Final exam (lectures 20-29) Flashcards
Why is understanding the interactions between organisms important in community ecology?
interactions influence the presence and abundance of species
Carnivory vs herbivory
- herbivores typically do not kill the plants they eat
- herbivores remove a leaf, bark, stem, roots,sap
By removing a leaf, bark, stem, roots, sap, how do herbivores influence the plant?
does not kill them but does influence a plant’s ability to grow, survive and reproduce
Herbivores tend to prefer which part of the plant? How do plants respond to this?
- prefer young tissue, lower quantities of structural components that are hard to digest
- respond by producing more young tissue, redirects energy/nutrients from reproduction and growth to survival
What types of adaptations (deterrents) are seen in plants to discourage herbivores (avoid predation)?
- Physical: thorns, sticky hairs
- Chemical: natural insecticides and pesticides, poison ivy is an example
- Behavioural: (part of its life history) attract predators of herbivores by sending out chemicals in environment to attract them
Why are herbivores critical for the community?
- they allow the transfer of carbon from plants to other animals
- at bottom of the food chain
Plants are in an evolutionary arms race with ______.
herbivores
Symbiosis
- an intimate relationship between two organisms
- The relationship can be either positive, negative or neutral for those involved
What are the three types of symbioses seen?
1) parasitism
2) mutualism
3) commensalism
From the three types of symbioses, what are the relationships for each?
Parasitism=parasite, host (+,-)
Mutualism=species 1 and species 2 (+, +)
Commensalism=commensal, neutral (+, 0)
What is parasitism and give an example.
- one of the partners benefits and the other suffers
- ex( strangler fig gains support but tree dies
What are the two kinds of parasites? Give an example.
1) ectoparasites: live outside the host (tick)
2) endoparasites: live inside the host (tapeworm)
Why do parasites usually not kill their hosts?
- no advantage to killing host since it provides a habitat and food source
- dead host means dead parasite = obligatory relationship
What happens to energy usage of the host when a parasite is present?
host uses energy to defend against parasite so redirects energy from growth and reproduction to survival
What are the results/consequences of the host redirecting its energy away from growth and reproduction?
1) decreased reproductive success (reduced ability to attract a mate)
2) increased mortality (secondary infections and increased susceptibility to predation)
How can parasites be transmitted? Examples?
indirect: transmission by intermediate host (ex-mosquito =vector)
direct: transmission by direct contact or dispersal in air or water (ex-ticks, fleas)
What are small and large parasites called? Examples?
microparasites: small viruses, bacteria, infection short compared to host’s lifespan, direct transmission
macroparasites” large worms, ticks, infection is long compared to host’s lifespan, indirect transmission
How do parasites regulate host populations?
- are density-dependent regulators of host populations
- disease outbreaks occur when host population size is high
- host population declines quickly and causes decline in parasite population creating an oscillating host-parasite population =Lotka-Volterra Models (predator-prey population oscillations)
What are some examples of manipulative parasites?
- a nematode is a parasite in the cricket that manipulates the cricket to commit suicide in water in order to complete its lifecycle
- Rabies makes the host more aggressive which can lead to biting and will transmit the virus
- Zombie ant, parasite has two intermediate hosts to then want to get into the cow that is grazing. Strange behaviour in ants to attach to top of blade of grass until high temp, so cow eats blade of grass with ant and the parasite enters the cow.
What population responses have been observed when parasites invade a host population that has not evolved defenses?
- reduced populations
- local extirpation
- restricted distribution
Each stage of the lifecycle of the parasite is dependent on what?
if the parasite is transmitted to the appropriate intermediate host?
Parasite population dynamics
are dependent on the population dynamics, dispersal patterns and interactions of all host species
Host population dynamics
are dependent on population dynamics of the parasite
Example of parasite-Brainworm: typical host? other hosts?
white-tailed deer
moose, caribou
Example of parasite-Brainworm: intermediate host?
terrestrial snails
Example of parasite-Brainworm: life cycle?
- snails infected with larval stage live in grass
- deer accidentally ingests snails while grazing
- larvae enter the abdominal membranes in deer through stomach wall
- travel via spinal cord to the spaces surrounding the brain
- in brain, worms mate and produce eggs
- eggs and larvae pass through bloodstream to lungs
- larvae break air sacs, coughed up, swallowed, leave body in feces
- snails acquire larvae when they come into contact with deer feces
Why are the deer not adversely affected by brainworm? Which are adversely affected by the brainworm?
- deer evolved defences
- moose and caribou have not evolved defences so caused neurological disorders
Which host of the brainworm seems to be outcompeting the other?
- Looks like deer are outcompeting moose but this is due to better adaptation to the parasite
- host-parasite interactions can alter species interactions among competitors
Coevolution
host-parasite and predator-prey relationships may become benefical to both species
Mutualism
- a relationship between two species where both species benefit
- individuals of both species enhance their survival, growth and reproduction
- reciprocal exploitation vs cooperative effort
Commensalism
- relationship between two species where one species benefits without significantly affecting the other
- uncommon or unrealistic since both should evolve into a mutualism since they want to take advantage of the benefits
What happens to the Lotka-Voleterra Model in mutualism?
- the interspecific part of the equation -(aijNj/Ki) becomes +(aijNj/Ki)
- positive rather than negative influence on each other’s population size
- K (carrying capacity) increases for species i due to the presence of species j
How are reef-forming corals an example of mutualism?
- corals secrete an external skeleton that polyps (coral animal) live in
- algae (plant cells) live within the carnivorous polyp (only 10% of daily energy from carnivory but 90% from carbon produced by algae (photosynthesis)
- algae get CO2 and nutrients from polyps
- without close association with algae, corals could not survive in nutrient poor environments
Why are coral reefs important?
provide a critical habitat for many species of invertebrate and fish
What are some examples of possible commensalism?
ex) barnacle and whale:
- barnacle benefits from space (limiting resource), transport and access to food
- whale has no cost or benefits
- however, at high densities of barnacles, may impair sight of the whale or steal its food since they both feed on the same thing=parasitic?
ex) shark-remora
- remora benefits from transport and protection, food (leftover fragments)
- shark has no cost or benefit
- however, remoras may remove bacteria and parasites from the host = mutualism?
Species interaction sunnmary - effects on the population?
- Competition=detrimental to both species (-,-)
- Predator-prey=detrimental to one, beneficial to the other (+,-)
- Parasite-host=(+,-)
- Commensalism=(+, neutral) or beneficial to one and no effect to the other
- Mutualism=beneficial to both species (+,+)
All species are interconnected. Both direct and indirect relationships among species are important for determining each species ___________ and ____________.
population dynamics
community structure
Community
a group of species or populations that occupy a given area that interact directly or indirectly under a particular set of environmental conditions
Community structure
physical structure of the environment and biological structure, the nature of species interactions
Physical structure
reflects abiotic (temperature) and biotic characteristics (spatial distribution of organisms)
Which areas are of high biodiversity?
