. What can be done in future to limit the problem of antibiotic resistance in disease-causing microorganisms?
(a) Doctors should only describe antibiotics when appropriate
(b) Doctors should prescribe larger doses of antibiotics
(c) patients should make sure to take all of the pills when antibiotics are prescribed
(d) a and c
(d) a, b, and c

Answers 1. d 2. d

Further Reading

Evolution of Antibiotic Resistance-
http://www.pbs.org/wgbh/evolution/library/10/4/l_104_03.html

Antibiotic resistance: Questions and Answers- CDC
http://www.cdc.gov/getsmart/antibiotic-use/anitbiotic-resistance-faqs.html

Antibiotic resistance- delaying the inevitable (parts 1 and 2) UC Berkeley
http://evolution.berkeley.edu/evosite/relevance/IA1antibiotics2.shtml

HIV the ultimate evolver (parts 1-3) UC Berkeley
http://evolution.berkeley.edu/evosite/relevance/IA2HIV.shtml


When Penicillin Pays: Why China Loves Antibiotics a Little Too Much http://www.time.com/time/world/article/0,8599,2103733,00.html

Here is a link to an article about India I just discovered.
The Super-Resistant Bacteria That Has India 'Hell Scared' http://www.theatlantic.com/international/archive/2012/01/the-super-resistant-bacteria-that-has-india-hell-scared/251731/

Here is an link to an article about what is going on in the US sent to my by a fellow BIOL 1404 students. Thanks!
Antibiotic-Resistant Bacteria Found in 37 U.S. States
http://news.yahoo.com/antibiotic-resistant-bacteria-found-37-u-states-204438989.html

Powerpoint Presentation

Here is a link the the powerpoint presentation I used in another class.

http://www.slideshare.net/secret/rPekyBdLalUvFY

The Evolution of Sex

Lecture Video to Watch- http://mediacast.ttu.edu/Mediasite/Play/e42a326764d74e86b6f290c258365a6b1d?catalog=4dc7289a-d3e0-4ae5-8fdc-5b86c027a06b

Based on our understanding of natural selection, at first glance sexual reproduction doesn't appear to be advantageous from the female perspective (due to the two-fold cost of sex). However, the fact that sexual reproduction is so common in all groups of organisms suggests that there must be some major benefits of sex that outweight the costs.

Expected Learning Outcomes

By the end of this course a fully engaged student should be able to

- explain "the two-fold costs of sex"
- discuss possible benefits of sexual reproduction including adaptation to environmental uncertainty and fighting disease
- be able to discuss the problem of the evolution of antiobiotic resistant microbes
- be able to discuss what the medical field may be able to learn from observing how nature fights disease.

The Honors Section Exam will not contain multiple choice questions but you can quiz yourself by looking at these.

Past Exam Question (answer at the bottom of the post)

1. What is the “two fold cost of sex”?
(a) female gametes are twice as expensive to produce as male gametes
(b) the genetic variation produced by sexually reproducing females provides a benefit if there is environmental uncertainty
(c) individuals reproducing asexually pass on twice as many of their genes
(d) a and b
(e) b and c

2. Which of the following hypotheses can explain a benefit of sex?
(a) males pass on more genes in sexual reproduction than in asexual reproduction
(b) the genetic variation produced by sexual reproductions provides a benefit in uncertain environments
(c) females reproducing asexually pass on twice as many of their genes
(d) a and b
(e) b and c


Further Readings

Although I am usually a little skeptical of articles form Wikipedia, this one is pretty good. It goes into more detail than you need to know, but provides some useful information

Evolution of Sexual Reproduction http://en.wikipedia.org/wiki/Evolution_of_sex

Interesting Article by Evolutionary Biologist David Barash

The Good News About Sex http://chronicle.com/blogs/brainstorm/the-good-news-about-sex/43292

Life in Local Playa Lakes

If you would like to learn a little more about local playa lakes-

Playa Lakes http://www.eoearth.org/article/Playa_lake

Drawings of cladocerans similar to those inhabiting playa lakes.










