Energy Transfer

Vocabulary

• Extremophiles - organisms that live in extreme environmental conditions such as high temperatures, pressures, acidity, salinity, or absence of light

• Matter - anything that occupies space and has mass. In the context of ecosystems, matter refers to nutrients, gases, and other substances that are essential for the functioning of living organisms.

• Energy - The ability to perform work or cause change. Energy is required for processes such as growth, reproduction, and movement

Ecology

• The scientific study of interactions among organisms and their physical environment

• Organisms are interdependent with each other and with the environment

Levels of ecological classification

• Individual/Organism

• Population - a group of organisms of the same species that typically interbreed, live in the same area at the same time, and share the same gene pool.

• Community - all of the populations living together within a defined area (aka all of the biotic factors - living things - in an area)

• Ecosystem - all of the factors in an area plus the abiotic factors - nonliving components

• Biome - Our entire planet, with all its organisms and physical environments

Biotic v. Abiotic Factors

• Biotic Factors - Living/biological influences on an organism

  • Ex. Predator, Prey, food, availability

• Abiotic Factors - Non-living influences on an organism

  • Ex. Soil, water, temperature

• Together, biotic and abiotic factors create the ecosystem

Energy transfer within an ecosystem

Thermodynamics classifies systems into three types:

1. open

2. closed

3. isolated.

Open systems

• Ecosystems are open systems

• Energy and matter can enter and leave an ecosystem either naturally or due to human involvement

• An open system allows both energy and matter to be exchanged with its surroundings

Closed Systems

• Only energy can enter or exit

• Closed systems could be as small as a mesocosm or as large as a biosphere

• A closed system allows for the exchange of energy with the surrounding environment but restricts the flow of matter.

  • Energy can enter and exit the system but matter remains contained within.

• Closed systems are typically created artificially or are rare in nature.

Isolated system

• Isolated systems are systems in which neither energy nor matter are exchanged with the surroundings.

• These systems do not occur naturally in our everyday environment

• The concept of an isolated system is purely theoretical

• Example:

  • The Universe

Sunlight is the principal source of energy that sustains most ecosystems

Autotrophs

• Organisms capable of synthesizing organic molecules from inorganic ones using an external energy source

• They serve as a source of energy and nutrients for other organisms in the community

• The chemical reactions that allow autotrophs to produce their own food are anabolic, requiring an energy input.

• Organisms that can produce their own organic molecules to then be broken down into ATP energy

• Also called producers

• Photoautotrophs use light energy to produce organic molecules

• Most of their energy is acquired from sunlight

• Examples:

  • Plants

  • Cyanobacteria

  • Algae

Photoautotrophs

• Photoautotrophs are organisms that use light as an external source of energy to synthesize organic compounds from inorganic molecules

• Most photoautotrophs derive their energy through the process of photosynthesis

Chemoautotrophs (chemosynthetic organisms)

• Chemoautotrophs live in sunlight-limited environments

• These organisms extract energy from inorganic compounds instead of relying on sunlight.

• Use the process of chemosynthesis to convert inorganic molecules into organic molecules

• These organisms act as the foundation for the food web within particular ecosystems

• Organisms that obtain energy through the oxidation of inorganic compounds, including iron, sulfur, and magnesium

  • These oxidation reactions release energy that is used for carbon fixation and the synthesis of macromolecules

• Chemoautotrophs are predominantly bacteria or protozoa typically found in hostile environments

• Example:

  • Extremophiles (prokaryotes and protozoa) - living near hydrothermal vents and in hot springs

Heterotrophs

• Organisms that cannot produce their own organic molecules - they must be obtained from other organisms

  • They rely on consuming organisms or organic matter to obtain energy and nutrients for survival

• Some are also called consumers

• Obtain energy by breaking down complex organic compounds derived from autotrophs or other heterotrophs

• They rely on external or internal digestion to break down complex organic compounds, such as:

  • Proteins

  • Nucleic acids

• Example:

  • Herbivores

  • Carnivores

  • Omnivores

  • Decomposers

External digestion - typically observed in organisms like fungi and some bacteria. these organisms release hydrolytic enzymes into their surrounding environment to break down complex organic compounds present in their food. Once the nutrients are broken down, they are absorbed by the organisms

Internal digestion - Occurs in more heterotrophs, including animals. It involves the ingestion of food, and digestion takes place within specialized organs, such as the stomach and intestines. these smaller molecules are absorbed through the intestinal lining and transported to the cells for assimilation

• Regardless of the mode of digestion, all heterotrophs use the nutrients obtained from their food as building blocks to construct molecules required for their own growth and reproduction

Mixotrophs - Some organisms have the unique ability to acquire nutrients through both autotrophic and heterotrophic means. These are known as mixotrophs.

• Example:

  • Venus flytrap

• The versatility of mixotrophs allows them to adapt to various environmental conditions and optimize their nutrient acquisition strategy based on resource availability

Types of heterotrophs

Herbivore

• An animal that eats producers (plants)

• Examples:

  • Cow

  • Deer

  • Goats

  • Caterpillars

Omnivore

• An animal whose natural diet includes plants and other animals

• Examples:

  • Humans

  • Bears

  • Pigs

Scavenger

• An animal that consumes the carcasses of other animals that have been killed by predators or have died of other causes.

• Examples:

  • Vultures

  • Hyenas

  • Condors

All four of these types of heterotrophs can do internal digestion so we commonly refer to them as “consumers”

Types of heterotrophs: Decomposers

• Break down dead organisms and organic matter

• Extract energy and nutrients from decaying matter (feces, leaf litter, dead animals, etc.)

• Through the secretion of enzymes, they break down complex organic compounds into simpler molecules

• Examples:

  • Bacteria

  • Fungi

  • Invertebrates

• Play a crucial role in the cycling of nutrients and matter

• The decomposition of organic matter returns monomers and nutrients to the soil - making it available for plants to reuse

  • Decomposers release carbon, nitrogen, and phosphorus during decomposition allowing other plants to acquire these nutrients for their growth and development

Types of decomposer: Saprotroph

• Saprotrophs obtain organic nutrients from dead organisms through external digestion

• Secrete hydrolytic enzymes and breakdown molecules outside of the organisms, then the nutrients are absorbed into their own body tissues

• Example:

  • Fungi

  • Bacteria

Types of decomposers: Detritivore

• Obtain nutrients from detritus using internal digestion

• Detritus - Organic matter created during the decomposition of dead organisms

• Unlike saprotrophs, detritivores directly ingest and consume dead organic matter, breaking it down internally using digestive enzymes

• Example:

  • Earthworms

  • Millipedes

  • Snails

Decomposers play an essential role in maintaining the balance and sustainability of ecosystems due to their ability to cycle nutrients.

