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Are there laws in ecology?

Are there laws in ecology?



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Are there clearly defined ecological laws, as in the science of physics? If not, why is this the case?


What is law and what is ecology?

I always find the definition of "law" a little hard to grasp but maybe only because I am a mediocre philosopher. To me, I don't quite understand the difference between a theory (a theory is not a hypothesis in science) and a law.

It is also hard to know what exactly you would consider being part of ecology and what you would be considered part of evolutionary biology, agriculture or paleoecology / paleogeology and those disciplines are very much related. Here are a few concepts that I don't if they would qualify for an answer

  • General latitudinal diversity gradient
  • The concept that symbiosis is more a rule than an exception (it also comes with the discovery that mitochondria are/were endosymbionts).
  • Theory of natural selection
  • Positive and negative feedbacks in glacial period
  • Geographical area law/hypothesis
  • Parental effects
  • Adaptive radiation
  • r/K selection theory
  • Theory of island biogeography

Are there science that create more laws than others?

I am really not qualified to answer this question but I would tend to think that in ecology, there is a lot of important discoveries that lead to a conceptual rephrase or to a reconsideration of the relative importance of different concept or to the realization of a single fact, more than to the phrasing of a law per say.

Laws in ecology

Here are a few concepts in ecology that are often being called law.

  • Liebig law of the minimum
  • Ten percent law
  • Allee effect law
  • Square-cube law, allometric scaling and the metabolic theory of ecology
  • Ecological systems theory

as well as all the laws regarding population growth such as

  • Malthusian, Verhulst and Lotka-Voltera laws.

Barry Commoner

Barry Commoner (May 28, 1917 – September 30, 2012) was an American cellular biologist, college professor, and politician. He was a leading ecologist and among the founders of the modern environmental movement. He was the director of the Center for Biology of Natural Systems [1] [2] and its Critical Genetics Project. [3] [4] [5] He ran as the Citizens Party candidate in the 1980 U.S. presidential election. [6] His work studying the radioactive fallout from nuclear weapons testing led to the Nuclear Test Ban Treaty of 1963. [7]


Research

Browse sites related to your topic, jot down information you think will be important to include in your final product. You may wish to assign individual group members specific tasks.

As you browse the sites related to your topic, think about the following questions that you will need to include in your final project presentation:

  • What is the problem? How do we know there is a problem (what evidence is there)?
  • What causes the problem?
  • What are the possible future effects of the problem? How will it effect the world?
  • What is being done to solve the problem? Are there laws related to the topic?
  • What can an individual do to help?

4 Laws of Ecology: Revisited

I undertook the task earlier this week of reviewing references for our upcoming RESTORE working group publication . One of those references was to Barry Commoner’s popular quote and definition on ecology, that the first law of ecology is that everything is connected.

This lead me to pick up a copy and re-read deeper into Commoner’s 1971 The Closing Circle and revisit the Four Laws of Ecology. The Closing Circle describes the ecosphere, how it has been damaged, and the economic, social, and political systems which have created our environmental crises. It gives us a clear and concise understanding of what ecology means that is evermore relevant today.

And timely, Commoner’s second law – everything must go somewhere – resonates with a comment I gave to our local Lancashire Evening Post on plastic pollution. (We need to We need to be critically questioning single use plastics and acutely aware of plastics impact on health and the environment – and be aware of what happens when we throw plastic away – as really, there is no ‘away’)

The First Law of Ecology: Everything Is Connected to Everything Else. There is one ecosphere for all living organisms and what affects one, affects all. “When we try to pick out anything by itself, we find it hitched to everything else in the universe.” John Muir

The Second Law of Ecology: Everything Must go Somewhere. There is no “waste” in nature and there is no “away” to which things can be thrown. Any waste produced in one ecological process is recycled in another. A core principle for the Circular Economy.

The Third Law of Ecology: Nature Knows Best. Humankind has fashioned technology to improve upon nature, but any human change in a natural system is, says Commoner, “likely to be detrimental to that system” And in the context of chemicals of concern we are looking to eradicate from buildings (through eg the ILFI Red List) “The absence of a particular substance in nature, is often a sign that it is incompatible with the chemistry of life”

The Fourth Law of Ecology: There Is No Such Thing as a Free Lunch. Exploitation of nature, will always carry an ecological cost and will inevitably involve the conversion of resources from useful to useless.

The four laws warn that every gain is won at some cost. Because our global ecosystem is a connected whole, any impact, anything extracted from nature by human effort must be replaced. There is no avoidance of this price and delay only creates the ecological disruption and biodiversity loss we are witnessing.

This reinforces statements I make so often in presentations (see Specifi Edinburgh and RESTORE Budapest for example) and within FutuREstorative, that sustainability is the point at which we start to give back more than we take, and that we no longer have the luxury to just reduce our impact but we have delayed too long to do more good to rebalance the ecosystem equilibrium.


46.1 Ecology of Ecosystems

By the end of this section, you will be able to do the following:

  • Describe the basic ecosystem types
  • Explain the methods that ecologists use to study ecosystem structure and dynamics
  • Identify the different methods of ecosystem modeling
  • Differentiate between food chains and food webs and recognize the importance of each

Life in an ecosystem is often about competition for limited resources, a characteristic of the theory of natural selection. Competition in communities (all living things within specific habitats) is observed both within species and among different species. The resources for which organisms compete include organic material, sunlight, and mineral nutrients, which provide the energy for living processes and the matter to make up organisms’ physical structures. Other critical factors influencing community dynamics are the components of its physical and geographic environment: a habitat’s latitude, amount of rainfall, topography (elevation), and available species. These are all important environmental variables that determine which organisms can exist within a particular area.

