Ecology Flashcards
What is Ecology?
The comprehensive science of the relationship of the organism to the environment - Haekel, 1866
Ecology is the science which concerns itself with the relations of plants and animals to each other and to the past and present conditions of their existence (Burdon and Sanderson, 1893)
What is the Abiotic environment?
The non-living things e.g. climate and geology.
What is the Biotic environment?
The living things e.g. plants and animals but also bacteria and viruses.
What is physiology?
The functions of living organisms and their parts, from the molecular and cellular level through to organ, tissue and whole system/individual level.
What is morphology?
The study of the form and structure of organisms.
How does Ecology interact with physiology and morphology?
Ecology aims at understanding how the physiology and morphology of individuals allow them to cope with environmental conditions. This creates two subdisciplines:
- Ecological physiology
- Ecological morphology
What is Behavioral Ecology?
This is where we focus on how an individual will respond to the environmental conditions and can adopt particular behaviors that allow them to exploit the available resources or avoid environmental perturbations.
What is the Operational Definition of Ecology?
- The distribution and abundance of organisms
- The interactions that determine that distribution and abundance
- The relationship between organisms and the transformation and flux of energy and matter
Ecology covers which scales of study?
- Levels of organization of living things
- Spatial Scales
- Temporal Scales
What are levels of organization in Ecology?
- -> Individual (morphology and physiology of individuals)
- -> Population (population dynamics and genetic structure)
- -> Community (interactions among different species)
- -> Ecosystem (flux of matter and energy)
- -> Biosphere (global distribution and contribution to global processes e.g. carbon cycling)
What is an example of a small spatial scale to study?
Individual level
What is an example of a medium-large spatial scale to study?
Population, Community or Ecosystem level
What is an example of a very large ecosystem scale to study?
Biosphere level
What is spatial scale in absolute and relative terms?
In absolute terms, the spatial scale at which ecologists work depend on the biological system they study.
in relative terms, what matters for spatial processes is how the organism you study perceives space.
What is the importance of temporal scale?
Environments change over time, therefore we need to consider temporal scales because different ecological processes take place along different time scales. Thus we need to carry out long-term observations to study a process. The life history of the organisms you study is also fundamental.
What is temporal scale time scales determined by?
Time scale is also determined by the species you are studying.
When might you consider several temporal scales?
When the object of your study may be subject to the control of several drivers that don’t operate on the same time scale.
What is ENSO?
ENSO (El Nino Southern Oscillation) is one of the most important climate phenomena on Earth due to its ability to change the global atmospheric circulation, which in turn, influences temperature and precipitation across the globe.
What are the three states/phases ENSO can be in?
- El Nino (warm)
- La Nina (cold)
- Neutral (the middle of the continuum)
How are time and space scales linked?
Time and space scales are linked by the factors that drive ecological processes. Small events (short time scales) such as surface gravity waves, and large events (large time scales) such as ENSO.
What is a gravity wave?
A gravity wave results when fluid is displaced from a position of equilibrium. Gravity waves on an air-sea interface of the ocean are called surface gravity waves or surface waves, while gravity waves that are within the body of the water (such as between parts of different densities) are called internal waves).
What are capillary waves?
Capillary waves are small, free, surface-water wave with such a short wavelength that its restoring force is the wavers surface tension, which causes the waves to have a rounded crest and a V-shaped trough.
How to study Ecology?
- Observations
- Experiments (lab or field)
- Mathematical Models
What do organisms need from the physical environment?
The presence of life in any given environment requires that organism to tolerate the environmental conditions and that they can find the essential resources for growth, reproduction and survival.
What are “conditions” needed for an organism?
Physical properties of the local environment.
What are “resources” needed for an organism?
Sources of matter and energy that can be transformed into biomass.
What are the three basic functions that an organism has to perform in order for a species to persist in a particular habitat?
- Survive
- Grow
- Reproduce
What are physicochemical conditions?
Physicochemical conditions induce physiological responses, which can have positive or negative effects on these functions depending on whether or not individuals tolerate them.
What limits the function and distribution of organisms?
Environmental conditions
What two steps are required for studying the effect of environmental conditions on the distribution of species?
- Describing and characterizing the spatial distribution of species, which involves fieldwork and spatial statistical analyses.
- Inferring the environmental factors that explain the observed spatial distribution through the utilization of so-called response curves.