Food chain

• Diagram to show the flow of energy & biomass through a community

• Food webs are several food chains that are interconnected

• Arrows show the direction of the transfer of energy and biomass

Food webs

• Show a more complete description of energy transfer

• Normally food webs sti aren’t fully complete either

Typically decomposers (detritivores and saprotrophs) are not included in food chains and/or food webs. However, they play a vital role in the ecosystem health

Trophic levels

• Trophic levels represent an organism’s position in a food chain or food web, defining its role in energy transfer

• The first trophic level is occupied by producers

  • These organisms use external energy, such as sunlight, to convert inorganic molecules into organic compounds, serving as the foundation of energy for the entire ecosystem

  • Example:

    • Plants

    • Some bacteria

    • Algae

• The second level consists of primary consumers

  • These organisms are herbivores or omnivores that directly consume producers to obtain energy

  • Examples:

    • Small mammals

    • Some birds

    • Insects

• The third trophic level consists of secondary consumers

  • These organisms feed on primary consumers as their main source of energy

  • Secondary consumers feed on herbivores or omnivores and transfer energy to higher trophic levels

  • Examples;

    • Larger mammals

    • Certain predatory birds

    • Some reptiles

• The final trophic level consists of tertiary consumers

  • These top-level predators feed on other organisms, including both primary and secondary consumers

  • They represent the highest trophic level in a food chain, and their diet typically consists of large predators or other top-level consumers

  • Example;

    • Large carnivores

      • Lions

      • Tigers

      • Killer whales

• Some organisms can occupy more than one trophic level in different food chains

• Certain species may display dietary flexibility, allowing them to adapt their feeding habits based on the availability of food sources

• Omnivores can be considered both primary and secondary consumers

• A significant amount of the energy available at each trophic level is not efficiently transferred to the next level, resulting in a decrease in energy at each consecutive trophic level.

Energy use

• Cellular respiration is a vital and shared process among both autotrophs and heterotrophs

• Organisms utilize most of the organic molecules that they produce/obtain for cellular respiration

• Cellular respiration produces ATP energy for the organism, however, some of the energy is lost as heat

• The heat will dissipate into the environment

Energy is lost at each level - higher trophic levels have less energy than lower trophic levels

The 10% rule - On average, only 10% of the available energy at a lower trophic level can be transferred to the next successive trophic level. 90% of the energy is lost at each level

Sources of Energy losses

• Heat dissipation

  • heat is produced as a byproduct of metabolic reactions (including cellular respiration), this heat is lost to the environment

• Incomplete consumption

  • Organisms don’t fully eat all of the biomass of their food, uneaten parts represent a loss of energy

• Use in metabolic processes

  • Organisms will use the energy extracted from their food to perform functions of life that require energy

• Insufficient energy conversion and storage

  • Not 100% of energy and nutrients can be stored within an organism

• Inefficient digestion

  • Organisms are unable to absorb all the energy contained in the consumed food during digestion

Energy loss limits Food Chain length

• Energy losses cause a great decrease in the amount of energy stored as biomass at each successive trophic level

• As energy moves up the food chain, the amount of energy available eventually becomes insufficient to sustain an additional trophic level

Typically we only see food chains 4-5 trophic levels long because there wouldn’t be enough energy available for higher energy levels

Energy pyramid

• Diagram to represent the amount of energy available at each trophic level

• The units used are energy units per area per time

Biomass

• The total dry mass of a group of organisms in a specific area or volume

• It is measured in units of mass per unit area, such as grams per square meter

• Naturally, biomass contains energy

• Measuring biomass requires organisms to be completely dehydrated, hence they do not survive the process

• Measuring biomass in a food chain over time enables ecologists to estimate the energy availability at each trophic level and assess the efficiency of energy transfers

• It can be used to measure energy because the tissues of organisms are composed of organic compounds which contain energy, biomass inherently contains energy

Energy pyramid - The amount of energy available at each trophic level can be represented by using an energy pyramid.

Primary productivity

• The rate at which producers accumulate carbon compounds in their biomass (aka do photosynthesis and store organic molecules)

• Biomass accumulates as organisms grow or reproduce

• Measured in units of mass per unit area per unit time

More producer biomass can support a greater number and diversity of consumers within an ecosystem

Factors impacting Primary productivity

• Temperature

• Precipitation

• Nutrient availability in the soil

• Etc.

More sunlight, water, and nutrient-rich soils = higher primary productivity

Gross & Net primary productivity

• GPP= total amount of energy captured as biomass by primary producers in an ecosystem. It represents the rate at which carbon is converted into organic matter by autotrophs

• NPP = the energy available to consumers at higher trophic levels

• NPP = GPP - R

  • Where R is loss of energy due to respiration

Secondary productivity

• The rate at which consumers accumulate carbon compounds as part of their own biomass

• Heterotrophs play a crucial role in energy and nutrient transfer within ecosystems through processes such as predation, herbivory, and scavenging

• Heterotrophs also experience a loss of biomass during cell respiration

Gross & Net secondary productivity

• Gross secondary productivity (GSP) = total biomass assimilated (absorbed) by heterotrophs in an ecosystem

• Net secondary productivity (NSP) = The biomass that remains after accounting for respiratory losses. NSP represents the energy available to sustain higher trophic levels and contributes to the overall flow of energy within the ecosystem.

• NSP = GSP - R

Populations and Communities

Population

• A population is a group of organisms of the same species who live in the same area at the same time

• A population refers to a group of organisms of the same species that typically interbreed, sharing a common gene pool

• Populations are reproductively isolated from other populations ~ reproductive isolation

  • Reproductive isolation is the inability of organisms of the same species to successfully breed due to geographical isolation, behavioral isolation, or temporal isolation

Population size

• Most of the time, it is not practical to count every individual in a population

• Swapping techniques will be utilized to estimate the population size

  • Random sampling is critical to give an accurate representation of the population as a whole

    • Every organism has an equal chance of being selected during random sampling

Quadrat sampling

• Quadrat sampling is a technique particularly useful to study populations of sessile organisms, such as plants and corals. A quadrant, a square frame of known area, is randomly placed over a section of the habitat being studied and the number of organisms of interest that fall within each quadrat is recorded.

  • Sessile organisms - an organism that is fixed to one location

1. A quadrant is placed randomly in a section of the habitat

   • Random sampling involves the unbiased selection of organisms, where each individual has an equal chance of being chosen

2. The number of organisms interest that fall within the quadrant is recorded

   • Generally, if an organism touches the lines of the quadrat and more than half of its total area falls within the frame, it is included in the count

3. The average number of organisms in each quadrant calculated

4. Total population size estimated based on area of quadrant v. total area

• To ensure accuracy and representativeness, it is important to sample an appropriate number of quadrats across the area of study.

• The number of quadrats being sampled should be large enough to minimise the effects of uncertainty, but not too large so that the task becomes impossible to carry out

• A minimum of 10 samples are recommended to obtain reliable estimates of population size and distribution

For hard-to-reach areas, you can use HD photos and use a grid overlay to act as your quadrant

Capture-mark-release-recapture method

• Good for motile (moving) organisms

• The Lincoln Index allows you to estimate the population size based on sampling numbers

1. Capture a sample of organisms

2. Mark the organisms in a way that doesn’t impact survival (record number marked)

3. Then release marked individuals back into the habitat

4. Allow for reintegration with unmarked individuals

5. Capture a second sample

6. Record the total number in the second sample AND the number of marked individuals in the second sample

• The capture-mark-release-recapture method does have some limitations such as:

  • This method assumes that the marking technique does not have any influence on the behavior or survival of the organism

  • It assumes that the marked individuals fully reintegrate into the population and have equal chances of being captured compared to unmarked individuals

  • The method assumes that there are no births, deaths, immigrations, or emigrations during the study period

Lincoln index formula

• Used after the capture-mark-release-recapture method to estimate the population size

• Population estimate = M x N/R

  • M = number of individuals marked in 1st sample

  • N = total number of individuals captured in 2nd sample

  • R = number of marked individuals recaptured in 2nd sample

• The Lincoln Index also has some limitations of its own:

  • It relies on the assumption that the marked individuals used in the estimation process are representative of the entire population

  • It assumes that the ratio of marked to unmarked individuals in the second sample accurately reflects the ratio of the population

• Despite these limitations, it is possible to enhance the accuracy of the Lincoln index by increasing the sample size and conducting repeated sampling to estimate a mean value.

