Week 7

herbivory

leaf-browsing giraffes and caterpillars, seagrass-eating sea turtles, frugivorous bats, lichen-grazing reindeer, the sap-sucking woodpeckers - bees/hummingbirds: can be classified as herbivores, but if they are also serving a role as pollinators for their host, the relationship is more appropriately categorized as a mutualism.

Darwin's "Tangled Bank"

metaphor for the interconnected complexity of the ecosystems

Haeckel's neologism

oklogy (oikos means home) and envisioned the ecosystem as a home "The comprehensive science of the relationship of the organism to the environment"

parasitoid vs. parasite

parasitoid: - common insect parasites among the wasps, bees, and flies - lay their eggs on (ecto) or in (endo) the eggs of their host. when the eggs hatch, the larvae consume the host, a lethal relationship - important in the regulation of herbivorous pest populations such as caterpillars parasite: - usually do not kill their host, in fact, they benefit from non-lethal interactions because they are able to continue to feed and find shelter as their host survives - eg: tapeworms that feed in the gut of vertebrates; brood parasites; hemi (photosynthesize, green, mistletoe) and holo parasitic plants (can't photosynthesize, white/orange) that insert their haustoria in the plant's phloem to rob it of its sap

species diversity vs. species richness

species diversity: a function of the total number of species (species richness) and the relative parity of species in terms of population size (species evenness) - species richness is the total number of species, species evenness is the relative # of individuals in each species

a scientist runs a transect across the gradient between serpentine and non-serpentine soils. He will most likely observe

species turnover

r/K selection theory

trade off between quantity or quality of offspring. where r is the growth rate of the population (N), and K is the carrying capacity of its local environmental setting. Typically, r-selected species exploit less-crowded ecological niches, and produce many offspring, each of which has a relatively low probability of surviving to adulthood. In contrast, K-selected species are strong competitors in crowded niches, and invest more heavily in fewer offspring

the dispersion of a species of kelp is clumped. the dispersion pattern of the snails that live on the kelp could be

uniform, clumped, or random

predator-prey relations (lynx and hare in Canadian boreal forest)

- both species have big feet that allow them to walk the heavy snows - hares have brown and white coats that help with camoflauge in different seasons - lynx have thick fur coats that are prized by hunters - the ecological record of these populations is "accurately" represented by the hunters who report these numbers

density dependent regulation

- biotic factors such as competition, predation, and parasitism affect population size to a greater degree where there is greater population density. - competition/density correlated with growth rate, survival, and reproductive output - really highly dense populations means more waste to the point of detrimental effects on the population - increased spread of pathogens in highly dense populations - more prey means more susceptibility to predators who don't have to expend a lot of energy in finding prey; subsequent decline in the prey population

fundamental vs realized niche

- Fundamental niche is the entire set of conditions under which an animal (population, species) can survive and reproduce itself - Realized niche is the set of conditions actually used by given organism after interactions with other species (predation and especially competition) have been taken into account - Jospeh Connell studied 2 species of barnacle (A and B). Under normal conditions, A occurs from the high-tide line about half way down to the low-tide line and B occurs in the opposite direction. In some plots, A was removed, and B was removed in others. When A was removed, B migrated upward towards high tide, but individuals were limited by their dessication intolerance and did not fully occupy the upper zone. When B was removed, A went down to low-tide, suggesting that this species was not limited by abiotic factors, but rather by competition with B (a biotic factor)

seasonal change

- NOT successional change! - Community change is correlated with annual, cyclical changes in regions with distinct seasons - vernal pools in Central Valley: winter rains, followed by spring snows that may add even more water to the ecosystem, resulting in abundance of green growth and the proliferation of organisms in the soil. As summer passes, the system becomes desiccated, the vegetation dies back, and organismal activity pauses until the rains returns

exploitative competition

- Organisms that rely on the same limited resource but without direct physical interactions - foraging of one species negatively impacts the amount of food available to its competitor - eg: grasshopper and bison eat the same grass but don't fight each other for it

species abundance

- Red Kangaroo is one of several in its genus and is only in Australia. They tolerate hot environments by licking their arms, so that the evaporation of the saliva triggers cool blood to circulate and keep them cool. However, this also means that they are more prone to dehydration. Only Red Kangaroos are able to maintain the delicate balance, so they survive best in hot, arid conditions, though other species of kangaroos can't.

