jv#0180 IBDP ENVIRONMENTAL SYSTEMS AND SOCIETIES TOPICS 2 & 3 SUMMARY Topic 2: Ecosystems and ecology 2.1 Species and populations Species, Habitat, Niche Ecosystem → a community of interdependent organisms (biotic) and their interactions with the physical environment (abiotic) they inhabit. Species → a group of organisms sharing common characteristics that can interbreed and produce offspring that also produce young. Limitations: doesn’t classify extinct populations, doesn’t account for asexual organisms Habitat → environment in which a species lives, where an organism can find food, shelter, protection, mates. Niche → the set of biotic and abiotic conditions and resources that an organism or population responds to (not just habitat, but how an organism interacts with others). No two species can have the same niche. Fundamental Niche: full range of conditions/resources an organism can survive and reproduce in. Realised Niche: actual conditions a species exists in due to biotic interactions. → different niches can still share the same habitat due to space, behaviour patterns etc Abiotic Factors The nonliving, physical factors that influence organisms and ecosystems. Eg. temperature, sunlight, pH, precipitation, soil, landscape/topography. → there are upper and lower level limits beyond which a population cannot survive (optimal range → physiological stress → intolerance) Population Interactions Predation → when one animal or plant hunts and eats another organism. → predator-prey relationships are controlled by negative feedback mechanisms → as prey increases, after time so do predators. Increase in predators reduces number of prey. → predation benefits prey - removes old/sick individuals, leaving superior breeding pool Eg. lemming and snowy owl, gray wolf and moose Herbivory → where an animal feeds on a plant - the animal is known as a herbivore. → the plants as a food source affect the carrying capacity of the environment for the herbivore Eg. hippopotamus grazing on vegetation / zooplankton feeding on phytoplankton Parasitism → where one organism benefits at the expense of another (the host), type of symbiotic relationship → endoparasites live inside hosts, ecto parasites live on the surface of hosts Eg. tapeworms (endoparasites) and ticks/mites (ectoparasites) Eg. plants such as the Rafflesia flower via root systems Mutualism → another form of symbiosis where both species benefit Eg. coral reefs: zooxanthellae live within coral animal (polyp; they photosynthesise to produce food for themselves and the polyp; in exchange they are protected. Disease → aka. pathogen - can be bacteria, virus, fungi - reduces carrying capacity of infected organism. Eg. Dutch elm disease, caused by fungus clogging vascular tissues in tree, preventing water movement. Competition → demand by individuals for limited environmental resources → can be intraspecific (within a species) or interspecific (between diff species) → the degree to which niches (inter) overlap determines the level of competitive exclusion Population Growth Population → group of organisms in the same species living in the same area at the same time, capable of interbreeding. → abundance of resources affects population structure over time. jv#0180 S Population Curve (aka sigmoid curve) Rapid initial growth, then slowing as carrying capacity is reached, where population fluctuates around K. → divided into lag phase, exponential growth phase, transitional phase, stationary phase J Population Curve Increasingly rapid exponential growth with no signs of slowing, exhibited by organisms that produce rapidly. → controlled by favourable abiotic components, results in a population crash Limiting Factors → slow population growth as carrying capacity is reached Density-Dependent Factors - lower birth rate/raise death rate as population grows Density-Independent Factors - affect a population regardless of density, abiotic factors 2.2 Communities and ecosystems Communities and Ecosystems Community → all populations living and interacting in a common habitat at a specific time (only biotic) → involves many interactions among species, communities with higher diversities are more stable and resilient to disturbances. Ecosystem → a community and the physical environment it interacts with (biotic interacting w/ abiotic) → divided into terrestrial, marine, and freshwater, defined uniquely by various abiotic factors Photosynthesis and Respiration → all organisms respire, only producers photosynthesise Photosynthesis → process by which a plant converts light energy from the Sun into usable chemical energy stored in organic matter. Produces the raw material for biomass. carbon dioxide + water → glucose + oxygen Inputs: sunlight as energy, CO2, H2O Outputs: glucose (foundation for other organic molecules) Transformations: light energy → chemical energy stored in biomass Respiration → conversion of organic matter to carbon dioxide and water in all living organisms, releasing energy for life processes. “Wasted” energy is lost as heat, increasing the entropy in the ecosystem while allowing organisms to maintain low entropy. glucose + oxygen → carbon dioxide + water Inputs: organic matter (glucose) and oxygen Outputs: release of energy to maintain order (counteract entropy) and heat jv#0180 Transformations: stored chemical energy → kinetic energy and heat energy Feeding Relationships Producers → autotrophs - organisms that convert abiotic components (sunlight) into living matter. Support the ecosystem through constant input of energy and new biomass. → convert sunlight energy to chemical energy using photosynthetic pigments Consumers → heterotrophs - organisms that eat other organisms to obtain energy and matter → pass energy and biomass from producers through to apex predators Decomposers → break down tissue of dead organic matter and release nutrients for reabsorption by producers → improves the ability of soil to retain nutrients - the organic byproducts of decomposed matter contribute to the humus in soil → essential for cycling matter within ecosystems, esp. in carbon and nitrogen cycles Trophic Levels, Food Chains, Food Webs Flows of energy and matter can be shown through food chains. Interconnected chains form food webs. → the position an organism occupies is known as its trophic level. Producers form the first trophic level. → organisms can occupy different trophic levels depending on which food chain it is in → decomposers feed at every level of the food chain Producer → Primary consumer → Secondary consumer → Tertiary consumer Autotroph → Herbivore → Omnivore/carnivore → Carnivore Efficiency of Energy Transfers Through an Ecosystem Only ~10% of energy is transferred to the next trophic level - trophic efficiency = 10%. → 2nd law of thermodynamics states energy transformations inefficient, so energy is lost at each level → most energy is lost as heat energy through respiration → each trophic level has a smaller energy pool from which it can withdraw energy, thus limiting the amount of trophic levels in a food web Pyramids of Numbers, Biomass, Productivity Ecological Pyramids → models showing the quantitative differences between the trophic levels of an ecosystem, measured for a given area and time. Shows feeding relationships in a community. Pyramid of Numbers → records number of individuals at each trophic level in an ecosystem → numbers tend to decrease along food chain and pyramid tends to narrow at apex → can be inverted when size of individuals at lower trophic levels is large (eg. tree) Advantages: easy method of comparing changes in population numbers over different times Disadvantages: numbers too great to be accurate, doesn’t represent energy flow accurately Pyramid of Biomass → the standing stock or storage of each trophic level → measured in g m-2 (grams per m2) or j m-2 (joules per m2) → can depend on seasonal variations as they are a snapshot in certain time Advantages: overcomes problems w/ pyramid of numbers Disadvantages: only uses sample populations, organisms must be killed to measure dry mass, subject to seasonal variations, gives no indication of productivity over time Pyramid of Productivity → shows flow of energy through trophic levels, the rate at which biomass is being generated. → measured in g m-2 yr-1 (energy per unit area per unit time) jv#0180 → shows amount of energy available as food to next trophic level, more useful in measuring a system’s changes over time → always show a decrease, as transfer of energy is inefficient Advantages: shows rate of productivity of a system Relevance of Thermodynamics First Law → energy cannot be created or destroyed, only transformed. → Solar energy is absorbed by plants and converted to stored chemical energy. Chemical energy is used and lost as heat energy. Second Law → energy transformations result in a loss of energy, leaving less energy to maintain order, thus increasing entropy over time. → Energy is transferred when trophic levels feed off one another, thus more energy is lost through each trophic level. Bioaccumulation and Biomagnification Bioaccumulation → build up of persistent / non-biodegradable pollutants within an organism/trophic level because it cannot be broken down. Biomagnification → increase in concentration of persistent / non-biodegradable pollutant along a food chain. ***biomagnification does not occur due to higher trophic levels eating more - the respiration of biodegradable biomass leaves non-biodegradable toxin in higher concentration. Impact of Pollutant → DDT, a non-biodegradable pollutant used as a pesticide by farmers. → producers take in DDT, organisms in 2nd trophic level retain the pesticide in their body tissue from the producers (bioaccumulation) as it is unable to be broken down → process continues, with more DDT accumulated at each level. Top carnivores are ultimate accumulators, and are the most vulnerable to ecosystem disruption due to their small population and high doses of toxins they receive. jv#0180 2.3 Flows of energy and matter Transfer and Transformation of Energy As solar radiation (insolation) enters the atmosphere, some energy becomes unavailable for ecosystems as the energy is absorbed by inorganic matter / reflected back into the atmosphere. → 51% of available energy from sun does not reach producers → 49% absorbed by ground - only 0.06% of all radiation is captured by chloroplasts Producers convert light energy to chemical energy, which is then available for other organisms to use; all energy is lost from an ecosystem in the form of heat → Ecological efficiency = energy used for growth (biomass development) x 100 Energy supplied Energy Pathways → 1. Light → chemical 2. Transfer of chemical from one trophic level to another 3. Conversion of visible light and UV to heat energy 4. Re-radiation of heat energy to atmosphere Primary and Secondary Productivity Primary Productivity (PP) → the gain by producers in energy/biomass per unit area per unit time. → depends on amount of sunlight, availability of factors needed for growth, ability of producers to use energy to create organic molecules → highest growth occurs in optimal conditions (warm, high nutrients, water etc eg. tropical rainforests) Gross Primary Productivity (GPP) → mass of glucose created by photosynthesis per area per time. Net Primary Productivity (NPP) → gain by producers in energy/biomass after accounting for loss of energy through respiration. Represents potential energy available for next level of consumers. NPP = GPP - R. Secondary Productivity (SP) → the biomass gained by heterotrophs through feeding and absorption, measured in unit mass/energy per unit area per unit time. → depends on amount of food present and efficiency of energy conversion to new biomass Gross Secondary Productivity (GSP) → total biomass assimilated by consumers. GSP = FOOD EATEN - FAECAL LOSS. Net Secondary Productivity (NSP) → gain by consumers in energy/biomass after allowing for respiration. Represents amount of potential energy available for next trophic level. Aka. assimilation. NSP = GSP - R Maximum Sustainable Yields Rate of increase in natural capital that can be exploited without depleting original stock. → equivalent to NP (whether NPP or NSP) of a system - net productivity is amount of energy stored as new biomass; removal of biomass above max sustainable yield reduces natural capital and is unsustainable. Nutrient Cycles → Energy flows; matter cycles between abiotic and biotic environments in an ecosystem. Factors Affecting Nutrient Cycles → soil erosion, runoff, amount of rainfall, decomposition, plant density etc. → Nutrients can be stored in organic (plants and animals) or inorganic (rocks etc.) matter. → Macronutrients are needed in large quantities, eg. carbon, nitrogen, oxygen, hydrogen jv#0180 Carbon Cycle → Carbon - essential in ecosystems, forms a key component of all biological molecules (proteins, fats etc) → can be stored in trees, fossil fuels, limestone for long periods of time as well as organic matter Storages: organic → organisms (plants + animals) inorganic → atmosphere, soil, oceans, fossil fuels Flows: transfers → herbivores x producers, carnivores x herbivores, decomposers x dead organic matter → CO2 in atmosphere dissolves into oceans transformations → photosynthesis (carbon dioxide turned into glucose + oxygen) → respiration (organic matter turned into carbon dioxide) → combustion (biomass is turned into carbon dioxide) → fossilisation (dead organic matter turned into fossil fuels via pressure and decay) Nitrogen Cycle → Nitrogen - building block for amino acids and DNA → the most abundant gas in atmosphere (80%) but largely inaccessible due to its stability → can only be converted by certain organisms Storages: organic → organisms Inorganic → soil, fossil fuels, bodies of water, atmosphere Flows: transfers → herbivores x producers, carnivores x herbivores, decomposers x dead organic matter → plants absorbing nitrates through roots, metabolic waste products from organism (excretion) transformations → fixation of nitrogen from atmosphere by lighting and nitrifying bacteria → nitrifying bacteria transforms ammonium ions into nitrite → nitrate → denitrifying bacteria transforms nitrates back to nitrogen → decomposers break organic nitrogen (proteins) into ammonia → nitrogen from nitrates used by plants to make amino acids and protein (assimilation) Impact of Human Activities on Energy Flows and Matter Cycles → combustion of fossil fuels, urbanisation, agriculture, deforestation impact both energy and matter flows Energy Flows → industrial revolution increased use of fossil fuels, allowing humans access to energy trapped in oil, coal etc. → amount of energy available to humans increased, increasing agricultural output → however, changes in ‘energy budget’ lead to climate change, reduction of natural capital etc → combustion of fossil fuels alters the way light energy interacts w/ surface of planet and atmosphere → increased CO2 → increasing temp → reduction in ice → less reflected sun energy → more GHG → pollution → increased trapping of solar radiation → more heat Matter Cycles → timber harvesting interferes w/ nutrient cycling through decomposition → removal of trees = canopy cannot intercept rainfall and rich floor litter is washed away → trees often cleared to grow oil palm (for food, domestic products and biofuel), thus increasing need for fertiliser in nutrient poor rainforest soil to produce yields → fertilisers contain nitrates, leading to contamination of nearby bodies of water (eutrophication) → harvested