An ecosystem is a community of living organisms and their interactions with their abiotic (nonliving) environment. Ecosystems can be small, such as the tide pools found near the rocky shores of many oceans, or large, such as the Amazon Rainforest in Brazil (Figure 46.2).

There are three broad categories of ecosystems based on their general environment: freshwater, ocean water, and terrestrial. Within these broad categories are individual ecosystem types based on the organisms present and the type of environmental habitat.

Ocean ecosystems are the most common, comprising over 70 percent of the Earth's surface and consisting of three basic types: shallow ocean, deep ocean water, and deep ocean surfaces (the low depth areas of the deep oceans). The shallow ocean ecosystems include extremely biodiverse coral reef ecosystems, and the deep ocean surface is known for its large numbers of plankton and krill (small crustaceans) that support it. These two environments are especially important to aerobic respirators worldwide as the phytoplankton perform 40 percent of all photosynthesis on Earth. Although not as diverse as the other two, deep ocean ecosystems contain a wide variety of marine organisms. Such ecosystems exist even at the bottom of the ocean where light is unable to penetrate through the water.

Freshwater ecosystems are the rarest, occurring on only 1.8 percent of the Earth's surface. Lakes, rivers, streams, and springs comprise these systems. They are quite diverse, and they support a variety of fish, amphibians, reptiles, insects, phytoplankton, fungi, and bacteria.

Terrestrial ecosystems, also known for their diversity, are grouped into large categories called biomes, such as tropical rain forests, savannas, deserts, coniferous forests, deciduous forests, and tundra. Grouping these ecosystems into just a few biome categories obscures the great diversity of the individual ecosystems within them. For example, there is great variation in desert vegetation: the saguaro cacti and other plant life in the Sonoran Desert, in the United States, are relatively abundant compared to the desolate rocky desert of Boa Vista, an island off the coast of Western Africa (Figure 46.3).

Ecosystems are complex with many interacting parts. They are routinely exposed to various disturbances, or changes in the environment that effect their compositions: yearly variations in rainfall and temperature and the slower processes of plant growth, which may take several years. Many of these disturbances result from natural processes. For example, when lightning causes a forest fire and destroys part of a forest ecosystem, the ground is eventually populated by grasses, then by bushes and shrubs, and later by mature trees, restoring the forest to its former state. The impact of environmental disturbances caused by human activities is as important as the changes wrought by natural processes. Human agricultural practices, air pollution, acid rain, global deforestation, overfishing, eutrophication, oil spills, and waste dumping on land and into the ocean are all issues of concern to conservationists.

Equilibrium is the steady state of an ecosystem where all organisms are in balance with their environment and with each other. In ecology, two parameters are used to measure changes in ecosystems: resistance and resilience. Resistance is the ability of an ecosystem to remain at equilibrium in spite of disturbances. Resilience is the speed at which an ecosystem recovers equilibrium after being disturbed. Ecosystem resistance and resilience are especially important when considering human impact. The nature of an ecosystem may change to such a degree that it can lose its resilience entirely. This process can lead to the complete destruction or irreversible altering of the ecosystem.

Food Chains and Food Webs

The term “food chain” is sometimes used metaphorically to describe human social situations. Individuals who are considered successful are seen as being at the top of the food chain, consuming all others for their benefit, whereas the less successful are seen as being at the bottom.

The scientific understanding of a food chain is more precise than in its everyday usage. In ecology, a food chain is a linear sequence of organisms through which nutrients and energy pass: primary producers, primary consumers, and higher-level consumers are used to describe ecosystem structure and dynamics. There is a single path through the chain. Each organism in a food chain occupies what is called a trophic level . Depending on their role as producers or consumers, species or groups of species can be assigned to various trophic levels.

In many ecosystems, the bottom of the food chain consists of photosynthetic organisms (plants and/or phytoplankton), which are called primary producers . The organisms that consume the primary producers are herbivores: the primary consumers . Secondary consumers are usually carnivores that eat the primary consumers. Tertiary consumers are carnivores that eat other carnivores. Higher-level consumers feed on the next lower tropic levels, and so on, up to the organisms at the top of the food chain: the apex consumers . In the Lake Ontario food chain shown in Figure 46.4, the Chinook salmon is the apex consumer at the top of this food chain.

One major factor that limits the length of food chains is energy. Energy is lost as heat between each trophic level due to the second law of thermodynamics. Thus, after a limited number of trophic energy transfers, the amount of energy remaining in the food chain may not be great enough to support viable populations at yet a higher trophic level.

The loss of energy between trophic levels is illustrated by the pioneering studies of Howard T. Odum in the Silver Springs, Florida, ecosystem in the 1940s (Figure 46.5). The primary producers generated 20,819 kcal/m 2 /yr (kilocalories per square meter per year), the primary consumers generated 3368 kcal/m 2 /yr, the secondary consumers generated 383 kcal/m 2 /yr, and the tertiary consumers only generated 21 kcal/m 2 /yr. Thus, there is little energy remaining for another level of consumers in this ecosystem.

There is a one problem when using food chains to accurately describe most ecosystems. Even when all organisms are grouped into appropriate trophic levels, some of these organisms can feed on species from more than one trophic level likewise, some of these organisms can be eaten by species from multiple trophic levels. In other words, the linear model of ecosystems, the food chain, is not completely descriptive of ecosystem structure. A holistic model—which accounts for all the interactions between different species and their complex interconnected relationships with each other and with the environment—is a more accurate and descriptive model for ecosystems. A food web is a graphic representation of a holistic, nonlinear web of primary producers, primary consumers, and higher-level consumers used to describe ecosystem structure and dynamics (Figure 46.6).