Resource Aquisition

- Resources are acquired by an organism in ecological time based on strategies that the organism's ancestors acquired evolutionarily - constant tug between saturation and constrain - eg: plants rely on sunlight for photosynthesis, and when that resource is limited (like in a closed canopy forest), they compete. As light levels increase, the rate of photosynthesis also increases but tapers off to some limit due to constraints (overheating, production of newer chloroplast) - eg: the more seeds there are, the faster the kangaroo rats will gather them; however, the rats are limited by their anatomy (skeleton, muscles, and nervous system). As resource abundance increases, the rate of their gathering also increases but again tapers off to some limit.

predator-prey relations (wolves and moose on Isle Royale)

- Wolves and moose were 2 populations introduced to Isle Royale, where animal population is constrained due to the size of the island and local extinctions sometimes occur - number of wolves on the island impacted the prey population, the moose. Both species, however, were also impacted by non-predator-prey factors, like weather and disease - eventually, the wolf population decreased tremendously due to inbreeding depression and a loss of genetic diversity; only 2 wolves were left on the island in 2016 - wildlife officials opened up the island and introduced more wolves

population

- a group of individuals of the same species that live in the same area and potentially interbreed - experience the same environmental factors, rely on the same resources, and are likely to interact and breed together - characterized by number and distribution of individuals - populations from different species that are close enough to interact make up an ecological community. in an ecological community, a group of species coexist and interact together.

guild

- a group of species that exploit the same class of resources in a similar way - members of a guild often show little direct competition since they are ecologically different - eg: Bluegray gnatcatchers that coexist with other species who prey on the same insects

population size (N)

- a response variable - will be on the y axis - tracking population size over time in line graphs, not examining correlation between 2 different variables

predation (predator-prey)

- a type of consumer-resource interaction in which

density-independent regulation

- abiotic factors, weather-related setbacks that impact individuals in a population without reference to how many individuals are present - If there are a large number of individuals in the population, the likelihood of any single individual dying—or having a reduced reproductive output—is the same as if there were only a small number of individuals present. - floods, tornadoes, landslides, volcanic eruptions, ice storms, strong winds that knock down trees - strong winds like hurricanes and typhoons MIGHT serve as density DEPENDENT factors

lab microcosms

- allow analyses of organisms in more controlled settings - many populations "overshoot" K, or oscillate around K before settling down, or oscillate indefinitely in a sort of dynamic equilibrium.

population cycling (predator-prey)

- alternation between increasing/decreasing populations of lynx/hares demonstrates that over-predation of hares by the lynx results in a population decline for the hares - as hare pop increases, so does the lynx - in absence of predator the hare pop can crash - lynx cycle peaks slightly later than the hare cycle: due to lag between the increase in the hare population and the associated increase in lynx reproduction as a result of increased food availability as well as the longer gestation period since offspring start to hunt for food at a much later age - lynx population is always smaller: Because predators are at a higher position in the food web than their prey, they tend to exist at smaller population sizes. - lynx create a top-down effect: population dynamics of organisms in higher positions in the food web are causing population cycles in organisms in lower positions in the food web - fluctuations in hare populations due to the increase/decrease of available vegetation: as the hare population gets too large, it depletes the vegetation that it depends on for food to such a degree that its population crashes - smaller population eats less vegetation, allowing for it to grow back, and the population to rebound again - since the lynx in this case does not cause cycling, this demonstrates a bottom-up effect: population dynamics of organisms in lower positions in the food web are causing population cycles in organisms in the higher positions in the food web

population size (N)

- an estimation of population abundance - relative (indirect) and absolute (direct) estimates are necessary depending on the study different methods of estimation: 1. Direct estimates of N - counting the actual organisms - counting trees in a small forest, using planes/drones to count larger mammals from higher levels - can utilize direct counts and "extrapolate" to a larger area (use of quadrats to accurately count all of the individuals of a particular species in the cells of a grid, and then they extrapolate the result to a larger area) - linear transect (fields, coral reefs): count all individuals of a particular species that occur within a certain set distance on either side of that transect, or all the individuals that touch the transect or that occur below or above it. The ecologist extrapolates from this subsample to estimate the size of the population overall. 2. indirect estimates of N - utilize signs of activity, such as chimneys built by the crayfish, footprints in the snow/mud, feces that also tell about the organisms' diet, etc 3. associated species - Peregrine falcons' presence associated with the absence of their prey, the Arctic foxes - Presence of Arctic foxes assocated with the absence of their prey, the geese; the nesting colony of the geese means that arctic foxes are absent and peregrines are present - reliable method 4. mark recapture method (diagram) - common for fish biologists - N = mn/x; m (# of fish caught in the first sample), n (# of fish caught in second sample), x (marked fish in the second sample) - assumptions: no reproduction/birth/death/immigration/emigration or these factors are equal