- tropical rain forest with waterfall
- coral reef
- islands
Structure-forming species provide what?
variation in microclimates
What sets a limit on the number of species and their relative abundance in a community?
the range of environmental conditions or resources
What represents the primary constraint on the biological structure of a community? What is the general pattern?
- the number of fundamental niches
- the more fundamental niches, the higher the number of species
Biological structure is defined by what two components?
1) species richness
2) relative abundance
Species richness
number of species
Biodiversity
the biological structure of a community
What is the relationship between dominance vs diversity?
high dominance means low diversity
low dominance means high diversity
Evenness
equitable relative abundance of species in a community
Dominance
- inequitable relative abundance of species in a community
- based on a combination of abundance and size
What is the relationship between evenness and diversity?
high evenness means high diversity
low evenness means low diversity
What are indicators of how much abundance a community has relative to plants or animals?
in plants=percent cover
in animals=percent biomass
How do we measure biodiversity?
diversity index to consider both the number and relative abundance of species
What are the two common indices used to measure biodiversity?
1) Shannon-Weaver Index (H)
2) Simpson’s Diversity Index (D)
Simpson’s Diversity Index equation and variables
What does a high D value mean?
D=1/[sum (ni/n)^2]
ni=number of individuals of species i
n=total number of individuals of all species
*high values means high diversity
Simpson’s Evenness (ED) equations and variables
What is the range of values possible and what does each extreme mean?
ED=D/Dmax
Dmax=the total number of species (S)
ED ranges 0-1
1=high evenness 0=low evenness
Diversity is _____ as species richness and evenness increase. Diversity is ______ as species dominance increases.
higher
lower
What is a “Whittaker Plot”?
- a rank abundance plot
- graphical representation of community diversity
- log abundance (y axis) vs species abundance rank from common to rare (x axis)
What does a rank abundance plot allow us to observe?
- species richness
- straight horizontale slope line indicates high evenness
- steep slope line indicates lower evenness
Colonization regimes
different mechanisms of community formation
Many scientists argue that all communities have one typical pattern in abundance. What is this pattern?
- few abundant species, few rare species, most species of moderate abundance (log normal)
- different curves reflect different sampling efforts
By examining many communities, ecologists have shown species abundances follow a _____________.
normal distribution log
Low vs moderate vs high sampling effort
low sampling effort: non-normal right-skewed
moderate sampling effort: more normal as increasing rare species are found in samples
high sampling effort: more and more normal as there is a higher probability of collecting rare species
Alpha vs beta vs gamma diversity
alpha: small, homogeneous area (1 site, local)
beta: difference in species among communities (gamma/average=level of endemism)
gamma: total species richness in a region, larger, heterogeneous area (>1 sites)
Level of endemism
of rare species
High vs low endemism
high: many distinct habitats with different species
low: same species found throughout
The lower geographic range (_______), the ______ the risk of extinction.
endemic
higher
Community structure includes ______, the nature of species interactions, and _______ of the environment.
biological structure
physical structure
The biological structure of a community is determined by the physical structure (number of _______) and the _________.
fundamental niches
species interactions
The biological structure of a community (or ______) incorporates both _______ and ________ of species.
biodiversity
species richness
relative abundance
The abundance of different species in a community can be equitable (_____) or inequitable (______) and can be described by __________ (Shannon-Weaver H, Simpson’s Diversity Index D) and __________.
evenness
dominance
biodiversity indices
rank-abundance plots
What is an important descriptor of biological structure?
- species interactions
- focuses on feeding relationships and how they acquire food and energy
Food chain
- pathway of food/energy transfer between species
- shows feeding relationships (who eats who)
- straight line, simple, not seen in nature
Food web
- numerous food chains interconnect to form this complex web
- the more species in a community, the more complex it is
Trophic levels
groups of species that derive food energy from a similar source
Guilds
groups of species within each trophic level that exploit a common resource in a similar manner
ex) all the herbivores
What are the different trophic levels of the food web?
1) basal species:
- feed on no other species but are fed upon by others
- primary produces=plants
2) intermediate species:
- feed on other species and are prey for other species
- primary consumers=herbivores
- secondary consumers=carnivores
3) top predators:
- feed on other species but are not prey for other species
- omnivores=feed on more than one trophic level
- cannibals=feed on itself
Functional group
Species that perform the same role in a community (decomposers, top predators, herbivores, carbon-fixers)
What do food webs emphasize and illustrate?
- Emphasize the numerous trophic connections among species within a community.
- illustrate indirect (or diffuse) species interactions
Indirect interactions
- Species do not directly interact but influence each other through a direct interaction with another species
- are usually only demonstrate under controlled experiments since they are difficult to quantify
There is a growing appreciation for the important role of ______ interactions in shaping community structure.
Indirect
Interaction strength
Number of trophic connections of a species
What are the two types of interaction strengths?
1) weak interactors: functionally not significant, low relative influence on biological structure
2) strong interactors: functionally dominant, a species that influences the biological structure of a community more relative to other species
Dominant or Foundation species
Species that has a dominant number or mass of individuals relative to other species
Keystone species
Species that influence the biological structure of a community disproportionately to their numerical abundance
Ecosystem engineers. Examples?
Species that create or eliminate habitats.
Ex) corals and beavers
What is a typical pattern seen in communities regarding interaction strengths of species?
Many rare-moderately abundant species are weak interactors and there are few common species that are strong interactors
If keystone species were to be removed, what would be the result to the community?
- initiates changes in community structure and results in loss of diversity
- keystone species includes ecosystem engineers
- influences species interactions
Why are beavers ecosystem engineers in Canada?
- many Canadian forest communities have increasing habitat diversity
- different stages of dam-building (flooding, pond, collapse) by beavers offer habitats for a large number of other species
- formation of ox-bows (bends in the river’s flow after many hundred of years caused by beaver dams)
What are two types of cascading impacts seen throughout the food webs when species interactions are altered?
1) bottom up: reduced abundance of basal species causes decreased abundance of species at higher trophic levels
2) top down: reduced abundance of top predators causes increased abundance at next trophic level, lower at the level below that and higher at the level below that (cycling of increasing and decreasing abundance)
Research done by Dr. Robert Paine found which results about the influence of predation and competition in community diversity of intertidal zones?
- predator species: sea star
- primary prey species: mussel, a competitively dominant species
- predator keeps population size of competitively dominant species low, many competitively inferiors species coexist
- when predator is absent, population size of competitively dominant species is high and competitively excludes inferior species=lower biodiversity, loss of some keystone species
Ability of a community to either ______ change or ______ to its original state is critical to maintain __________ under changing environmental conditions.
Resist
Rebound
Biological structure
Stability or resistance
- Ability to resist change in biological structure (maintain a relatively constant state) under environmental change
- linked to food web complexity
Resilience
- Speed and ability to return to its original structure after environmental change
- linked to food web complexity
Linkage density
Average number of actual links (arrows) per species in a food web
Connectence
Number of links divided by the number of possible links
Food chain length
Number of trophic levels (most food webs have about 4 trophic levels)
Food web complexity
Defined by a combination of:
1) food chain length
2) species richness
3) linkage density
4) connectence
What is the general pattern seen in regards to food complexity, stability, and resilience in the community?