What is quadrant sampling?
Quadrants of a set size are placed in a habitat of interest and the species within those quadrants are identified and recorded. Used to sample abundance patterns or coverage.
What is transect sampling?
Samples are take along a line. Used to sample abundance patterns or coverage.
What happens if your biological system is not amendable to experimentation?
Do an observational study based on the measurement of species “performance” across a large number of locations that differ in the environmental conditions. Problems with this can be variety’s in “performance” definition and isolating effects of individual environmental factors.
What is a Species Distribution Model (SDMs)?
They are used to generate predictions of species presence based on associations between environmental variables and geolocalized species records.
In the statistical model it uses a dependent variable (the probability of species presence) and a explicative variables (environmental factors)
How do you use experimental characterization for response curves?
Under experimental conditions, we can vary individual factors (temperature, salinity, pH, etc) while keeping the other factors constant and see how each function is affected. Not all functions are affected in the same way (organism can survive but not be able to grow or reproduce).
What are GAM models?
GAM models are an advanced statistical technique for presence/absence data and provides estimates of the probability of finding the organism of interest at each station. It can be combined with model selection techniques to identify the variables that are good predictors.
What are environmental conditions?
They are physicochemical features of the environment
- Temperature
- Humidity
- Salinity
- Solar radiation etc.
What is a species response curve?
The distribution of a species along an environmental gradient (e.g. altitude, salinity).
How are resources important?
Resources can be abiotic or biotic components of the environment. They are critical for survival, growth and reproduction and also inherent source of conflict and competition among organisms.
What are resources for autotrophs?
Resources are abiotic components of the environment (e.g. solar radiation).
What are resources for heterotrophs?
Resources tend to be biotic, but not always.
What is phenotype determined by?
The physiology, behaviour and morphology. The phenotype has a inheritable component (genetic). Some is also environmental. Environments will change, meaning the individuals will need to adapt to this, which will cause genetic change.
What are the subdisciplines of Ecology?
- Ecological physiology
- Ecological morphology
- Behavioural ecology
- Molecular ecology
- Evolutionary ecology
What is a response curve?
Its a curve showing the performance of a organism which can be shown through growth, survival and food. We can test this through using lab experiments to control specific conditions and look at the response/performance.
How do you define performance of an organism?
Measuring growth, survival or fecundity in natural conditions is extremely difficult - therefore use abundance as a proxy.
Isolating effects of individuals environmental factors can be done using statistical analysis.
What does environmental ecology aim to investigate?
- How large-scale physical processes influence the distribution and structure of ecosystems at the global scale -> Biomes
- How do species organise in complex systems -> Food Webs
- How is matter and energy transferred within and across ecosystems -> The role of energy in ecology
How is energy a fundamental resource?
No form of life is possible without a source of energy
What are different sources of energy?
- In terrestrial and shallow-water ecosystems the sun provides the energy that is used by photosynthetic organisms (plants, green algae, phytoplankton, cyanobacteria) to generate biomass.
- In extreme environments where sunlight is not available (e.g. deep-sea thermal vents and cold seeps) chemosynthetic organisms can obtain energy to make their organic food by oxidizing high-energy inorganic compounds (hydrogen gas, ammonia, nitrates, and sulphates).
What are the three main types of biomes?
- Terrestrial biomes (tropical rain forest, desert, tundra)
- Freshwater biomes (streams, rivers, ponds, lakes and wetlands)
- Marine biomes (ocean)
What determines the environmental conditions of terrestrial biomes?
Their recognisable patterns of life align along gradients of temperature and participation (climate).
What determines the environmental conditions of freshwater biomes?
Their distribution is determined by the physical characteristics of the landscape as well as by the characteristics of the terrestrial biomes in which they are embedded.
What determines the environmental conditions of marine biomes?
Their distribution is determined by available light and nutrients, which are themselves controlled by ocean currents and mixing patterns.
What is the importance of climate for communities and ecosystems?
Climate influences both conditions and resources and, therefore, plays a dominant role in determining the large-scale distribution of different types of communities and ecosystems (biomes) across the Earth.
What is climate controlled by?
Climate is controlled primarily by the differential heating of the planet by sunlight, and secondarily by the interaction of the atmosphere with the oceans and with mountain ranges.
Air is heated much more at the equator where the sunlight’s rays strike directly, than at the poles, where they strike at a slanted angle and spread over a much greater area.