• Some factors determine if a sample is significant or not in this method and help determine how big of a sample is needed. These factors are:

  • Population density

  • Availability of resources

  • Level of mobility

Population Dynamics

Carrying Capacity

• Every environment has a carrying capacity

• Carrying capacity - The maximum population size of a species that can be sustained (long term) by a given environment

• The carrying capacity of an ecosystem is dynamic, meaning that it varies over space and time depending on the abundance of limiting resources

Limiting factors

• Limiting factors are environmental factors that restrict the growth, distribution, or abundance of a population or organism within an ecosystem

• Examples:

  • Availability of food

  • Availability of water

  • Space

  • Shelter

  • Disease/Parasites

  • Predators

  • Climate

• When these resources are limited it creates competition between individuals.

  • This competition could be interspecific or intraspecific

Density Dependent Limiting factors

• Both density-dependent and density-independent factors influence the size of a population

• Density-dependent factors have a greater impact on population size as the population density increases

• Due to an increase in interspecific and intraspecific competition

• Density-dependent limiting factors include:

  • Competition for resources

    • This competition results in reduced productivity, decreased growth rates, and increased mortality

  • Predation

  • Disease/Parasites

• These fluctuations in population sizes hep maintain a relative balance in the ecosystem, ensuring the survival of both predator and prey species

Typically, density-dependent limiting factors keep the population size around the carrying capacity

Interspecific v. intraspecific Competition

• Interspecific competition - competition between organisms of different species

• Intraspecific competition - competition between organisms of the same species

Density Independent Limiting Factors

• Have an impact on population size regardless of its density

• These factors are external to the population and can cause sudden and drastic changes.

• Typically abiotic

• Examples:

  • Natural disturbances

    • Floods

    • Droughts

    • Hurricanes

    • Earthquakes

    • Volcanic Eruptions

  • Anthropogenic Events

    • Habitat destruction

    • Pollution

    • Climate change

• These density-independent factors can alter the availability of resources, therefore changing the carrying capacity of an ecosystem

Population Growth Curves

Exponential Population Growth

• Represented by a “J-shaped curve”

• Occurs in ideal conditions - resources are unlimited, biotic and abiotic factors are favorable

• Example:

  • Bacterial growth in the lab

In ecosystems limiting factors are present - preventing unlimited exponential growth

Exponential growth typically only occurs when the population is well below the carrying capacity

Sigmoid Population Growth

• Represented by an “S-shaped curve”

• Occurs in environments with limited resources

• Initially, a population experiences exponential growth when resources are abundant and competition is low

• As the population grows, density-dependent factors increase, and growth slows (transitional phase with environmental resistance)

  • The scarcity of resources intensifies competition among individuals, leading to a gradual decrease in the growth rate

• Eventually reaches an equilibrium around the carrying capacity (plateau phase)

  • At this point, the birth rate equals the death rate and the population stabilizes.

• The S-shaped curve represents the transition from rapid exponential growth to a more gradual increase until reaching the carrying capacity

• Sigmoid population growth is a common pattern observed in natural populations and provides insight into how populations interact with their environment and the constraints imposed by limited resources

Factors Affecting Population Growth

• Natality (N) = Brith rate

• Immigration (I) = individuals entering population

• Mortality (M) = Death rate

• Emmigration (E) = Individuals leaving population

• Population growth = (N+I) - (M+E)

N + I > M + E

• Population size increases (positive population growth)

• If (N + I) is significantly greater than the population is likely in the exponential phase and the population is growing rapidly

• If (N + I) is only slightly greater than (M + E) then the population is likely in the transitional phase and the population is growing slowly

• Slower growth due to density-dependent limiting factors

N + I = M + E

• Population size is constant (0 population growth)

• Likely in the plateau phase

N + I < M + E

• Population size is decreasing (negative population growth)

• Many countries have declining populations because birth rates are low

• Examples:

  • Japan

  • Italy

Intraspecific Interactions

Intraspecific interactions

• Intraspecific competition occurs when members of a species compete for limited resources.

• This competition can lead to:

  • Adaption of individuals to different niches

  • Displacement of less-competitive individuals

  • Regulation of population size

• Interactions between organisms of the same species

• Includes competition and cooperation

• Cooperation is also observed within ecological communities where the species collaborate to increase their chance of survival and reproduction

Intraspecific Competition

• Organisms of the same species compete for the same limited resources

  • food

  • shelter

  • mates

• Density-dependent limiting factors

Intraspecific cooperation

• Individuals collaborate to increase their chances of survival and reproduction

• Examples:

  • Group hunting/foraging

  • Defense against predators

  • Shared parenting

Interspecific Interactions

Community

• A group of interacting species (different species) in a particular area

• These populations interact and coexist, forming complex ecological relationships and contributing to the overall functioning of the ecosystem

• Communities will have intraspecific and interspecific interactions

Interspecific interactions

• Interactions between organisms of different species within an ecosystem

  • Herbivory

  • Predation

  • Interspecific competition

  • Symbiotic relationships

Interspecific Interaction: Herbivory

• Feeding relationship: herbivore eats plant material

• Examples:

  • Giant panda eating bamboo

  • Parrot fish eating algae on coral reefs

Interspecific interaction: Predation

• Feeding relationship: predator captures and consumes its prey

• Examples:

  • Grizzly bears and salmon

  • Wolves and deer

Predator-Prey Relationships

• Density-dependent limiting factor

• The cyclical pattern of population increases and decreases

• As prey numbers increase, predator numbers increase and the prey experiences increased predation

• Reduces prey numbers

• Less prey means less food available to predators and predator numbers drop

• Less predators mean prey population can increase

• Predator numbers increase/decrease slightly after prey numbers increase/decrease

Interspecific Interaction: Interspecific competition

• Competition between different species for the same limited resources

• This competitive interaction has significant implications for species distribution, abundance and the evolution of traits related to resource acquisition

• Example:

  • Eastern grey squirrels and American red squirrels compete for food

• Interspecific competition can be tested for by removing one species from the ecosystem

• If the second species is more successful, this suggests that there is interspecific competition

Interspecific Interaction: Symbiotic Interactions

• 2 Organisms living and interacting closely with each other where at least one organism benefits

  • Parasitism

  • Commensalism

  • Pathogenisity

  • Mutualism

• Symbiotic interaction: Parasitism

  • One organism (parasite) is helped and the other organism (host) is harmed: ±

  • Parasites live on or within the host, extracting nutrients and resources that often result in harm or disease

  • Example:

    • Tapeworms living in a human gut

  • Parasites have evolved to minimize damage (to keep the host alive longer)

