Ecology
This information is a cumulative record of my notes from an ecology course from my fall semester, 2026.
Ecology comes from the word oikos, Greek for "home" or "place."
Applies statistical approaches to test hypothesises: quantatative values. Sampling bias can be present (i.e. lots of sampling data done in western Europe).
Population distribution
Where each dot represents an individual
Tells us something about the environment.
Driven largely by food supply & other resources.
Richness of species / species diversity
Area 1 has an equal distribution of species, and therefore is more rich, whereas area 2 has one species dominating.
Relative abundance of each species; species evenness, species dominance.
Ecological units
Individual: survival & reproduction; per capita (per individual).
Emphasizes the way in which an individual's morphology, physiology, and behavior enable it to survive its environment.
Population: population dynamics; the unit of evolution.
Individuals of the same species living in the same area. Emphasizes variation over time and space in the number, density, and composition of individuals.
Community: interaction amoung spes[ecoes ;ovongcies; all of the living things; interspecific interactions (i.e. predation); intraspecific interactions (i.e. competition for resources).
Emphasizes the diversity & relative abundance of different kinds of organisms living together in the same place.
Ecosystem: one or more communities of living organisms interacting with their nonliving physical and chemical environments.
Emphasizes the storage and transfer of energy and matter, including the various chemical elements essential to life.
Landscape: multiple ecosystems that are connected by the movement of individuals, populations, matter, and energy.
Concerned with the movement of energy, matter, and individuals between ecosystems.
Biosphere: all of the ecosystems on earth.
Concerned with the largest scale, including movements of air and water - and the energy and chemical elements they contain - over earth's surface.
Principles of ecology
Law of conservation of matter: matter cannot be created or destroyed, can only change form.
Law of conservation of energy: energy cannot be created or destroted, it can only change form; aka law of thermodynamics.
Classifications of organisms via energy
Producer: an organism that uses photosynthesis to convert solar energy into organic compounds or uses chemosynthesis to convert chemical energy into organic compounds, aka an autotroph.
Consumer: an organism that obtains its energy from other organisms, aka heterotroph.
Mixotroph: an organism that obtains its energy from more than one source.
Classification
Predator: kills and partially or entirely consumes another individual.
Parasites: lives & feeds in or on another organism, rarely killing host.
Prasitoid: lives within & consumes the tissues of a living host, eventually killing it.
Pathogen: parasite that causes a disease in its host.
Herbivore: an organism that consumes producers such as plants and algae.
Competition: an interaction resulting in a negative effect between two species that depend on the same limited resource to surviva, grow, and reproduce.
Mutualism: an interaction between two species where each species recieves benefits from the other.
Commensalism: an interaction in which two species live in close association, and one species recieves a benefit, while the other experiences neither a benefir nor a cost.
Relationships
Symbiotic relationships: when two different types of organisms live in a close physical relationship.
Scavanger: an organism that consumes dead animals.
Detritivore: an organism that feeds on dead organic matter and waste products that are collectively known as detrities.
Decomposer: organism that breaks down dead organic material into simpler elements and compounds that can be recycled through the ecosystem.
Habitats
Niche: the range of abiotic and biotic conditions that an organism can tolerate.
Fundamental theory: two species cannot have the same niche because each has unique phenotypes that determine the conditions it can tolerate.
Fundamental niche: all the potential places an organism can live.
Realized niche: where an organism really lives.
Law of 10%: only 10% of energy is transferred to the next trophic level.
Applies statistical approaches to test hypothesises: quantatative values. Sampling bias can be present (i.e. lots of sampling data done in western Europe).
Population distribution
Where each dot represents an individual
Tells us something about the environment.
Driven largely by food supply & other resources.
Richness of species / species diversity
Area 1 has an equal distribution of species, and therefore is more rich, whereas area 2 has one species dominating.
Relative abundance of each species; species evenness, species dominance.
Ecological units
Individual: survival & reproduction; per capita (per individual).
Emphasizes the way in which an individual's morphology, physiology, and behavior enable it to survive its environment.
Population: population dynamics; the unit of evolution.
Individuals of the same species living in the same area. Emphasizes variation over time and space in the number, density, and composition of individuals.