fixed interval population growth

- based on per capita estimates: For per capita estimates, the number of births is calculated relative to the total number of individuals present deltaN/deltat = (r)Nt, where r represents the per capita growth rate (intrinsic rate of population growth) - r is equivalent to the difference between b (per capita birth rate) and d (per capita death rate)

birth-death model

- based on the key assumption that immigration and emigration rates are approximately equal, canceling each other out Nt+1 = Nt + B - D, or deltaN/deltat= B - D

ecological disturbances

- can be small to subglobal in scale - time it takes for the community to recover is positively correlated with the scale of the disturbance - the process of recovery from the disturbance is referred to as "ecological succession" (diagram!) - quantified based on intensity and frequency - lightning: usually affect smaller areas but can catalyze much bigger disturbances like fires. Normally occur in terrestrial ecosystems in the summer and are really frequent in the tropics. They cause fires in drier areas. - fire: ferns and other plants can be resilient afterwards

life tables

- can document natality (births) and mortality - eg: scientists studied a cohort (sample of individuals of a population in the same generation) of ground squirrels over the course of eleven years, and tracked their life and death rates

logistic curve ( S-Curve )

- can model density dependence - dN/dt = rN (K-N)/K - as N approaches K, the numerator of the equation goes to zero, and population growth rate (dN/dt) also goes to zero - N exceeds K, population growth rate goes negative, and the number of individuals in the population declines.

Two barnacles, B and C, can both survive on the lower rocks just above the low-tide line on the Scottish coast, but only B actually does so, with C adopting a higher zone. Which of the following best accounts for this niche separation?

- competitive exclusion principle

predation

- consumer-resource interaction in which predator eats prey - pos-neg relationship since one party benefits and the other doesn't; also includes herbivory - "honest sampling effort" since companies kept detailed records of how much fur was bought from fur-trappers; these records served as good estimates of population size of lynx/snowshoe hare

ecological succession

- continuous pattern of colonization and extinction of species in a local community - change in species composition over time! - non-seasonal and directional (1) primary succession: - begins in an area devoid of life, such as after a volcanic explosion (Mt. St. Helens); relatively rare - Glacier Bay in Alaska: series of stages identified include-- (a) pioneer stage with cyanobacteria, lichens, liverworts, and fireweed that lasts less than 10 yrs, (b) Dryas stage with thick stands of willows/cottonwoods are around 30 yrs, (c) an alder stage with thick stands of alder trees at around 50 yrs, and (d) a spruce-hemlock stage with heavy conifer forests after about 100 yrs; Sphagnum bogs take over and inhibit tree growth (2) secondary succession: - follows a disturbance that does not eliminate all of the living organisms from an area; very common - post-fires, many organisms in the soil, seeds, plants/animals are still alive and the soil allows for rapid recovery - "old-field succession", where areas are potentially left abandoned; along ocean coastlines, shifting sands continuously catalyze successional processes across space; in tropical forests, gaps created by the felling of large trees trigger succession in discrete patches (3) degradative succession: - succession of the organisms that inhabit dead organic matter as it decomposes - leaf on a tree undergoes this degradation, which continues after the leaf falls off the tree - fallen trees, carcasses of large animals; bloat, active decay, advanced decay, and dry decay

how we calculate K

- count/estimate the population size over time - assuming that natural populations already are at carrying capacity, multiple measurements of population size taken over time will tend to fluctuate around a constant value - average the measurements

resource partitioning

- different species pursue similar species of prey in a variety of microhabitats, without a clear preference of any particular one; eg: One anole species hunts insects around the pool chairs and on the cement, another species chases insects along the fence posts, another forages exclusively on the bark of the tree trunks, another works along small branches in the tree canopy, and a very common species occurs in all of these microhabitats, without a clear preference or any particular one - White-breasted nuthatches and Downy woodpeckers both eat insects that hide in the furrows of bark in hardwood trees. The Downy woodpecker searches for insects by hunting from the bottom of the tree trunk to the top, while the White-breasted nuthatch searches from the top of the trunk down. As a result, the two bird species tend to encounter different species of insect prey. - typically occurs in sympatric population with similar ecological niche

interference competition

- direct antagonistic interactions between organisms that are competing for limited resources (access to mates, food, or territory)