• Symbiotic interaction: Pathogenicity

  • A pathogen is a microorganism

    • Virus

    • Bacterium

    • Fungus

    • Infectious agent

  • Causes disease in the host

  • Pathogens typically invade and multiply within the hosts tissues, disrupting normal physiological function and leading to various symptoms of illness

  • Unlike parasites, pathogens often have a direct and immediate effect on the hosts health and can easily spread from one host to another

• Symbiotic Interaction: Commensalism

  • One organism is helped and the other organism is neither helped nor harmed: +/0

  • Examples:

    • Orchids growing on branches of trees

    • Sharks and remoras (Suckerfish)

• Symbiotic interaction: Mutualism

  • Both organisms are helped by the relationship: +/+

  • Examples:

    • Root nodules in Legumes

      • Root nodules contain nitrogen-fixing bacteria

      • Bacteria provide the legumes with usable nitrogen

      • Legumes provide bacteria with carbohydrates and other organic molecules/compounds

    • Mycorrhizae in Orchids

      • Fungi colonize orchid roots and form Mycorrhizae

      • Fungi increase surface area for nutrient absorption in the soil

      • Orchids provide the fungi with organic compounds produced during photosynthesis

    • Zooxanthellae in hard corals

      • Zooxanthellae are unicellular photosynthetic algae that live within the tissues of hard corals

      • Zooxanthellae provide corals with organic molecules made during photosynthesis and augmentation to protect them from UV exposure

      • Corals provide the zooxanthellae with a sheltered environment and easy access to sunlight

Invasive Species and Interspecific Competition

Endemic V. Introduced Species

• Endemic Species are native to the location

• Introduced species are non-native and were introduced by humans (also called alien species)

• Introduction can be accidental or deliberate

Non-invasive introduced species

• Sometimes an introduced species doesn’t become invasive

• Examples:

  • Potatoes brought to Europe from Peru

Invasive species

• An introduced species becomes invasive when it causes harm to the ecosystem and outcompetes native (endemic) species

• Examples:

  • Lionfish in the Caribbean

  • Kudzu in Georgia

• Invasive species can cause a decline in endemic species because they rapidly increase in number and are more efficient in resource use

• Invasive species can have detrimental impacts on native biodiversity, causing them to become invasive

• Humans play a significant role in the introduction and spread of invasive species

Invasive species case study: F in the US

• Kudzu is native to Japan and southeast China

• It was introduced to the US in 1876 as an ornamental plant and was promoted as a tool to prevent soil erosion in the 1930s-1950s

• Once established it can grow as quickly as 1 ft per day

• Outcompetes native species by shading native plants (preventing photosynthesis)

• Causes loss of native biodiversity because the native plants are choked out and the organisms rely on the native plants which are also impacted

Testing for interspecific competition

• Laboratory experiments provide controlled conditions where variables can be manipulated to observe their effects on species’ success

• One way to assess the impact of a species involves selectively removing it from the community and observing the response of the remaining organisms which sheds light on the impact of competition on their distribution and overall success

Control of Population Size

• Population control in ecology refers to the regulation of the size and growth within an ecosystem

• Various factors influence population control

  • Predators play a crucial role in regulating prey populations by exerting selective pressure and preventing unchecked growth

Top-down control

• The presence and activities of organisms at higher trophic levels regulate the abundance or behavior of lower trophic levels in a food chain

• Predators, at the top of the food chain, play a significant role in exerting top-down control. By consuming and limiting the abundance of their prey, predators indirectly shape the structure and dynamics of lower trophic levels

Top-down control case study: Wolves of Yellowstone

• The reintroduction of Grey Wolves caused a trophic cascade - wolves impacted many trophic levels within the ecosystem

Bottom-up control

• The availability of resources at lower trophic levels influences the abundance and distribution of organisms at higher trophic levels

• Several factors can exert bottom-up control:

  • Nutrient availability

  • Climatic conditions

  • Primary productivity

• Example:

  • Nutrient availability in soil determines the growth of plants which determines predator numbers (another type of trophic cascade)

Top-down and Bottom-Up control

• Both types of control are present in most ecosystems, however normally one tends to be the dominant type of control

Allelopathy

• Allelopathy - The process by which organisms release biochemical compounds into the environment, influencing the growth, survival, or reproduction of other organisms

• Organisms release biochemical compounds into the environment, influencing the growth, survival or reproduction of other organisms in the area

Antibiotic secretions

• Some microorganisms can secrete antibiotics to hinder the growth of bacteria

• Streptomyces bacteria commonly found in soil and marine environments, can synthesize a wide range of antibiotics, including streptomycin

Adaption to Environment

Diversity of environments

• Big picture: The earth contains a wide range of biomes characterized by different climates

• Organisms are adapted to specialize and thrive in their specific environments

Adaptions

• Adaption = any characteristic or trait that aids in an organism’s survival

• Adaptions are specific to the environment: If the environment changes, what is beneficial also changes

Habitat

• Habitat = the specific place where an organism or a group of organisms lives and interacts with its surroundings

• Defined by:

  • Geographical location

  • Physical location

  • Ecosystem

• Habitats consist of both biotic (living) and abiotic (non-living) factors

• To describe the habitat of a species, we need to look at:

  • Geographical location - this could be on a map or in a specific area

  • physical location - this includes the environment which incorporates factors such as the type of soil, availability of water and food, and other plants and animals around

  • Ecosystem - this is the bigger picture of all the biotic and abiotic factors and their relationships in a particular area

• Habitats on Earth can be classified into two broad categories based on their geographical location:

  • Terrestrial habitats (land-based environments)

  • aquatic environments (water-based environments)

• Each of these categories of habitat has distinct physical and chemical characteristics that support different types of organisms and contribute to the overall diversity of life on Earth

Natural selection and adaption

• Natural selection is a mechanism of evolution where organisms who are well adapted to their environment survive and reproduce more successfully than their beneficial traits to their offspring

• Adaption - A genetic change that increases an organism’s chances of survival and reproduction in a particular environment. these genetic changes can occur randomly through mutation or can be driven by selective pressures in the environment

  • Organisms develop adaptions to cope with the physical or abiotic conditions of their habitat, such as temperature, moisture, light, and other environmental factors

Biotic and Abiotic factors

• Adaptions help an organism cope with and survive in its environment biotic and abiotic factors

• Examples:

  • Biotic - predators, food type

  • Abiotic - climate, water availability

Adaptions on Sand Dunes

• Sand dunes are created by plants and grasses trapping sand that is carried inland by winds

• sand dunes are characterized by harsh and unstable conditions

• Marram grass is a species of grass that is adapted to live on sand dunes

• Plants require:

  • Drought and salt tolerance

  • Strong roots

  • Strong leaves

  • Rhizomes = horizontal underground stems

Adaptions in Mangroves

• Mangroves are found in brackish water (where saltwater and freshwater mix)

• The salinity of the water makes it difficult for plant species to survive

• Rhizophora apiculata is a species of plant that is well-adapted to mangrove environments

• It is a halophyte - a plant species that can survive in high-salinity environments

• It has specialized aerial roots (called pneumatophores) that help provide the plant with oxygen in the water-logged soil

