Genes to ecosystems Flashcards

Question

Six factors have been advanced to account for variations in species richness. These are:

Answer 1

Evolutionary speed Geographic area Interspecific interactions Ambient energy Productivity Intermediate disturbance More than one of the factors may be important – some drivers and some maintainers. * Importance varies amongst regions and/or taxonomic groups.

Answer 2

* Explanation for why so many species arise – not why so many can coexist * Length of time tropics have existed, promoting speciation * Stability of the tropics reducing extinction (difficult to text) * Climate favours small bodied, fast generation time, taxa * UV exposure higher, could (little evidence) increase mutations

Answer 3

Species diversity is the product of evolution. Faunas and floras that have evolved for longer time and/or at faster rate will be more diverse. Tropics are more diverse because: – Conditions are favourable – Evolution has not been interrupted by glaciation.

Answer 4

Species richness increases over evolutionary time scales, unless interrupted by catastrophes. * Evolution brings new species into communities (and extinction removes extant species). * Ecological time scales are much faster than evolutionary time scales, so other processes must operate as well.

Answer 5

Hypothesis: More species can be supported in larger areas because larger areas provide more niches. Number of habitats may increase with area. – more scope for speciation Total population may increase with area. – less likelihood of extinction

Answer 6

Hotspots are areas with high numbers of endemic species. * An endemic species is found in only one, relatively small, geographic area. * Species arise primarily by geographic isolation. * On global scale, patterns of isolation are a consequence of continental drift. * Locally, topography can be important. * Many, but not all, hotspots are in tropics.

Answer 7

Greater competition can increase diversity Stronger predation may increase diversity. Greater competition can increase diversity. – More stable, less stressful environmental conditions may lead to greater competition. – Greater competition leads to resource partitioning and narrower niches (more specialist species). – This leads to both greater habitat specificity (contributing to b-diversity) and within habitat diversity (a-diversity). Stronger predation may increase diversity by – reducing competition, allowing more species to share the same resource if predation controls prey abundance or removes competitively superior species.

Answer 8

Competition in “equilibrium” communities: – the number of species that can coexist is no greater than the number of limiting resources. * Where there is a range of resource availability, species can partition the resource to avoid competitive exclusion. * Species richness depends on the average niche width and extent of overlap.

Answer 9

Anolis are small, diurnal, insect eating lizards * sit and wait predators that perch in trees or bushes * food size is a critical niche dimension * niche breadth decreases with increased species richness

Answer 10

Predation can lead to increased species richness by removing animals that are superior competitors, because there is often a tradeoff between maximum reproduction rate and ability to resist predation. Removal of a keystone predator can lead to reduced diversity

Answer 11

Tropical forests have high tree diversity. * Seed deposition is high, but survival is low close to a mature tree of the same species. * Survival is reduced by host specific parasites or disease in the immediate vicinity of mature trees. * Some seeds carried away from the parent tree by fruitivores are more likely to survive.

Answer 12

Hypothesis: Energy availability generates and maintains species richness * because fewer species can tolerate extreme environments. * Key variables are solar radiation, temperature and water availability. * Annual evapotranspiration can be used as an index of energy balance.

Answer 13

Hypothesis: greater primary production results in greater species diversity. * In terrestrial systems, total primary productivity depends on – area of habitat, – sunlight and – precipitation.

Answer 14

Some of the most speciesrich plant communities occur on nutrient poor soils – fynbos in South Africa – heath scrublands in south-eastern Australia * Compare location of biodiversity hotspots with NPP map.

Answer 15

Hypothesis: at local scales, competitive exclusion, which should reduce species diversity, is prevented by disturbance. * Disturbance includes any event that disrupts competition: – fluctuations in physical/chemical factors – catastrophes such as fires or erosion – predation or herbivory Species of low competitive ability are lost when disturbance is infrequent. * Species are lost indiscriminately when disturbance is severe. * Maximum diversity should occur at intermediate disturbance.

Answer 16

DIVERSITY-PRODUCTIVITY HYPOTHESIS Niche Differentiation accounts for increased productivity in more diverse communities. Habitat is heterogeneous. * Different species have different niches. In the hypothetical case illustrated, each species has a circular radius in niche space in which it is a good competitor. * By occupying more of the habitat space, diverse communities use more of the available nutrients to produce more total biomass.