How does heat get redistributed through atmospheric movement?
Energy is transferred by convection in the atmosphere:
- Hot and wet air rises, cools, releases heat and moisture as precipitation
- The denser cool, dry air sinks, gets warmer and pick up moisture as it flows across the Earth’s surface
This generates large scale air circulation with air moving up in warmer regions and moving down in cooler regions -> large scale circulation cell.
What is the Coriolis Effect?
As the Earth rotates around its axis, its equator spins faster than its polar regions. Heated air masses rising above the equator and moving north and south are deflected to the west or east over different parts of the planet’s surface.
As a result, the prevailing surface winds blow from the east in the tropics and in the polar regions and from the west in temperate latitudes. The atmosphere over these different areas is divided into huge regions called cells (Hadley, Ferrel, Polar).
What are the names of the large air cells and how are they formed?
Hadley: The Hadley cells move heat away from the Equator
Ferrel: The Ferrel cells are created by the interaction of the Hadley and Polar cells.
Polar: The Polar cells move heat towards the poles
Heat is redistributed across the planet through the Hadley, Ferrel and Polar cells.
How does air mass affect precipitation?
The rising and falling of these various air masses dramatically affects precipitation patterns on the Earth’s surface.
The descending air at 30° and the poles has been stripped of much of its moisture as it rose and becomes even drier as its pressure increases. Thus, most of the major deserts of the world (including the Sahara, Kalahari, Sonoran) are found near 30° north or south.
What is another additional factor which causes Earths seasons?
The change in the tilt of the Earths axis relative to the sun over the course of its annual rotation around the sun causes seasonality.
How to mountain ranges influence climate on Earth?
Prevailing winds hit the side of mountains, so air masses rise to go over them, and cool and drop their moisture as they do so. On the downwind side of the mountains, decreasing air will be very dry, creating a so-called rain shadow.
How do ocean currents redistribute heat on Earth?
Ocean currents influence the redistribution of heat and affect the climate not only over the oceans themselves but also over large areas of the continents adjacent to or downwind of oceans.
The surface currents of the oceans are driven in part by prevailing winds and are also affected by the Coriolis effect. Global differences in density across the world’s oceans also drive the pattern and strength of currents.
What are characteristics of Terrestrial biomes?
Areas with warm climates:
High precipitation -> tropical forests
Intermediate rainfall -> savannas and tropical seasonal forests
Low precipitation -> deserts
Temperate regions:
High precipitation -> temperate forests
Intermediate precipitation -> temperate grasslands
Low precipitation -> Mediterranean biomes
Colder regions:
High and intermediate precipitation -> boreal forests
Extremely low precipitation -> deserts
Coldest regions -> Tundra
How are terrestrial biomes spread across the globe?
Biomes are not homogeneous within their boundaries; every biome has gradients of physicochemical conditions related to local topography and geology.
Local elevation can change the global patterns both because of the influence of rising and falling air on local patterns of precipitation and rain shadows.
How do biomes influence convergent evolution?
A map of biomes is not a map of the distribution of species due to geographical divergence. The geographical distributions of species, genera, families and even higher taxonomic categories of plants and animals often reflect this geographic divergence.
Thus, a map of biomes shows where we find areas of land dominated by plants with characteristic shapes, forms, and physiological processes. We recognise different biomes from the functional types, not the species indemnities, of organisms that live in them.
How much of the globe has aquatic biomes?
The freshwater ecosystems on the continents (lakes, ponds, rivers, streams, wetlands) cover <1% of the land mass. Most of the water on Earth is in the oceans, and most freshwater is frozen in glaciers and ice sheets.
Nonetheless, these aquatic ecosystems are immensely important in the ecological functioning of the landscape around them, are critical resources for human society, and are ecologically interesting.
What are the characteristics of streams and rivers?
Streams and rivers are linear in form, unidirectional flowing, fluctuate in discharge, and have unstable beds. The water entering a stream comes from its watershed - the land area where all the water draining from it comes to the particular stream or river - through groundwater flows, surface runoff or both.
Virtually all areas of terrestrial biomes form watersheds and are drained by some stream or river.
How does vegetation influence streams?
Streams in forested regions are shaded by trees, so with little of the light they need, production of algae in the stream is low. The ecological community of the stream is fuelled instead largely by inputs of organic matter from the forest (falling leaves and dissolved organic matter).
