Lecture 1: The Web of Life

What is Ecology

• The scientific study of interactions between organisms and their environment

• The scientific study of interactions that determine the distribution (geographic location) and abundance of organisms

• Answers questions like: Why do we have a certain species here? Why is it doing so well here but not so well there? What is happening to the species on a day-to-day, week-to-week, year-to-year basis?

Ecology is NOT Environmental Science, Why?

• Environmental science focuses on solving the societal issues and things like climate change and pollution problems

• Environmental science may use ecology or ecological approaches to solve problems like climate change or pollution, but it also has other aspects to it rather than just focusing on the interactions between organisms and their environment

• Environmental science also utilizes advocacy, understanding the human side of the equation, the sociology, and the history of the situation

Differences Between Ecology and Environmental Science

Ecology

• Is a branch of biology

• Studies the interactions between organisms and their environment

• Understand how individuals within a species react to factors like pollution

Environmental Science

• Is an interdisciplinary field that incorporates information from natural science (biology, chemistry, physics) and social science (politics, economics, geography)

• Studies the natural world, the impact of human activities on the environment, and how we can address environmental issues to preserve the world around us

• Looks at political or economic factors that could reduce pollution

Early Ecological Views

• There was a balance of nature - Ecosystems return to their original, preferred state after disturbance

• Each species played a distinct role in the balance

What has Changed and Stayed the Same Since our Early Ecological Views

• We have learned that ecosystems are always changing

• For a specific amount of time, like tens or hundreds of years, they might have a preferred state, however, over longer periods of time, we know that all ecosystems change

• Think about how the glacial cycles and how those impacted Earth’s ecosystems - Ecosystems have been changing ever since

• Think about similar environments, ex. a desert in Australia/Africa/America might have very similar climatic conditions, but the actual ecosystems that we are observing are very different. The species might be performing similar functions, but overall in terms of what specific species are found in each continent will be different

• Ecosystems are made up of dominant or keystone species, but there is a lot of functional overlap

• If a species goes extinct, there will be other species that fill their role

• What has stayed the same from our early ecological views is that what we’re dealing with are these interconnected ecosystems that might have short-term preferred states, but over long-term, things always change, and these interconnections are always present between the living and non-living parts of ecosystems

• Another view that has not changed: Events in nature are interconnected. A change in one part of an ecological system can alter other parts of that system

List Ecological Maxims (Truths/Facts)

1. Organisms interact and are interconnected

2. Everything goes somewhere

3. No population can increase in size forever

4. Finite energy and resources result in trade-offs

5. Populations evolve

6. Ecosystems change over time and across space

7. Scale matters

Maxim 1: Organisms Interact and are Interconnected

• Trees are not individual creatures, they can only exist in relationship - They depend on or have connections to bacteria, fungi, insects, birds, animals, and people

Maxim 2: Everything Goes Somewhere

• In our industrial society, we have a production system where we use natural materials, transform it, and we throw it out - it doesn’t get reused, causing heaps of trash in the ocean

• **NUTRIENTS CYCLE, BUT ENERGY FLOWS

• In nature, we have nutrient cycles, where intact ecosystems are very conservative with their nutrients - they reuse them instead of letting them go

• Energy flows through ecosystems: Energy enters ecosystems through the sun, it does it’s work, and they are reradiated into space

• The Earth is in radiative equilibrium

Maxim 3: No Population can Increase in Size Forever

• There are limits to growth, eventually any population that grows exponentially reaches resource limits, or is stuck with diseases that limit growth

• For limited time periods there may be exponential growth, but eventually growth rates will slow down, even in humans

Maxim 4: Finite Energy and Resources Result in Trade-Offs

• All of life on Earth is about trade-offs - You can’t have everything, you can’t be optimal in every category, you’re trading off one for the other

Maxim 5: Populations Evolve (Adaptation and Natural Selection)

Adaptation

• A characteristic of on organism that improves its ability to survive or reproduce

Natural Selection

• The process by which individuals with certain traits tend to survive and reproduce at a higher rate than other individuals because of those traits

Maxim 6: Ecosystems Change Over Time and Across Space

• Different ecosystem types with different composition of species, different interactions, go through this series of gradual changes over time

• Balance of nature example: A forest can face a disturbance and regrow, but there will be a change in its composition - it won’t be the exact same forest

Maxim 7: Scale Matters

Spatial Scales (Size):

• Scale influences what tools we use to study ecosystems

• Small - ex. soil microorganisms

• Large - ex. atmospheric pollutants

Temporal Scales (Time):

• Short - ex. leaf response to sunlight

• Long - ex. species change over geologic time

Population

• Group of individuals of a species that live in a particular area and interact with each other on a day-day basis

Communtiy

• Interacting populations of different species that live in the same area at the same time

Ecosystem

• A community of organisms and their physical environment

Landscapes

• Areas with substantial differences, typically including multiple ecosystems

Producers

• Use energy from an external source (ex. the sun) to produce their own food

• Also called primary producers and autotrophs

Consumers

• Get energy by eating other organisms or their remains

• Heterotrophs

Net Primary Production (NPP)

• Energy captured by producers minus amount lost as heat in cellular respiration

Advantages of Lab vs. Mesocosm vs. Field Experiments

• Lab manipulations have greater control over variables, but it has lower realism than field observation experiments

• Mesocosms try to balance these concerns, but may not replicate natural environments very well

• Field experiments have the most realism, but the least control over variables

How are Amphibians Biological Indicators?

• They have permeable skin, pollutant molecules can pass through easily

• Their eggs have no protective shell

• They spend part of life on land and part in water - exposed to pollutants and UW in both environments