Answer 17

Below ground niche complementarily due to resource competition The regulation of plant productivity by soil microbiota

Answer 18

Below ground niche complementarily due to resource competition The regulation of plant productivity by soil microbiota

Answer 19

Below ground niche complementarily due to resource competition The regulation of plant productivity by soil microbiota soil sterilisation treatments also remove beneficial organisms such as saprotrophs and mycorrhizae, and modify nutrient availability

Answer 20

Diversity-productivity hypothesis: Ecosystems containing more species are on average more productive or have greater total biomass because diversity allows more of the habitat space/resources to be occupied. Diversity-stability hypothesis: Ecosystems that have more species are more stable because more diverse communities contain some species that can thrive after a disturbance (change in a biotic or abiotic factor) and these can compensate for competitors that are stressed by the disturbance.

Answer 21

Response to change… Press perturbation: Sustained alteration to a system state variable, e.g. temp, pH, or biological subsidy. * Pulse perturbation: temporary change to a system state variable that can then recover. Four key aspects… Variability - the variation of community biomass over time 2. Resistance - the degree to which community biomass is changed following a perturbation 3. Resilience - how long it takes for community biomass to return to predisturbance or reference state levels following a perturbation 4. Persistence - the length of time that biomass remains unchanged

Answer 22

Examples of plant traits – Phenology – Height at maturity – Root depth – Seed size – Maximum photosynthesis rate – Water use efficiency – Affinity for limiting nutrients

Answer 23

Functional diversity: the amount of trait variation in an assemblage. * Species do not contribute equally to varied ecosystem processes and delivery of services. – Keystone predators – Ecological engineers

Answer 24

BIG ECOLOGICAL QUESTION FIRST! Extract starting material – Nucleic Acids DNA or RNA -> Amplify extracted DNA or RNA material via PCR -> Downstream processing of product -> Bioinformatics and data analysis

Answer 25

ds DNA separates into ss DNA > ca. 94°C. Causes DNA melting of the DNA template by disrupting the hydrogen bonds between complementary bases, yielding single-stranded DNA molecules The reaction temperature is lowered to 50–65 °C for 20–40s. Annealing of the primers to the ss DNA template. annealing temperature is ca 3-5 °C below the Tm of the primers used. Stable DNA-DNA hydrogen bonds are only formed when the primer sequence very closely matches the template sequence. The polymerase binds to the primer-template hybrid and begins DNA synthesis. The temperature depends on the DNA polymerase used Taq polymerase has its optimum activity temperature at 75–80 °C (72 °C is used) DNA polymerase synthesizes new DNA strand complementary to template strand by adding dNTPs in 5' to 3' direction Extension time depends both on the DNA polymerase used and length DNA fragment to be amplified DNA polymerase synthesizes new DNA strand complementary to template strand by adding dNTPs in 5' to 3' direction ≈1kb per min.

Answer 26

Used to quantify PCR product (commonly in real-time; hence confusion with RT-PCR). * Measures starting amounts of DNA, cDNA, or RNA. * Used to determine whether a DNA sequence is present in a sample and the number of its copies in the sample. * Quantitative real-time PCR has a very high degree of precision. One of the best methods for working out how much DNA/RNA is in a sample.

Answer 27

TaqMan probes: A fluorophore is attached to the 5’ end of the probe (additional oligo to primers) and a quencher to the 3’ end. The fluorophore is excited by the machine and passes its energy to the quencher. FAM as the fluorophore and TAMRA as the quencher. TaqMan probes: FAM does not fluoresce as it passes its energy onto TAMRA. As TAMRA fluorescence is detected at a different wavelength to FAM, the background level of FAM is low. The probe binds to the amplicon during each annealing step of the PCR. TaqMan probes: When the Taq polymerase extends from the primer which is bound to the amplicon, it displaces the 5’ end of the probe, which is then degraded by the 5’-3’ exonuclease activity of the Taq polymerase. Releases the fluorophore and quencher into solution, leading to an irreversible increase in fluorescence from the FAM and a decrease in the TAMRA.

Answer 28

qPCR: Inconsistent CT * Data not comparable between runs * Nonspecific amplification ddPCR: * No standard curve * Data is comparable between runs * No replicate wells needed (?)

Answer 29

Metagenetics: who is there? and number of species qPCR: How many are there and abundance Metagenomics: What can they do, abundance Metatranscriptomics: What are they doing?, activity

Answer 30

Amplicon: The short DNA sequence products of polymerase chain reaction (PCR) amplification using taxon- or gene-specific primers to target a particular region of the genome. Biodiversity genomics: Biodiversity assessed using high-throughput DNA-based methods or data from whole genomes integrated with a broad array of metadata describing biological and environmental indicators. Biomonitoring: Biodiversity analysis that is repeated across space and time that may focus on a target organism such as invasive or at-risk species, an assemblage such as the bioindicator groups (amphibians, birds, macroinvertebrates) as an indicator of ecosystem status.