This is what they don't look like.

answer- 1. c 2. b

Cultural Selection

In humans there are examples of alturistic behaviors that appear to be difficult to explain by kin selection of reciprocal altruism (e.g. soldiers sacrificing their lives in battle, police or firefighters risking their lives, catholic priests remaining celibate).

Genes are self replicating molecules. Genes produce our bodies which in turn produce more copies of their genes. Richard Dawkins has suggested that we think about genes as being "replicators" and our bodies as being "vehicles" whose job it is to make more copies of the replicators. If we can not explain altruistic behaviors as strategy for increasing the transmission of genes into the next generation them maybe we need to search for another kind of "replicator". Dawkins has suggested that "ideas" (he calls them "memes") are also capable of self replication. Because ideas differ in how long they survive and how well they are passed on it should be possible to have selection for ideas (cultural selection).

Expected Learning Outcomes

By the end of this course a fully engaged student should be able to

- identify examples of altruistic behavior that might be explained by cultural selection
- be able to compare and contrast "natural selection" with "cultural selection"

Further Readings

Cultural evolution http://plato.stanford.edu/entries/evolution-cultural/

As I mentioned in class, one of my favorite books of all time is "The Selfish Gene" by Richard Dawkings. He discusses some of his ideas about cultural selection in the final chapter of this book. Here is a link to that chapter in case you are interested
http://www.rubinghscience.org/memetics/dawkinsmemes.html

Reciprocal Altruism

Altruistic acts among non relatives can be understood by reciprocal altruism. As we discussed in class we would expect reciprocal altruism to be limited to species that show long term associations and are "smart" emough to be able to recognize individuals and remember who owes them and who does not.

Examples of Past Test Questions (answers at the bottom of this post)

1. It is not uncommon for college students to share items such as shampoo with their roommates. Which of the following hypothesis best explains this behavior?
(a) group selection
(b) kin selection
(c) reciprocal altruism
(d) selfish behavior
(e) altruistic behavior

2. Which of the following terms apply to a roommate who borrows your shampoo when she/he has run out, but will not allow you to borrow their shampoo when you need it?
(a) altruistic
(b) mutualist
(c) cheater
(d) a and c
(e) b and c



Further Readings

Reciprocal Altruism http://www.bbc.co.uk/nature/animals/mammals/explore/altruism.shtml

Reciprocal Altruism in Vampire Bats http://www.bio.davidson.edu/people/vecase/behavior/Spring2002/Perry/altruism.html

If you are interested in learning more about Evolutionary Psychology here is a link to a bunch of Frequently asked questions. Some of this goes into way more detail than we need to be worried about for this class.
FAQ Evolutionary Psychology http://www.anth.ucsb.edu/projects/human/evpsychfaq.html

Expected Learning Outcomes

By the end of this course a fully engaged student should be able to

- define reciprocal altruism
- discuss the conditions under which altruistic acts can be explained by reciprocal altruism
- examine an example of an altruistic behavior and determine whether reciprocal altruism is the best explanation
- explain how participants benefit by being involved in reciprodal altruism in real world examples (e.g, vampire bats)
- define a cheater in a reciprocal altruism system and discuss (a) why cheating is a problem in the system and (b) what organisms can do to reduce cheating
- discuss Trivers' ideas about how human psychology has been influenced by reciprocal altruism (be able to provide your opinion about Trivers' ideas and be able to back up your opinions)


Answers 1. c even though this is an example of altruistic behavior, the best explanation for this behavior is reciprocal altruism) 2. c

More Fun With Altruism

Question to Think About

Some birds have a behavior known as "helping at the nest". A female bird will sometimes help another bird rear offspring rather than laying her own eggs and raising them. There are two different hypothese to explain this behavior. First, this may be an example of an altruistic behavior that can be explained by kin selection. Alternatively, this may be an example of a purely selfish behavior. It is possible that young inexperienced birds are not very good at raising offspring the first time they try and by helping another bird to raise offspring they may get practice that makes them better at rearing offspring later on.

