Ecology Fundamentals & Biodiversity
To gain a base knowledge of ecology and biodiversity before diving in too deep to biodiversity at my study site specifically, I put together the slides below for a broad introduction to the topic! Be sure to read speaker notes for in depth information, and feel free to reuse this presentation with your groups! As an educator myself, I included lots of opportunities for audience participation and engagement too.
Enjoy!
Ecology Fundamentals & Biodiversity by Alicyn FormicaEDIT: It looks like this doesn't allow the speaker notes to be viewed on this page, to view the presentation in its entirety you can view the link below and hit the small down arrow next to "Present" and select "Presenter View", feel free to leave a comment below if you encounter any issues! (Note: this seems to only work for folks with an existing Canva account, so I'll just copy the notes below in case you can't access).
Slide 1: Intro
Welcome everyone! Today we’re going to explore ecology and biodiversity through a central question: How is life connected?
Ecology is often described as the study of relationships, but those relationships occur at many scales. Individual organisms interact with each other, populations interact with environments, ecosystems exchange energy and nutrients, and global processes such as climate influence all of those interactions simultaneously.
Throughout this presentation, we’ll move progressively outward in scale. We’ll begin with individual organisms and populations, examine interactions among species, and ultimately connect these ideas to ecosystem processes and human impacts. By the end, I want us to think about ecology not simply as a branch of biology, but as a framework for understanding how complex systems function.
Before defining ecology itself, let's think about why ecology matters!
Slide 2: Why Ecology Matters
Audience question:
"Before arriving here today, what benefits did nature provide you?"
Pause for responses.
Likely responses might include food, water, clean air, medicine, shade, or even recreation.
Many of us rarely think consciously about these benefits because ecological systems continuously provide them. Ecologists refer to these benefits as ecosystem services. The Millennium Ecosystem Assessment grouped these services into four broad categories (Millennium Ecosystem Assessment, 2005):
Provisioning services include products we directly obtain from ecosystems such as food, freshwater, and raw materials.
Regulating services include climate regulation, flood control, disease reduction, and pollination.
Supporting services include nutrient cycling and soil formation.
Cultural services include recreation, spiritual values, and aesthetic experiences.
One of the important ideas here is that humans are not outside ecological systems, rather we are embedded within them.
Slide 3: What is Ecology?
Audience question:
"Looking at this image, what arrows would you draw connecting these components?"
Allow responses.
Possible observations:
The rabbit depends on plants for food.
Plants depend on sunlight.
Water availability affects all organisms.
Animals may provide seed dispersal.
What I want us to notice is that ecology is not primarily about identifying individual organisms. Ecology is concerned with the relationships among components of a system.
Modern ecological research examines several major themes:
• interactions among organisms
• interactions between organisms and environments
• movement of energy and matter
• feedback processes across scales
Ecological systems are highly interconnected, meaning changes in one component can propagate through entire systems. (OpenStax Biology 2e, 2023)
Ecologists study these interactions at different levels of organization.
Slide 4: Levels of Ecological Organization
Ecologists organize biological systems hierarchically:
An organism represents an individual living thing.
A population includes members of the same species living within an area.
Communities involve interacting species.
Ecosystems combine living and nonliving components.
Biomes represent large climate-driven regions.
The biosphere includes all life on Earth.
One important concept in ecology is emergence. Patterns at larger scales often cannot be predicted solely from individual behavior.
For example, understanding one tree does not necessarily explain an entire forest ecosystem.
Now that we understand ecological scale, how do scientists organize living organisms themselves?
Slide 5: Classification of Organisms
Audience question:
"Could two organisms look similar without being closely related?"
Many people assume appearance always indicates relationship, but this is not necessarily true.
Classification systems originally relied heavily on visible characteristics. Modern taxonomy increasingly incorporates molecular evidence such as DNA sequencing.
Consider sharks and dolphins. They appear similar because they share aquatic environments and similar functional demands, yet one is a fish and the other is a mammal.
This process, known as convergent evolution, demonstrates that similar environments can produce similar solutions.
Classification therefore attempts to reflect evolutionary relationships rather than appearance alone.
If classification reflects relationships, where do those relationships come from?
(Integrated Taxonomic Information System [ITIS], n.d.)
Slide 6: Phylogenetic Tree
Audience question:
"What do the branches on this tree represent?"
Branches represent evolutionary divergence from common ancestors.