Pribilof islands

- drastic reduction in seal population, which later rebounded after hunting restrictions were placed

density-independent mechanism

- drought, fires, hurricanes, and human-caused environmental change, impacting population size regardless of the population density - the O'Shaugnessy Dam would have eliminated the population living in the valley regardless of what the density was; density had no impact on survival

competitive exclusion principle

- established by Guase, who understood from his paramecium experiments that P. aurelia was a superior competitor since it reached a carrying capacity when grown along with Cuadatum species - utilized by Hutchinson as a "limiting theory": sympatric organisms were predicted to differ by some minimum distance in niche space in order to maintain stable coexistence.

keystone species

- exerts strong control on community composition and function, without being numerically abundant in terms of number of individuals or biomass - eg: mussel populations dominate in the absence of the Pisaster keystone predator, greatly decreasing the diversity of the intertidal ecosystem; keystone predators increase diversity! - eg: sea otters are another example of a keystone predator, as their primary food source is the urchins. Due to overhunting, sea otter population greatly decreased, leading to a boom of urchins and a decline of kelp beds that were home to lots of marine life. Healthy sea otter populations could actually have a positive impact on global carbon cycle (since kelp beds influences global carbon budgets) - eg: The grasslands contain scattered woody plants, but they are kept in check by the uprooting activities of the elephants, which are not very common in this biome. Take away the elephants, and the grasslands convert to forests/shrublands. The newly growing forests support fewer species than the previous grasslands. Elephants can be defined as keystone species!

density-dependent mechanism

- exponential vs logistic growth (Review diagram!) - carrying capacity (K): max population size that can be supported by local resources; describes a population in a particular location with a specific amount of limited resources - exp. growth is dependent on the availability of resources; when resources are limited the population will no longer grow exponentially (lack of food, sunlight, breeding territory) - competition: use of a shared/limited resource; can be intra (within same species) or inter specific (between 2 different species) - inter-specific competition is a neg-neg relationship since both parties are negatively impacted - for resources that aren't shared, there is no competition: 2 diff species won't compete for mates - for resources that are unlimited, there is no competition: individuals don't compete for O2

the effect of competition on reproduction

- famous example of Song Sparrows - reproductive output declines when the density of females increases - negative relationship between reproductive success and density - At peak density, females produce only 25% the number of offspring that they produce at low density - females lay fewer eggs per capita (lower r) at high densities

bedbugs

- feed on human blood - most common in hotels, crowded apartment buildings - difficult to eliminate - can go up to one year without feeding - do not discriminate by socio-economic categories

estimating population size

- for songbirds, potentially use distinct songs - for ants, making a model of the underground nest and calculating the ant volume - for sessile animals, utilize quadrat method: take a small sample of a known area (quadrat) and count all of the individuals inside. By randomly sampling many quadrats in a habitat, estimate the density of the organism in that habitat and then multiply the density * total habitat area to estimate population size.

modern definition of ecology

- golden age of ecology due to the post-world war environment where radioisotopes were used to track the living/non-living organisms and their interactions with the ecosystem - this idea led to the establishment of Ecosystem Ecology - Species Ecology (Darwin + Elton) continued to develop, with an emphasis on natural history - the narrow definition of ecology was broadened and cemented as: "The scientific study of the interactions that determine the distribution and abundance of organisms"

metapopulation

- group of spatially separated populations that interact through immigration and emigration - a "population of subpopulations" - subpopulations that occupy a suitable habitat may go locally extinct for random reasons, but migration can re-establish the local population at a later date or entirely new subpopulations in vacant patches - eg: Fritillary butterflies are a non-migratory species that feed on plants in otherwise unsuitable habitats. Butterflies in high-density populations are more likely to leave their patch in search of new habitat in which to lay eggs. Inbreeding depression can affect individuals that remain isolated for prolonged periods in a single patch. They tend to disappear from local patches and take up residence in previously empty locations. - illustrates that complex dynamics of immigration and emigration based on biological imperatives interact with random (stochastic) factors

mutualism

- hard to identify - obligate mutualism: both species require their partner for mutual survival - eg: leafcutter ants transport clipped leaves back to fungal gardens in subterranean nests. The fungal symbionts live only in these gardens (obligate mutualism) cannot be found living freely on their own. Ants feed the fungi the clipped leaves, and the fungi produce fruiting bodies that are fed on by the ants - facultative mutualism of convenience: both participants benefit from the partnership when it occurs, but the relationship is not vital for survival, and both species are capable of independent survival - eg: Honeyguides locates a ripe hive and bring it to the attention of the honey badger, which follows the guide to the hive. Badger rips apart the nest, shaking off the stings. The honeyguide takes advantage of this mess and feeds on the scraps. - eg: microbiomes in the guts that get their nutrients/protection while the animal is able to digest food; useful for herbivores that have to digest tough cellulose/lignin - eg: lichen have mutualistic symbioses with fungi/cyanobacterium/algae - eg: coral polyps filter food, and zooxanthellae in them can photosynthesize and contribute their sugars to the polyps eg: flowering plant pollinators get food and assist flowers in reproduction