A comparison of the two types of structural ecosystem models shows strength in both. Food chains are more flexible for analytical modeling, are easier to follow, and are easier to experiment with, whereas food web models more accurately represent ecosystem structure and dynamics, and data can be directly used as input for simulation modeling.

Link to Learning

Head to this online interactive simulator to investigate food web function. In the Interactive Labs box, under Food Web, click Step 1. Read the instructions first, and then click Step 2 for additional instructions. When you are ready to create a simulation, in the upper-right corner of the Interactive Labs box, click OPEN SIMULATOR.

Two general types of food webs are often shown interacting within a single ecosystem. A grazing food web (such as the Lake Ontario food web in Figure 46.6) has plants or other photosynthetic organisms at its base, followed by herbivores and various carnivores. A detrital food web consists of a base of organisms that feed on decaying organic matter (dead organisms), called decomposers or detritivores. These organisms are usually bacteria or fungi that recycle organic material back into the biotic part of the ecosystem as they themselves are consumed by other organisms. As all ecosystems require a method to recycle material from dead organisms, most grazing food webs have an associated detrital food web. For example, in a meadow ecosystem, plants may support a grazing food web of different organisms, primary and other levels of consumers, while at the same time supporting a detrital food web of bacteria, fungi, and detrivorous invertebrates feeding off dead plants and animals.

Evolution Connection

Three-spined Stickleback

It is well established by the theory of natural selection that changes in the environment play a major role in the evolution of species within an ecosystem. However, little is known about how the evolution of species within an ecosystem can alter the ecosystem environment. In 2009, Dr. Luke Harmon, from the University of Idaho, published a paper that for the first time showed that the evolution of organisms into subspecies can have direct effects on their ecosystem environment. 1

The three-spined stickleback (Gasterosteus aculeatus) is a freshwater fish that evolved from a saltwater fish to live in freshwater lakes about 10,000 years ago, which is considered a recent development in evolutionary time (Figure 46.7). Over the last 10,000 years, these freshwater fish then became isolated from each other in different lakes. Depending on which lake population was studied, findings showed that these sticklebacks then either remained as one species or evolved into two species. The divergence of species was made possible by their use of different areas of the pond for feeding called micro niches.

Dr. Harmon and his team created artificial pond microcosms in 250-gallon tanks and added muck from freshwater ponds as a source of zooplankton and other invertebrates to sustain the fish. In different experimental tanks they introduced one species of stickleback from either a single-species or double-species lake.

Over time, the team observed that some of the tanks bloomed with algae while others did not. This puzzled the scientists, and they decided to measure the water's dissolved organic carbon (DOC), which consists of mostly large molecules of decaying organic matter that give pond-water its slightly brownish color. It turned out that the water from the tanks with two-species fish contained larger particles of DOC (and hence darker water) than water with single-species fish. This increase in DOC blocked the sunlight and prevented algal blooming. Conversely, the water from the single-species tank contained smaller DOC particles, allowing more sunlight penetration to fuel the algal blooms.

This change in the environment, which is due to the different feeding habits of the stickleback species in each lake type, probably has a great impact on the survival of other species in these ecosystems, especially other photosynthetic organisms. Thus, the study shows that, at least in these ecosystems, the environment and the evolution of populations have reciprocal effects that may now be factored into simulation models.

Research into Ecosystem Dynamics: Ecosystem Experimentation and Modeling

The study of the changes in ecosystem structure caused by changes in the environment (disturbances) or by internal forces is called ecosystem dynamics . Ecosystems are characterized using a variety of research methodologies. Some ecologists study ecosystems using controlled experimental systems, while some study entire ecosystems in their natural state, and others use both approaches.

A holistic ecosystem model attempts to quantify the composition, interaction, and dynamics of entire ecosystems it is the most representative of the ecosystem in its natural state. A food web is an example of a holistic ecosystem model. However, this type of study is limited by time and expense, as well as the fact that it is neither feasible nor ethical to do experiments on large natural ecosystems. It is difficult to quantify all different species in an ecosystem and the dynamics in their habitat, especially when studying large habitats such as the Amazon Rainforest.

For these reasons, scientists study ecosystems under more controlled conditions. Experimental systems usually involve either partitioning a part of a natural ecosystem that can be used for experiments, termed a mesocosm , or by recreating an ecosystem entirely in an indoor or outdoor laboratory environment, which is referred to as a microcosm . A major limitation to these approaches is that removing individual organisms from their natural ecosystem or altering a natural ecosystem through partitioning may change the dynamics of the ecosystem. These changes are often due to differences in species numbers and diversity and also to environment alterations caused by partitioning (mesocosm) or recreating (microcosm) the natural habitat. Thus, these types of experiments are not totally predictive of changes that would occur in the ecosystem from which they were gathered.

As both of these approaches have their limitations, some ecologists suggest that results from these experimental systems should be used only in conjunction with holistic ecosystem studies to obtain the most representative data about ecosystem structure, function, and dynamics.

Scientists use the data generated by these experimental studies to develop ecosystem models that demonstrate the structure and dynamics of ecosystems. They use three basic types of ecosystem modeling in research and ecosystem management: a conceptual model, an analytical model, and a simulation model. A conceptual model is an ecosystem model that consists of flow charts to show interactions of different compartments of the living and nonliving components of the ecosystem. A conceptual model describes ecosystem structure and dynamics and shows how environmental disturbances affect the ecosystem however, its ability to predict the effects of these disturbances is limited. Analytical and simulation models, in contrast, are mathematical methods of describing ecosystems that are indeed capable of predicting the effects of potential environmental changes without direct experimentation, although with some limitations as to accuracy. An analytical model is an ecosystem model that is created using simple mathematical formulas to predict the effects of environmental disturbances on ecosystem structure and dynamics. A simulation model is an ecosystem model that is created using complex computer algorithms to holistically model ecosystems and to predict the effects of environmental disturbances on ecosystem structure and dynamics. Ideally, these models are accurate enough to determine which components of the ecosystem are particularly sensitive to disturbances, and they can serve as a guide to ecosystem managers (such as conservation ecologists or fisheries biologists) in the practical maintenance of ecosystem health.

