ecosystem stability & change all experiences

1. Ecological Relationships

The Niche

organisms are adapted to biotic factors such as temperature, humidity, water availability

Tolerance

tolerance: ability of an organism to survive and reproduce under circumstances that differ from their optimal conditions

• temp rises or falls below normal range → individuals r stressed gng 💔 cs they need more energy for homeostasis and have less for growth and reproduction

• species cant survive beyond their upper and lower limit of tolerance

Defining the Niche

tolerance range helps determine where a species should live

niche: full range of physical and biological conditions in which an organism lives and

• tolerance is the address, niche is the occupation

Resources and the Niche

resource: any necessity of life such as water, nutrients, light, food, or space

• plants → sunlight, water, nutrients

• animals → nesting space, shelter, food,

Niches and Communities

the food a species eats, how it gets the food + competition, the predators it has, and beneficial relationships all determine a species’ niche and population

Competition

species using same ecological resources at same time, food mate and places for raising; intraspecific within species, interspecies between 2 dif species

→ The Competitive Exclusion Principle

direct competition has winner n loser

• bacteria grow separate cultures same conditions → survive

• bacteria grow same culture same conditions → one wins one dies

• led to:

competitive exclusion rule: principle that states that no two species can occupy the same niche in the same habitat at the same time

→ Dividing Resources

competition creates pressure for species to specialize the way they use resources to survive and reproduce

• ex: 3 species of warblers live on same tree and eat insects but:

  • 1 feeds on high branches, 1 on low branches, 1 in the middle

  • same resources, used differently

• causing species to divide resources → competition determines number n kind of species in a community and the niche

Predation and Herbivory

if predators eat all prey, no animals left to eat n they die

interactions bw predators/prey and herbivores/plants super important → changes impact ecosystem

→ Predator-Prey Relationships

predation: interaction in which a predator feeds on prey

• affect prey population size and where they live

→ Herbivore-Plant Relationships

herbivory: interaction in which a herbivore feeds on producers (plants)

• affect size and distribution of plants and where they can grow and survive

Keystone Species

some species r so so important that changes in their population can impact the whole ecosystem’s structure and stability

keystone species: single species that is usually not abundant in a community yet exerts strong control on the structure of a community

• ex: sea otters bc manage sea urchin population

• hunt otters → excess sea urchins

Symbioses

symbiosis: relationship in which two species live close together

→ Mutualism

mutualism: symbiotic relationship in which both species benefit from the relationship

• ex: clownfish protect sea anemone from predators, sea anemone tentacles improve clownfish circulation

→ Parasitism

parasitism: a symbiotic relationship in which one organism lives on or inside another organism and harms it

• takes all nutrients

• limits productivity and abundance of organisms

• tapeworms, lice

→ Commensalism

commensalism: symbiotic relationship in which one organism benefits and the other is neither helped nor harmed

• barnacles, whale

Communities, Ecosystems, and Stability

biomes: a group of ecosystems that share similar climates and typical organisms

• tropical rain forest, tropical dry forest, tropical grassland, temperate forest, northwestern coniferous forest, taiga, tundra

• unique seasonal temperature and precipitation

variations in communities bc of of exposure, elevation, soil conditions

shifting mosaic:

• different parts of an ecosystem within a biome can be in different stages of recovery from these disturbances

human activity like lumber, agriculture, and pollution affect local conditions

climate change has affects ecosystems globally and decreases biodiversity

2. Ecological Succession

Primary and Secondary Succession

ecological succession: series of gradual changes that occur in a community following a disturbance

Primary Succession

primary succession: succession that occurs in an area in which no trace of a previous community is present

• ex: volcanic explosions, glaciers

pioneer species: first species to populate an area during succession

• tolerance to many conditions → survive in environments lacking nutrients and good soil

• ex: mossess, grasses, lupin

secondary succession: type of succession that occurs in an area that was only partially ddestroyed by disturbances

• faster cs bits old community can survive and regrow fast

• ex: wildfire, hurricane, logging, farming

  • species can be adapted to this → some trees r spared in forest fires, and these fires help spread seeds to germinate

Why Succession Happens

in succession, each species changes the environment in some way so that the next generation is able to easily compete w other species for resources and can survive