crops are transported, along w/ sequestered nitrogen, altering storages → burning fossil fuels reduces storages of non-renewable energy and increases storage of carbon in atmosphere jv#0180 2.4 Biomes, zonation and succession Biomes Biome → collections of ecosystems that share distinctive abiotic factors, species and climatic conditions. → influenced by rainfall, insolation and temperature → water and insolation needed for photosynthesis, which determines productivity → water needed for transpiration and cell turgidity → temperature affects rate at which photosynthesis progresses (chemical reaction) → 5 classes: terrestrial (forest, desert, grassland, tundra), marine and freshwater (aquatic) → each biome has unique limiting factors, biodiversity and limiting factors Tricellular Model of Atmospheric Circulation → explains differences in temp + precipitation and how they influence the structure and productivity of different biomes. → latitude and atmospheric circulation are the primary factors affecting insolation, temp, and precip. → the higher the latitude, the colder the temperatures → areas around equator receive the most insolation / unit area of earth → polar areas have more atmosphere to pass through, = more loss of energy and cooler temps → Hot air heated at equator, rises to form Hadley cell. → as air rises, it cools and condenses, forming tropical storms (explains tropical rainforest at equator) → cooled air spreads and descends - descending creates high pressure and dry areas at 30° (explains desert biome) → air travels towards pole as warm winds, when met with cooler polar air at 60° it rises, condenses and forms precipitation (explains temperate forest biome) Different Biomes → distribution, structure, biodiversity, productivity (climate = temperature, precipitation, insolation only) DTPIPBS Tropical Rainforest → distribution: band around equator, within tropics of cancer and capricorn → temperature: high and consistent yearly (~26°C) → precipitation: high (2500mm yr-1 +) → insolation: high, little to no seasonal variation. Provides year round growing season. → productivity: comprises ~ 40% of NPP for terrestrial ecosystems. High photosynthesis and NPP caused by low latitude and ample direct sunlight. → biodiversity: high, up to 480 species / hectare, estimated half of world’s species in rainforest canopy. High diversity due to high climate factors year round. → structure: stratified tree canopy, many niches. Only ~1% of light on canopy reaches forest floor, canopy has highest NPP. → soil low in nutrients, majority stored in trees. High rates of decay maintain rates of growth. → heavy rains can result in nutrients being washed away, which limits PP. → canopy usually protects soils from rainfall, but logging causes soils to be eroded rapidly jv#0180 ***→ high light intensity → high temps → high NPP → high resources → high complexity of habitats → high biodiversity *** Temperate Forest → distribution: between 40° - 60°N of equator → temperature: cold winters, warm summers → precipitation: between 500-1500mm yr-1, determines whether temperate forests or grasslands develop → insolation: varies according to tilt of Earth, limits growing season → productivity: lower compared to rainforests due to power temps and rainfall. Second highest NPP in all biomes. → biodiversity: lower than rainforests, forests usually dominated by one species (90% of forests may consist of only 6 species) → structure: less stratification and layering, less dense canopy, reduces species diversity and complexity of niches → two types of trees (evergreen, deciduous - deciduous lose their leaves in winter) → forest floor leaf layer increases insulation and nutrients when it decays in warm temperatures Deserts → distribution: 30° N and S → temperature: high during day (45-49°C), low at night (10-0°C) → precipitation: low - 250mm yr-1, often very uneven → insolation: high (air is dry after leaving tropics) → productivity: lack of water limits photosynthesis and NPP, results in sparse vegetation → biodiversity: xerophytic species (adapted to fluctuations in temp and scarcity of water), reptiles most common vertebrates due to cold-blooded metabolism, cacti reduce surface area for transpiration via spines → structure: soil can be rich in nutrients as there is no leaching, decomposition is low due to lack of water Tundra → distribution: high altitudes, the north polar region → temperature: low for majority of year, -50°C, warmer during 6 week period. → precipitation: low, water mainly stored in ice → insolation: short days, limited sunlight; almost 24h of sunlight during summer. Life increases during summer. → productivity: very low due to variable light intensity, rainfall and temperatures affecting race of photosynthesis → biodiversity: low, very few species adapted to cold conditions - large animals to reduce heat loss → structure: low temperatures lead to low cycling of minerals → peat bogs form in carbon sinks Effect of Climate Change On Biome Distribution → increases in CO2 and other GHG increases mean global temperature, affecting rainfall patterns → climate change alters biome distribution Spatial and Temporal Changes in Communities → spatial changes occur along environmental gradients due to changes in altitude, latitude, distance from sea → temporal changes occur as a community develops from early to later stages Zonation → the arrangement or pattern of communities in bands in response to a change in environmental factors over distance (eg. altitude, latitude, distance from shore) jv#0180 Case Study: Rocky Shores → organisms high on shore exposed to air for long periods of time, have adapted to withstand changes in salt concentration and temperature → organisms low on shore are covered by seawater, experience less variation in temperature and salt concentration, with greater wave stress Succession → change over time in an ecosystem involving pioneer / intermediate / climax communities → each distinct community in the succession is a seral stage → succession explains how ecosystems develop from a bare substrate over time → lithosere (bare rock) → fresh water (hydrosere) → dry habitat (xerosere) pioneer community: first stage of ecological succession - species able to withstand difficult conditions climax community: final stage of succession, more stable than earlier stages, in equilibrium primary succession: occurs on previously uncolonised substrate (eg. rock) secondary succession: occurs in places where a previous community has been destroyed. Faster than primary succession due to soil and seed bank. → one species changes the habitat they colonise and make it more suitable for new species → lichens, moss etc. are good pioneer species as they photosynthesise and are effective at absorbing water; they need no soil to survive. When they decompose they form simple soil for other intermediate species. → newer species more able to trap light for photosynthesis and outcompete previous species → final stage is climax community, species of larger biomass increase, decomposers break down soil for other species etc. 1. Bare, inorganic surface 2. Colonisation by lichens, dead organic material results 3. Further weathering, beginnings of soil formation 4. Growth of small herbaceous plants, competition between pioneer species 5. Larger plants grow in more nutrient rich soil 6. Climax community dominated by shrubs and trees Case Study: Primary Succession on Shingle Ridge → lichens and mosses pioneer species that photosynthesise and trap water on nutrient-poor shingle → pioneer species trap particles blowing by and weather the rock → decomposition of pioneers results in a thin layer of soil → red fescue colonise area, roots trap soil and prevent erosion, pioneers begin to be outcompeted → xerophytic