Answer 31

DNA Barcoding: A minimal standardized signature DNA sequence is used for species identification, for example, a 658-bp region ofCO1 mtDNA is used for identification of animals. Other DNA barcode markers have been proposed for fungi, plants and protists.16S rDNA has been used for the identification of bacteria. eDNA: Environmental DNA comprised of free degraded DNAs in the environment as well as DNA co-extracted from whole organisms such as microscopic organisms, arthropods, nematodes; shed cells; faeces; as well as the DNA contained within dead or dormant cells such as seeds or spores. ESV: Exact sequence variant. Also known as an amplicon sequence variant (ASV), zero-radius OTU (ZOTU) or simply an OTU defined by 100% sequence similarity

Answer 32

HPC: High-performance computing, computer clusters can be used to run the same analysis for many samples in parallel, or splitting large jobs into many smaller ones for a quicker overall runtime. Available through private clusters or third-party cloud computing services. HTS: High-throughput sequencing, sometimes referred to as nextgeneration sequencing or second-generation sequencing. Distinguished by the high number of sequencing reactions that occur in parallel. Metadata: Supplementary data linked to DNA sequences that provide information in a standard and searchable way such as organismal or bulk environmental sample description.

Answer 33

Multiplex sequencing: The addition of a unique DNA sequence tag to each sample, such as when multiple samples are pooled and sequenced at the same time, allows sequences from different samples to be distinguished from each other during data analysis. Oligonucleotides: Relatively short nucleotide molecules used as primers for PCR, as probes on microarrays, or baits during target enrichment. OTU: Operational taxonomic unit, a group of similar DNA sequences sometimes used as a proxy for “species” in diversity measures. Primers: Short oligonucleotides that are complementary to a particular region of the genome and are a starting point for DNA replication by DNA polymerase during PCR. Taxon: An organism identified to any taxonomic rank (e.g., species to kingdom); plural taxa.

Answer 34

Potential to revolutionize ecology * Low cost, high throughput sampling * Resolves biodiversity across levels of organization * Applicable in any environment with globally comparable results * Can capture difficult to identify species * Rapid low-cost biomonitoring etc etc.. * But, each step has many pitfalls and challenges to overcome….

Answer 35

Extract and isolate DNA from a sample (can be environmental matrix, mix of whole organisms, eDNA etc) 2) Amplify via PCR the gene region of interest (phylogenetic marker gene – e.g. 16S rRNA, COX1, ITS) for target taxa producing multiple copies of the same region from each of the different taxa present in your sample 3) (optional) Secondary PCR is used to add on a “tag” (multiplex index, or barcode) that identifies which sample the PCR amplicons came from 4) All samples are pooled (normally in equimolar concentrations) and prepared for HTS (aka NGS) and sequenced Raw sequences are processed via a bioinformatics pipeline, which use the tags included in step #3 to de-multiplex sequences into their original samples. 6) Sequence variability is used to cluster sequences in OTUs – i.e. group all sequences that are within 3% similarity as an OTU (analogous to species) 7) Count how many OTUs each sample has, and how many reads come from the same OTU (measure of relative abundance) 8) Match OTUs to reference databases on known sequences types to identify which species where present and have been recorded 9) Do some ecology…

Answer 36

Ancient Ecosystems Plant-Pollinator Interactions Diet Analysis Invasive Species Detection Pollution Response Air Quality Monitoring

Answer 37

Potential to revolutionize ecology * Costly, but produces large amounts of useful data * Resolves taxonomic and functional diversity across levels of organization * Applicable in any environment with globally comparable results * Can capture difficult to identify species * Same sample design considerations as metabarcoding, but with computational limits as well… Also Essentially identical environmental sampling to used in metabarcoding studies

Answer 38

1) Extract and isolate DNA from a sample (can be environmental matrix, eDNA, gut biome etc) 2) Quantify DNA, ensuring you have enough to sequence – requires a larger amount of DNA extract than amplification-based approaches 3) Randomly fragment DNA into shorter reads appropriate for NGS platform (e.g. 150x150bp PE) – not required for metabarcoding as amplicons typically ~350-650bp in length 4) Tag all samples with multiplex identifier (or run one sample per lane) and pool into equimolar concentrations before sequencing on appropriate NGS platform 5) Raw sequences are processed via a bioinformatics pipeline, which use the tags included in step #4 to de-multiplex sequences into their original samples. 6) Do some bioformatics…. 7) Do some ecology…