Higher food web complexity (species richness) means higher community stability (resistance to change), but lower resilience (take longer and harder to return to its original state if structure of food web changes)
Simple food web: ______ stability, _______ resilience
Complex food web: _______ stability, ________ resilience
Simple food web: low stability, high resilience
Complex food web: high stability, low resilience
Evidence shows that the removal of a strong interactor (keystone species) results in changes to community structure. But what if we remove a weak interactor, what are the two models that try to explain this concept?
1) Redundancy model
- species are passengers on a plane
- a few key passengers required to fly the plane
- loss of any one passenger has no effect
- loss of key passengers like the pilot results in the plane not flying = dominance effect
- implies species within funcitonal groups are redundant
2) Rivet model
- species are rivets on a plane
- each rivet plays a small but significant role
- loss of a rivet weakens the plane
- loss of many rivets, plane falls apart = complementarity effect
- implies all species within functional groups are important
Which model, the redundancy or rivet model, is actually seen in nature?
Rivet Model: all species are interconnected and removing one would have a cascading effect
What is experimentally (small-scale) seen for species richness under changing environmental conditions?
-higher stability in species-rich communities under changing environmental conditions
What is observed (large-scale) for species richness under changing environmental conditions?
-phase shifts (instability) often follow gradual loss of richness
High species richness is _______ for stable community structure under changing environmental conditions.
essential
Species within a ________ (perform the same roles in the food web) are ____ redundant.
functional group
not
Why is it critical to protect species richness?
because we rarely know which species are strong interactors
Why are weak interactors important?
Diversity-Stability (insurance) hypothesis : species richness provides insurance and buffers or minimizes chances of changes in structure under environmental change
Response diversity
variation in responses to environmental change among species within a functional group
Typical pattern: higher variability in responses among species to environmental change, the _____ the variability community structure (response diversity ________ community)
lower
stabilizes
Why is response diversity critical?
because species will respond differently to environmental change, these different responses will maintain community structure in its original state
How is coral and algae of Jamaica an example of a phase shift?
- changing from one ecosystem to another (coral to algal)
- herbivore functional group (sea urchins, fish) graze algae
- if herbivores are removed, algae kill coral colonies and inhibit their regrowth=phase shift
- overfishing for decades of large predators and herbivores reduced herbivores to 1 sea urchin species lowered the response diversity of the herbivore functional group (lowered response diversity)
What is the result of erosion of response diversity (soecies richness) within a functional group?
can lead to reduced community stability and phase shifts
Phase shifts
changing from one ecosystem to another
What is another example of phase shifting?
- Kelp forests
- Functional elimination of apex predators
- Thermal event, storm, disease
- Now sea urchin dominance
How can we conserve biodiversity?
1) function-based biodiversity species (keystone species, conserve the species that are active determinants of biological structure)
2) non-function based species (endangered/threatened species, indicator species, flagship species)
3) protect target areas which have high biodiversity (biodiversity hotspot approach)
What are indicator species?
status reflects the status of other species
ex) canary in the mines, sensitive to gases, so if it dies, better get out
What are flagship species?
cute and cuddly, get the public’s attention
ex) seals
Which environment has the largest biodiversity?
the ocean
Biodiversity hotspot approach
- identified concentrated areas of high species richness (“hotspots”)
- primary based on plant species (assumed would reflect insect species)
- secondary based on vertebrate species (birds, mammals, reptiles, amphibians)
Hotspots are defined by what two criteria?
1) exceptional concentration of endemic (rare) species (used endemism because of low scientific information on number of species)
2) exceptional loss of habitat (endemic species are highly vulnerable to habitat loss, extirpation can mean extinction)
What is the most cost effective way of conserving the largest number of species with the least amount of scientific information?
using the biodiversity hotspot approach
How many biodiversity hotspots were defined around the world? Percentages of known species that are found in these hotspots?
- 25 hotspots
- mainly found in tropical rain forests and around equator
- 44% of known plant species
- 35% of known vertebrate species
Tropical rain forests contain what percentage of the world’s species?
50%
90% of insect species, 60% of plant species, 30% of bird species
Communities can be described by their ability to resist change (______) as well as by their speed and ability to return to their original state (________) after environmental change.
stability
resilience
Food web complexity is described by a combination of _________, ________, __________, _________.
food chain length
species richness
linkage density
connectance
We can use two models (_______ and _______) to summarize the importance of _______ versus _______ in maintaining community structure.
rivet
redundancy
species richness
species composition
General pattern: The more complex a food web is, the more _____ it will be.
stable
_________ among species within a functional group ______ community structure, so species within a functional group ________ redundant.
Response diversity
stabilizes
are not
Environmental heterogeneity
environmental conditions change across landscapes to alter community structure across a landscape
Zonation
- changes in community structure across a landscape
- borders between communities can be abrupt (shoreline) or a gradual transition (mountain side)
- depends on steep vs gradual changing environmental gradients
Succession
- change in community structure at a specific location through time
- involves a pattern of species colonization and extirpation from a specific region with species displacing other species from a community over time
Changes in community structure reflect the population ______ of the component species. Births and death species change in response to __________. Shifting patterns of _______ and _________.
dynamics
environmental conditions
species dominance
diversity
Primary succession
- process occurs at a site not previously occupied by a community (rare)
- ex) rock outcrops, cliffs, sand dunes, sand gets worn down where plants can now grow
Secondary succession
- process occurs on a site previously occupied by a community after a disturbance
- the number of species and their relative abundances within the remaining community will have a major influence on the proceeding successional dynamics in secondary succession due to species interactions
- ex) short time scale=tides
Disturbance
- any process that results in the removal (either partial or complete) of the existing community
- natural fire, windstorm, flood, cold, drought
Pioneer or colonizing species
- early successional species
- are the first to colonize an area
- r-selected life history traits
R-selected life history traits
- high growth rates
- smaller size
- short-lived
- high rates of population growth
- high degree of dispersal (colonization)
- can often survive under extreme abiotic conditions but are poor competitors
Climax species
- late successional species
- replace early successional species in a community over time
- k-selected life history traits
K-selected life history traits
- slower growth rates
- larger size
- long-lived
- low rates of population growth
- low degree of dispersal (colonization)
- generally better competitors (outcompete early species) but could not colonize because cannot survive under extreme abiotic conditions, can result of extirpation of the early species
Our understanding of succession is based mainly on which type of communities?
plant communities
Patterns of species replacement (_______) in a community during succession are _______, depend on species ______ throughout the process.
extirpation
not random
interactions
What are the three models of species interactions that occur during succession?
