Unit 1 Compilation

Chapter 1: Understanding Our Environment

We live on a planet that is completely self-sustaining with its various ecosystems and millions of species occupying it. Through the global subject of environmental science, we are able to come to a better understanding of how these species interact with one-another, and especially how we affect the planet that we occupy. With a drastically growing human population, we are finding the many ways in which we are detrimental to our own existence, as well as, the existence of our planet and its longevity for future sustainable life. We have created various forms of pollution that are leading to destruction of habitats for human life, and also, the habitats of the millions of other species that share our planet. 

 “There are 7 billion people on earth, and we are adding about 80 million each year” (Principles of Environmental Science, Pg.4)

However, there are various signs of hope for the future of our planet through study of environmental biology. As we constantly grow technologically, we are producing more waste material and pollution. Yet, through information and education we have been able to curb some of this destructive behavior. Some of which include conservation of forests and nature preserves, protection of marine resources, and renewable energy (e.g. wind, solar, and tidal energy). Most importantly, if we can limit the affluent lifestyles that the richer countries enjoy, we can greatly limit waste and pollutants. 

 “Indigenous people are guardians of much of the world’s biodiversity” (Principles of Environmental Science, Pg. 10) The key is to sustaining life for future generations is to find progressive ways to live off the land that are not detrimental to the land itself. Scientific methods and practices are key in discovering more of these important ways to shift our destructive lifestyles.

Chapter 2: Environmental Systems

Studying systems can show us many ways in which we can progressively live and maintain stability. Systems can show us the ways in which energy is transferred from one trophic level to another in a natural habitat, and how variables such as pollution can negatively affect these systems. 

Plants gain energy through the process of photosynthesis to which energy is produced for various other life forms. Through various food chains and trophic levels, this energy is passed from producers (plants) to primary consumers (herbavores), to secondary consumers (carnivores), to tertiary consumers (top carnivores). The waste from these species is then transferred into energy through a process of decomposition with detritivores (e.g. beetles and ants); and thus the cycle repeats itself to sustain ecosystems.

“If we consider organisms according to trophic levels, they often form a pyramid, with a broad base of primary producers and only a few individuals in the highest trophic levels” (Principles of Environmental Science, Pg. 40)

Each trophic level relies on the others to sustain itself and transfer energy accordingly, thus, if any part of the pyramid is disrupted, the entire pyramid may be affected greatly. For example, if a large population of rabbits drink from a toxic water source and develop and disease which kills them off, each higher trophic level will be limited of its energy source, while lower levels may become overpopulated. This, in turn, will negatively disrupt the environment, and in extreme cases, could lead to unlivable conditions; leading to extinction in the most severe case. There are many variables to which we as humans can help to decrease the possibility of this.

Chapter 5: Biomes and Biodiversity

The number and variety of species (biodiversity) is directly affected by biomes, which are described as the "characteristic types of biological communities that occur under different conditions of temperature and precipitation" (Chapter5 Lecture). Once we are able to study and understand biomes, we are able to come to a broader understanding of the types of the habitat in general, as well as, the kinds of organisms that are likely to occupy this habitat.

Each varying ecosystem's attributes define the ways in which organisms adapt and function within it's habitat. Biodiversity is the central theme regardless of the habitat. Whether it be marine environments or temperate grasslands, biodiversity keeps the habitat functional and the cycle of life present.

Disrupting and potentially destruction is the main threat amongst biodiversity and ecosystems. Human impact plays a major role in the destruction of various habitats, forcing organisms to adapt to their new environment, face extinction, or search for a nearby livable ecosystem. Through pollution, hunting, and other problems brought by humans to various ecosystems, the invasive inhabitants face many of these risk factors.

Various ways to help prevent such habitat destruction have since been introduced. Some of these include endangered species protection and hunting regulations. With these efforts and more study and action, we may be able to sustain invasive life within many of these natural habitats.

Chapter 3: Evolution, Species interaction, and Biological Communities

Interaction between species in a habitat is what essentially shapes the biological community. Species also adapt and evolve to protect themselves from predators. In order for a species to greater its population size it must adapt in order to avoid predators at all cost. Through varying physical adaptations, species have found ways to effectively sustain themselves and grow as a species.

Animals and plants live within an certain varying ecosystems because it is where they have learned to evolve and adapt in order to live and survive amongst that ecosystem. You would never see an African elephant in arctic conditions because they simply do not have the natural ability to survive in such an ecosystem. Animals are limited to where they can live due to "physiological stress due to inappropriate levels of some critical environmental factor, competition with other species, predation, and luck" (Principles of Environmental Science, Pg. 53). Species, through evolution, will adapt greatly to tolerate their habitat to the best of their abilities.

Predator/Prey Lab

Introduction



The objective of this experiment is to discover the connection between a predator and it's primary prey in a mock habitat. We will attempt to understand better how the populations of each affect one-another directly.