plants eg. sea kale prevent water loss, nitrogen-fixing plants eg. rest harrow increase soil nutrients → decomposition continues and allows growth of larger plants eg. shrub community of bramble → climax community of temperate forest (oak/sycamore) develops, shrubs are replaced by shade-adapted species like ferns Case Study: Secondary Succession in Yellowstone, 1988 Fires in Yellowstone National Park wiped out many aspects of the park’s forest - some fires burned soil and ground biomass, some burned the canopy. Fires burned for several months. → recovery began almost immediately with herbaceous fireweed as a pioneer species jv#0180 → lodgepole pines, though a climax species, are serotinous, allowing fast regeneration in burned areas → comprising 80% of park’s forests, they only release seeds when high temperatures eg. fires create favourable open canopies for seedling establishment → aspen, wildflowers had an increase in productivity as nutrients were released from forest litter during burning → soil depth only charred to 14mm, leaving diverse root systems unharmed → minimal overall loss of wildlife from fires, only browsers eg. moose populations declining → other k-strategists eg. elk, bison, deer rebounded due to rapid plant growth, birds able to find ants and worms easily in newly uncovered soil → as pine, larkspur, aspen and other climax species increased, other animals began migrating to the area Changes Through Succession → productivity, mineral cycles, diversity etc. all change during succession. GPP → pioneer communities have low GPP because of the low density in producers. Climax communities have high GPP as there is an increased consumer community. NPP → high in pioneer communities as community respiration is low (low # organisms). High NPP means biomass is continuing to accumulate. Approaches zero in climax community as GPP is balanced by increased respiration Production/Respiration Ratio: when production = respiration, P/R = 1 when P/R is greater than 1, biomass increases when P/R is less than 1, biomass depletes Pioneer communities have low GPP and high NPP due to lowered rates of respiration, P/R is greater than 1. Climax communities have high GPP but increased respiration, therefore low NPP, P/R approaches 1. Diversity → pioneer communities have low biomass, low species diversity and few niches. Climax community have complex niches and more biomass; the increase in niches leads to habitat and species diversity. Complex interactions result in a steady-state equilibrium Mineral Cycling → pioneer communities have open systems, carbon/nitrogen cycles easily. Climax communities have closed systems as the role of decomposition in cycling nutrients from soil to biomass increases. Climax Communities → a community of organisms that is in steady-state equilibrium with natural environmental conditions. It is the endpoint of ecological succession. → greater biomass, high species, habitat and genetic diversity → favourable soil conditions and structure (deeper, greater water retention/aeration) → more k-strategist organisms (taller plants etc) → greater community complexity, resilience and stability → climax communities are more stable as greater energy pathway and biodiversity means species can turn to alternate food sources in the event of a shock; nutrient cycles are self sustaining. r and K-strategist Species → species can be determined by how rapidly they produce, the degree of parental care, and the type of environments they are most suited to. *species that lie in between are C-strategists. r-strategists → opportunistic, fast rates (r) of increase, inhabit rapidly changing + unpredictable environments (ie. pioneer communities), produce many small offspring that mature quickly. Little to no parental care. ● Colonisers K-strategists → slow growing organisms limited by carrying capacity (K). inhabit stable environments/later seral stages (ie. climax communities). Offspring mature slowly and species is vulnerable to high death rates. ● Dominant species jv#0180 ● ● ● ● ● ● ● ● Highly adaptable Rapid growth/development Short lifespans Small size, many offspring Early, high reproduction Type III survivorship Suited to pioneer communities Continuous J-curve population ● ● ● ● ● ● ● ● Specialist, susceptible to change Slow growth/development Long lifespans Large size, few offspring Delayed reproduction Type I or II survivorship Suited to climax communities S-population curve r- and K- Selection Theory → 1. In disturbed habitats, natural selection favours individuals with high reproductive rates over those with slower reproductive rates, but better competitive ability, as they can respond quickly. 2. In predictable environments, species that maximise natural resources and produce few young are more favoured. Survivorship Curves → show changes in survivorship of a species’s lifespan → r-strategists produce large numbers of offspring to colonise new habitats quickly and make use of limited resources → most individuals die very young, those that survive live long → K-strategists produce small numbers of offspring to increase their survival rate and live in climax communities. → almost all individuals survive for potential lifespan and die roughly simultaneously Impact of Human Activities On Succession → interrupted succession = plagioclimax. Human disturbance can halt the process of succession and divert it so a different stable state other than a climax community is reached. → activity modifies the ecosystem (eg. use of fire, grazing, agriculture, deforestation, overfishing); depending on the resilience of an ecosystem changes may be more or less permanent. Eg. deforestation of tropical rainforest biome → increased demand for meat demands land for cattle ranching and agriculture, 90% of the reason why land is deforested in the Amazon. Results in habitat destruction and loss of climax community. → replacement with agricultural system affects global biodiversity, weather, sedimentation patterns → CO2 released returns to atmosphere 2.5 Investigating ecosystems Ecosystems can be better understood to the investigation and quantification of their components. Standardised methods and studies allow ecosystems to be modelled, monitored and evaluated over time. Identifying Organisms in Ecosystems → can use a dichotomous key, a stepwise tool for identification of unfamiliar organisms. Limitations: keys examine physical rather than behavioural characteristics →often use technical terms only understood by experts → may not be a key for the type of organism available → some features of organisms are difficult to identify in wild Measuring Abiotic Components of Ecosystem jv#0180 MARINE → salinity, pH, dissolved oxygen, wave action, temperature FRESH WATER → turbidity, dissolved oxygen, pH, flow velocity, temperature TERRESTRIAL → light intensity, slope, wind speed, temperature, mineral content, drainage, soil moisture **measurements must be repeated to increase reliability of data. Errors in sampling may result in an inaccurate representation of an environment.