ecological niche concept

- has been a confusing concept in ecology - Grinnell conducted studies on the California thrasher and learned that it is built for the Californian chaparral. Its short wings and long legs of the thrasher are suitable for the dense shrubs, and long, decurved bills allow it to probe the dry leaves for food. - thus defined the niche as: set of adaptations to the habitat, including all of the behavioral, physiological, morphological, and psychological connections that the organism has to its local environment

ecosystem engineers (foundation species)

- have a major physical impact, either pos or neg, on local ecosystem - don't necessarily drive increase in diversity - eg: beavers, humans, elephants

challenges in defining a population

- how do we define the "same area"? - islands are often used since boundaries are more easily defined - also difficult to measure size/geographic distribution

you observe a population of lizards and notice the number of adults increase. what likely happened?

- increased rates of immigration

trophic cascade

- indirect effects in a community that are initiated by a predator - eg: killer whales began to prey on the sea otters when their normal prey source wasn't readily available. The subsequent cascade on the kelp beds and the physical environment had a positive impact on 1º producers when the number of trophic levels is odd (e.g., the sea otter-urchin-kelp chain, a 3-level cascade) but a negative impact when the number is even (e.g., the killer whale-sea otter-urchin-kelp chain, a 4-level cascade).

K species

- individuals produce few, large offspring that are well-provisioned for survival, and these offspring grow slowly to the age of first reproduction, but they continue to produce a small number of offspring each season over the course of their long lives. Parental care is more commonly seen in K species. - often large mammals - slow to respond to environmental change; intense, sustained predation may overwhelm their naturally slow rate of increase

r-species

- individuals produce many small offspring, most of which die early in development, with the few survivors developing rapidly and reproducing at a young age - eg: pin cherries are eaten by birds, which defecate seeds that accumulate in the forest as persistent seed banks. An opening in the forest canopy due to some natural circumstance allows sunshine in, such that the seeds quickly germinate in dense clusters. They compete very intensely for light and nutrients, and take advantage of high resource availability very quickly (hallmark of r-species). Mature pin cherry saplings can produce an abundance of offspring at a young age. - often small mammals; eg: voles reproduce when they are only one-month old and can produce several litters annually. They have a high r value (rate of increase) and low death rate due to abundance of food will cause population to irrupt.

brood parasites

- instead of feeding on the host, they lay eggs in the nests of their hosts - brown-headed cowbirds lay eggs in nests of hosts, which care for the offspring as their own. - often result in reduced survival/resources for the host's offspring - problematic for endangered species that are unable to increase their population due to the parasitism - chicks are often bigger than their hosts - nomadic lifestyle from initially following herds of bison and feeding on the small invertebrates

species interactions

- interactions between 2 different species within an ecological community - (inter-specific) competition, consumer-resource, mutualism, and commensalism - characterized by the effects that species have on each other - effects of species interactions on populations are measured in terms of population size

ecotone

- interface community that exists between two distinct, adjacent communities - very diverse since they include species from neighboring communities as well - eg: the space between land and water, where lake species may come to land and land critters may come to water for certain resources/needs - serpentine/sandstone communities: differ in species composition, and generalist species occupy both zones. in between them are ecotonal species, some of which are specialists, others occur in one or both of the adjacent zones

survival vs reproduction trade-off

- making female gametes is very expensive and requires a lot more energy to produce/maintain - Kestrel bird species: both parents care for their young until autumn. During the cold winter months, the adult birds don't have enough fat stores to survive. It was found that parents with artificially enlarged broods actually had a reduced survival rate, and the opposite effect was seen in parents with reduced broods.