Answer 39

Viruses are the most abundant biological entities in the biosphere * Can infect Bacteria, Archaea, and Eukaryotes * Virome is >10x more abundant than the microbiome with 107 - 109 viruses per gram of sediments or soils * Important role in the genomic plasticity of their hosts, and species interactions. * Large regulator of dynamics of microbial populations * Difficult to isolate and study using targeted approaches

Answer 40

A population is a group of organisms of the same species occupying a particular space at a particular time. * Populations have attributes that transcend those of individuals… – Age distribution – Genetic composition – Spatial distribution * Some simple models of population dynamics ignore these attributes.

Answer 41

Population size, usually denoted N, is the number of individual organisms in a population. * Elephants – 3-5 million African elephants roamed Africa in the 1930s. – Today, the elephant populations in southern Savannahs in Africa total 300,000 elephants. * Ants – E.O. Wilson estimated 10 million billion (10,000,000,000,000,000 = 1016) – However, this is amongst an estimated 22,000 species.

Answer 42

Absolute population density is the number of individuals per unit area or per unit volume. * Population size is the absolute density multiplied by the area (or volume) of the population’s range. * Extremely wide range of densities, depending on organism.

Answer 43

population size = (Population density) x (Area of Range) Are the organisms motile or sessile? * Anticipated size/density and patchiness of distributions. * Ease/difficulty of detection or collection. * Efficiency of sampling method. * Time and resources available to undertake a survey. * Two broad approaches: – absolute population size or density – relative population size or density.

Answer 44

Random Even = Regular (uniform) Clumped = Aggregated = Patchy

Answer 45

Random (unpredictable): Distance between individuals is random. – Position of an individual is independent of the positions of other individuals. -Individuals do not interact! * Can arise during colonization from random dispersal in homogenous environments. – e.g., larvae (oysters) or seeds (dandelion). Why are random distributions rare in nature? * Abiotic factors are variable: climate, edaphic (soil) * Biotic interactions: social interactions (behaviour) lead to clumping (e.g. herds or swarms)

Answer 46

Distance between individuals is minimized * Most common pattern in nature Patchy resources * e.g., watering holes * Social interactions that allow * earlier detection of predators * more effective defence * increase hunting performance (wolf pack)

Answer 47

Distance between individuals is maximized * Minimizes competition – Moisture: creosote bush – Sunlight: even distribution of trees in a forest * (Anti)Social interactions: – Territoriality * Alleopathy – Sage (Salvia leucophylla) releases terpenes that inhibit growth of neighbouring plants

Answer 48

Population dynamics is the study of how a given population's numbers grow and shrink over time. Formally described using mathematical equations, which form the bases for population models. Many assumptions and considerations (“all models are wrong, but some are useful” – George Box) – logistic vs exponential growth - resource limitation vs no resource limitation – closed vs open populations - without immigration/emigration vs with – discrete vs continuous generations - regular new generations without overlap or not Population size and density change as a result of – births, – deaths, – immigration and – emigration

Answer 49

Discrete generations consist of populations that do not overlap. – e.g., univoltine insects or annual plants have one generation per year * Closed populations are not affected by immigration or emigration. – This simplification is often applied in studying population dynamics.

Answer 50

Realized per capita growth rate (R0 ) per generation – units for R0 are per generation – R0 varies due to biotic and abiotic factors 1 + Proportion of population at time t+1 that are not present at time t. Net growth, Birth > Death No growth, Birth = Death Net decline, Birth < Death

Answer 51

If unchecked, a given population will continue to increase in size at an exponential rate. This occurs when birth > death for closed populations; and when either birth > death and/or immigration > emigration for open populations. Populations may increase exponentially during initial stage of recovery from overexploitation. * e.g., whooping crane in wintering grounds near Aransas, Texas * breeds in Canada, but winters on Texas coast

Answer 52

Populations vary from place-to-place – good habitats with high densities, poor habitats with low densities No populations increase indefinitely without a limit, even introduced/invasive species will eventually reach an asymptotic density If population sizes do not increase pass a limit, why not? Consider a closed population. It will grow until it reaches an equilibrium where: per capita births = per capita deaths It will remain at or around equilibrium if either per capita births and/or per capita deaths are density dependent.

Answer 53

First principle of population regulation: No closed population stops increasing unless either the per capita birth rate or per capita death rate is density dependent Second principle of population regulation: Difference between two populations in equilibrium density can be caused by variation in either density-dependent or density-independent per capita birth and/or per capita death rates.