• pioneer → organic matter = soil for mosses and grass

• moss and grass develop into trees

• trees give shade and protection to plants and animals

increasing complexity + biodiversity

Climax Communities

past idea: succession occurs in predictable ordered stages to eventually make a uniform, stable climax community

now: not the same path, climax doesn’t mean stable and uniform

Succession After Natural Disturbances

healthy ecosystems → secondary succession produces something similar to original climax community, not always tho

patches in larger communities could be experience diff stages

disturbance, season, etc. affect the path of succession and what it produces

“patchwork quilts” → always disturbed ecosystems, can never be uniform or stable

Succession After Human-Caused Disturbances

North America → land cleared for farming, then abandoned → secondary succession produces a community that’s not really similar to the og climax

maybe? recover from extensive human disturbances, not sure

• changes soil, soil microbiome, and weather to prevent og regrowth

Studying Patterns of Succession

pioneer species can arrive to environments over long distances

hardy pioneers @ volcanoes stabilize debris

early stages of primary succession are slow

3. Population Growth

Describing Populations

factors explaining population booms n shrinks:

Geographic Range

geographic range: the area inhabited by a population

Density and Distribution

population density: number of individuals per unit of area

• vary per species even in the same environment

population distribution: the way individuals are spaced out across their range

• random, uniform, clumped

Growth Rate

determines if size stays constant (0), increases (+), or decreases (-)

Age Structure

age structure: the number of males and females of each age in a population

• mostly females produce offspring

• plants and animals can’t reproduce until a certain age

Population Growth

factors affecting population size:

Birth and Death Rate

• birth rate > death rate →increases

• birth rate = deathrate → constant

• birth rate < death rate → decreases

Immigration and Emigration

immigration: movement of individuals into an area occupied by an existing ecosystem

• ex huge food resource in habitat encourages immigration

emigration: movement of individuals out of an area

• ex: limiting resources

Exponential Growth

3 things help produce offspring:

• provide all food and space

• protection from predators & disease

• remove waste products

exponential growth: growth pattern in which the individuals in a population reproduce at a constant rate

• J-shaped curve slowly starts and then rises faster and faster

• no disturbances → continues to infinity

Invasive Species and Exponential Growth

often grow exponentially, 2 things necessary:

• aspects of native niche (temp, water, prey) r similar to keep high birthrate

• predators, parasites, abiotitic factors r absent to keep low deathrates

• reduces biodiversity

Logistic Growth

Phases of Growth

→ Phase 1: Exponential Growth

short term: rapid growth as resources r unlimited

• high birth rates, low death rates

→ Phase 2: Growth Slows Down

rate of growth slows down → increases slowly

→ Phase 3: Growth Stops

some point, growth rate = 0, population size levels off and oscillates

The Logistic Growth Curve

logistic growth: growth pattern in which a population’s growth slows and then stops following a period of exponential growth; S-shape

Carrying Capacity

equal birth/death rates, equal immigration/migration → no growth. can oscillate but always around an avg number.

carrying capacity: largest number of individuals of a particular species that a particular environment can support

• influenced by factors like availability of food, space, etc.

Limiting Growth

Density-Dependent Limiting Factors

density-dependent limiting factors: limiting factor that depends on population density

• affects LARGE populations

• ex: competition, predation, herbivory, parasitism, disease, overcrowding stress

• affects range n biodiversity

→ Competition

competition for the same limited resources lowers birth rates and/or increases death rates

• competition within a species drives evolutionary change

→ Predation and Herbivory

• predator prey rls: constant cycle. tm prey → predators eat all and increase in population. → no more prey left so prey population decreases → too much decrease leads to decrease in predator population → leads to increase in prey bc less death, repeat

• herbivore effects: cycle similar

• humans as predators: we eat tm codfish n their birthrates cant keep up

→ Parasitism & Disease

denser host population = parasites spread easily and weaken and kill off them

→ Stress from Overcrowding

species fight within if little space cs of stress → more susceptible to disease, females kill their kids → low birth, high death, more emigration

Density-Independent Limiting Factors

density-independent limiting factors: limiting factor that affects all populations in similar ways, regardless of population density

• ex: extreme weather like flood, hurricane, drought, wildfire → crash

storms, hot weather, prolonged droughts, etc. all affect stability. human activity lowers their natural ability to recover, decreasing biodiversity.

→ Controlling Introduced Species

artificial independent measures like herbicides and pesticides can control, but theyre expensive n not good long term

dependent measures, like using one organism to control an invasive species growth could js introduce another bad species

Human Population Growth

population slowly increased for most of human history. disease and food availability caused higher death rates. developed technologies and cities allowed humans to grow rapidly, but these new dense areas were susceptible to infectious diseases, i.e. black death

Exponential Human Population Growth

rapid rapid growth after industrial revolution bc sanitation n technology shi significantly lowered death rates and birthrates remained very high → exponential

World Population Growth Slows

population is growing wayy slower than before

4. Human Activity and Ecosystem Stability

Human Impact and Global Change

Ecological Footprint

ecological footprint: total amount of functioning ecosystem needed to both provide resources a human population uses, and to absorb the wastes that population generates

• every single resource that allows u to live

• phone, food, waste, shower, etc.