1) facilitation: early species modify the environment so that it becomes more suitable for later species to invade (nitrogen fixing plants enrich soil)
2) inhibition: involves strong competitive interactions, 1st species to arrive dominate the site and may make environmental conditions less suitable for all other species, space is only released to other species when individuals of this initial species are damaged or die
3) tolerance: later species are not inhibited/aided by earlier species, communities are composed of those species most efficient in exploiting the available resources at any given time
Common to all plant succession is ______ environmental change which is a direct result of the organisms within the community.
autogenic
What are two key things to succession?
autogenic changes and differential responses of species to those environmental changes
Autogenic changes and differential responses of species to environmental changes results in?
resource availability changes over the course of succession, the competitive ability of species will change, leading to shifting patterns of species dominance over time
What is the process of succession, an example of primary succession?
- sand is a product of pulverized rock
- sand is deposited by wind and water, becomes piled to form dunes
- beach grass functions to stabilize the dunes with extensive system of roots (beach grass is an example of facilitation)
- mat-forming shrubs invade
- vegetation shifts to dominance by trees
- colonizing species modify the local abiotic conditions, generally making them less extreme and “paves the way” for invasion of other species
Disturbance
any process resulting in the removal of existing community
Disturbance event
relatively discrete event that disrupts community structure and function (fire, flood)
Disturbance regime
pattern of disturbance events that characterize a landscape over a longer period of time
Disturbance regime-Intensity
proportion of a species’ population that the disturbance kills or eliminates
Disturbance regime-Scale
spatial extent of the impact of the disturbance relative to the size of the affected landscape
Disturbance regime-Frequency
mean number of disturbances that occur within a particular time interval
Small-scale disturbance
- creates a gap
- provides access to physical space for colonization by new individuals (often enhances diversity by increasing environmental heterogeneity)
- ex) death of an individual tree, can occur frequently due to wind storm, now decomposers can exist here and thus increases biodiversity
Large-scale disturbance
- reduces or eliminates local populations
- significantly modifies physical environment
- secondary succession
- ex) large scale fire, occurs more rarely, drastically decreases biodiversity at present, but over a long time period it will increase biodiversity
Disturbance can both reduce or enhance species _____, generally _________.
diversity
enhances
Succession is driven by which two processes?
-species colonization (increases species richness) and extirpation (decreases species richness)
When does diversity peak during succession?
in the middle stages of succession, after arrival of later species but before replacement of early species
How do different levels of disturbance affect the different stages of succession?
- without disturbance=later species will replace early species and diversity declines
- with high disturbance= succession is kept at early stages and with low diversity
- with intermediate disturbance=colonization is maintained and competitive replacement is minimal
Intermediate disturbance hypothesis
pattern of high diversity at intermediate frequencies of disturbance
Natural vs human disturbances
Natural disturbances: wind storms, ice storms, lightning, fires, occur at higher frequencies due to human activity
Human disturbances: fires, land-clearing, have a more profound and long-lasting impact on communities than natural disturbances, human activities involve continuous management of communities
*often natural disturbances are enhanced by human activities
Human disturbances completely remove natural communities and replace them with what?
- cultivated cropland
- pastures
- monoculture forests
- paved highways, cities (are worse)
Why are forest fires an important disturbance regime in the forest communities in North America?
- lightning fires are important disturbance regimes in forest communities in North America
- fires naturally occur every 50-200 years
- require enough dry fuel (dead plant material) for ignition
- park managers put in place the fire management regime
What is the attitude of park managers of Canada and US National Parks regarding forest fires?
- fires are destructive
- fire supression program initiated
- leads to the accumulation of dry fuel and uncontrollable fires
- ex) Yellowstone National Park in USA had dry year in 1988 caused 36% of park’s forest to burn down and large changes occurred to plant animal communities
Fire management regime
- controlled burns: allow some natural fires to burn to reduce fuel (dead leaves)
- prescribed burns: start small fires
- accept the importance of fire in long-term dynamics of forest communities
How do jack pine reproduce?
- reproduce due to adaptation where the cone only releases seeds under extreme heat like forest fires
- More of these pine trees due to increased forest fires today
Why are insect outbreaks important disturbance regimes in the forest communities in North America?
- bark beetles attack older or weakened trees by boring into bark
- turn needles from green to red
- beetle-killed trees provide nesting and roosting habitat for birds
- beetles are specific to certain tree species, so enhances biodiersity, not detrimental to the forest
- then windfall makes dead trees due to beetles fall over and creates gaps in mature forests for secondary succession to begin and increase biodiversity
What are forest managers’ attitude toward insect outbreaks?
- grow trees as a crop rather than a forest
- clearcut and spray herbicides
- plant or seed only one tree species (monoculture)
- monocultures leads to massive insect outbreaks
What happened to the forest in Northern British Columbia?
- 50% of BC central interior economy is driven by the forest industry
- forest managers aggressively logged infested areas to slow the beetle outbreak
- 1976-2002: clearcutting resulted in the largest clearcut in the world “Bowrun cut” = could be seen from space
What is a traditional view of communities?
communities are in a state of equilibrium (climax state) or a stable balance unless seriously disturbed
Stability
tendency of a community to reach and maintain an equilibrium, or relatively constant condition, regardless of disturbance
True or false? Most communities often have a certain level of disturbance occurring normally all the time.
True
True or false? Communities are generally in a climax state.
False. Communities are generally in a state of recovery from disturbance (not usually in a climax state)
Disturbances alter the ______ and ________ structures of communities.
biological (form new habitat patches)
physical
Landscape is composed of a number of _______ communities in habitat patches, each in a different phase of ______.
localized
succession
What is one of the main causes of Anthropogenic extinction?
habitat destruction/loss resulting from human activities
What are the results of habitat destruction?
- results in highly fragmented landscapes, leaving much smaller habitat patches than originally present
- within these patches, the communities function as islands, populations are part of larger metapopulations linked by dispersal of individuals
________ is the change in community structure involving species colonization and extirpation at a given location through time.
succession
Succession can occur on a site previously occupied by a community (______) or not (_______).
secondary
primary
Early successional species tend to have _____ life history traits and can often survive under extreme abiotic conditions.
r-selected
Late successional species tend to have ________ life history traits (better competitors) but often cannot survive extreme abiotic conditions.
K-selected
Patterns of species replacement in a community during succession depend on species interactions throughout the process, including: ________, ________, _________
facilitation
inhibition
tolerance
________ is any process resulting in the removal of a community (partial or complete) and a pattern of disturbance events (________) is described by its ____, ______, and _______.
disturbance disturbance regime intensity scale frequency
High diversity tends to occur at intermediate frequencies of disturbance = ______________
Intermediate disturbance hypothesis
Communities are generally in a state of recovery from disturbance and thus, may infrequently reach a ___________.
climax state
Habitat patch
- a homogeneous area containing suitable conditions and resources needed to sustain a population
- populations of many species (community) occur within a habitat patch
Habitat patches are _________ distributed over the landscape separated by unsuitable habitat. Results in many local, isolated _________.
heterogeneously
communities
How do local communities of habitat patches interact?
through dispersal (emigration and immigration)
Dispersal
- a degree of interaction
- ability to disperse between habitat patches
The degree of interaction (dispersal) depends on ability to disperse between habitat patches. What may affect dispersion?