In grasslands, streams are often shaded by riparian trees that grow in the narrow strip along the stream where water is plentiful - organic matter from trees and grasslands fuel the stream ecological community.
Desert streams are less shaded, and the food webs are more fuelled by productive micro-algae growing attached to rocks and pebbles.
What are the characteristics of lakes and ponds?
Ponds and lakes are defined by the relatively stationary nature of water within them. In temperate regions, seasonal variations in temperature and wind forcing influence the structure of large and deep lakes.
Water is most dense at 4° Celsius and as water warms or cools it gets less dense. The denser water is heavier and will be at the bottom of the lake while the less dense water is lighter and will generally be at the top of the lake. Vertical stratification is a critical component of lake ecology.
What are the mechanisms of lake stratification?
During the summer the warmer surface layer is seperated from the lower layer by the thermocline, in which temperature rapidly decreases.
In the fall the upper layer cools and water density difference between layers decreases. Fall winds mix surface and bottom layers, putting oxygen into the bottom layer and nutrients into the surface layer.
In winter the upper layer is below 4°C and therefore less dense than the bottom layer, which remains at 4°C so stratification sets in.
In spring, the upper layer warms up, its density increases and wind mixes the two layers again.
In the tropics, many lakes are permanently stratified, with a constantly warm surface layer and a somewhat cooler lower layer below the thermocline.
What are the characteristics of Wetlands?
Wetlands are an intermediate type of ecosystem between terrestrial and aquatic ones.
Where tree dominate, the wetland is called a swamp.
Marshes and fens are dominated by grasses and/or sedges.
Mosses of the genus Sphagnum dominate bogs, which are usually very acidic
Large wetlands are a combination of all of the above in which case its biodiversity can reach very high levels.
Because water never limits, plant growth and nutrients are frequently very high, plant production in wetlands is among the highest in any natural ecosystem on Earth. The oxygen in wetland soils is rapidly depleted by the high rates of microbial decomposition, fed by abundant inputs of dead plant materials.
The bacterial conversion of dissolved nitrate to N2 gas in wetlands, is a critical influence on the global distribution of this major nutrient.
What are the general characteristics of Ocean Biomes?
Oceans cover 70% of the area of the planet and contain 97% of the planets water.
On average, the rate of primary production per area in the oceans is about half that in terrestrial biomes –> the total amount of primary productivity on Earth is roughly the same in oceans as on land
Marine algae supply much of the worlds oxygen and take in a huge amount of atmospheric carbon dioxide.
Evaporation of the seawater provides rainwater for the land
Average oceans depth is 4km, but maximum depth is 11km.
How does sunlight behave in oceans?
As in lakes, sunlight is absorbed and scattered by the water itself and by particles in the water (including phytoplankton)
In the very clear, blue water of some open-ocean regions, light penetrates as deeply as 200m into the water.
The surface layer where light penetrates is called the photic zone.
How are ocean biomes defined?
Defined by the interaction of light (the depth of the photic zone) and nutrients. They can also be defined by the type of vegetation and animal communities present.
The influence of terrestrial biomes decreases as we move away from continents.
What are the characteristics of Near-shore Coastal Marine Ecosystems?
These diverse types lie right on the costal fringe, including the intertidal zone, the near-shore submerged littoral zone (subtidal), and estuaries.
These ecosystems serve as nursery grounds for many species of fish and invertebrates and provide critical habitat for other species (turtles, shore birds, marine mammals).
Accessible to people (very well studied by egologists but greatly affected by human activities).
What is a Estuary?
Salty, semi-enclosed water bodies that exchange water with more open coastal waters.
Occur near the mouth of rivers, where outflowing freshwater mixes with seawater.
Horizontal salinity gradient: salinity decreases from the ocean towards the head of the estuary due to freshwater input.
Provide a mix of the conditions normally experienced in rivers, shallow lakes, and ponds, and nearshore littoral zone.
They support a very diverse fauna. Extreme variation in vegetation type across estuaries.
What is the intertidal zone?
The part of the shoreline that is submerged at high tide but exposed to air at low tide.
It is a very harsh environment subjected to the physical force of wave action and the extremes of hot and cold and desiccation that occurs during low tide.
Both algae and animals are specially adapted to these extreme conditions.
Physical nature of substrate and wave action determine the types of ecosystems we find in the intertidal zone.