Abiotic Factors and Species Distribution

• Abiotic factors can affect species distribution

• Examples:

  • Temperature

  • Humidity

  • Light

  • Water

  • Soil composition (typically not relevant for animals)

• Certain species are adapted to specific abiotic conditions, such as extreme temperatures, low water availability, or acidic soil, whereas others may not be able to survive in these conditions and will be limited to regions that have more favorable abiotic conditions

• Abiotic variables can also influence the interaction between different species in an ecosystem

• No species is capable of surviving under all the varying conditions found on the Earth, thus leading to restrictions in their distribution

• The marine ecosystem is strongly influenced by various abiotic factors, such as:

  • Water depth

  • temperature

  • Salinity

  • pH

  • Currents

  • Water clarity

Range of tolerance

• Range of tolerance - the range of environmental conditions, within which an organism can survive and function optimally

• Organisms have a specific range of tolerance to each environmental factor, beyond which they may experience stress or even death which varies among different species

• Species have a range of conditions that they can tolerate based on their adaptions

• This range of tolerance will determine its species distribution

Range of tolerance as Limiting factors

• Range of tolerance can be affected by environmental changes such as:

  • Climate change

  • Pollution

  • Habitat destruction

• If environmental conditions fall outside of an organism’s range of tolerance, the environmental condition becomes a limiting factor

• Example:

  • Freshwater availability

Biomes

Biomes

• Biome - a large community of plants and animals that occupy a distinct geographical region and are adapted to its climate and other environmental conditions

• Biomes are characterized by the dominant vegetation, animals, and climate patterns found in a particular area

• Biomes are groups of similar ecosystems that share common abiotic and biotic factors (fauna and flora)

• Terrestrial biomes are characterized by the dominant vegetation, animals, and climate patterns

The two major abiotic factors that determine a type of biome present are: Temperature and Rainfall

These interact with each other to form climates that are unique to each biome.

• temperature has a direct impact on the distribution of biomes because it affects the rate of biological processes such as photosynthesis, growth, and metabolism

• Rainfall determines the availability of water, which is essential for the survival of plants and animals

Climatograph

• The average temperature and rainfall can be graphed in a climatograph

• The graph typically shows temperature on the horizontal axis and rainfall on the vertical axis

• Different biomes are represented as distinct regions on the graph

• The graph can help to illustrate the patterns of temperature and rainfall that are associated with each biome type

Biomes and convergent evolution

• Convergent evolution- the process where different species have evolved to have similar traits in response to similar environmental pressures, even though they have different evolutionary histories

• Biomes ar groups of ecosystems that share similar abiotic conditions, such as climate, soil, and water, which in turn result in similar communities of plants and animals due to convergent evolution

• Similar biomes in different areas of the world have many similar organisms

• Many of the similarities are due to convergent evolution

A biome is a larger and more broadly defined area, whereas an ecosystem is a smaller and more specific area. Biome > ecosystem

Adaptions in hot deserts

• Adaptions made by a plant:

  • Vibrant red flowers attract pollinators for reproduction

  • Leaves sprout after rainfall to perform photosynthesis

  • Long thorny stems can expand to store water during drought, allowing it to survive when water is scare; thrones also serve as a deterrent to herbivores

  • Greenish chlorophyll-containing bark allows it to carry out photosynthesis even when there are no leave present

  • Deep root system which allows it to access water from deep in the soil and an additional root system which allows it to quickly absorb even small amounts of precipitation

• Adaptions made by an animal:

  • Venom contains toxins that can cause intense pain and swelling, making it a strong creature to encounter in the wild.

  • Powerful jaws and venomous saliva, which it uses to overpower its prey and protect itself from predators.

  • Slow metabolic rate allowing it to go for long periods without food and water.

  • Skin is covered in bumpy scales, which help it retain moisture.

  • Unique ability to store fat in its tail helping it survive long periods of time without food.

Adaptions in tropical Rainforests

• Adaptions made by a plant:

  • The unique root system allows it to anchor itself to the muddy bottom of the river and extract nutrients from the nutrient-rich soil.

  • The plant's large flowers open at night and emit a strong fragrance to attract pollinators.

  • Large circular leaves which can grow up to 3 metres in diameter are covered in a waxy coating that helps them repel water, allowing them to stay afloat on the surface of the water.

• Adaptions made by an animal:

  • Strong and sensitive hearing allows it to detect the sounds of prey moving through the forest.

  • Binocular vision allows it to accurately judge distances and track fast-moving prey.

  • Sharp beak that allows it to capture and feed on large prey.

  • Broad and strong wings enable it to move through the dense forest canopy with ease and to glide through the air silently.

  • Strong talons to crush the skulls of its prey.

Ecological Niches

Ecological Niche

• The distribution of species is determined by interactions from the environment of both biotic and abiotic factors

• An organism’s ecological niche is an organism’s role in the ecosystem

• This includes both the habitat (location) and how it interacts with other organisms and with other organisms and with the abiotic factors in the ecosystem

Organisms are adapted to their specific ecological niche

Ecological specialization

• Organisms that live in very specific conditions and have highly specialized niches are consideredspecialist species

• Example:

  • Koalas

Ecological Generalization

• Organisms that can survive in a broader range of conditions are called generalist species

• Example:

  • Black Rats

Organism’s Impact on the Environment

• An organism’s niche includes its interactions and impact on the environment

• Many species have significant impacts on their environment, like Beavers or Elephants

Niches and Modes of Nutrition

• An organism’s niche is influenced by its mode of nutrition:

  • Autotrophs - Use energy from the sun to generate their nutrition

    • Producer

  • Heterotrophs - Organisms that need to take their nutrition from external sources

    • Consumer

    • Decomposer

      • Detritivore

      • Saprotroph

Holozoic Nutrition

• Holozoic nutrition refers to organisms that take in solid or liquid food internally

• Heterotrophic organisms are holozoic

Mixotrophic Nutrition

• Mixotrophic organisms can use a combination of methods to generate their nutrition

• They are neither fully autotrophic nor heterotrophic

• Mixotrophic microbes can photosynthesize like a plant and therefore take in carbon dioxide, but they can also take in nutrition like an animal

• As they respire they then release carbon dioxide

Saprotrophic nutrition

• Saprotrophic nutrition is a method by which the organism secretes digestive enzymes that can break down the dead organic material, including tough components of dead plants such as cellulose, hemicellulose, and pectin

• These organisms are vital to break down dead leaves and logs

Modes of respiration

Throughout the world, organisms have evolved to generate ATP in different ways

• obligate anaerobes

• facultative anaerobe

• obligate aerobe

Obligate Anaerobes

• Obligate anaerobes are organisms that respire in situations without oxygen and cannot survive in air

• Oxygen is toxic to them

• Rather than use oxygen as the electron acceptor for respiration they use other compounds such as:

  • Sulfate

  • Nitrates

  • Iron

  • Manganese

  • Mercury

  • carbon monoxide

• These types of organisms lack certain enzymes that enable them to deal with the oxygen, and hence it becomes toxic

Facultative Anaerobe

• Facultative anaerobe - Organisms that can survive in environments that contain or lack oxygen

• If oxygen is present it can make ATP

• If oxygen is absent it can switch to fermentation

• They grow better in aerobic (with oxygen) conditions

Obligate aerobe

• Requires oxygen as a final electron acceptor in order to carry out respiration and release energy