- distance between habitat patches
- suitability of habitat between patches
- barriers (mountain, ocean)
Mosaic
Landscapes are a collection of communities that exist as patchwork assembly called a mosaic
Landscape ecology
- study of the causes and consequences of mosaic spatial variation
- focus on features such as distribution, shape, and spatial arrangement of patches
- naturally occurring patches reflect regional variations in geology, topography, soil, and climate
- conducted at different scales
Landscape ecology can be applied where?
Can apply landscape ecology to multiple islands, a desert oasis or multiple one, or even just a single bush (looking at leaves, roots, branches and the different insects that live there)
What are two components of landscape ecology? Components of landscape structure
1) landscape composition
2) landscape structure
- large versus small patches
- how dispersed patches are
- shape of patches (simple versus complex)
- how fragmented the landscape is
- landscape scale
Grain
the smallest homogeneous unit that is the focus of the study
Extent
the total area/time period covered
What is an example of landscape ecology?
The islands of Lago Guri in the Amazon was flooded from hydroelectric dam activity split the community in different little islands (one large community to multiple smaller fragmented communities)
What assumption is made in the island biogeography theory?
larger islands (habitat patch) hold more species than smaller islands
Island Biogeography Theory: The number of species on an island (habitat patch) is determined by the dynamic equilibrium between what two things?
1) colonization (immigration) of species to the island
2) extirpation of species from the island
Island Biogeography Theory: What happens to colonization as the number of species increases?
As the number of species increases, the rate of species successfully colonizing decreases because early arrivals use up available habitats and resources (fundamental niche)
Island Biogeography Theory: What happens to extirpation as the number of species increases?
As the number of species increases, the rate of species being extirpated increases due to competition increasing (competitively dominant species outcompete others)
In a graph showing the island biogeography theory, what components can be seen?
- y-axis: rate
- x-axis: number of species
- colonization decreases
- extirpation increases
- S is where colonization and extirpation cross
- S is the climax state or species equilibrium richness
Equilibrium species richness (S) is reached when?
- colonization=extirpation
- species richness is stable but species composition can change
What influences colonization and extirpation rates and the equilibrium species richness (S)?
distance between islands (habitat patches) and island size
What are two predictions made by the island biogeography theory?
1) as the distance between patches/islands increases, the colonization rates will decrease leading to lower S per patch, species become less likely to successfully make the journey as distance increases
2) a larger patch/island will have lower rates of extirpation leading to higher S, more resources and available habitats (fundamental niches) on larger islands meet the needs of a wider variety of species, smaller patches/islands will have a lower S
In a graph showing the island biogeography theory, what happens when the distance between patches or islands increases?
- y-axis: rate
- x-axis: number of species
- colonization decreases
- S (equilibrium species richness) decreases
In a graph showing the island biogeography theory, what happens when the patches or islands gets larger?
- y-axis: rate
- x-axis: number of species
- extirpation decreases
- S (equilibrium species richness) increases
How can the island biogeography theory be applied?
- one of the main causes of anthropogenic extinction is habitat destruction/loss
- habitat destruction results in highly fragmented landscapes, leaving much smaller habitat patches that are farther apart relative to natural conditions (lower S)
- communities within these patches function as islands, linked by dispersal of individuals
- determine the size of patches and the distance between patches appropriate to maximizing and maintaining biodiversity (species richness)
- important theory used to conserve biodiversity
How does human activity affect habitat fragmentation of existing patches into smaller and more isolated patches?
- conversion of grassland and forests to agriculture
- roads and infrastructure
- settlements
Each habitat patch is composed of?
- interior: habitat has its own environmental conditions and community structure
- edge of border: transition zone where community structure and environmental conditions of adjacent patches are blended, no abrupt changes in abiotic/biotic conditions associated with border environments
Edge effect
diverse environmental conditions allow edges to support high species diversity
Interior species
require the stable environmental conditions of interior habitats
Edge species
can survive under the unstable (variable) conditions of the edge habitat
What is an example of edge and interior species?
owls live in the forest (edge) but hunt in the fields (interior)
How does size and shape of patches affect the edge:interior ratio?
1) as patch size increases, edge:interior decreases, small patch=mostly edge habitat, large patch=mostly interior habitat
2) as patch width increases, edge:interior decreases, long narrow=mostly edge habitat, square or circular=mostly interior habitat
What is the relationship between the edge:interior ratio and the diversity of the community?
should have higher diversity with increasing edge habitat, but only if interior habitat remains
Transition zones
- patches border each other creating transition zones (edges) from one patch to the next
- area of contact, separation and transition
- connect patches allowing flow of energy, material and organisms
- vary in shape, size, and length of the transition
Corridors
- across the landscape, corridors connect different patches together
- strips of habitat that contain favourable conditions
- contain similar vegetation to the patches they connect or contain similar conditions
- act as travel lanes connecting sub populations
- aid in colonization of new patches
- important in a landscape dominated by human activities
How do roads affect populations?
- roads partition and fragment populations
- alters movements, reproduction, and may induce stress
- increased mortality
What could be a solution to reconnect populations that are separated by roads?
- artificial corridors may be one solution to reconnect populations
- bridges contain vegetation to mimic natural habitat
In general, for preserving endangered interior species, the best spatial configuration for Core Natural Area and ecosystem management is what?
1) larger is better than smaller (even if total area is similar)
2) closer together is farther apart
3) better if connected by habitat corridors
4) compact shapes are better for minimizing boundary length
5) a buffer zone is preferable
_________ focuses on the spatial distribution of habitat patches with distinct communities.
Landscape ecology
Patches can be described as ______ of isolated __________ that are distributed over the landscape separated by unsuitable habitat.
islands
communities
____________ assumes that species richness on an island (_____) is determined by the dynamic equilibrium between the _______ and _______ of species from the island/patch.
Island biogeography theory
patch
colonization
extirpation
The island biogeography theory predicts:
1) ______________
2) ______________
1) as the distance between patches/islands increases, the colonization rates will decrease leading to lower S per patch
2) a larger patch/island will have lower rates of extirpation leading to higher S
Apply Island Biogeography theory to conserve biodiversity, determine the _____ of patches and the _______ between patches appropriate to maintaining species richness.
size
distance
General pattern: large habitat patches contain a ______number of individuals of a species and a _______ number of species.
higher
higher
Size and shape of patches together affect the _______ habitat ratio and as this ratio changes, so will species richness
edge:interior
Changes in species richness with size and shape of patches depends on the species composition of ________ and _______ species within the patch.
interior
edge
What is the ecosystem concept concerned with? Interested in?
- concerned with describing patterns of species composition of communities over the globe
- interested in how community biological structure was influenced by interactions with physical surroundings
What did Clements say about the ecosystem concept?
Ecosystems are superorganisms (correct):
- communities cannot be described simply as a collection of independently functioning populations of species
- communities are much like an organism, describing each organ system (species) will not describe how the body (community) functions
What did Gleason say about the ecosystem concept?