What are different types of intertidal zone?
- Rocky shores exposed to strong wave action. Populated by species that can securely attach to the substrate and filter feed on plankton during high tide.
- Shallow sloping shores where the tides deposit and stir up sand and mud. Populated by species living buried in the substrate that filter feed during high tide.
- Strong wave action zones dominated by sandy beaches and mudflats.
- Areas sheltered from waves: - temperate zones (salt marshes dominated by flowering grass) and tropics (dominated by mangrove trees).
What are submerged littoral zones?
Below the low-tide mark begins the submerged littoral zone
A variety of types of communities occur in this zone, depending upon the characteristics of the bottom
Three of them are particularly important and equivalent to several of the terrestrial biomes in terms of biodiversity and productivity:
Kelp forests -> temperate forests
Seagrass meadows -> temperate grasslands or savannas in the tropics
Coral reefs -> tropical rainforests
Each one of them is dominated by a different ecosystem engineer (or foundation species)
What are the characteristics of seagrass meadows?
sandy bottoms at depths of less than 10 m are frequently covered by seagrass meadows
like kelp, seagrasses are foundation species that modify their environments to create unique habitats for many other species
Nursery habitats: their leafy underwater canopy provides shelter for small invertebrates (crabs), small fish and juveniles of larger fish species
Many species of algae and microalgae (such as diatoms), bacteria and invertebrates grow as “epiphtes” directly on living seagrass leaves
What are the characteristics of coral reefs?
Coral reefs are a common feature of the submerged littoral zone along many tropical coastlines, where water quality is sufficently high to support their growth
They boast some of the highest biodiversity for any type of ecosystem on Earth, supporting a quarter of all marine organisms but covering less than one percent of the sea floor
Global change poses huge risk to corals
- Warmer temperatures can lead to coral “bleaching” - the loss of algal symbionts from the coral
- Ocean acidification from the increasing carbon dioxide in the atmosphere makes it more difficult for the coral animals to secrete their carbonate reefs
How can honey bees be classed as “special species”
They are special due to their function in the ecosystem and economy
What is a species niche?
The function or the role that a species plays in its environment and how it interacts with biotic and abiotic environmental factors.
What are the three different definitions of species niche in history?
Joseph Grinnell (1917): habitat requirements that allow a given species to survive (long term persistence) in a given environment.
Charles Elton (1927): the role the species plays in the community
George E. Hutchinson (1957): hypervolume of conditions and resources required and used by the species
Special species can be categorised into which two groups?
- Ecosystem engineers
- Keystone species
What is an ecosystem engineer species?
An organism that directly or indirectly modulate the availability of resources to other species by causing physical state changes. By doing so leads to changes in biotic and abiotic conditions.
Can also be known as niche construction species. Links Grinnell and Eltons definition of species niche. Niche constructor species needs the resources to exist and to provide the function to the ecosystem, however by exploiting that resource it will change the physical conditions of that resource.
What are the two types of ecosystem engineer species?
Allogenic engineer: alter the environment by transforming materials (dead and living) from one state to another, e.g. beaver with trees creating dams which changes physical state of tree and river.
Autogenic engineer: alter the environment through their own physical structure, e.g. trees physical presence can alter pH of soils, provide shade which can alter temperature in given area therefore affecting which species can live there. Trees also affect precipitation patterns.
What are keystone species?
A species which if removed then the ecosystem will be completely or dramatically changed (some cases ecosystem might completely collapse).
“organism that have outsized ecological impacts relative to their biomass/abundance”
Example: Sea otters are keystone species. Exert top down pressure via predation on sea urchins (which graze on kelp forests).
- Useful to promote conservation
- Concept frequently misused (sometimes based on social aesthetics and cultural importance)
- Absence of functional redundancy i.e. there is no replacement for that unique role that the keystone species plays on the ecosystem
What is an ecosystem?
The relationship between all living organisms and how they interact with the physical environment (temperature, humidity, precipitation, soil ect).
Biotic community + physical environment
Ecosystems can be further divided into their processes (transformation from one state into another one) –> function (process that can be quantified) –> services (function that adds value to humans).
What composes species diversity in an ecosystem?
Function.
Based on the composition of species and their functional role, we can categorise an ecosystem as being functional complementarity.
What is functional complementarity?
When ecosystems are characterised by have species that play different/dissimilar functional roles in the ecosystem.