  • Cannot survive without oxygen

• Obligate aerobe - Organisms that cannot survive in environments that contain oxygen

Fundamental v. Realized Niche

• Fundamental niche - The range of environmental conditions in which a particular species can live and reproduce

• Realized niche -The environmental condition in which the species actually lives considering constraints such as the presence of other species

• An organism’s fundamental niche is the total range of environmental conditions and ecological roles that an organism could fulfill in the absence of competition

• An organism’s realized niche is the actual role that an organism occupies in an ecosystem

• The realized niche is smaller than the fundamental niche because of interspecific competition

• Realized niche is formed when the species within a fundamental niche has to deal with the pressure of co-existing with the other species in the environment

Competitive exclusion

• Competitive exclusion principle - States that if two species with identical niches compete, then one will inevitably drive the other to extinction

• No two species can occupy exactly the same niche at the same time

• Implications of direct competition:

  • One species outcompete the other

  • The “losing” species will either: adapt or face local extinction

The realized niche is smaller than the fundamental niche due to the competitive exclusion principle

Niche Partitioning

• Niche partitioning - The process by which competing species use the environment differently in a way that helps them to coexist. This may be spatial or temporal

• Competing species use the environment differently in a way that helps them to coexist

• Eliminates direct competition for exactly the same niche - allows for the survival of both species

Spatial niche partitioning

• Organisms still live near each other, but slight differences in locational preference allow the niche to be divided

• Example:

  • Different species of warblers living in coniferous trees

Temporal Niche Partitioning

• Organisms live near each other - a difference in active time of day allows the niche to be divided

• Example:

  • A common spiny mouse is active during the night and Golden spiny mouse is active during the day

Transfer of matter, Climate Change, and Human Impacts on the Environment

The Carbon Cycle

The carbon cycle is a fundamental process that allows carbon atoms to be exchanged between the Earth’s systems.

Energy v. Matter Transfer

• As energy transfers through an ecosystem, it is eventually lost as heat

• As matter transfers through an ecosystem, the atoms get recycled and re-enter the food web at the producer level

Carbon sinks

• In the carbon cycle, carbon is stored in various reservoirs known as carbon sinks

• Any environment that absorbs more carbon dioxide than it releases

• These are essential for countering acting greenhouse gas emissions by storing carbon

• Implication: Carbon sinks reduce atmospheric CO₂

• Example:

  • Forests continuously absorb carbon as the plants perform photosynthesis

Carbon sources

• Locations or processes that release more carbon in the atmophere than they absorb

• Implication: Increase atmospheric CO₂

• Example:

  • Respiration and burning of fossil fuels

Carbon fluxes

• Carbon atoms on Earth don’t stay in one place, they constantly move between the Earth’s systems:

  • Atmosphere

  • lithosphere

  • hydrosphere

  • biosphere

• Movement of carbon through the ecosystem

  • These movements are known as fluxes

• Drawn as arrows in the carbon cycle

• Example:

  • Consumption of plants, fossilization (formation of fossil fuels)

(insert diagram here)

need to know:

• Photosynthesis

• Feeding

• Respiration

• Combustion (sorta need to know)

1. Carbon dioxide is released into the atmosphere via carbon fixation

2. Carbon dioxide is absorbed and used as energy via photosynthesis

3. Carbon compounds enter the food chain through feeding

4. Carbon is released back into the atmosphere via respiration from consumers

5. Carbon enters the the atmosphere through decomposition

Ecosystems as carbon sinks or sources

• Whether an ecosystem is a sink or a source is dependent on the balance of photosynthesis and cellular respiration in the ecosystem

• If more photosynthesis occurs, CO is absorbed meaning it is a carbon sink

  • Photosynthesis > CR = carbon sink

  • Examples:

    • Environments with lots of trees

• If more cellular respiration occurs, CO is released back into the atmosphere

  • CR > photosynthesis = carbon source

  • Examples:

    • Environments with lots of decaying organisms (dead trees)

  

Human Impact on the Carbon Cycle and Climate Change

Combustion and the Carbon Cycle

• Combustion is a carbon source - increases atmospheric CO₂

• In the carbon cycle, producers absorb CO during photosynthesis, converting it into organic compounds and storing it as biomass

• Natural carbon sinks, such as forests and oceans, can absorb some of the excess CO, but they have limits to their capacity

• Natural combustion occurs naturally

  • Natural combustion events contribute very little to the carbon cycle compared to human-induced combustion

  • Example:

    • Lightning strike causing a wildfire

• During the process of combustion, the carbon stored within these organic compounds is released in the form of CO

Combustion of fossil fuels

• Humans increase the impact of combustion by burning fossil fuels (coal, oil, and natural gas)

• Releases carbon that was previously sequestered in a carbon sink for millions of years

The Keeling Curve

• Shows atmospheric CO₂ fluctuations over time

• Shows the concentrations of carbon dioxide in Earth’s atmosphere over time.

The Keeling Curve: Annual cycle of atmospheric CO₂ concentration

• Decrease in atmospheric CO₂ (negative slope) during the growing season (late spring and summer) because the rate of photosynthesis is greater than cellular respiration

• Increase in atmospheric CO₂ (positive slope) during the dormant season (late fall and winter) because the rate of photosynthesis has dropped and is less than cellular respiration

The Keeling Curve: Overall trend of atmospheric CO₂ concentration

• A rapid increase in atmospheric CO₂

• Due to anthropogenic impacts

  • Example:

    • Burning fossil fuels

CO₂ is a greenhouse gas

The greenhouse effect

• The warming effect that occurs when greenhouse gases trap heat as it radiates off of the Earth’s surface

• Necessary for life on Earth (it would be too cold without it)

Greenhouse gases (GHGs)

• The impact of greenhouse gas takes into account: abundance and ability to trap heat

• The two greenhouse gases that have the largest impact on the greenhouse effect: CO₂ and water vapor

• Other greenhouse gases: methane and nitrous oxides

• CO₂ and methane are the most worrisome greenhouse gases because they are increasing due to anthropogenic causes

Climate Change

• A long-term change in the Earth’s overall temperature with massive and permanent ramifications

• There is a warming effect but weather events become more extreme (hotter summers, colder winters, stronger storms, more flooding, etc.)

• One of the causes of climate change is an increase in the greenhouse effect

• 2 major causes of increasing the greenhouse effect:

  • Combustion of fossil fuels

  • Deforestation

Ecosystem Sustainability

The link between photosynthesis and cellular (aerobic) respiration

• Aerobic preparation and photosynthesis are two linked processes vital for life on Earth to exist

• Photosynthesis and aerobic respiration have a reciprocal relationship with each other

  • Aerobic respiration requires O which is created during photosynthesis.

  • Photosynthesis requires CO which is created during aerobic respiration

• The products of photosynthesis are the reactants of aerobic respiration and vice versa

• The interaction between aerobic respiration and photosynthesis forms an essential interaction between autotrophic and heterotrophic organisms

Sustainability and cycling of matter

• Big picture:

  • For an ecosystem to be sustainable, it must be able to cycle matter, including:

    • Carbon

    • Nitrogen

    • Phosphorus

• In addition to carbon, all the chemical elements required by living organisms are recycled within ecosystems.