Modern phylogenetic trees are hypotheses about relationships among organisms constructed using multiple lines of evidence including morphology, genetics, and comparative biology.
An important misconception to address is that evolution does not progress toward perfection or greater complexity.
Evolution resembles branching rather than a ladder.
Humans are not the "highest" branch of evolution. We simply represent one lineage among many.
Slide 7: Natural Selection
Audience question:
"What environmental pressures might change which traits become advantageous?"
Possible responses:
- temperature
- predators
- food availability
- competition
Natural selection requires several conditions:
First, variation must exist.
Second, traits must be heritable.
Third, individuals differ in reproductive success.
Over time, traits associated with higher reproductive success become more common.
Importantly, natural selection does not work toward predetermined goals. Environmental conditions determine which traits become advantageous.
Selection therefore depends strongly on context.
Natural selection acting over time produces adaptations.
(Understanding Evolution, University of California Museum of Paleontology, n.d.)
Slide 8: Adaptations
Audience question:
"Looking at these organisms, what features appear useful for survival?"
Allow responses.
Possible observations:
- Camel: water conservation
- Polar bear: insulation and camouflage
- Cactus: water storage and reduced leaf area
Adaptations generally fall into three categories:
- Structural adaptations involve physical characteristics.
- Behavioral adaptations involve actions.
- Physiological adaptations involve internal processes.
One important clarification is that adaptation does not mean intention. Individual organisms do not intentionally evolve traits. Instead, populations change across generations through selection.
Over long periods of time, evolutionary processes generate biodiversity.
(OpenStax Biology 2e, 2023)
Slide 9: Biodiversity
Audience question:
"When you hear biodiversity, what comes to mind?"
Most people initially think about species richness, or simply the number of species present.
Scientists generally distinguish among three major levels:
Genetic diversity represents variation within species.
Species diversity refers to richness and relative abundance.
Ecosystem diversity reflects variation among habitats and ecological communities.
Genetic diversity is especially important because it provides the raw material for adaptation and resilience.
Populations with low genetic diversity often have reduced capacity to respond to environmental change.
Now that we've discussed why organisms differ, we can ask where organisms live and why.
(Convention on Biological Diversity, 2020)
Slide 10: Habitat vs. Niche
Audience question:
"If I told you someone's address, would I know their occupation?"
Pause.
Probably not.
Habitat describes where an organism lives.
Niche describes the organism's ecological role.
Niche includes:
- resource use
- environmental tolerances
- interactions with competitors
- predator-prey relationships
- reproductive requirements
Ecologists also distinguish between a fundamental niche and a realized niche.
A fundamental niche represents the full range of conditions an organism could theoretically occupy.
A realized niche represents the conditions actually occupied after competition and other ecological interactions occur.
Activity: Try to identify relationships between organisms, or ones between organisms and the environment.
What environmental factors influence where species can survive?
(OpenStax Biology 2e, 2023)
Slide 11: Abiotic Factors
Audience question:
"Which of these environmental variables would matter most to a cactus? What about a trout?"
Pause for responses.
Most people immediately recognize that these organisms occupy very different environments, but it is worth asking why. Organisms exist within specific physiological limits, meaning there are ranges of conditions under which they can survive and reproduce.
Abiotic factors are the nonliving components of ecosystems that shape biological systems. Examples include temperature, water availability, light intensity, nutrient availability, pH, salinity, and soil composition.
Ecologists often think about these variables in terms of limiting factors. One useful framework is Liebig’s Law of the Minimum, which proposes that growth is constrained not by the total amount of resources available, but by whichever essential resource is most limited. For example, adding more sunlight to a nutrient-limited plant system may not increase growth if nitrogen remains scarce.
Abiotic factors therefore establish boundaries for where organisms can persist.
Physical conditions influence organisms, but organisms also influence one another.
(OpenStax Biology 2e, 2023)
Slide 12: Biotic Factors
Audience question:
"What might happen if one species disappeared from this interaction web?"
Pause.
Students often focus on direct effects. For example, a predator losing prey, but ecological consequences can extend much further.
Biotic factors include all living components influencing an organism's survival and reproduction, including competitors, predators, prey, pathogens, parasites, and mutualistic partners.
Ecologists distinguish between direct and indirect effects.
A direct effect occurs when one species immediately influences another, such as predation.
Indirect effects occur through intermediate species.
For example, predators may indirectly increase plant abundance by reducing herbivore populations.
Because ecosystems contain interconnected relationships, effects frequently propagate beyond the original interaction.