Answer 54

Extrinsic processes include the actions of other species, and the physical/chemical environment Intrinsic processes result from actions and interactions of the individuals making up the population. Population regulation results from interaction of extrinsic and intrinsic factors. e.g., predators typically take certain ages groups e.g., size of territory defended by many birds or mammals can limit population density

Answer 55

Stable populations do not show wide fluctuations from equilibrium density. Unstable populations vary widely in abundance. Instability may arise from biotic instability – e.g., predator-prey oscillation (snowshoe hare – lynx). Instability may also arise from environmental fluctuations such as – severe weather.

Answer 56

A population is a group of organisms of the same species occupying a particular space at a particular time. Open populations can change in size due to immigration and emigration as well as births and deaths. Closed populations are not subject to immigration or emigration. – Population dynamics in closed populations are driven only by births and deaths.

Answer 57

Spatial scale is important in stability of populations. * Population may be stable at regional scale, but unstable locally. * Local populations show much more extreme fluctuations, including extinction, than regional metapopulations.

Answer 58

A collection of local populations that are linked together by dispersal (immigration and emigration). * Local populations arise from colonization. * Local populations are more likely to become (locally) extinct.

Answer 59

Some habitats can support high population growth rates. * These can serve as sources of individuals to less favourable habitats. * Territoriality, for example, may led to emigration (dispersal). * In habitats where death rates exceed birth rates, populations can still be maintained by immigration.

Answer 60

Mutualism: Two species live in close association with one another to the benefit of both. * Two examples related to terrestrial plants – Leaf cutter ants and fungi where the fungi relies on the ants. and the fungi produces stuff for the ants to eat – ants and ant cows (aphids) where the ants protect the aphids and in return eat the honey dew that the aphids produce.

Answer 61

Almost all plants have mycorrhizae growing on root tips. These fungi provide nutrients (P, Fe) to plants in exchange for sugars. Plants with mycorrhizae are – more competitive in infertile soil and – better able to tolerate environmental stress.

Answer 62

Ubiquitously distributed soil microbe * Obligate plant-root endosymbiont * Colonise ⅔ terrestrial plants species * Acquire all their carbon from host plant * Beneficial impacts on the plant include: increased P & N uptake, protection from pathogens and improved water relations Arbuscular mycorrhizal (AM) fungi (Phylum: Glomeromycota) form obligate root symbioses with the majority (≈ ⅔) of terrestrial plants. In return for photosynthates, AM fungi provide host plant species with increased phosphorus and nitrogen uptake and protection against soil pathogens.

Answer 63

Predation occurs when one living organism (the predator) consumes all or part of another living organism (the prey). * Herbivory: One animal species (the predator) eats all or part of a plant species (the prey). * Herbivores consume plants, including seeds and fruits. – Often the plant is not killed, but may be damaged. * Carnivory: One animal species (the predator) eats all or part of a second animal species (the prey), often killing the prey.

Answer 64

Parasites are plants or animals that live in or on other organisms (the hosts) and depend on their hosts for nutrition, but do not kill their hosts. Insect parasitoids lay eggs on or near the host insect, which is subsequently killed or eaten by the larvae Cannibalism is a form of predation in which the prey is a member of the same species

Answer 65

Predators may restrict the distribution or reduce the abundance of prey. * Predators may compete by consuming the same prey (when in short supply). * Predators may consume different prey, which themselves compete for a common resource. * On short (ecological) time scales predation can affect community structure. * On evolutionary time scales, predation is a selection pressure that can lead to predator-prey coevolution.

Answer 66

Predators and prey cannot co-exist in two-species “communities“ in a closed system. * Co-existence can occur provided that immigration and emigration are allowed. * Gauss (1934) achieved this by introducing immigrants at intervals to Didinium-Paramecium microcosms. * Huffaker (1958) achieved this by increasing environmental heterogenity (creating a patchy environment) Typhlodromus-Eotetranychus microcosms. * In both cases, the food supply to the prey was unlimited. Also adding places for the species to hide.

Answer 67

Multiple prey species are eaten by multiple predator species. * Habitat is more variable (spatially heterogeneous) for both predator and prey . * Prey have a greater range of refuges from predation. * Time scale for laboratory experiments is limited, precluding evolutionary changes.

Answer 68

Inverse density dependence of per capita population growth rate (r) at low density. Mortality rate increases and birth rate decreases as population density declines. When density drops too low, – mates may be difficult to locate – group defences against predators become less effective. If size drops below a critical threshold density, the population will go extinct.