Hutchinsonian niche

- mathematically defined a niche with n-dimensional hypervolume, where the axes of this theoretical space represent the dimensions of the organism's relationship to the environment - most important adaptations are arranged in an array, and the quantitative modeling can provide a foundation for community ecology and the organism's relation to other species

methods of tracking distribution/movement

- most accurate methods are those in which the organism is caught and marked. Even though this method may pose risk to the organism and is time-consuming/expensive for scientists, it produces usable data. - eg: tagging the wings of monarch butterflies and recording the time/place where the sticker was applied; knowing their migration routes is useful in conservation studies of this species - RFID/PIT tags for larger organisms: small devices injected under the skin that have chips that encode time/place of application. These tags are not battery-powered and never lose their ability to convey data, but the data that they store is only available from a close-range scanner. So, the animal must be in close range to the scanner in order for the chip to be scanned - telemetry: battery-powered radio-transmitters that track large animals in real time as they move about a landscape; important for a balance between the battery size and the organisms' safety; can be tracked on laptops via satellites/cell-phone towers - camera traps: a standard tool that is useful to track organisms in their natural behavior; do not impede animal movement or have IR technology for night-time movement; work for long periods of time and can withstand harsh conditions; can also beam back to laptops so that we can view organisms in real-time; can also be charged via solar energy

population density

- number of individuals of a species per unit area or per unit volume (# of oak trees per km^2) - provides population size relative to area - gives us a better idea of how crowded a population is - often more descriptive than population size alone - eg: Los Angeles has a much larger population size but a much lower population density than SF because the population is spread out over a larger area

dominant species

- numerically abundant in individuals or biomass - when removed from an ecosystem, there can be drastic consequences (eg: the spread of a fungus that eliminated a dominant tree species; Chestnut blight)

character displacement

- often considered more important factor than competition in community structure/dynamics - can be evidence of competition - eg: 2 species of Galapagos finches occur sympatrically (coexist) in 2 island chains and allopatrically (isolated) in 2 other islands. In allopatry, they exhibit similar beak sizes, but in sympatry, they do not overlap in beak size. The beak size is directly correlated with seed size, so the species with the bigger beak is considered stronger than the opposing species in sympatry.

parasitism

- parasite: organism that feeds on the another species (host) while in/on the host organism - pos-neg relationship since host is harmed and parasite benefits - usually smaller than hosts, do not always kill them, can live in multiple hosts, not always living in intimate contact with hosts (eg: ticks/mosquitoes) - density-dependent mechanism for pop. growth regulation: host population density increases, the likelihood of infection by parasites increases - eg: covid, bubonic plague are diseases that spread quickly in crowded populations

Guase

- performed experiments on paramecium to understand the effects of competition on population growth - both species reached similar K when grown separately, whereas when grown together in a mxed population, one reached stability in population size whereas the other went to 0 - established the competitive exclusion principle: when populations of two similar species compete for the same limiting resources, one population will use the resources more efficiently and have a reproductive advantage that will eventually lead to the elimination of the other population. 2 species competing for the same resource can not coexist for a long time if other ecological factors are constant.

Population Dispersion Patterns

- population dispersion: spatial relationship among the members of a population, whether on the earth surface or in a volume of water or air. - How an ecologist classifies the dispersion pattern of a species depends on the scale at which the species is observed and measured (cheetahs are uniformly distributed locally, but patchily distributed across a country) 1. Uniform: more common pattern in which there is relatively even spacing amongst organisms; A distribution in which the average distance between an individual and its closest neighbor is greater than predicted by chance - cheetahs mark their territories such that individuals occupy non-overlapping home ranges of similar size across the landscape - squirrels that defend territories against members of the same species - nesting birds that situate their nests at certain distances where no one else will interfere - shrubs that compete for resources or are chemically inhibited (alleopathy) 2. Clumped: most common pattern in which organisms exist in discrete patches; mostly seen in plants/animals - elephants along a river - barnacles, mussels, green algae in the intertidal zones 3. Random: wind dispersion of seeds or dispersion of flowers; not very common

commensalism

- pos-0 relationship since one species benefits while the other is neither helped/harmed - Great horned owl builds its nest in the tree to protect it from predators - extremely rare

mutualism

- pos-pos relationship since both species benefit - lichen (mycobiont) + green algae/cyanobacterium - mycobiont receives photosynthate from photobiont, which received protection/inorganic materials from the mycobiont - ants, acacia trees, elephants: ants defend the acacias from herbivory by attacking and stinging elephants that try to feed on the acacia, which provide food (nectaries)/shelter (domatia) to the ants.

exponential growth curve (j-shaped)

- positive exponential growth seen in the seal populations that were hunted nearly to extinction, but due to protective measures, experienced one of the biggest population increases in mammals

intermediate disturbance hypothesis (graph!)