Conceptual Models

Conceptual models are useful for describing ecosystem structure and dynamics and for demonstrating the relationships between different organisms in a community and their environment. Conceptual models are usually depicted graphically as flow charts. The organisms and their resources are grouped into specific compartments with arrows showing the relationship and transfer of energy or nutrients between them. Thus, these diagrams are sometimes called compartment models.

To model the cycling of mineral nutrients, organic and inorganic nutrients are subdivided into those that are bioavailable (ready to be incorporated into biological macromolecules) and those that are not. For example, in a terrestrial ecosystem near a deposit of coal, carbon will be available to the plants of this ecosystem as carbon dioxide gas in a short-term period, not from the carbon-rich coal itself. However, over a longer period, microorganisms capable of digesting coal will incorporate its carbon or release it as natural gas (methane, CH4), changing this unavailable organic source into an available one. This conversion is greatly accelerated by the combustion of fossil fuels by humans, which releases large amounts of carbon dioxide into the atmosphere. This is thought to be a major factor in the rise of the atmospheric carbon dioxide levels in the industrial age. The carbon dioxide released from burning fossil fuels is produced faster than photosynthetic organisms can use it. This process is intensified by the reduction of photosynthetic trees because of worldwide deforestation. Most scientists agree that high atmospheric carbon dioxide is a major cause of global climate change.

Conceptual models are also used to show the flow of energy through particular ecosystems. Figure 46.8 is based on Howard T. Odum’s classical study of the Silver Springs, Florida, holistic ecosystem in the mid-twentieth century. 2 This study shows the energy content and transfer between various ecosystem compartments.

Visual Connection

Why do you think the value for gross productivity of the primary producers is the same as the value for total heat and respiration (20,810 kcal/m 2 /yr)?

Analytical and Simulation Models

The major limitation of conceptual models is their inability to predict the consequences of changes in ecosystem species and/or environment. Ecosystems are dynamic entities and subject to a variety of abiotic and biotic disturbances caused by natural forces and/or human activity. Ecosystems altered from their initial equilibrium state can often recover from such disturbances and return to a state of equilibrium. As most ecosystems are subject to periodic disturbances and are often in a state of change, they are usually either moving toward or away from their equilibrium state. There are many of these equilibrium states among the various components of an ecosystem, which affects the ecosystem overall. Furthermore, as humans have the ability to greatly and rapidly alter the species content and habitat of an ecosystem, the need for predictive models that enable understanding of how ecosystems respond to these changes becomes more crucial.

Analytical models often use simple, linear components of ecosystems, such as food chains, and are known to be complex mathematically therefore, they require a significant amount of mathematical knowledge and expertise. Although analytical models have great potential, their simplification of complex ecosystems is thought to limit their accuracy. Simulation models that use computer programs are better able to deal with the complexities of ecosystem structure.

A recent development in simulation modeling uses supercomputers to create and run individual-based simulations, which accounts for the behavior of individual organisms and their effects on the ecosystem as a whole. These simulations are considered to be the most accurate and predictive of the complex responses of ecosystems to disturbances.

Link to Learning

Visit The Darwin Project to view a variety of ecosystem models, including simulations that model predator-prey relationships to learn more.


Levels of Ecological Research

When a discipline such as biology is studied, it is often helpful to subdivide it into smaller, related areas. For instance, cell biologists interested in cell signaling need to understand the chemistry of the signal molecules (which are usually proteins) as well as the result of cell signaling. Ecologists interested in the factors that influence the survival of an endangered species might use mathematical models to predict how current conservation efforts affect endangered organisms. To produce a sound set of management options, a conservation biologist needs to collect accurate data, including current population size, factors affecting reproduction (like physiology and behavior), habitat requirements (such as plants and soils), and potential human influences on the endangered population and its habitat (which might be derived through studies in sociology and urban ecology). Within the discipline of ecology, researchers work at four specific levels, sometimes discretely and sometimes with overlap: organism, population, community, and ecosystem (Figure 2).

Figure 2. Ecologists study within several biological levels of organization. (credit “organisms”: modification of work by “Crystl”/Flickr credit “ecosystems”: modification of work by Tom Carlisle, US Fish and Wildlife Service Headquarters credit “biosphere”: NASA)

Organismal Ecology

Researchers studying ecology at the organismal level are interested in the adaptations that enable individuals to live in specific habitats. These adaptations can be morphological, physiological, and behavioral. For instance, the Karner blue butterfly (Lycaeides melissa samuelis) is a rare butterfly that lives only in open areas with few trees or shrubs, such as pine barrens and oak savannas. It is considered a specialist because the females preferentially oviposit (that is, lay eggs) on wild lupine (Figure 3). This preferential adaptation means that the Karner blue butterfly is highly dependent on the presence of wild lupine plants for its continued survival.

Figure 3. (a) The Karner blue butterfly (Lycaeides melissa samuelis). (b) The wild lupine (Lupinus perennis) is the host plant for the Karner blue butterfly (credit a: modification of work by J & K Hollingsworth, USFWS credit b: Joel Trick, USFWS)

After hatching, the larval caterpillars emerge and spend four to six weeks feeding solely on wild lupine. The caterpillars pupate (undergo metamorphosis) and emerge as butterflies after about four weeks. The adult butterflies feed on the nectar of flowers of wild lupine and other plant species. A researcher interested in studying Karner blue butterflies at the organismal level might, in addition to asking questions about egg laying, ask questions about the butterflies’ preferred temperature (a physiological question) or the behavior of the caterpillars when they are at different larval stages (a behavioral question).