National and Global Ecological Footprints

the footprint of a typical citizen x population of the country

• so imagine everyone living the way the avg american does

Global Systems and Change

nonhuman processes like Earth’s orbit, solar activity, movement of continents → slowly, main global changes for most of history

human ecological footprint + environmental changes → huge changes in stability n biodiversity

Changing the Atmosphere

co2 atmosphere has been increasing a lot since the industrial revolution

current concentrations are at its highest ever bc of fossil fuels

atmosphere affects temp, weather, precipitation, climate n therefore human communities and environmental stability

Fossil Fuels

carbon emissions nearly doubled after the industrial revolution bc of burning fossil fuels for factories, cars, airplanes which we still use to power thru our lives

also, nitrous gases r released and can limit growth of certain organisms in some environments or cause algae blooms

Climate Change

global warming: increase in avg global temp → climate change

• caused by more heat being trapped w carbon dioxide

climate change: measurable long-term changes in averages of temperatures, clouds, winds, precipitation, and frequency of extreme weather events, such as droughts, floods, major storms, and heat waves

• distribution of heat in biosphere + currents affect precipitation and environmental factors globally

Effects of a Changing Climate

• increased atmospheric temps worldwide → insanely fast and high, esp in arctic circle

• rising sea levels → affects coastal communities and populations in coastal cities

  • glaciers melting also ruin habitats

  • warming of water = expansion of water

The Importance of Climate Models

models help predict future concentrations and locate source of pollution

• compare predictions of previous models w predictions against existing temps and shi

• hindcasting → most accurate models r able to hindcast or go backward and still match the historical records

obv expected to increase

models that include only nonhuman causes don’t predict the warming trends worldwide compared to human activity models

Biological Effects

• beyond tolerance → need to adapt, emigrate, or die

• most die → lower biodiversity, less flow of energy and cycling of matter = bad stability

• crops die, aquatic life move or die

Acid Rain

• as so2 or co2 dissolve into raindrops to acid → acid rain, snow, etc.

• combined w pollutants → precipitation leaves metal in soils

• soil acidification = poor decomposition and nutrient cycling

• acid rain kills freshwater species, more algae blooms

Ocean Acidification

more CO2 in air, more CO2 in water

• once dissolved, combines w water to form carbonic acid

• breaks down into bicarbonate and hydrogen (more acidity)

• hydrogen combines with carbonate ions to make bicarbonate ions again

corals die, shellfish die, and shells dissolve bc less calcium to make skeletons (also more stress on them)

CFCs and Stratospheric Ozone

CFCS contain chlorine and fluorine, formerly widely used for aerosol, fridges, plastic foams, but we found out it kills the ozone

ozone layer: atmospheric layer in which ozone gas is relatively concentrated; absorbs ultraviolet light, acting like a global sunscreen

growing ozone hole observed above Antarctica bc CFCs destroy ozone molecules by combining w ice and sunlight somehow → fixed the problem as countries agreed to banning use of CFCs, restoring the ozone layer

Ground Level Ozone

upper atmosphere is ok, not ground level → smog, ozone, n pollutants released from cars and factories r bad

Agriculture and the Atmosphere

Cattle farming and cultivation of rice in flooded paddies release Methane which is super super bad and contributes to climate change + warming

Changes in Land Use

Agriculture

Green Revolution allowed farmers to use technology and techniques to increase crop yields n feed rising population → covers most of earth’s land today

→ Use of Nitrogen Fertilizers

fertilizers doubled amt of nitrogen cycling through the biosphere

lots of nitrogen leaks out in soil water runoff and ruins water sources

→ Monocultures

monoculture: planting large areas with a single highly productive crop year after year

• lots of pesticides and fertilizers, and in big areas, using this for a long time ruins soil quality and reduces biodiversity of the microbiomes, prevent secondary succession good

Deforestation and Reforestation

good forests hold soil, protect freshwater quality, absorb n store co2, cool climate