Ecosystems with great functional complementarity often have great efficiency which means higher productivity.
Functional complementarity is not always good; if conditions changed rapidly causing a species to be removed/die out, this would mean there is more of a risk there isnt another species of a similar role to replace that species
What is functional redundancy?
An ecosystem with different species which have similar functional roles.
Functional redundant ecosystems are often less efficient however they have defence against environmental change.
How do we measure biodiversity usually?
Species richness: counting the number of different species. Most commonly used due to simplicity. Doesn’t take in functional diversity within species. Doesn’t tell you the function of an ecosystem.
What is Cedar Creek Experiment?
Used to look at the relationship between biodiversity and ecosystem function through experiment manipulation. 168 different plots with different species of plants and are used to see how this affects productivity. Extremely successful and influential. However, the experimental design was replicated and had different results so controversy remains.
What are the six main points about the relationship between biodiversity and ecosystem function.
- Biodiversity loss reduces efficiency in resource capture, biomass production and nutrient recycling
- Biodiversity increases stability of ecosystem functions. More complex ecosystems are more stable (Robert MacArthur). This is because of asynchrony in species responses to environmental fluctuations. Also reduced competition. Point is controversial.
- Ecosystem function is a non-linear saturating function of biodiversity, e.g. Null model, Linear model, Idiosyncratic model and redundancy model
- Diverse communities are more productive because they include key species, and functional diversity increases resources capture
- Loss of diversity across trophic levels has a bigger effect on the ecosystem than loss within a trophic level
- Effect of species extinction depends on species functional traits
What is a community in an ecological sense?
Community:
Composition of all organisms that live within a given location. Community is defined solely by the geography of the species.
Another way to group organisms into a community is by their taxa, class etc which would be defined by the phylogeny of the species.
Another way to group organisms into a community is by looking at the way they share/exploit a resource.
Group of organisms that can be defined by the interaction or intersection of their geography, phylogeny and resources.
What does community assembly try to understand?
Tries to understand the factors that shape/influence how species distribute.
3 main factors/mechanisms that shape community assembly:
- environmental filtering (availability of resources and suitability of physical conditions, maps of suitable areas, niche modelling, special and temporal distribution of environmental conditions limits species distribution)
- competitive exclusion (at a community level with more than 2 species involved, the principle of competitive exclusion gets more difficult to explain and little support for its existence. Number of parameters involved increases as the number of species involved increases, get competition loops e.g. a1,2 > a3,3 > a3,1. Priority effects also)
- dispersal (Number of species found on an island is proportional to the size of the island and proportional to the distance from the mainland)
What is the fundamental niche?
range of conditions and resources in which a species can survive and reproduce.
What is the realised niche?
Range of conditions and resources in which a species does survive and reproduce
environmental filtering * competition
What is Gauses principle?
In a stable environment, two species with identical niches cannot coexist.
What is spatial evidence of community assembly?
Zonation: distribution of organisms in distinctive areas, layers or zones according to the availability of habitat and resources, as well as competition.
What is temporal evidence of community assembly?
Succession: directional change in the chronological distribution of organisms within an area.
No previous occupation –> Pioneer species (dispersal, tolerance) –> Late successional species (competitive)
When looking at growth rate in a population, what are the 3 main demographic traits?
N/T = Growth Rate Population
3 main demographic traits:
B = Birth rates D = Deaths N = Size of the population
What are the 4 parameters you need to estimate a variation population size?
- B = Birth rates
- D = Deaths
- R = Resources
- N = Size of population
N/T = Growth rate population
What is the equation you need to use to look at how two species can coexist in the same niche?
dN/dt = BR - D * N
which leads to
R* = D/B
Species with the lowest R* will out compete all others
How can multiple species coexist?
- Environments are not stable. Disturbances prevent communities from reaching equilibrium
Disturbance is a temporary and localised event affects community dynamics. Has a direct affect on demographic rates (birth, death, resources). Examples of disturbances are drought, wildfire, hurricane, oil spill).
What is the storage affect?
The covariance in demographic traits between two species across two environmental conditions that allow the coexistence of these two species. Both species can produce a seed bank to resist the tougher conditions. Each species respond differently in terms of their demographic responses to the same environmental conditions.
What is a non-linear based coexistence?
A non-linear relationship between the number of births/reproduction and the resources.