Population Ecology

A population is a group of interbreeding organisms that are members of the same species living in the same area at the same time. (Organisms that are all members of the same species are called conspecifics.) A population is identified, in part, by where it lives, and its area of population may have natural or artificial boundaries: natural boundaries might be rivers, mountains, or deserts, while examples of artificial boundaries include mowed grass, manmade structures, or roads. The study of population ecology focuses on the number of individuals in an area and how and why population size changes over time. Population ecologists are particularly interested in counting the Karner blue butterfly, for example, because it is classified as federally endangered. However, the distribution and density of this species is highly influenced by the distribution and abundance of wild lupine. Researchers might ask questions about the factors leading to the decline of wild lupine and how these affect Karner blue butterflies. For example, ecologists know that wild lupine thrives in open areas where trees and shrubs are largely absent. In natural settings, intermittent wildfires regularly remove trees and shrubs, helping to maintain the open areas that wild lupine requires. Mathematical models can be used to understand how wildfire suppression by humans has led to the decline of this important plant for the Karner blue butterfly.

Community Ecology

A biological community consists of the different species within an area, typically a three-dimensional space, and the interactions within and among these species. Community ecologists are interested in the processes driving these interactions and their consequences. Questions about conspecific interactions often focus on competition among members of the same species for a limited resource. Ecologists also study interactions among various species members of different species are called heterospecifics. Examples of heterospecific interactions include predation, parasitism, herbivory, competition, and pollination. These interactions can have regulating effects on population sizes and can impact ecological and evolutionary processes affecting diversity.

For example, Karner blue butterfly larvae form mutualistic relationships with ants. Mutualism is a form of a long-term relationship that has coevolved between two species and from which each species benefits. For mutualism to exist between individual organisms, each species must receive some benefit from the other as a consequence of the relationship. Researchers have shown that there is an increase in the probability of survival when Karner blue butterfly larvae (caterpillars) are tended by ants. This might be because the larvae spend less time in each life stage when tended by ants, which provides an advantage for the larvae. Meanwhile, the Karner blue butterfly larvae secrete a carbohydrate-rich substance that is an important energy source for the ants. Both the Karner blue larvae and the ants benefit from their interaction.

Ecosystem Ecology

Ecosystem ecology is an extension of organismal, population, and community ecology. The ecosystem is composed of all the biotic components (living things) in an area along with the abiotic components (non-living things) of that area. Some of the abiotic components include air, water, and soil. Ecosystem biologists ask questions about how nutrients and energy are stored and how they move among organisms and the surrounding atmosphere, soil, and water.

The Karner blue butterflies and the wild lupine live in an oak-pine barren habitat. This habitat is characterized by natural disturbance and nutrient-poor soils that are low in nitrogen. The availability of nutrients is an important factor in the distribution of the plants that live in this habitat. Researchers interested in ecosystem ecology could ask questions about the importance of limited resources and the movement of resources, such as nutrients, though the biotic and abiotic portions of the ecosystem.

Watch this video for another introduction to ecology:

Dividing Ecological Study

Ecology can also be classified on the basis of:

  • the primary kinds of organism under study (e.g. animal ecology, plant ecology, insect ecology)
  • the biomes principally studied (e.g. forest ecology, grassland ecology, desert ecology, benthic ecology, marine ecology, urban ecology)
  • the geographic or climatic area (e.g. arctic ecology, tropical ecology)
  • the spatial scale under consideration (e.g. macroecology, landscape ecology)
  • the philosophical approach (e.g. systems ecology which adopts a holistic approach)
  • the methods used (e.g. molecular ecology)

Individual organisms can eat one another, compete for shared resources, and help each other survive. Each pair of species in an ecosystem can be characterized by the kind and strength of these interactions, measured as their contribution to dN/dt.

The abundance of a population is influenced by the chains of interactions that connect it to the other species in its ecosystem. This often leads to complex behavior, and a key challenge in ecology is to determine what patterns of abundance and diversity can be predicted.


14 Career Paths for a Biology Major That Don’t Require Med School

There are plenty of professions out there for those who’ve studied living organisms and aren’t interested in pursuing a career as a doctor.

By Hannah Docter-Loeb, Wesleyan University

Thoughts x August 25, 2020

14 Career Paths for a Biology Major That Don’t Require Med School

There are plenty of professions out there for those who’ve studied living organisms and aren’t interested in pursuing a career as a doctor.

By Hannah Docter-Loeb, Wesleyan University

As a biology major, I am constantly asked if I am on the med school track, or “pre-med” as it’s colloquially known. While I have no intention to go to med school­ –– and yes I know if I did my name would be Dr. Docter-Loeb –– I feel like there’s an expectation for biology majors to attend. However, there are countless other ways to put a biology degree to good use, many of which don’t require anything past a bachelor’s degree.

1. Biologist

Enjoy the lab and the hands-on parts of the biology major? Biologists do all that as a career. A crucial part of scientific advancement, biologists spend their days performing experiments and gathering data to try and understand the underlying mechanisms of biological systems. They can specialize in anything from microbiology to zoology, depending on their interests.

2. Nonprofit work

Nonprofits can also be a great place for those with a degree in biology. From the Innocence Project, an advocacy group that uses DNA evidence to exonerate the wrongfully convicted, to Scientista, a foundation devoted to encouraging and supporting women interested in STEM, there are many options for those interested in using their biology knowledge in the nonprofit sector. Idealist.org is a great resource for browsing nonprofits, as you can indicate your area of interest with the search function.