** Light → measured using a light meter, meter must be held at a fixed height and at the same angle. Limitations: cloud cover/other changes in light means value must be taken at same time of day and same atmospheric conditions. Temperature → measured using electronic thermometer with probes, soil / air / water. Data loggers allow long term fluctuations to be taken into account. Limitations: if thermometer depth is not consistent, problems arise pH → using pH meter or data logger. Values change depending on fresh/salt water, probe must be cleaned between readings. Turbidity → measured using secchi disc lowered into water - cloudy water = high turbidity, clear water = low turbidity. Indirectly corresponds to rate of photosynthesis. Limitations: Sun glare on water, subjective nature of eyesight. Measuring Biotic Components of Ecosystem Estimating Abundance of Organisms motile → pitfall traps, nets, light interception traps, small mammal traps non-motile → quadrats, point frames Abundance → the relative representation of a species in an ecosystem. Can be done by directly counting # organisms (non-motile) or indirectly estimating using Lincoln index (motile). Lincoln Index → estimates total population size of a motile animal - ‘capture-mark-release-recapture’ technique. [indirect] N1 = number in first sample N2 = number in second sample Nm = number caught in second sample that were marked Limitations: animals may move in/out of sample area, seasonal variations may affect population size. Density of a species’ population may differ in different habitats. Direct Methods For Estimating Motile Animal Abundance → actual counts+sampling to give a relative abundance of different animals in a sample. Limitations: sample size and collection methods must be standardised, some animals may remain hidden / unsampled. Eg. canopy fogging to knock insects into collection trays, number can be extrapolated Quadrats [Non-motile] → limits the sampling area when measuring non-motile organisms. A square frame. → random sampling: if habitat is same throughout, quadrats should be located at random. → stratified random sampling: if two/more areas of habitat, results from both areas should be obtained. → systematic sampling: if area occurs along environmental gradient, quadrats should be placed at set distances along a transect. Continuous sampling occurs across the whole length of the transect. Limitations: often subjective - mistakes easy to make in identifying, difficult to measure plant colonies Population density → (total number of a species in all quadrats) (area of one quadrat) x (total number of quadrats) jv#0180 Percentage cover → estimate of an area in a quadrat covered by the organism in question Percentage frequency → number of actual occurrences Number of possible occurrences Abundance Scales → DAFOR - Dominant, Abundant, Frequent, Occasional, Rare Estimating Biomass of Trophic Levels Biomass → a measurement of dry mass (mass - water content), indicates the total energy within a living organism. The greater the mass, the greater the amount of energy. Measured in g / m-2. → mass of one/the average of a few organisms x total number of organisms Limitations: involves killing living organisms. Biomass of root systems difficult to measure. Species Richness and Diversity Richness → number of species in a community Diversity → a species’ relative abundance in a given area. Simpson’s Diversity Index D → diversity N → total number of organisms of all species found n → number of individuals of a particular species → The higher the value of D, the greater species diversity and the more stable the ecosystem/population. Only useful when comparing similar habitats or ecosystems, as diversity is relative, not absolute. Measuring Changes in Ecosystems Changes Along Environmental Gradient → grid quadrat, point quadrats → line transect, belt transect (continuous or interrupted) → transects should be controlled for atmospheric conditions and repeated to ensure reliability. Changes Due to Human Activity → eg. landfills, eutrophication, oil spills, change in land use, overexploitation → can use: diversity index, measure of abiotic variables, soil erosion (pH etc), lincoln index on various disturbed and undisturbed sites jv#0180 Topic 3: Biodiversity and conservation 3.1 An introduction to biodiversity Biodiversity → the variety of life on earth (ie. species, habitat and genetic diversity). → often used to evaluate the health and complexity of an ecological area Species Diversity → the variety of species per unit area - includes # species present and their relative abundance. → higher the species diversity = greater ability to support different niches → measured in richness (number of species) and evenness (relative proportions) → community with high evenness has a similar abundance of all species; low evenness means one or few dominant species, indicating lower complexity. → Simpson’s Diversity (D) can be used to compare communities: → low D can indicate pollution, eutrophication, recent disturbances → high D suggests a stable and mature site Habitat Diversity → the range of different habitats in an ecosystem or biome, indicating niche variety Genetic Diversity → the range of genetic material present in a population of a species → genes: sections of DNA found in the nucleus of all cells → gene pool: different types of gene found within every individual of a species. A large gene pool leads to high genetic diversity; low genetic diversity makes species prone to extinction. Overview of Biodiversity → conservation of habitat diversity leads to conservation of species and genetic diversity diverse habitats have a diverse variety of species, which tend to have different genes Conservation of Biodiversity → conservation aims... ● to protect habitats, ecosystems and species from human disturbances ● to slow the rate of extinction caused by unsustainable exploitation of natural resources ● to maintain biotic interactions between species → the quantification of biodiversity is crucial so high biodiversity can be identified, explored and conserved → human activity causes disturbance that can remove an ecosystem from steady-state equilibrium → measuring biodiversity vital to identify endemic species and their habitats that should be protected 3.2 Origins of biodiversity Biodiversity Arising From Evolutionary Processes Evolution → the cumulative, gradual change in the genetic composition of a species over many successive generations, giving rise to a species different from the common ancestor. → evidence for evolution can be found in fossil records Natural Selection → an evolutionary driving force - the selection of beneficial biological variations best suited to survival in a given environment. 1. Species over-reproduce 2. Genetic variation (genetic diversity / mutation) occurs randomly in a species 3. Natural variation makes some individuals fitter for survival than others 4. Selection occurs as fitter individuals have a survival advantage and are more likely to live to reproduce 5. Offspring of fitter individuals more likely to inherit the advantageous gene, adaptation more likely to be passed to subsequent generations → mutations that give advantages are selected for - the individual will have better competitive advantages and will survive long enough to pass on the trait → mutations that give disadvantages are selected against - mutations that make and individual less suited to the environment make survival more difficult jv#0180 → variation arises randomly and can either be beneficial, damaging or have no impact on survival Isolation and Formation of New Species Reproductive Isolation → must occur between populations so genes cannot be exchanged between them. If the environments of isolated populations are different, natural selection will form new species. Speciation → the formation of a new species when populations of a species become isolated and evolve differently. Geographic Isolation → a physical barrier that causes a population to become separated. Without this, new species cannot form as genes from populations continue to mix. 1. Two populations of one species interbreed - gene flow occurs 2. Populations separated by geographical barrier and cannot interbreed; species develops own variations as gene flow is interrupted 3. Two separate species develop in response to different selection pressures - environmental changes produce new challenges to species and natural selection takes place 4. Even without a barrier, species are now