→ Deforestation

deforestation: cutting of forests

• shit water quality, soil erosion, landslides

• fragments ecosystems, less biodiversity

→ Natural Regrowth Through Succession

• forests today r now secondary after primary was cut

• it’s ok cs logged areas go under secondary succession

• but in rainforests, the soil is thin and matter decays quick, so huge cutting down here isn’t good bc it prevents succession

→ Reforestation

reforestation: replanting of forests, can replace trees that have been cut

• helps ecosystems

• restores clean water

Development and Urbanization

most ppl live in urban areas → dense = huge waste, improper disposal affects all resources

development takes away farmland and fragments habitats

alltogether:

• more sewage and runoff → not all poisonous, but excess nitrogen, phosphorus, drugs, n hormones affect aquatic

• large improper sewage disposal causes toxic algae blooms n can spread disease

Direct Human Effects on Population

Hunting and Fishing

• Hunting used to be ok cs only for food

• Growth in population and tech increased harm to wildlife.

• Animals now hunted for fun, trade, and medicine.

• Regulations can manage some species

• Illegal hunting threatens rhinos, gorillas, elephants.

• Overfishing lowers fish populations worldwide.

• U.S. Endangered Species Act protects at-risk animals.

• CITES bans trade in endangered species products.

• Law enforcement is hard in remote areas

Invasive Species

invasive species: any nonnative species whose introduction causes, or is likely to cause, economic harm, environmental harm, or harm to human health

• competition, parasitism, etc.

• carried by human trade and travel

Pollution

pollutant: any harmful material created by human activity and released into the environment

air → smog, greenhouse, metals, aerosols

water → industrial/agricultural chemicals, human sewage, nonpoint source

Industrial and Agricultural Pollution

• Modern life uses lots of energy, mostly from polluting fossil fuels.

• Industry has released waste into air, water, and soil since the Industrial Revolution.

• Monoculture farming increased chemical use, which pollutes water through runoff or seepage.

Biological Magnification

biological magnification: increasing concentration of a harmful substance in organisms at higher trophic levels in a food web or food chain

• Some pollutants build up in organisms and aren’t broken down.

• Primary producers absorb small amounts of pollutants.

• More concentrated going up the food chain.

• Top predators have most pollutant levels

• harms wildlife and humans.

→ DDT

• DDT was a cheap, long-lasting pesticide used widely in the 1950s.

• It entered water supplies and became concentrated through biological magnification.

• Harmed birds like pelicans, ospreys, falcons, and bald eagles.

• DDT mimicked estrogen, causing thin eggshells and lower hatching rates.

• Bird populations declined but have been recovering since DDT was banned in the 1970s

→ PCBs

toxic chemicals difficult to eliminate, pollutant in magnification, banned but efforts to remove them from places where theyve been absorbed r ehh

→ Heavy Metals

• Harmful industrial pollutants include heavy metals like arsenic, cadmium, lead, mercury, and zinc.

• These metals build up in food webs and can cause serious health issues.

• Mercury builds up in fish like tuna and swordfish; mercury and lead can cause neurological damage.

• Leaded gasoline once polluted air, soil, and water—phased out between 1973 and 1996.

• Lead levels dropped after switching to unleaded gasoline.

• Lead-based paint was banned in 1978, but it remains an issue in older homes.

5. Biodiversity and Environmental Change

Types of Biodiversity

biodiversity: total of the variety of organisms in the biosphere

• ecosystem diversity: variety of habitats, communities, and ecological processes in a biome, or in the biosphere

• species diversity: number of different species in a biome, ecosystem, or habitat

• genetic diversity: total of all different forms of genes present in a particular species or population

  • impacts variation of species

Biodiversity Benefits

• maintains food webs

• medicine and agriculture

• enables populations to better adapt to change

Biodiversity and Medicine

• medicine like antibiotics discovered from wild plants, which offer cost-friendly health benefits for physical and mental conditions

Biodiversity and Agriculture

• wild plants (which crops came from) r very resistant, useful genes can be transferred to newly bred plants thru genetic engineering and breeding

Biodiversity and Ecosystem Resilience

removal of keystone species literally trashes the whole food web

resilience: the ability of a natural or human system to recover after a disturbance

• able to adapt

• more species + more genetic variation = more chances some species r tolerant of new conditions in environment

Ecosystem Goods and Services

ecosystem service: the benefits for humans that are provided by healthy ecosystems

Nutrient Cycling

producers help remove excess nutrients, but human activities can disrupt

Food Production

• Grassland → food for livestock, fertile soil, and protect water.

• kelp forests, estuaries, and coral reefs offer habitats and nurseries for fish and other animals.

• Wild relatives of domestic plants and animals help preserve genetic diversity.