3. Genetic Counselor

Genetic counselors interpret family and medical histories to advise clients on the risk of disease or genetic disorders. They are often consulted before conception to determine, based on the parent’s genetic makeup, whether or not their offspring will be healthy. Genetic counselors are required to have a solid understanding of biology, specifically genetics, so that they understand the genetic contributions to disease and disorders.

4. Health Communications Specialist

For anyone torn between a career in public relations and biology, health communications may be a good compromise. A health communications specialist’s job is to inform the general public of health issues. While a background in biology is not required, it can be helpful in educating populations on the effects of health concerns such as communicable diseases.

5. Health Educator

6. Pharmaceutical Sales Representatives

At the intersection of business and biology lies the pharmaceutical industry. An important part of the industry, pharmaceutical sales reps are charged with selling medical supplies, medical technology and medicines to hospitals, clinics and other medical practices. Biology majors make great sales reps, as they are able to understand the fundamental elements of products and explain them thoroughly to potential buyers.

7. Biomedical Engineer

Biomedical engineering (BME) is a multidisciplinary field that combines engineering and biology. Deemed by Forbes to be one of the “Highest Paying, Low-Stress STEM Job You Probably Haven’t Considered,” biomedical engineers apply engineering principles to biology and medicine, usually for health care purposes. Although BME specifically requires a degree in biomedical engineering, a biology bachelor’s degree can be a good stepping stone to a master’s or doctorate in the field.

8. Medical Lab Technician

An entry-level job for biology majors, medical lab technicians work in hospitals, medical and diagnostic laboratories or doctor’s offices and are tasked with preparing lab tests and collecting patient samples. People are always looking for lab technicians in fact, the Bureau of Labor Statistics expects the employment of clinical laboratory technologists and technicians to grow 11 % from 2018 to 2028 — much faster than the average for all other occupations.

9. Lawyer

Many different law sectors look for lawyers with backgrounds in biology. There’s patent law, where attorneys represent clients looking to obtain patents, and often require lawyers with a bachelor’s degree in a technical subject such as biology. A background in biology can also be helpful in environmental law in understanding the ecological and human health impacts of pollution and construction projects (such as dams, buildings, etc.). There’s also the option of becoming a medical malpractice lawyer, who use biological knowledge and evidence to prosecute health professionals for unethical treatment or malpractice.

10. Writer

If you lack the oral communication skills recommended for many of the aforementioned jobs, perhaps scientific writing is for you. Whether it’s using your biological knowledge to compose the next science fiction sensation, or writing and editing articles for a scientific journal ­­–– a career that is actually called “Science Writer” –– there is always room for scientific writing.

11. Park Ranger

Use your biology knowledge in the great outdoors! Park rangers are responsible for protecting and preserving parklands at the local, state and national levels. Rangers are also responsible for educating the public on the history and ecology of parks. Biology backgrounds, specifically in ecology, are thus encouraged.

12. Emergency Medical Technician

Emergency medical technicians, known by the acronym EMT, provide emergency medical services to those in need. To become an EMT, you don’t need to go to med school however, you must be formally trained and certified. As one would imagine from a job that works directly with humans, a solid foundation in human biology, anatomy and physiology is required.

13. Forensic scientist

Are you a biology major and crime show junkie? Then forensic science may be for you. Forensic scientists use techniques, such as DNA profiling and fingerprint analysis, to examine evidence. This evidence is often collected from crime scenes and can be used to help convict, or exonerate, the accused.

14. Biology Teacher or Professor

While I’m biased in that this is what I’m interested in pursuing as a career, I truly think one of the best things you can do with biology knowledge is to share it with others through teaching. Whether you’re teaching at the high school or university level, there is always a demand for good biology teachers. The experience can be extremely impactful and rewarding, as you have the opportunity to instill an excitement for biology in a younger generation.


29 The Laws of Thermodynamics

By the end of this section, you will be able to do the following:

Thermodynamics refers to the study of energy and energy transfer involving physical matter. The matter and its environment relevant to a particular case of energy transfer are classified as a system, and everything outside that system is the surroundings. For instance, when heating a pot of water on the stove, the system includes the stove, the pot, and the water. Energy transfers within the system (between the stove, pot, and water). There are two types of systems: open and closed. An open system is one in which energy can transfer between the system and its surroundings. The stovetop system is open because it can lose heat into the air. A closed system is one that cannot transfer energy to its surroundings.

Biological organisms are open systems. Energy exchanges between them and their surroundings, as they consume energy-storing molecules and release energy to the environment by doing work. Like all things in the physical world, energy is subject to the laws of physics. The laws of thermodynamics govern the transfer of energy in and among all systems in the universe.

The First Law of Thermodynamics

The first law of thermodynamics deals with the total amount of energy in the universe. It states that this total amount of energy is constant. In other words, there has always been, and always will be, exactly the same amount of energy in the universe. Energy exists in many different forms. According to the first law of thermodynamics, energy may transfer from place to place or transform into different forms, but it cannot be created or destroyed. The transfers and transformations of energy take place around us all the time. Light bulbs transform electrical energy into light energy. Gas stoves transform chemical energy from natural gas into heat energy. Plants perform one of the most biologically useful energy transformations on earth: that of converting sunlight energy into the chemical energy stored within organic molecules ((Figure)). (Figure) examples of energy transformations.

The challenge for all living organisms is to obtain energy from their surroundings in forms that they can transfer or transform into usable energy to do work. Living cells have evolved to meet this challenge very well. Chemical energy stored within organic molecules such as sugars and fats transforms through a series of cellular chemical reactions into energy within ATP molecules. Energy in ATP molecules is easily accessible to do work. Examples of the types of work that cells need to do include building complex molecules, transporting materials, powering the beating motion of cilia or flagella, contracting muscle fibers to create movement, and reproduction.