- predicts positive effect on community diversity of disturbances that are intermediate in intensity and frequency - # of species in a community will be low in extremities

Shannon Diversity Index (H)

- quantifies diversity and compares communities directly - accounts for both richness and evenness H = - ((pA * ln pA) + (pB * ln pB) + (pC * ln pC) + ... ), - higher index means more diverse - it does not allow two communities to be easily compared with respect to the magnitude of the difference in diversity (is a community with H of 0.8 twice as diverse as a community with H = 0.4?) - when the species richness between 2 communities differs greatly, H can be converted into the effective number of species, a marker of "true" diversity - effective number of species: e^H, where the result tells you how much more diverse a community is than another =

species distribution (range)

- range of a species refers to the limits of its distribution in space; eg: range is the total area of Australia in which red kangaroos can be found, whereas distribution refers to where populations of red kangaroos are found within the overall area that they occupy - eg: Cattle Egret was limited to Africa and south Asia, where it followed the animals of the savannah. Due to some natural phenomena, they became established on a new continent in North America, and followed different species (horses/cattle)

survivorship curves (diagram)

- reflect the death rate of a species population over an average individual lifespan - both sexes are often modeled separately since males/females have different mortality rates - show death rate on the y-axis with a logarithmic scale - death rate reflects the percentage of individuals alive at the start of a given time interval - x-axis shows individual age, units of which depend on the species. In the case of comparing different species, it is better to represent the age by % of max life span. - eg: for the ground squirrels, males have a slightly higher mortality chance than females, and the survivorship curve forms a straight line for this species (Type II) - Type II curves: pretty rare, seen in the ground squirrels and in some birds - Type III curves: steeply concave, used for plants/invertebrates with abundant larvae; large number of offspring, majority of which die after birth - Type I: seen in humans/large mammals; few big babies that are protected by parents; high survival rates early in life before steep decline as the individual reaches max lifespan - paleontologists analzyed size/shape of ancient dino bones to determine the age of the skeletons; the curve followed a pattern similar to a standard Type I curve but with relatively high mortality rates among juveniles.

Eltonian niche

- role of the organism in the community as a whole, and specifically in regards to its trophic position - niche = organism's job; habitat = home address

community concept

- set of species that live in sympatry and interact - includes all species in local area

community boundaries

- species function independently of one another, but it can still be difficult to mark physical boundaries of a community - discrete abiotic boundaries can form, such as edge of a grassland/lake, such that boundaries are more clear

Interspecific population dynamics

- species that interact directly via predation: graphs with "entrained sinusoidal patterns" indicate that peaks of prey abundance precede peaks of predator abundance, which are then followed by minima in prey abundance, and then by minima in predator abundance, etc. - the peaks and troughs are closely correlated but are offset in time

trophic guild

- stoats have canine teeth, which, like in other carnivores, are the primary morphological mechanism through which they attack the prey - Least Weasel coexists (sympatric) in Israel with five other species that also use canine teeth to bite the cervicals of their prey - size of canine tooth correlates with prey size in carnivorous mammal species - stepwise differentiation in canine size exists across the carnivore guild of Israel, from female to male to female to male, across six species

natural history

- study of natural phenomena based on observation and description - produce usable data - roots of modern ecology traced back to Linnaeus who set the foundations of a "Struggle for existence" against resource scarcity - organisms against each other and the environment in the battle to survive/reproduce

ecology of social groups

- the social lifestyle of organisms depends on the availability of food, the time of year, etc. the pros of life in a group: - better defense system - better success hunting together than alone (multiple lions attacking one prey, multiple ants taking over a beetle) - tighter groups can alter the local environment (penguins huddle together to conserve heat via thermoregulation) - fish schools: likelihood of survival is higher in groups than in isolation - many eyes hypothesis: the larger the flock of pigeons, the greater the distance at which the predator was perceived, and the lower the success rate of predator attacks the cons of life in a group: - more likely to transmit disease - more easily located by predators - competition for resources

African elephants in Kruger NP

- these elephants were hunted a lot, until major conservation efforts led to a subsequent boom in their population. However, it was determined that too many elephants was leading to serious ecological harm (digging the soil/toppling trees), so the Kruger reserve was only able to support 8500 elephants, and hunting was allowed to reduce the population as such.

population growth models

- track the overall number of individuals in a population (N) - 4 variables that determine N are: B (birth) & I (immigration) which add individuals, D (death) & E (emigration) which remove individuals from the population - Nt+1 = Nt + (B + I) - (D + E)

Principle of Allocation

- under normal resources/conditions: organism is able to meet its basic survival needs and can expend remaining resources to growth, defense against enemies, and reproduction - under normal conditions and an abundance of resources: any extra available resources can be dedicated to growth, defense, and/or reproduction - under stressful conditions and normal resources: organism must spend more of its acquired resources on basic maintenance, and fewer resources are available for growth, defense, and reproduction. - growth and investment in defense might shrink to zero, but reproduction could actually be maintained or even increase.