Let's look more closely at some of the major interaction types.
(OpenStax Biology 2e, 2023)
Slide 13: Species Interactions
Audience question:
"Can the same two species interact differently under changing environmental conditions?"
Pause.
Many ecological interactions are context dependent.
Competition occurs when organisms use limited resources.
Predation occurs when one organism consumes another.
Mutualism occurs when both organisms benefit.
These relationships are often represented using positive and negative effects.
Competition: − / −
Predation: +/ −
Mutualism: +/ +
However, ecological interactions are rarely static.
For example, relationships that appear beneficial under one environmental condition may become competitive when resources become limited.
Ecologists increasingly examine not only whether interactions occur, but also their relative strength within communities.
Some ecological interactions become highly specialized and persistent.
(OpenStax Biology 2e, 2023)
Slide 14: Symbiosis
Audience question:
"Any ideas what the relationships shown on the screen might be? Who is impacted positively or negatively?"
Explanation:
Clownfish/anemone – Mutualism (+/+): The clownfish gains protection by living among the anemone’s stinging tentacles, while the clownfish helps the anemone by cleaning it, providing nutrients through waste, and sometimes attracting prey. Both organisms benefit from the relationship.
Barnacle/whale – Commensalism (+/0): Barnacles attach themselves to whales and gain transportation through nutrient-rich waters, increasing their access to food. The whale is generally unaffected and experiences little to no benefit or harm.
Tick/deer – Parasitism (+/−): The tick benefits by feeding on the deer’s blood, gaining nutrients needed for survival and reproduction. The deer is harmed because ticks remove resources and may spread diseases.
Symbiosis refers to prolonged close interactions between species.
Three common forms include:
Mutualism: Both species benefit.
Examples include flowering plants and pollinators.
Commensalism: One benefits while the other experiences little measurable effect.
Examples include epiphytes growing on trees.
Parasitism: One benefits at the expense of another.
Examples include ticks feeding on mammals.
Ecologists increasingly recognize that these categories exist on a continuum rather than as rigid boxes.
Environmental conditions may shift the costs and benefits experienced by organisms.
So far we've discussed individuals and interactions. Let's zoom outward to populations.
(OpenStax Biology 2e, 2023)
Slide 15: Population Ecology
Audience question:
"What processes increase population size, and what processes reduce it?"
Allow responses.
Population ecology examines changes in the abundance and distribution of organisms through time.
Population change can be simplified as:
Population growth =
Births + Immigration − Deaths − Emigration
However, this equation represents only a starting point.
Population dynamics are also influenced by resource availability, species interactions, environmental variability, and demographic structure.
Ecologists study populations because changes in abundance often provide early signals of broader ecological change.
Populations rarely remain constant through time.
Slide 16: Population Growth
Audience question:
"If resources were unlimited, what would happen to population size?"
Under idealized conditions, populations exhibit exponential growth.
Exponential growth assumes unlimited resources and constant growth rates.
In reality, resources become limiting.
This leads to logistic growth, where population increase slows and eventually stabilizes.
It is important to recognize that these models simplify reality.
Real populations often fluctuate due to changing environmental conditions, predation, and stochastic events.
Models remain useful because they allow ecologists to identify major processes influencing populations.
If unlimited growth rarely occurs, what limits populations?
(OpenStax Biology 2e, 2023)
Slide 17: Carrying Capacity
Audience question:
"What resources eventually become limiting in ecosystems?"
Examples may include:
- food
- water
- space
- nesting sites
Carrying capacity represents the maximum population size an environment can sustainably support.
Ecologists frequently distinguish between density-dependent and density-independent controls.
1) Density-dependent factors strengthen as populations become larger.
Examples include:
- competition
- disease
- resource limitation
2) Density-independent factors influence populations regardless of density.
Examples include:
- storms
- fires
- extreme weather events
Real systems often involve interactions among multiple limiting factors simultaneously.
Population size is important, but location matters too!
(OpenStax Biology 2e, 2023)
Slide 18: Population Distribution
Audience question:
"Which pattern might you expect in a herd of elephants?"
Teaching explanation:
- Clumped: resources patchy
- Uniform: competition or territoriality
- Random: rare natural occurrence
Population distributions typically occur in three major patterns:
Clumped distributions involve groups of individuals occurring together.
Uniform distributions involve relatively even spacing.
Random distributions occur when individuals are positioned independently of one another.