The Second Law of Thermodynamics

A living cell’s primary tasks of obtaining, transforming, and using energy to do work may seem simple. However, the second law of thermodynamics explains why these tasks are harder than they appear. None of the energy transfers that we have discussed, along with all energy transfers and transformations in the universe, is completely efficient. In every energy transfer, some amount of energy is lost in a form that is unusable. In most cases, this form is heat energy. Thermodynamically, scientists define heat energy as energy that transfers from one system to another that is not doing work. For example, when an airplane flies through the air, it loses some of its energy as heat energy due to friction with the surrounding air. This friction actually heats the air by temporarily increasing air molecule speed. Likewise, some energy is lost as heat energy during cellular metabolic reactions. This is good for warm-blooded creatures like us, because heat energy helps to maintain our body temperature. Strictly speaking, no energy transfer is completely efficient, because some energy is lost in an unusable form.

An important concept in physical systems is that of order and disorder (or randomness). The more energy that a system loses to its surroundings, the less ordered and more random the system. Scientists refer to the measure of randomness or disorder within a system as entropy . High entropy means high disorder and low energy ((Figure)). To better understand entropy, think of a student’s bedroom. If no energy or work were put into it, the room would quickly become messy. It would exist in a very disordered state, one of high entropy. Energy must be put into the system, in the form of the student doing work and putting everything away, in order to bring the room back to a state of cleanliness and order. This state is one of low entropy. Similarly, a car or house must be constantly maintained with work in order to keep it in an ordered state. Left alone, a house’s or car’s entropy gradually increases through rust and degradation. Molecules and chemical reactions have varying amounts of entropy as well. For example, as chemical reactions reach a state of equilibrium, entropy increases, and as molecules at a high concentration in one place diffuse and spread out, entropy also increases.

Transfer of Energy and the Resulting Entropy Set up a simple experiment to understand how energy transfers and how a change in entropy results.

  1. Take a block of ice. This is water in solid form, so it has a high structural order. This means that the molecules cannot move very much and are in a fixed position. The ice’s temperature is 0°C. As a result, the system’s entropy is low.
  2. Allow the ice to melt at room temperature. What is the state of molecules in the liquid water now? How did the energy transfer take place? Is the system’s entropy higher or lower? Why?
  3. Heat the water to its boiling point. What happens to the system’s entropy when the water is heated?

Think of all physical systems of in this way: Living things are highly ordered, requiring constant energy input to maintain themselves in a state of low entropy. As living systems take in energy-storing molecules and transform them through chemical reactions, they lose some amount of usable energy in the process, because no reaction is completely efficient. They also produce waste and by-products that are not useful energy sources. This process increases the entropy of the system’s surroundings. Since all energy transfers result in losing some usable energy, the second law of thermodynamics states that every energy transfer or transformation increases the universe’s entropy. Even though living things are highly ordered and maintain a state of low entropy, the universe’s entropy in total is constantly increasing due to losing usable energy with each energy transfer that occurs. Essentially, living things are in a continuous uphill battle against this constant increase in universal entropy.


Section Summary

In studying energy, scientists use the term “system” to refer to the matter and its environment involved in energy transfers. Everything outside of the system is the surroundings. Single cells are biological systems. We can think of systems as having a certain amount of order. It takes energy to make a system more ordered. The more ordered a system, the lower its entropy. Entropy is a measure of a system’s disorder. As a system becomes more disordered, the lower its energy and the higher its entropy.

The laws of thermodynamics are a series of laws that describe the properties and processes of energy transfer. The first law states that the total amount of energy in the universe is constant. This means that energy cannot be created or destroyed, only transferred or transformed. The second law of thermodynamics states that every energy transfer involves some loss of energy in an unusable form, such as heat energy, resulting in a more disordered system. In other words, no energy transfer is completely efficient, and all transfers trend toward disorder.

Review Questions

Which of the following is not an example of an energy transformation?

  1. turning on a light switch
  2. solar panels at work
  3. formation of static electricity
  4. none of the above

In each of the three systems, determine the state of entropy (low or high) when comparing the first and second: i. the instant that a perfume bottle is sprayed compared with 30 seconds later, ii. an old 1950s car compared with a brand new car, and iii. a living cell compared with a dead cell.

  1. i. low, ii. high, iii. low
  2. i. low, ii. high, iii. high
  3. i. high, ii. low, iii. high
  4. i. high, ii. low, iii. low

Critical Thinking Questions

Imagine an elaborate ant farm with tunnels and passageways through the sand where ants live in a large community. Now imagine that an earthquake shook the ground and demolished the ant farm. In which of these two scenarios, before or after the earthquake, was the ant farm system in a state of higher or lower entropy?

The ant farm had lower entropy before the earthquake because it was a highly ordered system. After the earthquake, the system became much more disordered and had higher entropy.

Energy transfers take place constantly in everyday activities. Think of two scenarios: cooking on a stove and driving. Explain how the second law of thermodynamics applies to these two scenarios.

While cooking, food is heating up on the stove, but not all of the heat goes to cooking the food, some of it is lost as heat energy to the surrounding air, increasing entropy. While driving, cars burn gasoline to run the engine and move the car. This reaction is not completely efficient, as some energy during this process is lost as heat energy, which is why the hood and the components underneath it heat up while the engine is turned on. The tires also heat up because of friction with the pavement, which is additional energy loss. This energy transfer, like all others, also increases entropy.