Can disturbances generate stable coexistence?
Yes - however it depends on how you incorporate them into the model. Only via a non-additive and non-linear way.
What is ecosystem resilience/robustness?
The ability of an ecosystem to return to its normal function.
The amount of disturbance a system can withstand before leaving a stable state.
What is ecosystem resistance/persistence?
Measures the ability to respond to a disturbance. The type of disturbance (size) and also the size of the ecosystem will vary how much of an impact the disturbance will have. Resistance is a component of resilience.
What is multiple equilibria in ecosystems?
More than one stable community composition in a single habitat. Alternate stable state.
What are the conditions needed to show evidence of alternate stable states?
- Must occur in the same environment
- Change from one state to another must be rapid (disturbance led)
- Must be self sustaining (i.e. not transient)
What is Hysteresis?
An ecosystem response to disturbance when there are two tipping points, one going towards a different stable state and one going back to the original stable state. No warning signs of the presence of tipping points. Restoring initial stable conditions is not proportional to the effect that led to the current state.
What are sleeping functional species?
Species that until experimented on, their functional role in an ecosystem was unknown.
What are the 4 summarised reasons as to why the lower latitudes/tropics have high diversity?
- Species/Energy: the amount of radiant energy that is emitted by the sun and then captured by the ecosystems is negatively correlated with latitude. Energy transfer to ecosystem is inversely proportional to the angle of the sun. Therefore we increase both our primary productivity (photosynthesis) and are able to maintain a constantly high temperature. More energy = More photosynthesis = More food = Extinction rate lowered in tropics than outside = therefore more species. Higher temperature therefore higher evolutionary change (short generation times, faster genetic divergences amongst populations, therefore higher speciation rate)
- Area Hypothesis: Tropics have more ecoregions. Ecoregion is a region characterised as being dissimilar from other areas. So more ecoregions you have, the more the similarity, the similar regions you have within a region. 12 polar ecoregions, 40 temperate ecoregions, 112 tropic ecoregions.
- Historical/Disturbance: Regions outside the tropics are comparatively younger in geological times than the tropics. Additionally the outside regions also have encountered a lot of disturbances therefore not reached maximum number of potential species.
- Mid Domain: Hypothesis assumes that species are randomly distributed and ecosystems can be considered to be like close spaces. So the peak of species distribution will be at the centre of their geographical distribution (imagine shaking a box).
Is diversity evenly or unevenly distributed?
Diversity is unevenly distributed. First identified by Alexander Von Humboldt. Latitudinal diversity gradient.
Of the 4 main mechanisms for higher diversity in the tropics (Energy/Temperature, Area, Historical/Disturbance, Mid Domain), can be divided into what 3 processes?
- Cradle
- Museum
- Out-of-the-tropics
Last one getting more support due to climate change.
How is climate change affecting species distribution and density?
There is a shift in species distribution because of climate change. Species are moving out of the tropics and maintain on the boundaries of the tropics to still obtain those essential resources without being directly impacted by the higher/increasing temperature. Variation in this due to metabolic differences between species.
How rare or abundant are species?
Some species are abundant but the majority are rare - an ecological law
How is Fisher a significant scientist?
Single most important statistician Anova F-Fisher P value 0.05 Fisherian Runaway/Sexy sons
What is the Fishers log series?
Universal distribution of species abundance which states that a few species are extremely abundant but the majority of species are rare.
[lazy j space on graph]
When measuring biodiversity, how does scale come into things?
When measuring or quantifying biodiversity you need to understand that things come in different scales. There are three main scales which biodiversity can be quantified:
- Alpha: mean diversity of species in different sites or habitats within a local scale
- Beta: compositional differences between sites or habitats
- Gamma: total species diversity in a landscape
What are the 4 most common used metrics when quantifying biodiversity?
- Species richness: most common and most simple
- Common Species: look at the frequency of common species. can use equation Dominance Berger Parker index.
- Evenness: Also common along with species richness. measures the level of inequality in abundances.
- Rarity: proportion of species with abundance below a threshold which is considered to be rare. singletons - represented by one individual.
What is functional diversity?
Facet of biodiversity that describes the species traits that have an influence on ecosystem functioning.
What are the metrics which can be used to quantify functional diversity?
- Functional richness: Proportion of functional space occupied by an assemblage.
- Functional evenness: How evenly spread the species are in trait space