Answer 69

“doomed surplus” = excess of population growth over that which can be supported by the habitat * The doomed surplus would die due to exposure or disease, if not killed by predators. * To confirm, requires comparing populations of prey in – experimental treatments where predators are removed – versus controls where predators are present.

Answer 70

Predators (hyenas, wild dogs, cheetahs, leopards, lions) appear to have little effect on populations of large mammal prey (wildebeest, buffalo, zebra, gazelle). * Most prey are migratory, entering the Serengeti Plains during the wet season. * Predators are resident, and their populations are limited by prey availability during the dry season.

Answer 71

Surplus killing occurs when predators kill more prey than they can immediately food requirements. * May be an outcome of evolutionary selection for aggressive behaviour towards prey. – in particular, when confronted with agile prey that are typically difficult to subdue * Observed in many types of animals including foxes, wolves, but also invertebrate predators. * Surplus killing occurs when prey are particularly vulnerable. – e.g., chickens in a hen house – poor nutrition during severe winters in deer populations – lack of defence mechanisms against introduced species (e.g., red fox in Australia) * Predators may store food for latter consumption.

Answer 72

Numerical response: change in the numbers or density of a predator population in relation to the size or density of its prey species. Functional response: change in the feeding rate of an average predator in relation to the abundance of its prey

Answer 73

Competition * Predation – Carnivory or Herbivory * Parasitism or Disease * Mutualism * Commensalism * Amensalism

Answer 74

Intraspecific competition is an interaction in population ecology, whereby members of the same species compete for limited resources. This leads to a reduction in fitness for both individuals. Interspecific Competition: Two species use the same limited resource or seek that resource, to the detriment of one or both. Predation: One animal species (the predator) eats all or part of a second species (the prey), often killing the prey.

Answer 75

Mutualism: Two species interact with one another to the benefit of both. Commensalism: Two species interact with one another to the benefit of one without harming or benefitting the other Amensalism: Two species interact with one another to the benefit of one but to the detriment of the other. Symbiosis: interaction between two different organisms living in close physical association such as in mutualism, commensalism or parasitism

Answer 76

Exploitative (e.g., resource) competition Interference (e.g., contest) competition Indirect competition ------------------------- - Space - Mates - Nutrients, Light , Water - Food

Answer 77

Exploitation competition occurs when organisms from the same or different species utilize a common resource that is in short supply. – They consume the resource, thereby reducing the amount that is available. Buffalo and grasshopper eat the same grass, but do not interfere with one another. Trees compete for light, but do not directly harm each other.

Answer 78

Interference competition occurs directly between individuals. – via aggression, – or when the individuals interfere with foraging, survival, reproduction of others, – or directly prevent others from occupying a portion of the habitat. Two species of birds do not eat the same food, but compete for a limited number of tree holes for nesting sites.

Answer 79

Indirect competition occurs when two species interact via a third species, for example via a common predator. * Pheasants & rabbits do not compete directly for food or space, but may appear to interact when they are subject to a common predator (e.g., foxes). * An increase in the abundance of rabbits leads to in increase in the fox population. * The pheasant population then declines due to increased predation from the larger fox population. * This leads to an inverse relationship between population sizes of rabbits and pheasants.

Answer 80

The ecological space occupied by a species, and the role (occupation) of the species in a community. --------- * Define the term “fundamental niche.” * The set of resources that a species can use, and the range of habitats that it can occupy, in the absence of competition with or predation by other organisms. ---------- Define the term “realized niche.”: * The observed resource use of a species in the presence of other organisms in the community.

Answer 81

Coexistence requires that intraspecific competition is greater than interspecific competition. * In the green area, species 1 increases at the expense of species 2. * In the orange area, species 2 increases to the detriment of species 1. * In the white area, populations of both species decline.

Answer 82

Lotka-Volterra competition model considers consumption of a single resource. – It predicts competitive exclusion. * Coexistence can occur if there is more than one limiting resources and different species have different requirements for these resources. – The number of species that can coexist depends on the number of limiting resources. * Coexistence can also occur in nature if there is: – heterogeneity in the environment, – fluctuation in resource level, – episodic resource availability, or – competition is not the only type of interaction between the species.

Answer 83

Environments where resources are not limiting (e.g., where predation controls abundance of prey). Environments where species do not compete for the same resources. Both the Lotka-Volterra zero growth isoclines and Tilman’s competition model predict the outcomes of competition at EQUILIBRIUM. – Is equilibrium ever reached in the real world? Fluctuating environments can reverse the direction of competition.