Glossary


Frequently Asked Questions

At the time of application to Duke, students choose to apply either to Duke's Trinity College of Arts and Sciences or the Pratt School of Engineering. All students matriculating into Trinity College begin as undeclared with regards to major and can freely select from among all of Duke's available majors, including Biology, when they declare their major (usually in the 4th semester).

Admissions at Duke is handled by a centralized Undergraduate Admissions Office, and academic departments such as Biology do not have a role in that process. Visit the Admissions Office website for tips on preparing for the college admissions process, characteristics they seek in applicants, how the process works, transferring to Duke from another institution, and more. Questions pertaining specifically to Admissions are best directed there. Please note that students who have already earned a Bachelor's degree are not eligible to also receive a Bachelor's degree from Duke.

What kind of Biology degrees are available at Duke?

Duke offers several programs in the biological sciences. Most students will pursue the BS degree with a Biology major. This program requires two ‘gateway’ courses in molecular biology, genetics and evolution, or a one semester 'gateway' with AP Biology 5, as well as introductory courses in chemistry, math and physics. It also requires at least eight or nine upper-level courses in the biological sciences (depending on gateway sequence). Three of those courses will involve exposure to essential areas in biology: organismal diversity, biological structure and function, and ecology. The other five or six courses (depending on gateway sequence) will be 'electives', allowing for advanced courses in whatever you're most interested in. So, although we do not have separate majors in specialties like molecular biology or botany or marine biology, it is possible to complete a biology major that 'concentrates' on these or many other areas.

In addition to the Biology major, Duke also has related majors in Neuroscience, Evolutionary Anthropology (primatology and human origins), Chemistry (with a biochemistry focus), Environmental Science and Policy, and Biomedical Engineering, as well as minors an certificates in Genome Sciences and Global Health. And it's certainly possible to use courses from these other programs to count towards a Biology degree.

What is the difference between a Bachelor of Arts in biology and a Bachelor of Science?

The Bachelor of Arts (A.B.) in Biology is the liberal arts major program, appropriate for students planning a career in law, policy, or secondary school teaching. It requires math and chemistry only through Calculus I and introductory chemistry.

The Bachelor of Science (B.S.) in Biology is the degree recommended for students contemplating a career in biological or biomedical sciences. The B.S. degree requires either Calculus II or statistics, organic chemistry, and physics corequisites.

Can I specialize my studies in biology?

Yes. As part of the Biology major, students may elect to complete requirements in specified sub-disciplines in the biological sciences. Currently available areas of concentration in the biology major are: anatomy, physiology and biomechanics, animal behavior, biochemistry, cell and molecular biology, evolutionary biology, genetics, genomics, marine biology, neurobiology, pharmacology, and plant biology. Completion of concentration requirements will result in a note on the student's transcript at graduation.

Can I use advanced placement in Biology?

A score of 4 or 5 on the AP Biology exam will provide you with advanced placement credit, Biology 20. All biology majors will start the biology ‘gateway’ courses: Students with Biology AP 5 may take Biology 203L in the Spring semester. All students may take Biology 201L and 202L (if not 203L). These courses will introduce the three foundations of modern biology: molecular biology, genetics and evolution. The gateway courses will take you deep into the topics, beyond AP Bio, and provide a foundation for other advanced courses in biology.

In addition, advanced placement is possible in chemistry, math and physics, depending on your exam scores and by the decision of the respective departments. Students who place out of the first year of chemistry or math will not have to retake those courses for the biology major.

Note that although you can only use two AP credits to reduce the number of credits you need to take for graduation (from 34 to 32), any number of AP credits can be used for placement out of introductory courses. So, advanced placement in chemistry, math and physics will reduce the courses needed to complete the biology major, freeing you up to take more advanced courses or courses in other disciplines.

Can I get involved in research?

Yes! Most biology majors will do at least one or two semesters of research as part of their major. You will be participating in state of the art research with world-class scientists in any one of the many of research labs in the University or the Medical Center (e.g, Cell Biology, Immunology, Cancer Biology, etc.). Most students will start in their junior or senior year, although many begin earlier. Most students will do research as part of their regular course work, receiving grades and academic credit for their research. Many students will have their work published in the scientific literature and use their research as the basis for graduation with honors. Special research opportunities are also available during summer. These fellowships generally pay a stipend so that students can live on campus or at the Marine Lab while immersed in their research experience.

How many bio majors are there? What are classes like? Who teaches them?

There are typically about 170 biology majors in each graduating class. In addition, there are about an equal number of students in other majors that will be taking introductory and 'pre-health' courses. So, the introductory courses may have as many as 150-200 students in lecture. The second level courses usually have 25-40 students each and the advanced lab courses and seminars are generally less than 20 students. However, even the larger lecture courses always split up once a week for lab or discussion with 15-20 students per section. While these sections may be led by a graduate teaching assistant, all the lecture and seminar courses are taught by regular faculty.

Can I study away and still do a biology major? Can I transfer courses during the summer?

Yes! Many Biology students will do at least one semester of Study Abroad, typically in their junior year. There are several programs that are especially popular with Biology majors including semester and summer programs in marine biology at the Duke Marine Lab and summer programs Australian biogeography and Alaskan biodiversity. In addition, there are many other study away programs that allow students the opportunity to take courses in biology as well as other fields. Moreover, the major in Biology is sufficiently flexible to allow students to take semester abroad with out any biology, to study art in Florence, for example.

What do Biology majors do when they graduate?

Following graduation, about 40% of Biology majors will go off to medical school and about 30% will attend graduate programs in the biological/biomedical sciences, though not all directly—many will take a few years to work in labs before starting graduate school. The remainder will do many things, including secondary school teaching, law school, business pursuits, or volunteer work with Teach for America, Peace Corps, etc. Duke Biology grads generally place well. For example, they have a rate of medical school acceptance that is twice the national average.