Ecosystems do not function like an organism (rejected Clements and is incorrect):
- communities are chance associations of species, species coexist due to similarities in their requirements and tolerances
- species interact but the presence or absence of any one species is independent of all others
What did Elton say about the ecosystem concept?
Ecosystems are structured by feeding relationships:
-developed the concepts of food chains and food webs
What did Lotka say about the ecosystem concept?
Ecosystems are energy-transforming systems:
- conceptualized populations and communities as thermodynamic systems
- represented by a set of equations describing the transfer of energy among species
What did Lindeman say about the ecosystem concept?
Trophic-dynamic ecosystem concept:
- integrated the concepts of food chain, food web with thermodynamic principles
- first to describe trophic level as steps comprising a food chain
- described the flow of energy and nutrients (carbon) through an ecological system
- using currencies of energy and nutrients allowed the direct comparison of plants, animals, microbes and abiotic sources of energy and nutrients in the ecosystem
- developed the pyramid of energy
- transfer and cycling of nutrients and energy through an ecosystem provided the basis of modern ecosystem ecology
Pyramid of energy
less energy is available to each higher tropic level owing to inefficiency of energy transformations within each trophic level
How did Lindeman describe the flow of energy and nutrients (carbon) through an ecological system?
using currencies of energy and nutrients allowed the direct comparison of plants, animals, microbes, and abitoic sources of energy and nutrients in the ecosystem
Ecosystem
- all interacting parts of the physical and biological world
- the biological community and physical components act as a single interactive system (are not independent of each other)
What does an ecosystem include?
- living (biotic) components like species composition and species interactions
- nonliving (abiotic) components like soil, water, air, light, inorganic nutrients
What is ecosystem functioning governed by?
by processes that result in the transfer and internal cycling of nutrients and energy
What key process governs ecosystem functioning?
Energy from the sun drives the transformation of inorganic carbon (CO2) into organic carbon compounds (carbohydrates-glucose) by plants during photosynthesis
How does energy flow through a functioning ecosystem?
- energy is stored in the chemical bonds of organic carbon-based compounds
- energy then flows from primary producers up the food chain through feeding relationships
- the flow of nutrients (carbon) and energy follow similar pathways in ecosystems
Ecosystems are considered to be _______ systems? ______ systems have no inputs and outputs.
open
closed
Inputs vs outputs
Inputs: exchanges from the surrounding environment into the ecosystem
outputs: exchanges from inside the ecosystem out to the surrounding environment
What happens to nutrients in an ecosystem?
- nutrients are typically recycled within the system
- inputs and outputs of nutrients exist but they are predominantly recycled within an ecosystem
What happens to energy in an ecosystem?
energy comes from the sun (input) and leaves the ecosystem as heat (output)
Energy in an ecosystem exists in which two forms?
1) potential energy: stored energy (available for performing work)
2) kinetic energy: expended energy (used to perform work)
Two ___________ govern the expenditure and storage of energy within an ecosystem.
laws of thermodynamics
What is the first law of thermodynamics?
1st law: the amount of energy is constant (in a closed system), energy cannot be created or destroyed, energy can change form but no gain or loss in total energy from a system occurs
Give examples of the first law of thermodynamics.
- burning wood is transformed from potential energy (stored in molecular bonds) to kinetic energy (released as heat)
- energy from the sun is harvested by primary producers and used to form chemical bonds in carbon-based compounds, potential energy is stored in these chemical bonds is transferred to consumers when they eat plants
What is the issue with having a closed system?
-although energy cannot be created or destroyed, often much of the potential energy degrades into an unusable form
What is the second law of thermodynamics?
whenever energy is transformed, some energy becomes unavailable for further use, energy becomes unavailable when transferred among trophic levels through feeding relationships
Give examples of the second law of thermodynamics.
- burning wood transforms into kinetic energy that dissipates as heat
- as energy is transferred from one organism to another, a portion is used (stored as energy in living tissues as the organism grows) but a large part dissipates as heat
- in a closed system over time, the amount of energy in unusable form increases until no usable energy is available, but ecosystems are open systems (receive constant energy input from the sun)
Primary production
refers to the rate at which plant tissue (organic matter) is created during photosynthesis
The photosynthetic rates of plants will be influenced by what (but not tested directly)? What adaptations do primary producers have that allow them to do production differently to other plants?
1) quantity of above (shoots and leaves) and below ground (roots) tissue
2) leaf morphology (surface area)
3) modified photosynthetic pathways to increase water-use efficiency (C4 and CAM plants)
4) adaptations to low light (shade-tolerant) or high light (shade-intolerant)
Secondary production
refers to the efficiency of consumers to transform energy consumed into growth and offspring
The total energy consumed/ingested in the form of plant material flows through each individual consumer how?
- a portion is assimilated through the gut wall
- remainder is expelled from the body as waste (urine, feces)
- waste becomes energy for the decomposing food chain
- a portion of assimilated energy is used in respiration
- some dissipates as heat during capture or harvest of food, muscular work, repair wear and tear on the animal’s body
- leftover energy is used in growth and reproduction =secondary reproduction
Production efficiency
-the efficiency of consumer species to transform energy consumed into secondary production
=production/assimilation
Compare the production efficiency of invertebrates and vertebrates, ectotherms and endotherms, carnivores and herbivores.
- invertebrates»vertebrates
- ectotherms»endotherms (higher energy allocation to maintain constant body temperature)
- carnivores»herbivores (harder to assimilate plant tissue)
What should we eat to have more energy?
Insects since they have the highest product efficiency
Production/assimilation of all species at each trophic level will determine the energy available for ___________.
the next higher trophic level
What can be found in the pyramid of trophic levels? What are the trends observed regarding energy and biomass?
at bottom of pyramid: producers second at bottom: primary consumer second at top: secondary consumer top: tertiary consumer *energy decreases higher you go up *biomass population decreases higher you go up
Trophic efficiency
the relationship between the energy produced at a trophic level (Pn) that is available for use at the next higher trophic level (Pn+1)
=Pn+1/Pn
What is the general pattern of trophic efficiency?
quantity of energy available for use by a trophic level decreases with each successive trophic level in the food chain due to production efficiencies (2nd law of thermodynamics)
What is the ecological rule of trophic efficiency?
only 10% of the energy stored as biomass within a given trophic level is converted to biomass at the next higher trophic level (10% rule)
Pyramid of biomass
results in the decrease in the biomass of organisms within each successive trophic level
Variation in _________ of each species within each trophic level will determine exactly how much energy is transferred to the next trophic level in different ecosystems.
production efficiencies
Development of ecosystem concept: 1) 2) 3) 4) 5)
1) ecosystems are superorganisms (Clements)
2) ecosystems do not function like an organism (Gleason)
3) ecosystems are structured by feeding relationships (Elton)
4) ecosystems are energy-transforming systems (Lotka)
5) Trophic-dynamic ecosystem concept (Lindeman)
________ is all interacting parts of the physical (abitoic) and biological (biotic-community structure and species interactions) world
Ecosystem
Although energy cannot be created or destroyed (is constant) in an ecosystem (____________), much of the energy at a trophic level becomes unavailable for transfer to higher trophic levels through feeding relationships (__________)
1st law of thermodynamics
2nd law of thermodynamics
The efficiency of consumer species to transform energy consumed into growth and offspring (_______) results in the _______.