1) Explain how you as a scientist would conduct a study to distinguish between these two alternative hypothese.

2) Should a female bird who is capable of raising three offspring on her own help her sister to raise her sister's offspring if helping her sister allows her sister to raise five more offspring? Be sure that you would be able to explain to someone else how you determined your answer.

If you post your answers to the blog then I will be able to take a look at them and you can also get some feedback from fellow students.

Old Exam Questions

Here are some examples of old exam questions dealing with altruism. See if you can figure out the correct answers (answers provided at the bottom of this post).

Researchers studying black-tailed prairie dogs conducted an experiment where they dragged a stuffed badger (a predator of prairie dogs) across the colony. They repeated the experiment 698 times over the course of 3 years. The researchers observed that individuals with no offspring in the colony gave a warning call 19% of the time whereas individuals with offspring in the colony called almost 50% of the time. Which of the following could explain why individuals with no offspring would ever call?
(a) group selection
(b) other squirrels will return the favor in the future
(c) they have other relatives in the colony
(d) a and b
(e) a, b, or c would explain this observation


Which of the following are examples of an altruistic trait?
(a) an African wild dog sharing food with other members of the group
(b) a female choosing to mate with a symmetric male
(c) a sterile worker bee helping her sister (the queen) to reproduce
(d) a and c
(e) neither a, b, or c


Further Reading

Here are links to a couple of articles you might want ot take a look at-

Altruistic behaviors http://www.eoearth.org/article/Altruistic_behaviors

Kin selection http://www.eoearth.org/article/Kin_selection

More advanced reading

One of the problems with introductory courses is that we have to cover so many topics that it is not possible to go into very much detail over any of them. If you are interested in learning more about kin selection and altruism the following article would be good to look at.

Kin selection: fact and fiction. http://westgroup.biology.ed.ac.uk/pdf/Griffin&amp;West_02.pdf

Why Group Selection Does Not Work

Photo: Large flock of European Starlings (a bird)




Group selection is the hypothesis that organisms have the traits they do (including altruistic traits) because selection has produced traits that assure that species survive. Although this is intuitively an OK idea, it turns out that it doesn't work.

Have you ever noticed large "roosts" of birds in trees around town. Roosting birds gather by the hundreds or thousands in one, or a few, trees (maybe you have mistakenly parked you car underneath a roost and suffered the consequences). Biologists are interested in understanding the causes of roosting behavior. People who support the group selection hypothesis have proposed that the reason that these birds are roosting is that it gives them an opportunity to examine how large their population is. Becasue the birds do not want to overpopulate their environment, because overpopulation could lead to a loss of all of the food so that the entire species dies, birds want to know how many other birds are there so they know how much to reproduce. If birds see that the roosts are large then they know that the population is large so they decide to produce only a few babies. However, if the birds see that the roost is small then they are decide to produce many babies. Thus, the population never gets so large that they eat up all of the food.

Unfortunately, the math required for group selection just doesn't work out. Imagine a species of birds that mated monogamously for life. If the parents wanted to keep population sizes constant than their best strategy would be to produce two offspring during their life so that they make just enough kids to replace themselves. For this to happen all females would have a gene that said "make two babies". Imagine that a mutation occurs that says "make three babies". This mutation would quickly spread througout the population so that eventually all females would produce babies.  If mutations that said produce 4 or more babies occurred then these mutations would also spread. It is thus possible to imagine that each female would make so many babies that the population would indeed get large enough to consume all of the food which would cause the population to go extinct.  Thus, the math of natural selection does not allow organisms to artificially reduce their fitness for the "good of the species".

The observation that led group selectionist to thinking that roosting and reproduction could be explained by group selection was that females produced fewer eggs when more individuals were at the roost than when fewer individuals were at the roost. Can you think of another hypothesis to explain this observation?