Soil Structure

resilient soil microbiomes maintain soil fertility (turning over, decomposition)

Purifying Water

plants, algae, etc. in wetlands n forests keep clean water → preserving ts is cheaper than water purifying facilities

Storing Carbon

good ecosystems w many producers help remove and store carbon, more resilient

Buffering Effects of Extreme Weather Events

• Coastal wetlands protect against erosion and storms.

• Mangrove forests protect tropical shorelines; salt marshes and dune grasses protect temperate coasts.

• Diverse forests protect mountainsides from erosion and landslides.

Pollinating Crops

diverse ecosystems have many pollinating insects and animals to help grow plants

Regulating Pests

predators that feed on native herbivorous plant pests

Measuring and Conserving Biodiversity

Measuring Biodiversity

best way to calculate is to find species diversity, combining richness and relative species abundance

Conserving Biodiversity

conservation biology: understand, preserve, and protect natural resources, ranging from individual species to entire ecosystems, biodiversity, and ecosystem services

• protecting individual species, preserving ecosystems, preventing habitat loss and fragmentation, and identifying biodiversity hotspots

→ Protecting Individual Species

• Captive breeding programs for individual species

• Success with California condor, Texas horned lizard

• Protecting high-quality habitats for endangered species

indicator species: an organism whose presence, absence, or abundance is used as an “early warning system” to detect problems in ecosystems

• ex: lichens determine water quality

→ Preserving Ecosystems

• protect entirely → govt groups n organizations make national parks n forests to protect large land

• marine sanctuaries

→ Preventing Habitat Loss and Fragmentation

habitat fragmentation: Development and agriculture can split ecosystems into pieces

• Ecosystem fragments = habitat “islands”

• Biological islands can be any habitat patch surrounded by different habitats

• Multi-lane freeways cause habitat fragmentation by separating populations

• Smaller fragments support fewer species and smaller populations

• Causes loss of species and genetic diversity

• Makes ecosystems more vulnerable to disturbances

• Risks to biodiversity are harder to see and understand

→ Habitat Restoration

• Damaged habitats can be repaired with study and effort

• Ecological restoration aims to recreate original ecosystem conditions

• Wetlands restored by removing fill material

• Degraded estuaries improved by dredging to restore tidal and river flow

→ Identifying Biodiversity Hotspots

• Biologists identify global biodiversity “hot spots” to prioritize protection

• Hotspots must have many unique species and be in immediate danger

• Protect hotspots from human-caused changes like habitat loss and fragmentation

6. Humans and the Environment

Sustainable Development

sustainable development: using resources in ways that preserve ecosystem resources

• concentric circles (inside to outside): economy, society, environment

• aims to provide human services while preserving ecosystems

• no long term harm, use as little as possible nonrenewable resources

Renewable Resources

renewable resource: Resources that can be produced or replaced by healthy ecosystems

• water, tree, electricity from wind and sun

Nonrenewable Resources

nonrenewable resources: Resources that natural processes can’t replenish

• coal, oil, natural gas

• fisheries n forests mismanaged r nonrenewable, managed r renewable

Economy and Human Needs

• allows economies to improve standard of living

Innovation and Resilience

constant innovation (new ideas + engineering solutions) should provide services at a good price

• ex: solar electricity was possible a while ago but too expensive → innovations from engineers allowed it to be more affordable for consumers

unpredictability can result in loss of biodiversity in ecosystems

• result of more droughts n extreme weather events

development must create resilience → systems can deal w change

• survive flood, heat waves, etc. unexpected changes

Environmental Successes

• Research on lead in streams identified car exhaust as the source

• Engineering solutions led to unleaded fuel, reducing lead concentrations

• Ozone depletion linked to CFCs, leading to the Montreal Protocol

• 191 countries signed the Montreal Protocol, banning most CFC uses

• Alternatives to CFCs were developed, helping ozone recovery

• Addressing climate change is the next global scientific challenge

Humans in the Biosphere

• Human interactions with ecosystems add complexity to understanding ecosystems

• Current research uses mathematical models to study human-ecosystem interactions

• MIMES (Multiscale Integrated Model of Ecosystem Services) predicts outcomes of human-nature interactions

• MIMES models involve complex systems like food webs and analyze cost-benefit impacts

• Models look at economic changes and their effects on ecosystem services (e.g., fishing, agriculture)

• Research explores how ecosystem services depend on nutrient cycling and biodiversity

• Ongoing research aims to improve understanding of ecosystem-society interactions for sustainable planning