production efficiency
10% rule
Only 10% of the energy stored as biomass within a given trophic level is converted to biomass at the next higher trophic level (_________)
pyramid of biomass
Autotrophs
- primary producers, green plants
- harvest the sun’s energy (photosynthesis) to transform inorganic carbon (CO2) into organic carbon compounds (carbohydrates)
- energy stored in the chemical bonds of carbon compounds flows from primary producers to up the food chain
Heterotrophs
- divided into 2 highly interrelated food chains
1) grazing food chain: consumers use these organic compounds found in living tissue as a food source
2) detrital food chain: decomposers use organic compounds found in dead tissue and waste products of plants and animals as a food source
Which food chain is critical for the recycling of nutrients in the ecosystem and plays a dominant role in energy flow and nutrient cycling through most terrestrial and aquatic ecosystems?
detrital food chain
Which are the components of the grazing food chain?
1) autotrophs, primary producers, basal species, plants
2) heterotrophs, primary consumers, intermediate species, herbivores
3) heterotrophs, secondary consumers, intermediate species, carnivores
4) top predator, carnivores
Which are the components of the detrital food chain?
1) detritus, waste and dead organic matter
2) primary consumers, intermediate species, decomposers, worms, bacteria, fungi, beetles
3) secondary consumers, intermediate species, carnivores
What is the source of nutrients (carbon, nitrogen, phosphorous) and how do they move through the food chain?
- source is atmosphere or weathering of rocks and minerals
- taken up by plants and move through the food chain via feeding relationships
A significant portion of nutrients are stored where in the ecosystem?
stored in organic form within living tissue of plants and animals
Internal cycling
most of the essential nutrients are recycled within the ecosystem by decomposers
What do decomposers do?
- decomposers breakdown the chemical bonds formed during construction of plant and animal tissue
- releases energy originally fixed by photosynthesis
- converts organic compounds into inorganic nutrients (mineralization) for use by plants
Mineralization
converting organic compounds into inorganic nutrients for use by plants
What is the opposite process of photosynthesis?
mineralization: organic to inorganic compounds
photosynthesis: inorganic to organic compounds
Microbial decomposers
- bacteria (primarily decompose dead animal matter, may be aerobic or anaerobic) and fungi (primari;y decompose dead plant matter)
- bacteria and fungi secrete enzymes into plant and animal tissues to breakdown the complex organic compounds, some products are absorbed as food
Aerobic vs anaerobic
aerobic: require oxygen
anaerobic: does not require oxygen
What happens after a group of species has exploited the material as much as they can (decomposers)?
- a different group moves in to use the remaining material
- succession of species occurs until the material is finally reduced completely to inorganic nutrients
Detritivores
- animals that feed on dead organic material and waste products (primarily invertebrates)
- aide decomposition by fragmenting leaves, twigs, and other dead organic matter
What are the 4 major groups of detritivores?
1) microfauna and microflora (protozoans, nematodes, inhabiting water in soil pores)
2) mesofauna (mites, springtails, live in soil air spaces)
3) macrofauna
4) megafauna (terrestrial=millipedes, earthworms, snails and aquatic=crustaceans, amphipods, crabs, burrow into the soil or substrate to create their own space and can have major influences on soil structure)
Order the 4 major groups of detritivores from smallest to largest in size.
1) microfauna and microflora
2) mesofauna
3) macrofauna
4) megafauna
_______ of species occurs until the material is finally reduced completely to inorganic nutrients.
Succession
True or false? All organic matter decomposes at the same rate.
False it does not decompose at the same rate
Net energy gain
= energy gain - energy loss
Which has stronger net energy gain, simple or complex compounds?
simple compounds have higher net energy gain
What are some simple and complex compounds?
simple carbohydrates: glucose, are high quality, breaking chemical bonds yields much more energy than required to synthesize the enzymes to break them down
more complex structured carbon-based compounds: ceullose, main constituent of cell walls of plants, are low quality , more costly to decompose
even more complex: lignins, major component of wood, are lower quality, yield almost no net energy gain
What has a direct influence on decomposition rates and influences microbial activity?
- abiotic factors like temperature and moisture
- cool, dry conditions reduce or inhibit activity
- warm, moist conditions are optimal conditions for activity
The rates of internal cycling of nutrients depend directly on the rates of which two processes?
- primary production determines the rate of nutrient transfer from inorganic to organic form (nutrient uptake)
- decomposition determines the rate of transformation of organic to inorganic form (mineralization)
Reduced availability of inorganic nutrients in the soil reduces what?
- directly reduces photosynthetic rates and primary production
- influences the input of dead organic matter to the decomposer food chain by reducing the total quantity of dead organic matter produced
- results in a feedback system in the internal cycling of nutrients within an ecosystem
Explain the continuous feedback system of internal cycling of nutrients within an ecosystem
- abiotic factors influence the rates of primary production and decomposition
- primary production determines the amount of secondary production
- the amount of primary and secondary production determine the amount of waste and dead organic matter
- the amount of waste and dead organic matter determines the amount of nutrients recycled by decomposers (available for primary production)
Trophic cascade or top-down regulation appears in which kinds of food webs?
- low species diversity (response diversity)
- few trophic levels (food web complexity)
- one or a few herbivores have a strong influence on primary producer populations
Give an example of algae-based food webs of freshwater lakes and trophic cascade.
- primary production (phytoplankton) limited by nutrients and sunlight
- zooplankton herbivores eat phytoplankton
- Daphnia are large herbivores that consume phytoplankton and store nutrients within their bodies
- high Daphnia biomass=nutrient availability is low (stored in body) and consumption of phytoplankton is high
- reduced phytoplankton production and biomass
- high populations of Daphnia predators=high phytoplankton production and biomass production
- half the variation in primary production among lakes is the result of varying zooplankton biomass and top-down mechanisms
What provides support for the Rivet model?
trophic cascades or top-down regulation
Why are there few clear examples of top-down regulation in terrestrial ecosystems?
- high species diversity (=high response diversity)
- many different species of consumers
- if consumer species tend to have a narrow diet (specialists) then considered weak interactors
- a single consumer species may have little effect on overall primary and secondary production but if reduce species richness within a functional group there may have a large effect (ex-atlantic cod)
Ecosystem function is likely under the simultaneous control of nutrient input and recycling (_________) and trophic interactions (_________)
bottom-up
top-down
The _______ use organic compounds found in living tissue as a food source whereas the _______ use organic compounds found in dead tissue and waste products of plants and animals as a food source.
grazing food chain
detrital food chain
_______ are critical for the recycling of nutrients (________) in ecosystems because they convert organic compounds into inorganic nutrients (________) for use by plants.