Answer 84

Research on competitive exclusion has focused on taxonomically related species that inhabit the same environments. Much of this work has been done on birds. Robert MacArthur’s (1958) studies of warblers (Dendroica spp.) Ecology 39: 599-619 (available electronically from the library) 5 species coexist in New England forests. All eat insects and are comparable in size. How is competitive exclusion prevented? Warblers will eat at different parts on the tree, meaning they can co-exist. Some warblers occupy the same space and one is clearly a stronger competitor, however the other warbler will live off the boom and bust of the insect population of the more dominant warblers feeding niche.

Answer 85

These Dendroica species partition the forest by – feeding at different positions in the canopy – feeding in different manners – moving in different directions through the trees Conclusion: closely related species of warbler avoid competition either by living in different places, or feeding in different ways on different types of food. In addition, Cape May warbler is a poor competitor (only feeds on tips of highest braches) – Coexistence of this species depends on eruptions of insects to provide superabundant food

Answer 86

Divergence of species in areas where they co-occur to either maintain reproductive isolation or reduce interspecific competition. Observations of character displacement support Gause’s hypothesis.

Answer 87

Character Displacement can be used as evidence of evolutionary adaptations to reduce competition provided that... The pattern could not have occurred by chance. * Sites should not differ greatly in environmental conditions whether both species or only one of the species is present. * Morphological differences reflect differences in resources used. * There is other evidence for competition. * Phenotypic differences have a genetic basis * Trait results from actual evolutionary change.

Answer 88

The essence of Darwin's theory is that natural selection will occur if three conditions are met. These conditions, highlighted in bold above, are a struggle for existence, variation and inheritance. These are said to be the necessary and sufficient conditions for natural selection to occur.

Answer 89

Locally rare species are expected to have a survival advantage because rarity reduces their risk of damage from pathogens. This "rare-species advantage" may help maintain plant diversity in natural systems and explain how introduced plant species become invasive weeds. There will also be less competition between species if they are rarer. They will also have less predation pressure.

Answer 90

In many studies, species of intermediate abundance are more common than very rare species. * This is seen as a maximum in the plot of number of species versus geometric class. * A log-normal distribution is the expected statistical distribution when the – number of species is high, and – relative abundances are determined by a large number of independently operating factors.

Answer 91

Sequential Niche Breakage Hypothesis: – A community contains a total set of niche requirements. – This niche space is broken up sequentially as new species enter the community one at a time. The log-normal distribution is a consequence of the sequential RANDOM partitioning of the total niche space by the component species. * A competitively superior species occupies more of the space.

Answer 92

Two possible ways for a 3 species community to arise by subdividing total niche by sequential random partitioning. In both cases, the niches are structured in a hierarchy.

Answer 93

Homogenous means alike. Heterogenous means unalike or distinct from one another. Thus, a homogenous population has little variation. You could refer to a specific trait, such as hair color or you could refer to genetic diversity.

Answer 94

The habitat-heterogeneity hypothesis, developed initially by MacArthur and MacArthur (1961), proposes that an increase in number of different habitats can lead to an increase in species diversity. The “habitat heterogeneity hypothesis” (MacArthur, 1972) states that the number of available ecological niches will increase as habitats become more complex, and that this will have positive effects on the ability of species to coexist (e.g. McClain & Barry, 2010; Stein, Gerstner, & Kreft, 2014; Tews et al., 2004).

Answer 95

Alpha diversity: the diversity within a particular area or ecosystem. – usually expressed as the number of species (i.e., species richness) in that ecosystem. Beta diversity: a comparison of diversity between areas or ecosystems – usually expressed as the number of different species between the ecosystems. – rate of accumulation of diversity with an increasing number of sites sampled Gamma diversity: a measure of the overall diversity within a large region. – usually expressed as the total number of species in a geographical area.

Answer 96

Logging reduces habitat heterogeneity * Sample alpha diversity relatively unchanged * Between-sample beta diversity deceases * Thus – slope of SAR (The species–area relationship) decreases

Answer 97

Neutral theory: relative abundance of different species within a community is determined by chance. Neutral theory is a null hypothesis to niche theory. All species in the community are assumed to be ecologically equivalent. -all species have the same per capita birth rates, death rates and speciation rates. -All species are equally competitive. As individuals die, they are replaced by offspring of another individual, chose at random regardless of species. The community is saturated with species and is in equilibrium (the total number of species is constant).