• Decomposers play a vital role in this recycling of matter by breaking down organic compounds and returning the nutrients back into the environment

Nitrogen and Phosphorus Cycles

Nitrogen cycle

• Nitrogen is necessary for building protein and nucleic acids

• Plants must absorb nitrogen compounds from the soil because atmospheric nitrogen (N₂) isn’t usable by plants

Nitrogen fixation

• Nitrogen fixation is the process of converting N into usable forms of nitrogen such as:

  • Ammonium (NH₄)

  • Nitrite (NO)

  • Nitrate (NO)

Nitrogen-fixing bacteria

• Nitrogen-fixing bacteria live in the soil and live in the root nodules of legumes

• Provide usable nitrogen for plants

• Remember: the root nodules in the legume family are a type of mutualism

Nitrogen fixation and Lightning

• Lightning also causes the nitrogen fixation process

Denitrification

• Converts the usable forms of nitrogen back into atmospheric N₂

• Implication: reduces nitrogen availability for plants

• Denitrifying bacteria perform this

Phosphorus cycle

• Phosphorus is necessary for building:

  • Nucleic acid (DNA and RNA)

  • ATP

  • Phospholipids

The rate of turnover is MUCH SLOWER for the phosphorus cycle compared to the nitrogen cycle

Phosphorus stores

• certain types of rocks contain large amounts of phosphate stores

• Weathering of the rocks releases the phosphates and allows plants to absorb it from the soil

Phosphate mining

• Humans will mine phosphate to extract it from the rocks to make fertilizer

• The rate of removal due to mining FAR exceeds the rate of replenishment

Eutrophication

Leaching of nutrients

• Nitrogen and phosphates are leached out of the top layers of the soil due to excess water

• This could be because of flooding or excess irrigation

• Often ends up in waterways

Runoff of nutrients

• Excess water due to rains/flooding or irrigation causes nutrients to runoff the top of the soil and into the waterways

• Amplified by excess application of fertilizers

Eutrophication

• Bodies of water become enriched with excessive nutrients (nitrogen and phosphorus)

Process of eutrophication

1. Nutrient enrichment

   • Excessive nutrients enter bodies of water.

   • Act as a fertilizer for aquatic plants and algae

2. Rapid growth of algae and plants

   • Algae and aquatic plants begin growing rapidly

   • Causes an algae bloom

3. Accumulation of organic matter

   • An increase in algae death (because of excessive numbers) causes an accumulation of organic matter (including dead algae) in the body of water

   • Acts as fertilizer

4. Increases decomposition and decrease of oxygen

   • Bacteria break down organic matter while consuming oxygen = increasing the demand for oxygen (biochemical oxygen demand - BOD)

5. Collapse of the aquatic ecosystem

   • Fish and other aquatic animals are choked out because of the lack of dissolved oxygen

   • Aquatic plants are choked out because the algae bloom blocks light and reduces photosynthesis (reducing dissolved oxygen even more)

Eutrophication and bottom-up control

• typically lack of nutrients acts as a bottom-up limiting factor to prevent algae blooms

• Eutrophication removes that limiting factor, which allows for overgrowth of aquatic producers (algae and aquatic plants)

Control of Algae blooms

• Algae blooms are controlled by bottom-up and top-down control

  • Bottom-up - limited nutrient availability (control removed with eutrophication)

  • Top-down - herbivorous fish (ex. parrot fish) consume algae to prevent overgrowth

Biomagnification

Bioaccululation and Biomagnification

• Certain pollutants and chemicals in the ecosystem persist and don’t get broken down

• Bioaccumulation - gradual build-up of chemical substances in the tissues of organisms over time. Occurs when pollutants enter an ecosystem

• With each successive level of the food chain, the connection of the pollutant can become magnified in the long term, which is called biomagnification

• Consumption of organisms whose tissues have accumulated chemicals leads to biomagnification

• Biomagnification - concentration of pollutants increasing as trophic levels increase

Biomagnification: Mercury

• Mercury cannot be easily excreted by organisms, and so it bioaccumulates

• Top predators have high mercury levels in their tissues due to biomagnification

  • example:

    • Tuna and polar bears

DDT

DDT is an insecticide that is used to reduce diseases transmitted by insect vectors (ex. malaria)

Biomagnification: DDT

• Biomagnification of DDT decimated the populations of birds of prey

• High levels of DDT lead to weaker eggshells

Restoration of natural processes in ecosystems by rewilding

• Rewilding - The process of restoring and reintroducing natural ecosystems and species to areas where they have been lost or significantly altered

  • Species reintroduction - This may involve bringing back keystone species, such as apex predators or large herbivores, which play critical roles in shaping ecosystems

  • Habitat restoration - Actions such as reforesting areas, removing invasive species, restoring wetlands, and creating wildlife corridors to reconnect fragmented habitats are some rewilding strategies.

  • Rewilding urban areas - Urban rewilding focuses on reintroducing nature into cities and urban environments. It involves creating green spaces, rooftop gardens, and wildlife-friendly habitats within urban areas

  • Rewilding rivers and waterways - Restoring natural processes in rivers and waterways is another rewilding strategy.

  • Ecological management and natural processes - Rewilding also emphasizes allowing natural ecological processes to occur without excessive human intervention.

Stability and Change

Transpiration - The loss of water vapor from plant leaves. Water vapor is lost by evaporation at the surface of the mesophyll cells; this water vapor then diffuses through the stomata and out of the plant

Sustainability - Refers to the capacity to meet the needs of the present generation without compromising the ability of future generations

Stability

Most ecosystems exhibit stability over time.

Biotic and Abiotic factors interact together and are dynamic, however, there are still relatively high levels of stability over millions of years.

Stability of Ecosystems

• Stability refers to an ecosystem's ability to maintain its structure and function over time despite disturbances

• A stable ecosystem can resist changes that may disrupt its steady state

• If a change or disturbance affects the structure or function of an ecosystem, a stable ecosystem should be able to restore itself back to its original state

• Implication: After disturbances, a stable ecosystem will restore its typical structure and function

• The accumulation of biodiversity also increases the overall stability of ecosystems, as the loss of a particular species is less likely to cause a significant disruption

• Ecosystem stability is important to all life forms because it ensures the continuity of ecosystems.

Stable ecosystems have resistance and resilience which allows them to maintain stability despite disturbances

Resistance and resilience

• Resistance - The ability of an ecosystem to withstand or resist changes caused by disturbances

• Resilience - The ability of an ecosystem to resist or recover from disturbances

Factors contributing to Stability

• Supply of energy

  • Ecosystems need a steady supply of energy to maintain stability

  • Producer diversity maximizes an ecosystem’s ability to harness energy and maintain stability

  • An ecosystem with a higher diversity of producers will likely be more resistant to changes in biotic and abiotic factors

• Recycling nutrients

  • Nutrients flow/transfer through the food web

  • They are returned to the soil as organic matter decomposes

• Biodiversity

  • Higher biodiversity tends to mean a more stable ecosystem

  • Species diversity ensures that there are enough different species to fulfill various ecological roles, which creates a more resilient ecosystem

• Climatic factors

  • Physical factors such as topography and water availability can greatly affect the stability of an ecosystem.