genetically distinct and can no longer interbreed → during the ice ages, a fall in sea levels (decrease in temperature and water locked in glaciers) lead to a land bridge forming between Alaska and Siberia. When sea levels rose, the areas became isolated again. Plate Tectonics Tectonic Plates → have moved throughout time, creating physical barriers and land bridges that lead to gene pool isolation and speciation Plate Tectonics: the movement of plates → move parallel to, be pushed under or collide with each other. → during Palaeozoic and Mesozoic eras, land mass existed as supercontinent Pangaea → Pangaea later split to form Gondwana and Laurasia → the different species found on different land masses can be explained by the movement apart and formation of land bridges of these plates - plate movement across Earth allows new habitats to form. Plate Boundary Types Divergent Boundary → constructive - new crust being formed Convergent Boundary → destructive - crust being destroyed Transform Boundary → conservative, friction is created Continental-Continental Divergent Boundary → continental plates diverge and form rift valleys → deep lakes/seas can form in the gaps, the creation of new aquatic habitats drives speciation. Magma from rift can create new land, giving more opportunities for evolution Oceanic-Continental Convergent Boundary → subduction of denser oceanic crust beneath less dense continental crust → leads to new island arcs and mountain areas forming as magma rises from subduction zone. Often volcanic. Oceanic-Oceanic Convergent Boundary → oceanic crust subducted beneath oceanic crust → rising magma causes volcanic activity and new islands to form, providing new habitats and driving speciation Continental-Continental Convergent Boundary → continental plates collide and increase plate thickness jv#0180 → new mountain ranges are formed - habitats at different altitudes contribute to biodiversity Mass Extinctions Mass Extinction → a period where at least 75% of total species on Earth were wiped out at the same time. Species disappear in a geologically short time period due to abiotic phenomena. → all mass extinctions have resulted in an increase in biodiversity - the large-scale loss of species left new opportunities for surviving populations to undergo adaptive radiation and fill different niches Ordovician - Silurian Extinction → 439 million years ago, killed 86% of all species → causes: drop in sea levels as glaciers formed; rise in sea levels as glaciers melted Late Devonian Extinction → 364 million years ago, killed 75% of all species → causes: global cooling followed by global warming Permian - Triassic Extinction → 251 million years ago, killed 96% of all species → causes: debated - some believe flood volcanism destroyed algae and plants and reduced oxygen in sea. Others believe tectonics and movement of Pangaea may have lead to environmental changes on the landmass, decreasing the quantity of shallow seas and exposing isolated areas and organisms to increased competition. End Triassic Extinction → 199 million years ago, killed 80% of all species → causes: flood volcanism (lava) erupting from opening in Atlantic, leading to climate change Cretaceous Tertiary Extinction → 65 million years ago, killed 76% of all species → causes: impact of miles wide asteroid created crater in Gulf of Mexico - dust thrown into atmosphere by impact could have reduced sunlight, limiting productivity and dropping temperature. Plate tectonics and re-arrangement of world’s land masses could have resulted in climatic changes that deteriorated habitats. 3.3 Threats to biodiversity Number of Species on Earth → estimates vary considerably, as they are based on models and limited classification data. As a result, many habitats and groups are significantly under-recorded. → current consensus at ~9 million species → most described species are larger organisms, mostly animals, easier to study → most diverse groups (insects, bacteria, fungi) are most difficult to study → of 1.8 million described species, 1% are vertebrates, yet they are the most studied Rates of Species Loss → ~30,000 - 60,000 species a year, 100 - 100,000x greater than background extinction rate → existing species must be identified and named in order to understand extinction → humans contribute greatly to diversity loss, eg. mammals 1 every 200 years should be lost, yet 90 species extinct in past 400 years. Causes of Species Loss Natural Causes → typically hazard events eg. volcanoes, ice ages, drought Human Causes → habitat destruction, invasive species, pollution, overharvesting, hunting all reduce diversity Habitat Destruction → habitat degradation, fragmentation and loss → agricultural practices destroy native habitats and replace them with less diverse monocultures → non-specific pesticides often used in agriculture and wipe out both native and pest species → mining activities often destroy forests containing endangered species jv#0180 → plantation crops replace natural ecosystems → invasive species compete with endemic species, leading to extinction of native species → pollution eg. chemicals, plastics, oil spills damages habitats and kills organisms → overharvesting and hunting - animals are hunted for food, medicines etc Threats to Tropical Biomes Tropical Biomes → 5.9% of earth’s land surface, some of the most globally biodiverse areas. Unsustainable exploitation of these areas results in loss of biodiversity and ability to perform ecological services. → ~1.5 ha of tropical rainforest is lost every 4 seconds. → includes rainforests, coral reef, mangrove forests → complex structure and warm, stable climate increase productivity and allow many niches to be supported. → perform crucial ecosystem functions eg. soil erosion prevention, controlling water cycle and weather, carbon sequestering etc. Human Activity and Disturbance → deforestation and forest degradation driven by increasing demands for timber, beef, land for crops, and biofuels impact rainforests → palm oil plantations replace a diverse climax community with a monoculture → large timber removal means fast growing species block out light for slower K-strategists → the rate of loss of biodiversity varies depending on the ecosystems present, protection policies available, environmental viewpoints and stage of economic development Example: Oil Palm Plantations → second most traded vegetable crop, comprises 90% of exports in Malaysia and Indonesia → projected 16.5 million hectares of oil palm in 2020 in Indonesia → 6.5 million hectares of oil palm in Borneo estimated to have destroyed 10 million ha of rainforest Conflict Between Exploitation, Sustainable Development and Conservation → ecosystem exploitation often prevalent in LICs due to their need to provide income for local economies; HICs can preserve ecosystems as they do not rely on them for income → argument to preserve biodiversity is different in LICs, where most tropical biomes are found → for sustainable development to occur in LICs towards becoming MICs, balance between using land for income and conservation must be struck using local and governmental support. Determining Conservation Status The Red List → published by IUCN (international Union of Conservation of Nature), seeking to conserve genetic diversity through awareness and providing a basis for conservation decision at local and global levels. → to identify species requiring conservation → to identify species with conservation status concern → to catalogue species facing a high risk of global extinction Factors Determining Red List Conservation Status → population size: smaller populations have low genetic diversity, reducing their ability to adapt to changes → trophic level: top predators are highly sensitive to disturbances at lower