Answer 98

species abundances will better fit the ZSM distribution than the log-normal. * changes in community composition will be related to solely to distance between samples (reflecting effects of dispersal limitation). * no relationship between community composition and either abiotic or biotic variables.

Answer 99

A stochastic process means that one has a system for which there are observations at certain times, and that the outcome, that is, the observed value at each time is a random variable. This comprises essentially everything we speak about.

Answer 100

In brief, metagenomics could be defined as the characterization of the vast number of genomes present in an environmental sample, using both a taxonomical and a functional analytical approach. DNA metabarcoding, on the other hand, principally focuses on taxonomically describing the species present within a sample.

Answer 101

Ecological efficiency describes the efficiency with which energy is transferred from one trophic level to the next. It is determined by a combination of efficiencies relating to organismic resource acquisition and assimilation in an ecosystem.

Answer 102

The production of organic matter by the consumers is called secondary productivity. In secondary productivity, the energy is obtained by the transfer of energy through the food chain.

Answer 103

The main energy source in an ecosystem is sunlight. This is absorbed by plants, called 'producers'. This energy is then passed on to the animals through the plants they eat, these animals are called 'primary consumers'.

Answer 104

Autotrophs, the producers in a food web, convert the sun's energy into biomass. Biomass decreases with each trophic level. There is always more biomass in lower trophic levels than in higher ones. Because biomass decreases with each trophic level, there are always more autotrophs than herbivores in a healthy food web. So, the correct answer is 'Net Primary Productivity'. Note: From one trophic level to the next trophic level only 10% of energy will be transferred and 90% of the energy gets lost. This is called the 10 percent law.

Answer 105

Ecological Succession. Ecological succession is the process by which a whole community of populations changes through time. It occurs following a disturbance that creates unoccupied areas for colonization. During succession, some species colonies area and their population become more numerous, whereas, the population of other species declines and even disappears. It is a process of systematic progression of types of species invading an area. There are two main types of succession, primary and secondary. In primary succession, newly exposed or newly formed rock is colonized by living things for the first time. In secondary succession, an area that was previously occupied by living things is disturbed, then re-colonized following the disturbance.

Answer 106

Plant species richness may vary with variation in local soil properties. Animal species richness may vary with the complexity of the habitat form, for example vegetation structure. Thus habitat heterogeneity is both context and species dependent. An obvious pattern of communities is the variation in species abundances. Many factors affect small-scale species richness, including geographic (e.g. species pool, dispersal), biotic (e.g. competition, predation, facilitation) and abiotic (e.g. resource availability, environmental heterogeneity, disturbance frequency and intensity). Heterogeneity is defined as the variation in biotic and abiotic conditions across space and through time

Answer 107

Facilitation occurs when one species positively impacts the fitness of another, and has predominantly been studied in free-living species like plants. Facilitation can also occur among symbiont (mutualistic or parasitic) species or strains, but equivalent studies are scarce. or example, pollinators, such as bees, butterflies, and hummingbirds, benefit because they eat the collect pollen and/or nectar that they collect from flowers. The plants also benefit because their pollen is dispersed to other plants, allowing them to reproduce.

Answer 108

Individualistic hypothesis The view, first proposed by H. A. Gleason in 1917, that vegetation is continuously variable in response to a continuously varying environment. Thus, no two vegetation communities are identical. Clements's Organismal community is a spatial concept: variety of plant and animal species interacting and influencing the overall structure. Gleason's Continuum view is a population concept, focusing on the response of the component species to the underlying features of the environment.

Answer 109

Animals help plants by helping pollinate flowers or by dispersing seed. They also help supply nutrients when they die and decompose.

Answer 110

MacArthur and Wilson thus assume that there will be an equilibrial point where the immigration rate equals the extinction rate. They further hypothesize that an increase in island size will lower extinction curves while a decrease in distance between the island and the source region will raise immigration curves.

Answer 111

Primary productivity is usually determined by measuring the uptake of carbon dioxide or the output of oxygen. Production rates are usually expressed as grams of organic carbon per unit area per unit time. The type of terrestrial ecosystem found in a particular place is dependent on the temperature range, the average amount of precipitation received, the soil type, and amount of light it receives. The niche will also affect the primary production for the different species in the ecosystem.

Answer 112

Primary producers use energy from the sun to produce their own food in the form of glucose, and then primary producers are eaten by primary consumers who are in turn eaten by secondary consumers, and so on, so that energy flows from one trophic level, or level of the food chain, to the next. Energy can pass from one trophic level to the next when organic molecules from an organism's body are eaten by another organism.