  • Extreme weather and climate changes create a less stable ecosystem

  • Changes to climate can reduce species diversity

Tipping points

• Tipping point - A critical threshold in a system where a small change can have significant and potentially irreversible effects

• Once the tipping point is reached, the ecosystem undergoes a profound transformation, often leading to the loss of biodiversity, collapse of population, or degradation of ecosystem services.

• Tipping points are often associated with hidden dynamics, where small changes can accumulate and trigger larger effects

Mesocosms

• Mesocosms - A closed experiment system that examines the natural environment or part of the environment under controlled conditions

• Scientists use mesocosms to investigate a variety of issues

• They allow researchers to easily manipulate environmental variables under controlled conditions

• Mesocosms can be used to investigate a wide array of factors, such as:

  • pH of water

  • Temperature

  • Light intensity

  • Color of light

  • Concentration of ions

  • Population size of producers

  • Diversity of producers

  • Population size of consumers

  • Community composition

Keystone species

Keystone species

• Have a disproportionately large impact on the community compared to their abundance of biomass

• Presence or absence has a significant impact on ecosystem stability

• Keystone species is an organism that helps define an entire ecosystem

• When the population of a keystone species declines or becomes unbalanced, it can trigger a cascade of ecological effects

Top-down control

• Many keystone species exhibit top-down control of the ecosystem and cause a trophic cascade

• Examples:

  • Sharks in marine ecosystems

  • Grey wolves in Yellowstone

  • Parrot fish on coral reefs

Other keystone species

• Even though many apex predators are keystone species, any species on any trophic level can be a keystone species

• Example:

  • Bees facilitate the reproduction of about 80% of the global plant population

Removal of Keystone Species

Because of their significant impact on overall ecosystem health, if a keystone species is removed, it will disrupt the balance within the food web and will cause ecosystem collapse

• Keystone species often influence nutrient cycling and key ecosystem processes

• If their populations decline, these important ecological processes may be disrupted, leading to imbalances in nutrient availability and biogeochemical cycles

Habitat Modification

• Many keystone species will modify their habitat

• Examples:

  • Beavers and dams

  • Elephants and falling trees

• Loss of the keystone species can impact habitat structure in addition to the food web

Ecological succession

Ecological succession

• The natural progression of changes in species composition and community structure over time

• Through ecological succession, ecosystems undergo a series of transformations, shifting from bare and disturbed environments to thriving and diverse habitats

• Ecological succession occurs in response to various causes, including natural disturbances, human activities, and changes in environmental conditions

• Predictable pattern of changes

• Causes by disrupting existing vegetation and communities

Causes of Ecological Succession

• Natural disturbances

  • Wildfires

  • volcanic eruptions

  • Hurricanes

  • Floods

• Human activities

  • Deforestation

  • Agriculture

  • Urbanization

  • Mining

• Changes in environmental conditions

  • Natural or anthropogenic

  • Shifts in temperature, precipitation patterns, or soil fertility, or the introduction of new species

Primary succession

• Primary succession - Process of ecological change that occurs in an area that is barren and/or wasn’t previously colonized or has been completely devoid of life due to extreme conditions

• Examples:

  • Newly formed volcanic rock

  • Retreating glacier

• Pioneer species - the first species to colonize barren land

  • Small and hardy organisms

  • Example:

    • Lichens

    • Mosses

  • Breaks down rocks to create soil

• After the soil is formed, herbaceous plants can arrive

  • Examples:

    • Grasses

    • Wildflowers

    • Ferns

  • A deeper root system stabilizes soil

  • Eventually provides habitats for small animals

• Next shrubs and small trees arrive

  • An even deeper root system is formed

  • Enrich soil by providing organic matter to break down

  • Provide habitat for more animals

• Then a forest canopy is established

  • As the small trees grow, they form a dense forest canopy

  • Creates diversity in microhabitats and provides shelter for more organisms

• At the end of a succession, a climax community is created

  • Stage of relative stability

  • Characterized by a mature and diverse community of plants and animals

  • Can take 100s or 1000s of years to reach a climax community after primary succession

Secondary Succession

• Process of ecological change that occurs in an area that has been previously colonized by living organisms

• Has experienced a disturbance that disrupts the existing community

  • Wildfire

  • Deforestation

Unlike primary succession, secondary succession begins with pre-existing soil and sometimes remnant species. Because of this, secondary succession proceeds faster than primary succession.

• Begins with fast-growing pioneer species

• Plant species that were previously there before the disturbance quickly re-establish themselves/ increasing biodiversity

• The natural community continues to develop until a climax community is established

Cyclical Succession

• Some ecosystems require a cyclical pattern of succession

• Cyclical succession can be seasonal or can occur when certain conditions cause organisms to replace each other

• This process involves a continuous cycle of change and regeneration, often driven by natural events

• Example:

  • Plants in the chaparral biome in California are adapted to the periodic wildfires that occur there - and have become a natural part of that ecosystem

Arrested Succession

• Occurs when the succession process is disrupted (halted or slowed down) and sometimes prevents a climax community from being achieved

• Climax community - A climax community refers to a stable and mature ecological community that remains relatively unchanged over an extended period of time

• Arrested succession - Refers to a disruption or interruption in the normal progression of ecological succession. It occurs when the development of a community is halted or slowed down due to external factors

• Caused by: repeated changes in environmental conditions or the presence of persistent stressors

• Arrested succession can also occur when the environmental conditions become unfavorable for the growth and survival of certain species

Agriculture and eutrophication

Sustainability

• Sustainability in agriculture refers to the practice of cultivating and producing agricultural products in a manner that preserves and enhances the long-term environmental, social, and economic well-being of farming systems

soil erosion

• Excessive tillage and monocropping can lead to soil degradation and erosion

• Soil erosion is a process that involves the detachment, movement, and transportation of soil particles from one location to another

• Without plants to hold the soil in place, erosion rates can increase significantly

Agrochemicals

• Agrochemicals, including synthetic fertilizers and pesticides, can have significant effects on soil degradation and erosion.

• Some fertilizers can contribute to soil acidification, reducing soil pH levels.

• Acidic soils are less productive and can become more susceptible to erosion

• Agrochemicals may lead to a decline in soil organic matter. This decreases the soil's ability to hold water and nutrients, making it more susceptible to erosion

Water use

• Inefficient water use and improper management of agricultural runoff can lead to water scarcity and pollution

• Over-extraction of groundwater can deplete aquifers

• If irrigation is not managed properly, excessive water application can lead to the leaching of nutrients beyond the crop root zone

• Excessive use of fertilizers and pesticides can contaminate water bodies, harming aquatic ecosystems and human health

Carbon footprint

• During agricultural activities such as tilling, fertilization, livestock farming, transportation, and food processing, greenhouse gases are produced and emitted

• These emissions primarily consist of carbon dioxide, methane, and nitrous oxide

• Agriculture is both a contributor to and a victim of climate change

Eutrophication

• Eutrophication - the process by which a body of water becomes enriched with excessive nutrients, such as nitrogen and phosphorus, leading to an overgrowth of algae and other aquatic plants. The excessive plant growth can deplete oxygen levels and negatively impact the health and biodiversity of the aquatic ecosystem