competition for enemy free space

- urchins compete for space at night to protect against predators, but the number of urchins that the reef can support is limited by the amount of available enemy-free spaces

instantaneous population growth

- useful for modeling animals who have overlapping reproductive cycles or do not breed in distinct seasons deltaN/deltat = (r)N - r = 0 (if the birth rate equals the death rate, and thus b-d = 0), then the growth rate of the population as a whole (dN/dt) is zero - r > 0, the population grows. - r < 0, the population growth rate is negative, and the number of individuals in the population declines.

charles elton (Scientific natural history)

- worked with communities in the arctic - "Ecology is a new name for a very old subject. It simply means scientific natural history." - believed in the importance of quantification and experimentation to study the natural ecosystem

types of interspecific interactions

1. competition (neg-neg) 2. consumer resource (pos-neg): predator-prey, parasite-host, herbovires-plant 3. mutualism (pos-pos) 4. commensalism/facilitation (pos-neutral) 5. amensalism (neutral-neg) - these are not rigid, as the relationship type is always subject to change; eg: egret causes commotion when it sees a group of lions, so it gets food and also alerts the buffalo (mutualistic relationship)

an introduced species is found to have a fundamental niche identical to that of the native species. Possible outcomes include

1. one of the species driven to extinction as they compete 2. evolution causes their niches to diverge 3. they exhibit distinct realized niches and coexist 4. the introduced species becomes extinct due to factors other than competition

As habitat patch size gets smaller, what happens?

1. patch supports fewer species 2. patch is increasingly influenced by edge effects 3. extinction rates increase

assumptions of the logistic model

1. relationship between per capita increase and density is linear 2. all individuals reproduce equally 3. no emigration or immigration 4. effect of density on the rate of increase is instantaneous

Two species of fish are found in a lake. Species 1 is typically found in deep water toward the center of the lake. Species 2 is typically found near the shallow edges of the lake. What are the outcomes of each scenario

1. remove Species 1 from the lake and Species 2 remains just near-shore: The near-shore environment is both the fundamental and realized niche for Species 2 2. remove Species 1 from the lake and Species 2 is soon found in both the near-shore environment and near the center of the lake: The near-shore environment is the realized niche for Species 2 but not the fundamental niche 3. remove Species 2 from the lake and Species 1 is soon found in both the near-shore environment and near the center of the lake: The deep water environment is the realized niche for Species 1 but not the fundamental niche

Lotka-Volterra Model

A model of predator-prey interactions that incorporates oscillations in the abundances of predator and prey populations and shows predator numbers lagging behind those of their prey - models the effect of interspecific relationships on population dynamics - interaction coefficients: alpha (effect of species 2 on species 1) and beta (effect of 1 on 2)

Growth vs reproduction (trade-off)

Douglas Fir tree that grows in warm summer/spring seasons produces distinct rings in their stems that reflect the amount of secondary growth that year. Ring width was strongly and negatively correlated with fecundity (the more the width, the less the fecundity); most growth occurred when no cones were produced, and minimal growth occurred when exceedingly large numbers of cones were produced.

conditions vs. resources

conditions: - include all of the environmental factors that affect organisms but are not used by the organisms - eg: ambient temperature, water salinity, wind speed - an organism might have a range of tolerances for these conditions, but organisms do not consume them resources: - physical, chemical, or biological materials that are consumed by organisms - finite and limited - eg: phosphorus for a plant, small sticks for a nest-building wood-rat, krill for a blue whale

carrying capacity (K)

Maximum population size that a particular environment can support. - most populations can not experience multiplicative growth, leading to the S-shaped curve rather than the exponential J-shaped one

life history

REVIEW DRAIGRAM

mechanisms of population growth regulation

density-independent vs density-dependent - d-ind: regulate population growth regardless of population density; often involve physical factors - d-dep: regulate population growth in relation to population density; death rate increases with density and/or birth rate decreases with density

Amensalism vs Commensalism

amensalism: buffalo steps on a lizard (no harm/benefit to the buffalo, but lizard is harmed) commensalism: buffalo has an egret on its back, which jumps off and eats the lizard (no harm/benefit to the buffalo, which did not expend energy to help the egret, but was beneficial for the egret) facilitation: the Saltmarsh Rush faciliates life for the abundance of plant species in the saline muds, where both species thrive. When the marshes are subject to intense solar radiation, the plant species are bound to dessicate, but in the presence of the thick Rushes, the earth remains damp/shaded and evaporation rates are low, allowing plants to flourish.