Hypothesis

I believe that as the rabbit population grows, the lynx population will as well. I believe that if the lynx population grows too large, it will have the potential to wipe out the rabbits completely. My reasoning for this is that with a growing rabbit population, the lynx will have a much more expansive food source. This will lead to a much larger lynx population, which could be highly detrimental to the rabbits' growth.

Procedure

I used 300 1" rabbit cut-outs to represent the rabbit population and 1 3" lynx cut-out to account for the lynx population. The habitat takes place in a 12" square that I marked with tape.

For generation 1, I began by population the habitat with three rabbits (spaced out evenly within the 12 inch square) and one lynx. The lynx has one opportunity to "capture" (land on top of after tossing into habitat) three or more rabbits in order to survive, as well as, create 1 lynx offspring leading into the next generation.


At this early stage it's nearly impossible for the lynx to survive, thus, another lynx will replace it for the next generation. Also, the rabbit population will double by the amount of survived rabbits for the next generation. Thus, generation 2 will include 6 rabbits evenly spaced and 1 lynx. The lynx will still struggle, but now have a better opportunity of surviving a moving into the next generation with 1 offspring.

As generation 2 on the right shows, the lynx caught only 2 rabbit, meaning that it will not survive. Generation 3, then, will include 1 lynx, and 8 rabbit (number of rabbit survived doubled).

For every 3 rabbits that a lynx "catches" it will survive and create 1 offspring (if it catches 6 it will survive and create 2 offspring). Each lynx will account for 1 toss into the habitat. This process will continue for about 18 to 20 generations and will be documented on a spreadsheet to show a rise in both populations and how they affect each other.

Results

Predator-prey Simulation Data
Generation of Rabbits	Number of Lynx	Number of Rabbits	Rabbits Eaten (Total)	Rabbits Remaining	Lynx Starved	Lynx Surviving
1	1	3	0	3	1	0
2	1	6	2	4	1	0
3	1	8	1	7	1	0
4	1	14	3	11	0	1
5	2	22	4	18	2	0
6	1	36	5	31	0	1
7	2	62	10	52	0	2
8	5	104	35	69	0	5
9	15	138	89	49	2	13
10	36	98	98	0	23	13
11	39	3	3	0	39	0
12	1	3	0	3	1	0
13	1	6	2	4	1	0
14	1	8	2	6	1	0
15	1	12	3	9	0	1
16	2	18	5	13	1	1
17	2	26	7	19	0	2
18	4	38	16	22	0	4
19	9	44	31	13	2	7
20	14	26	23	3	10	14

The spreadsheet above looks slightly confusing, but the number to the bottom right of the above title displays the accurate information. As you can see, as the population of rabbits increases, so does the lynx population. This eventually accounts for too many lynx which greatly decreases the rabbit population and, thus, greatly decreases the lynx population. The cycle then repeats.

Once I got to generation 9 (pictured above), I had the largest amount of rabbits, as well as, the largest amount of lynx. The picture on the left is the beginning of generation 9, while the right shows the end of generation 9. As you can see, a large rabbit population coupled with a large lynx population is highly detrimental to the rabbit population.

In the following generations, there simply weren't enough rabbits for lynx, which became highly detrimental to the lynx population. This caused for a crash in the food cycle and eventually brought us back to the beginning of the cycle.

Questions:

What sort of variables could subject a natural population to pressure or disturbance?

There is potential for various separate variables that could take place which would directly affect the natural population. Some of these may include: Introduction of a foreign species which may prey on rabbits and limit the food source for the lynx, introduction of a foreign species which may prey on lynx and cause for overpopulation of rabbits, destruction of habitat (e.g. expanding agriculture, drainage, etc.) which may cause the species to adapt differently or move elsewhere, pollution of water or elsewhere which may infect and decrease population of either species, disease which may decrease either species, natural disaster which could wipe out both species.

What might be the outcome if the lynx was exterminated?

If the lynx were exterminated, the rabbit population would grow immensely. This could potentially lead to overgrazing and become detrimental to the rabbit population due to lack of food source per the high rabbit population. This would also greatly affect the organism at the trophic level below the rabbit.

What patterns did you observe? Describe any evident lag times.

The most clear observation, as shown in the spreadsheet, is that it takes about 4 or 5 generations for the rabbit population to grow large enough to sustain the lynx population. At this time it only takes about 3 or 4 generations for the lynx population to grow too large to sustain itself. The most evident lag times are between 1 and 4 or 5 generations. The cycle repeats after about 10 generations.

Conclusion


This experiment accurately shows how separate organisms in the food chain directly affect one another. A high population of prey accounts for a high population of predators, yet, too high of a predator population will kill of the prey population and eventually cause for killing off its own population. It is a great representation of a food chain cycle and how top trophic levels rely on lower levels to survive, while lower levels need the higher level in order to not over-populate.