Community: interaction amoung spes[ecoes ;ovongcies; all of the living things; interspecific interactions (i.e. predation); intraspecific interactions (i.e. competition for resources).
Emphasizes the diversity & relative abundance of different kinds of organisms living together in the same place.
Ecosystem: one or more communities of living organisms interacting with their nonliving physical and chemical environments.
Emphasizes the storage and transfer of energy and matter, including the various chemical elements essential to life.
Landscape: multiple ecosystems that are connected by the movement of individuals, populations, matter, and energy.
Concerned with the movement of energy, matter, and individuals between ecosystems.
Biosphere: all of the ecosystems on earth.
Concerned with the largest scale, including movements of air and water - and the energy and chemical elements they contain - over earth's surface.
Principles of ecology
Law of conservation of matter: matter cannot be created or destroyed, can only change form.
Law of conservation of energy: energy cannot be created or destroted, it can only change form; aka law of thermodynamics.
Classifications of organisms via energy
Producer: an organism that uses photosynthesis to convert solar energy into organic compounds or uses chemosynthesis to convert chemical energy into organic compounds, aka an autotroph.
Consumer: an organism that obtains its energy from other organisms, aka heterotroph.
Mixotroph: an organism that obtains its energy from more than one source.
Classification
Predator: kills and partially or entirely consumes another individual.
Parasites: lives & feeds in or on another organism, rarely killing host.
Prasitoid: lives within & consumes the tissues of a living host, eventually killing it.
Pathogen: parasite that causes a disease in its host.
Herbivore: an organism that consumes producers such as plants and algae.
| Type of interaction | Species 1 | Species 2 |
|---|---|---|
| Predation/parasitoidism | + | - |
| Parasitism | + | - |
| Herbivory | + | - |
| Competition | - | - |
| Mutualism | + | + |
| Commensalism | + | 0 |
Competition: an interaction resulting in a negative effect between two species that depend on the same limited resource to surviva, grow, and reproduce.
Mutualism: an interaction between two species where each species recieves benefits from the other.
Commensalism: an interaction in which two species live in close association, and one species recieves a benefit, while the other experiences neither a benefir nor a cost.
Relationships
Symbiotic relationships: when two different types of organisms live in a close physical relationship.
Scavanger: an organism that consumes dead animals.
Detritivore: an organism that feeds on dead organic matter and waste products that are collectively known as detrities.
Decomposer: organism that breaks down dead organic material into simpler elements and compounds that can be recycled through the ecosystem.
Habitats
Niche: the range of abiotic and biotic conditions that an organism can tolerate.
Fundamental theory: two species cannot have the same niche because each has unique phenotypes that determine the conditions it can tolerate.
Fundamental niche: all the potential places an organism can live.
Realized niche: where an organism really lives.
Law of 10%: only 10% of energy is transferred to the next trophic level.
Climate determines biomes; types of plant (primary producer) communities. Determined by:
- Average annual temperature
- Average annual precipitation (appt)
Subtropical: underneath the tropics
~25.5° to 30° : deserts
Solar radiation & the natural greenhouse effect
The atmosphere is a 600km thick gas layer that surrounds our planet.
The greenhouse effect is the process of solar radiation striking earth, being converted to infrared radiation, and being absorbed and reemmitted by atmospheric gases.
Solar radiation: absorbed by / reflected off clouds; the earth's surface (i.e. glaciers).
Greenhouse gases:
- Carbon dioxide
- Water vapor
- Methane
Solar inputs
Determined by seasonality; not equal, vary by latitude.
Position about the sun determines seasonality.
Solar equator is the latitude recieving the most solar radiation at a given time.
Tilt of the earth: 23.5°
Surface temperature reflects the difference between incoming & outgoing radiation.
Solar radiation: electromagnetic energy.
Shorter wavelength = higher energy / hotter.
Thermal radiation: heat you can feel; cities are heat sinks, they hold onto / radiate that heat.
Albedo effect
Associated with the reflection of solar radiation based on the composition / color of objects.
Effects on temperature based on Albedo.
Some goes back into space. Most is absorbed by gasses in the atmosphere.