So why do birds form roosts? There are at least two hypotheses. First, some scientists propose that organisms roost because they are safer from predators when living in large groups. Others think that organisms form roosts because they can benefit from information gained by living with lots of other individuals. For example, if you flew to the south to look for food and didn't find much and you noticed that those birds returning to the roost from the north looked well fed, then you might head out to the north the next day.

Expected Learning Outcome

By the end of this course a fully engaged student should be able to

- discuss why the classic notion of group selection does not work in nature

Altruism part 1

Lecture Video to Watch


http://mediacast.ttu.edu/Mediasite/Play/63042145bb50446dbff54ad0f1d7c7611d?catalog=4dc7289a-d3e0-4ae5-8fdc-5b86c027a06b


From our discussion about natural selection you should have learned that organisms have the traits they do because traits that produce phenotypes that are more successful at transmitting genes to the next generation (surviving and reproducing) become more common in a population over time. Thus, we expect organisms to have traits that maximize their individual survival and reproduction (we call these selfish traits).



Examples of Altruistic Behaviors



1. Broken wing display by kildeer
kildeer live around here so you should be able to see this behavior later on this spring (that will require going outside!)

http://www.youtube.com/watch?v=TNG7y0caqj0



2. Group defense in musk oxen
you can't see this around here even if you go outside.

http://www.youtube.com/watch?v=pb6Rke7jiTc



3. Food sharing in African Wild Dogs

http://www.sandiegozoo.org/animalbytes/t-wild_dog.html



4. Prairie dogs giving warning calls

http://www.youtube.com/watch?v=rXCPaNWcTFo



We should originally be a little bit confused when we learn about altruistic traits. How can genes that produce traits that decrease an organisms abilty to survive or reproduce become more common in a population?!? Luckily, we have learned that understanding what happens in natural selection requires us to focus on the transmission of genes. Apparently, organisms that behave altruistically are actually passing on more genes by behaving altruistically than they would by behaving selfishly.  How can this be? (this problem perplexed Darwin).



Fortunately, a lot of really smart scientists have thought about altruism and have recognized that their are a variety of different ways that organisms behaving altruistically could pass on more genes than organisms acting selfishly. There are at least 4 different hypotheses that can explain the evolution of altruistic behaviors (one of these will probably only help to explain altruism in humans).

The first explanation for why organisms were altruistic was the idea of group selection. Group selection is the idea that organisms have traits becasue those traits "assure the survival of the species". At first glance this seems like a pretty useful idea, but it actually does not work and it has been a very difficult idea to remove from the minds of the general public even though scientists have know that it is wrong and unecessary (there are much better theories about the causes of altruism) for over forty years. It would take a while for me to explain why group selection doesn't work so I won't spend any more time talking about it either in class or here on the blog. However, if you are interested in learning more about this I would be happy to chat with you.



It is important for this class that you are able to understand under which conditions the other hypotheses could explain the presence of altruistic behaviors.



Hamilton's Rule



Hamilton's Rule is a mathematical equation that helps scientists understand under which conditions organisms should behave altruistically and when they should behave selfishly. It is important that you understand (1) how sceintists use mathematical models to help us understand the world and (2) what Hamilton's Rule tells us about when organisms should behave altruistically.



Suggested Readings

Biological Altruism- http://plato.stanford.edu/entries/altruism-biological/



Expected Learming Outcomes



By the end of the course a fully engaged students should be able to

1) define altruistic traits and provide several examples

2) compare and contrast selfish traits and altruistic traits

3) explain why altruistic traits at first glance appear to be difficult to understand based on what we know about the process of natural selection

4) discuss at least four possible hypotheses that explain the presence of altruistic traits and explain under which circumstances these theories are expected to apply

5) use “Hamilton’s Rule” as an example to illustrate how biologists use mathematical models to help them understand biology

6) discuss how Sherman’s work with Belding’s Ground Squirrels provided support for Hamilton’s Rule

7) be able to determine which hypothesis best helps you understand any examples of altruistic traits that I give you and be able to justify that answer