Clumped patterns are generally most common because resources themselves are often distributed unevenly across landscapes.
Uniform patterns frequently emerge from territorial behavior or competition.
Understanding spatial patterns helps ecologists identify mechanisms influencing populations.
Species distributions are not static; organisms also move across landscapes.
(OpenStax Biology 2e, 2023)
Slide 19: Dispersal
Audience question:
"What advantages might movement provide to organisms?"
Allow responses.
Potential answers:
- finding resources
- escaping competition
- avoiding predators
- reaching mates
Dispersal affects both ecological and evolutionary processes.
Movement influences gene flow among populations and determines how species colonize habitats.
Modern movement ecology emphasizes several interacting components:
- internal state: why organisms move
- motion capacity: how movement occurs
- navigation capacity: how direction is determined
- external factors: environmental influences
Dispersal also becomes increasingly important under climate change because species may need to shift geographic ranges.
Movement influences where organisms ultimately settle and reproduce.
(Movement ecology literature; Frontiers in Ecology and Evolution)
Slide 20: Habitat Selection
Audience question:
"Would organisms always choose habitats containing the most resources?"
The intuitive answer may seem like yes, but ecological decisions involve tradeoffs.
Habitat selection reflects the balance among:
- resource availability
- predation risk
- competition
- reproductive success
One useful framework is the Ideal Free Distribution model, which predicts that organisms distribute themselves among habitats in ways that maximize benefits.
However, real organisms rarely possess perfect information.
Ecological systems therefore often contain imperfect decisions and behavioral constraints.
Understanding habitat selection helps explain species distributions and patterns observed across landscapes.
We've discussed populations and movement. Next we'll combine these ideas into larger ecological systems.
(OpenStax Biology 2e, 2023)
Slide 21: Ecosystems
Audience question:
"Looking at this ecosystem illustration, what arrows/connections might you draw?"
Pause for observations.
Likely responses might include:
- plants using sunlight
- animals eating plants
- decomposers recycling nutrients
- water moving through the system
One of the defining characteristics of ecosystems is that they are dynamic systems rather than collections of isolated parts. Ecosystems consist of interacting biotic components, including living organisms, and abiotic components, including physical and chemical conditions.
A key idea in ecology is that ecosystems involve the movement of both matter and energy. Matter cycles repeatedly through systems, while energy generally moves in one direction and is gradually transformed.
Modern ecological research increasingly examines ecosystems as complex adaptive systems, where relatively simple interactions can generate large-scale patterns.
If ecosystems function as systems, they require an input that powers biological processes.
(OpenStax Biology 2e, 2023)
Slide 22: Energy Flow
Most ecosystem energy originates from the sun through photosynthesis.
Primary producers convert solar energy into chemical energy stored within organic molecules.
That energy then moves through ecological systems as organisms consume one another.
Two fundamental principles from physics are relevant here.
1) First Law of Thermodynamics: Energy cannot be created or destroyed; it changes form.
2) Second Law of Thermodynamics: Energy transformations are inefficient and increase entropy.
This inefficiency explains why ecological systems require continual energy input, and why energy is lost with each transformation/each step up the trophic ladder.
Let's follow a few pathways that energy might take through different ecosystems!
(OpenStax Biology 2e, 2023)
Slide 23: Food Chains
Food chains represent simplified pathways through which energy moves among organisms.
1) Producers occupy the first trophic level because they generate biomass through photosynthesis.
2) Primary consumers feed on producers.
3) Secondary and tertiary consumers occupy increasingly higher trophic levels.
Food chains are useful teaching tools because they illustrate energy transfer clearly.
However, natural systems are rarely this simple.
Most organisms interact with multiple species simultaneously.
Real ecosystems therefore resemble networks rather than simple linear pathways.
(OpenStax Biology 2e, 2023)
Slide 24: Food webs
Audience question:
"Why are food webs more realistic representations than food chains?"
Food webs incorporate multiple interconnected feeding relationships. Ecologists increasingly use network theory to understand these systems.
One particularly important concept is the keystone species.
Keystone species exert disproportionately large effects relative to their abundance.
Removing one important species can produce cascading effects throughout ecosystems.
Classic examples include sea otters influencing kelp forests and wolves influencing terrestrial systems.
Food web studies demonstrate that ecological systems frequently contain indirect effects that are difficult to predict.
Energy moves through these systems, but only a fraction reaches each successive level.