Net radiation = (incoming shortwave - reflected shortwave) - (emitted longwave - downward longewave)
Can be mapped on a globe.
0° - ~ 23.5° : hotter, higher net radiation; dissipates polewards.
As you move polewards, annual surface radiation decreases because:
- Angle of the earth is greater and the incoming solar radiation is spread over a larger area.
- The solar radiation must travel through more of the atmosphere, so more is reflected.
Leads to a distinct pattern in global tempearture.
Seasonal trends
Regions at the equator show very little seasonal variation in temperature.
Regions in the north & south pole show the most seasonal variation in day length (zero -> 24 hours) & solar radiation.
Spring & fall equinoxes
When the earth is directly facing the sun (axis is parallel):
- Sun is directly overhead at the equator
- All places on earth have 12 hours of daylight / 12 hours of darkness
Vernal (spring) and autumnal (fall) equinoxes, or "equal light."
Summer equinox
- Northern hemisphere is tilted towards the sun
- Sun is directly overhead of the Tropic of Cancer (23.5°N)
- Days are longer, temperatures are warmer; Summer in the U.S.
- Longest day: summer solstice (~June 22)
Winter equinox
- Southern hemisphere is tilted towards the sun
- Sun is directly overhead at the Tropic of Capricorn (23.5°)
- Days longer, temperatures warmer in Australia; shorter/cold in the U.S.
- Shortest day in the northern hemisphere is on the winter solstice (~December 22)
- Average annual temperature
- Average annual precipitation (appt)
Subtropical: underneath the tropics
~25.5° to 30° : deserts
Solar radiation & the natural greenhouse effect
The atmosphere is a 600km thick gas layer that surrounds our planet.
The greenhouse effect is the process of solar radiation striking earth, being converted to infrared radiation, and being absorbed and reemmitted by atmospheric gases.
Solar radiation: absorbed by / reflected off clouds; the earth's surface (i.e. glaciers).
Greenhouse gases:
- Carbon dioxide
- Water vapor
- Methane
Solar inputs
Determined by seasonality; not equal, vary by latitude.
Position about the sun determines seasonality.
Solar equator is the latitude recieving the most solar radiation at a given time.
Tilt of the earth: 23.5°
Surface temperature reflects the difference between incoming & outgoing radiation.
Solar radiation: electromagnetic energy.
Shorter wavelength = higher energy / hotter.
Thermal radiation: heat you can feel; cities are heat sinks, they hold onto / radiate that heat.
Albedo effect
Associated with the reflection of solar radiation based on the composition / color of objects.
Effects on temperature based on Albedo.
Some goes back into space. Most is absorbed by gasses in the atmosphere.
Net radiation = (incoming shortwave - reflected shortwave) - (emitted longwave - downward longewave)
Can be mapped on a globe.
0° - ~ 23.5° : hotter, higher net radiation; dissipates polewards.
As you move polewards, annual surface radiation decreases because:
- Angle of the earth is greater and the incoming solar radiation is spread over a larger area.
- The solar radiation must travel through more of the atmosphere, so more is reflected.
Leads to a distinct pattern in global tempearture.
Seasonal trends
Regions at the equator show very little seasonal variation in temperature.
Regions in the north & south pole show the most seasonal variation in day length (zero -> 24 hours) & solar radiation.
Spring & fall equinoxes
When the earth is directly facing the sun (axis is parallel):
- Sun is directly overhead at the equator
- All places on earth have 12 hours of daylight / 12 hours of darkness
Vernal (spring) and autumnal (fall) equinoxes, or "equal light."
Summer equinox
- Northern hemisphere is tilted towards the sun
- Sun is directly overhead of the Tropic of Cancer (23.5°N)
- Days are longer, temperatures are warmer; Summer in the U.S.
- Longest day: summer solstice (~June 22)
Winter equinox
- Southern hemisphere is tilted towards the sun
- Sun is directly overhead at the Tropic of Capricorn (23.5°)
- Days longer, temperatures warmer in Australia; shorter/cold in the U.S.
- Shortest day in the northern hemisphere is on the winter solstice (~December 22)