trophic levels → reduction in population size: can indicate species is under threat → geographic range: species occupying a restricted habitat are likely to be wiped out → degree of specialisation: species with specific diet or habitat are threatened when their habitat is threatened → distribution: species in a small area are more threatened than those distributed widely → reproductive potential and behaviour: k-strategists take longer to recover from reductions in population jv#0180 → degree of habitat fragmentation: leads to islands within ecosystems and increases impact of edge effect → quality of habitat: poor quality habitats can support less species Case Study: Extinct - Passenger Pigeon Description → located in NA, once the most abundant bird, travelled in 3-5 billion flocks. Known for migratory habitats and was adapted to reach speeds of 100 km/h. Ecological Role → determined forest composition - forests dominated by white oaks as pigeons ate seeds of read oaks in spring, leaving white oaks to germinate in fall Pressures on Species → 19th century Europeans commercialised pigeon meat, mass hunting began depleting populations in 1800 and intensified in 1890. Last bird was shot in 1901. Consequences of Extinction → increase in # of white footed mouse as competition for food decreased, increase in mice linked to increase of lyme disease as they are hosts Species Restoration Strategies → genetic engineering to revive species Case Study: Critically Endangered - North Atlantic Right Whale Description → most endangered whale in world, currently 300 or less estimated. A migratory species. Ecological Role → baleen whale, important predator of krill and other plankton, prevents populations from skyrocketing. Pressures on Species → slow moving nature made it an attractive target for 19th century hunters - 10,000 whales killed. High blubber content yielded whale oil and made carcasses float on surface of water. Current threats are vessel strikes and entanglement in fishing equipment - extinction estimated in 190 years. Species Restoration Strategies → International Convention for Regulation of Whaling in 1935 banned hunting of right whales, Marine Mammal protection Act established in 1972. Climate change control can assist in managing changes in right whale’s food availability (zooplankton). Case Study: Improved By Intervention - Gray Wolf Description → very widely distributed mammals, found primarily in Northern Hemisphere biomes. Live in packs of up to 36, have a nomadic phase and stationary phase depending on when pups are reared. Ecological Roles, Consequences of Extinction → apex predators and play a crucial role in regulating prey populations. Remove weaker individuals to form a superior breeding pool. Extinction would result in an increase in prey and depletion of primary producers. Pressures On Species → hunting increased mid 20th century due to human fears of livestock depleting, thousands of wolves were hunted and in some regions entirely exterminated. Continued competition with humans for game species, as well as threat of habitat fragmentation. Species Restoration Strategies → hunting outlawed in 1970s, populations began to increase after this year. Legal protection and recolonisation of former habitats stabilised populations, now classified as ‘least concern’. Case Study: Threats to Area of Biological Significance → Great Barrier Reef → extremely diverse coral reef stretching along 2300 km of coast with high productivity. → 1500 species of fish, 359 types of coral, 6 of the 7 threatened species of turtle → tourism and fishing generates $1 billion AUD per year → crucial to Aboriginal culture and spirituality Human Threats to GBR → tourism: though contributes to local economy, coral is fragile and tourists often break them off for souvenirs → overfishing: can disrupt balance of species in food chain; seafloor trawling leads to unintentional capture of other species and damage to floor jv#0180 → land use: changes from subsistence agriculture to large scale farming needing fertilisers and pesticides - runoff causes increase of nitrogen pollution by 3000% → deforestation: coastal mangrove removal leads to increase in sedimentation by 800% as mangroves typically filter sediment. Pollution clouds water and reduces productivity. → global warming: increase in sea temperature has bleached 60% of the reef in 2002, causing loss of biodiversity Natural Threats → climate change increases cyclones and El Niño which cause structural damage to coral → crown-of-thorns starfish prey on polyps (increased by removal of predators by humans) Consequences → continued threats to reef can make damage irreversible → if system reaches tipping point, it will not be able to recover → the loss of biodiversity and ecosystem services (eg. defence against sedimentation) leads to a reduction in the value of the natural capital 3.4 Conservation of biodiversity Arguments to Preserve Biodiversity → can be aesthetic, ecological, economic, ethical and social → goods are easier to quantify than indirect values and services Aesthetic Reasons → species/habitats are pleasant to look at Ecological Reasons → habitats with endemic species must be preserved → higher biodiversity = more resilience & stability = continued ecosystem services in future → species extinctions have knock-on effects throughout food webs Economic Reasons → value of ecotourism, genetic resources & commercial considerations of capital → genetic diversity can allow improvements in crops etc. to be made - a genetic resource → commercial resources (capital as medicines etc. or successful tourism) Ethical Reasons → intrinsic value of a species - all have a right to survive, responsibility to protect for future Social Reasons → ecosystems provide homes, livelihoods and cultural cohesion for indigenous peoples Reasons to Conserve Rainforests (consider someone who relies on the forest vs. an outsider) → aesthetic: habitats & species pleasant to look at → ecological: life support functions - stabilising soil erosion, regulating temp and hydro cycles, sequestering carbon, maintaining atmospheric balance of CO2 → economic: natural capital (fuel, food, medicine, ecotourism) can bring in income → ethical: forests have intrinsic value & a necessity to be protected for future generations → social: spiritual, cultural, religious value to local indigenous communities Conservation Organisations → can be international, governmental or non-governmental, with varying levels of success when approaching conservation due to their use of media, their speed of response, diplomatic constraints, finances and influence. NGOs eg. Greenpeace, WWF IGOs eg. United Nations Environment Programme → not run by, influenced or funded by governments → field based, gathering information to support their claims → radical to spread their message and be heard → established through agreements to allow global cooperation between governments → information from paid scientific research → less controversial, more conservative approach jv#0180 Use of media → gain coverage through protests & campaigns (charismatic species), putting pressure on governments Speed of response → fast, members already at consensus regarding course of action Agenda → using public pressure and lobbying to influence government policies and legislation Funding → from private donations Political pressures → environment focused, working towards idealistic conservation strategies Use of media → cooperates with media to effectively communicate policies and decisions to the public Speed of response → slow (bureaucratic), decisions directed by governments & require consensus Agenda → provides guidelines and implementing international conservation treaties Funding → budget from national economies Political pressures → can be politically/economically driven rather than environmental → both provide information to educate public on environmental issues, publishing reports and data → both encourage partnerships between nations and organisations to conserve ecosystems → both monitor species and conservation areas at local, regional and global scales International Conventions on Biodiversity → conventions aim to create collaboration between nations for biodiversity conservation IUCN (International Union for Conservation of Nature) → founded in 1948, concerned with importance of conservation of resources for sustainable development → established Red List and World Conservation Strategy with the UNEP and WWF → World Conservation Strategy: → stresses importance of making the users of natural resources the guardians of those resources 1. maintaining essential life support systems and ecological processes (climate, water, soils) 2. Preserving genetic diversity 3. Using species and ecosystems sustainably Conservation Approaches → 3 main types: habitat conservation, species based conservation, mixed approach Local vs. Global → when problems are global, international cooperation is often useful and can motivate governments to take action and honour their commitments (eg. global warming) → IGOs have the funding to mobilise and coordinate a united, transboundary response → global summits and conventions play a vital role in setting targets and shaping action (eg. 2000 Millennium Summit) → when problems are local, local populations should be involved in providing solutions In-Situ Conservation → the conservation of species in their natural habitat → endangered animals & their habitats are protected, conserving many other species Ex-Situ Conservation → the preservation of species outside their natural habitat → in botanic gardens, zoos, with captive breeding programmes → focuses on vulnerable species → aims to attract interest & public pressure in conservation, more funding Habitat Conservation → buffers to human influence, area, edge effects, shape, corridors must be considered (BAESC) Buffer Zones → successful areas are surrounded by buffers to minimise disturbances from outside influences Area → larger conservation areas preferable to several smaller ones → they include more habitats, promoting large population sizes especially among large vertebrates → the best indication of reserve success is the population of individual species → several reserves allow habitats to guard against possible effects of fire etc. that could threaten species jv#0180 Edge Effects → changes in abiotic factors at the edge of a protected area (eg. temp, humidity, wind) → edges attract species not found deeper within the reserve, leading to competition and an overall reduction in biodiversity → larger habitats reduce the perimeter relative to the area, minimising the edge effects Shape → circles are the ideal shape as they have the lowest edge effects → long, thin reserves have large edge effects → depending on location of habitats, parks are usually irregular Corridors → close, clumped conservation areas with corridors are better than fragmented areas → animals can migrate, disperse and recolonise in the event of a disturbance → corridors allow genetic flow through migration and seasonal movements, reducing barriers to movement like roads and car collisions → strengths: protects whole ecosystem and complex relationships, ensuring long-term survival of species → allows research to take place in intact habitats, enhancing understanding of biodiversity → preserves many niches, prevents hunting and other disturbances → ecotourism and education raises awareness, generating profits to fund conservation programs → species that haven’t been discovered yes can still be protected → limitations: requires considerable funding and continuous protection to ensure minimal disturbance → difficult to establish due to conflicting EVSs → areas can become islands and lose biodiversity due to reduced gene flow and edge effects Species Based Conservation → CITES, captive breeding, flagship species, keystone species CITES (Convention On International Trade in Endangered Species → established in 1973, int’l agreement regulating trade in endangered species → while trade in plants & animals is worth billions, it reduces wild populations & exhausts species → strengths: CITES currently protects 35,000 species, with countries becoming voluntary members (monitoring trade, extracting fines to discourage trade) - works transboundary → ensures the overall sustainability of international wildlife trade → appendix I (endangered & illegal trade) → appendix II (non-endangered & sustainable trade) → legally binding - participating countries must implement the convention → limitations: species can be re-classified as appendix II → penalties and fines may not be severe enough to deter smugglers → CITES lacks financial mechanisms for implementation at the national level → interpretations vary between countries → does not replace national legislation; countries must make their own laws to apply CITES Captive Breeding & Reintroduction Programmes (Zoos) → facilities where animals are housed & breeding can take place → development level of country must be considered (can the programme be supported in the long term) → in situ or ex situ - habitat threatened species must be ex situ, species with local involvement can be in situ → ‘five freedoms’ - freedom from thirst, hunger, physical discomfort, injury & disease, fear & distress, freedom to express normal behaviours → strengths: able to educate public about need for conservation by allowing them to empathise with wildlife → captive breeding can be used to increase population sizes of threatened species → offers a temporary protected area to maintain genetic diversity, animals reintroduced later → allows research to be conducted → limitations: captive animals have trouble re-adapting to the wild jv#0180 → not all species breed easily in captivity → habitats are very different from natural environment, species isolated from their typical niche zoos don’t treat the ecosystem as holistic → ethical issues surrounding using captive animals for profit → popular species are not necessarily the ones at the most risk Flagship Species → charismatic species designed to appeal to the public and protect other species in an area → iconic species allow conservation to catch attention and raise necessary funds for initiatives → strengths: money can be raised for conservation of other threatened but less appealing species → preserving the habitat of flagship species preserves other organisms in the same habitat → limitations: favours charismatic species at the expense of less publically attractive, more endangered species → does not guarantee habitat conservation - species may be preserved in zoos instead Keystone Species → species vital for conserving the function of an ecosystem → limitations: species difficult to identify due to complexity of ecosystems → establishing protected areas rather than conserving individual species preserves complex interrelationships → keystone eg. agouti in SA feeding on the Brazil nut tree breaks open nut pods, burying seeds in forest floor and allowing them to germinate. Other organisms dependent on trees for food + shelter. Mixed Approach → combining both in-situ and ex-situ conservation (protected areas & zoos) is often most effective → eg. Giant Panda Conservation in Beijing Zoo → flagship species → on appendix I of CITES → successful breeding established in 1960s through artificial insemination and breeding → 56 conservation areas and nature reserves established → Chengdu Panda Base does both in and ex situ conservation, emphasising wildlife research, captive breeding and educational tourism