(PLOS Biology ecological network literature)
Slide 25: Trophic Pyramid
Audience question:
"Why are top predators generally less abundant than organisms lower in food webs?"
Pause.
Energy transfer among trophic levels is relatively inefficient.
Only approximately 10% of available energy typically transfers from one trophic level to the next, although actual values vary among ecosystems.
Energy may be lost through:
- metabolism
- movement
- heat production
- waste
This pattern explains why biomass generally decreases at higher trophic levels.
Ecological efficiency therefore limits food chain length and influences ecosystem structure.
Large-scale ecological patterns emerge when energy interacts with climate.
(OpenStax Biology 2e, 2023)
Slide 26: Biomes
Biomes represent broad ecological regions characterized by climate and dominant vegetation patterns.
Major terrestrial biomes include:
- tropical forests
- grasslands
- deserts
- temperate forests
- taiga
- tundra
Temperature and precipitation strongly influence biome distributions because they determine water availability and primary productivity. (Think back to carrying capacities & limiting factors!)
Although biome categories simplify reality, they provide useful frameworks for understanding broad ecological patterns.
Climate is one of the major factors creating these biome differences.
(NASA Earth Observatory; OpenStax Biology 2e, 2023)
Slide 27: Climate & Ecology
Climate affects ecological systems through multiple pathways.
Temperature and precipitation influence species distributions, ecosystem productivity, and seasonal timing.
Phenology, the timing of biological events such as flowering or migration, is increasingly shifting in response to changing climate conditions.
Many species now exhibit altered geographic distributions as environmental conditions change.
Ecological responses to climate change vary considerably among species.
Humans are increasingly altering ecological systems through multiple mechanisms.
(IPCC, 2021)
Slide 28: Human Impacts
Audience question:
"What environmental changes have you personally observed?"
Pause.
Responses may include:
- urbanization
- declining pollinators
- changing weather patterns
- habitat fragmentation
The IPBES assessment identified several major drivers of biodiversity loss:
- land-use change
- direct exploitation of organisms
- climate change
- pollution
- invasive species
One important idea is that these factors rarely operate independently.
Multiple stressors frequently interact and amplify ecological effects.
Understanding ecological mechanisms becomes increasingly important for predicting future change.
If ecological systems are changing, an important question becomes how we respond.
(IPBES, 2019)
Slide 29: Conservation Biology
Audience question:
"What should conservation prioritize: species, habitats, ecosystems, or processes?"
There is no universally correct answer.
Conservation biology integrates ecology, genetics, evolution, and policy to protect biodiversity.
Modern conservation increasingly emphasizes preserving ecological processes rather than isolated species.
Examples include:
- habitat connectivity
- wildlife corridors
- restoration ecology
- protected areas
Maintaining ecological function often provides broader benefits than focusing exclusively on individual species.
Conservation efforts ultimately matter because ecosystems provide benefits affecting society directly.
(Convention on Biological Diversity, 2020)
Slide 30: Ecosystem Services
Many ecological functions occur largely unnoticed.
Ecosystem services are generally grouped into four categories:
- Provisioning services: goods obtained from ecosystems, like
food and freshwater
- Regulating services: benefits from ecosystem processes controlling natural conditions, like climate regulation and pollination
- Supporting services:underlying processes maintaining ecosystems, like nutrient cycling and soil formation
- Cultural services: nonmaterial benefits people gain from the environment, like recreation and aesthetic value
One major takeaway from ecology is that human well-being and ecosystem health are fundamentally connected rather than separate.
Let's summarize the major themes from today's discussion.
(Millennium Ecosystem Assessment, 2005)
Slide 31: Key Takeaways
Today we moved through ecology from small scales to global systems.
We began by defining ecology as the study of interactions among organisms and environments.
We examined evolutionary processes that generate biodiversity.
We explored how populations, species interactions, and ecosystems function.
Finally, we considered how human activities increasingly influence ecological systems.
The major idea connecting all of these concepts is that ecological systems are interconnected.
Changes occurring in one component often propagate throughout larger systems.
Understanding ecology therefore provides a framework for understanding both natural systems and our role within them.
I'd like to end with an opportunity for discussion!
Slide 32: Discussion
Here are a few questions to guide group discussion, but feel free to bring up any other topics of interest related to today's talk.
My portion of the presentation is all wrapped up now, so thank you all for joining me and learning a bit more about ecology today! (and a special thank you for bearing with my clip art diagrams :) )
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