Decomposers
internal cycling
mineralization
The rates of internal cycling of nutrients depend directly on the rates of _______ (inorganic to organic) and _________ (organic to inorganic) which results in a feedback system in the __________ of nutrients within an ecosystem.
primary production
decomposition
internal cycling
Abiotic factors (sunlight, temperature, moisture) will also have a direct influence on _________ with warm, moist conditions being optimal for decomposition.
decomposition rates
_________ is likely under the simultaneous control of nutrient input and recycling (_____) and trophic interactions (_______).
Ecosystem function
bottom up
top-down
_________ of nutrients is primarily concerned with the flow of nutrients through the ecosystem dominated by the biological processes of _______ and ______..
internal cycling
primary production
decomposition
But not all transformations of nutrients in an ecosystem are mediated by biological interactions. What else could transformations be mediated by?
- chemical reactions that take place in the nonliving (abitoic) component like atmosphere, water, soil
- ex) weathering (physical and chemical breakdown) of rocks and minerals releases inorganic nutrients into the soil and water, available for plant uptake
Biogeochemical cycle
flow of all nutrients from the nonliving to the living and back to the nonliving components of the ecosystem in a more or less cyclic path
What are the 2 major types of cycles based on primary source of nutrient input?
1) gaseous cycles
2) sedimentary
Gaseous cycles
- main pool of nutrients: atmosphere, ocean
- ex) nitrogen (78%), oxygen (21%) and CO2 (0.03%) are dominant components of atmosphere (stable quantities)
Sedimentary cycles
- main pool of nutrients: soil, rocks, minerals
- nutrients required by organisms com initially from inorganic sources via weathering
- main pool of nutrients in both sedimentary and gaseous cycles (sulfur cycle)
- main pool of nutrients in primarily sedimentary (phosphorous)
What is the medium in which inorganic nutrients travel through the ecosystem?
water, without it biogeochemical cycles would stop!
What three basic components do all biogeochemical cycles share?
internal cycling, inputs, and outputs
Inputs of nutrients into the ecosystem depends on which types of cycles?
- gaseous cycle (carbon, nitrogen): enter via the atmosphere
- sedimentary cycle (phosphorous, calcium): enter through the weathering of rocks and minerals
Inputs of nutrients into the ecosystem depends on which types of ecosystems?
- terrestrial: nutrient inputs are supplemented by rain, snow, air currents and animals
- aquatic: major source of nutrients are from the surrounding land in the form of drainage water, detritus, and sediment (also wet and dryfall), input of organic carbon from terrestrial ecosystems constitutes the majority of energy input into stream and river ecosystems
What are two types of terrestrial inputs?
- wetfall: precipitation inputs nutrients
- dryfall: airborne particles with associated nutrients fall from the atmosphere (ex-volcanic ash)
True or false? Output of one ecosystem means an output of another ecosystem.
False. Output of one ecosystem means an input into another ecosystem
How can outputs occur?
1) released into the atmosphere (carbon is lost as CO2 via respiration of organisms)
2) inorganic nutrients released via leaching (dissolved and washed out of the soil in underground water to streams)
3) organic matter exported from forest ecosystems by streams and rivers to lakes
4) organic matter transferred between ecosystems in the form feces and other wastes via movement patterns of consumers (organic matter can be a significant source of nutrient loss but because organisms store significant amounts of nutrients in their bodies, this prevents rapid losses from the system)
5) harvesting (farming and logging) nutrients that are stored in organisms and are directly lost during removal from the ecosystem (balanced by adding fertilizers because nutrients become limited)
The processes of inputs and outputs of nutrients during biogeochemical cycles links different _______.
ecosystems
What are the main pools of the gaseous cycle?
atmosphere and ocean
Which is the basic nutrient found in all organic compounds?
carbon
Which is the main source of carbon for all organisms?
CO2 in the atmosphere
What is the carbon cycle in terrestrial ecosystems?
- photosynthesis: CO2, organic form, herbivores, carnivores, organic matter, decomposers, plant tissue
- CO2 released back into the atmosphere via respiration (plants, consumers, decomposers)
What is the carbon cycle in swamps and marshes?
- dead organic matter falls into water, does not completely decompose (inhibited by high moisture)
- carbon stored as humus or peat
- buildup of partially decomposed organic matter forms fossil fuels (oil. coal, natural gas) in the long term
What is the carbon cycle in freshwater and marine ecosystems?
- CO2 diffuses into the surface water from atmosphere, carbonates
- phytoplankton uses carbonates, plant tissue, herbivores, carnivores, organic matter, decomposers, plant tissue
- CO2 released via respiration (plants, consumers, decomposers) is either reused or released into the atmosphere (diffusion)
Diffusion
movement of a substance from high concentrations to low concentrations
What does the global carbon cycle involve?
involves exchanges between the atmosphere, oceans and land
What is the earth’s carbon budget? The global cycle?
-100,000,000 Gt but most is buried in sedimentary rocks and is not involved in the carbon cycle
the global cycle is 55000 Gt
Order the global carbon cycle from least to most carbon in Gt.
1) atmosphere
2) terrestrial
3) fossil fuels
4) oceans
What is the main exchange site and rate of oceans in the carbon cycle?
- exchange site:surface water with the atmosphere
- exchange rate: governed by diffusion gradient
What happens when we burn fossil fuels?
releases CO2 into the atmosphere that was trapped inside
Historically, exchanges of CO2 between terrestrial and atmosphere were thought to be in equilibrium. What has happened recently?
CO2 in the atmosphere has increased
What is the main exchange rate governed by for terrestrial ecosystems regarding the carbon cycle?
exchange rate governed by the diffusion gradient between plant leaf and atmosphere (photosynthesis)
Why is CO2 a greenhouse gas?
- CO2 in atmosphere has increased more than 25% in the last 100 years
- Industrial Revolution caused CO2 to increase steadily and by mid 1900s increasing exponentially
- CO2 predicted to double by 2020
How is CO2 becoming a greenhouse gas?
1) burning fossil fuels (coal, oil, gas) in industrialized nations accounts for 73% of total CO2 emissions (US accounts for 24% of this total)
2) deforestation, forested lands are typically cleared and burned for farming
Greenhouse effect
- some thermal energy of the sun reaches the surface of the earth, is reradiated back into the atmosphere, chemical compounds in the Earth’s atmosphere (greenhouse gases) trap this thermal energy
- emits it back to Earth’s surface, warms the earth’s surface and lower atmosphere
During the industrial period, increasing _______ in atmosphere is predicted to _____ the Earth’s surface.
CO2
warm
Can the ocean absorb the increasing CO2 in the atmosphere and act as a buffer?
- oceans cover 75% Earth’s surface
- acts as a two layer system
- thermocline traps CO2 in surface water
- as CO2 concentration increases in surface waters, diffusion of CO2 into the ocean decreases
- result is it absorbs some but not all of the extra emissions
thermocline
little mixing between the surface of the ocean and deeper water
Will increased CO2 concentrations increase photosynthesis (primary production, autotrophs), reducing the amount of atmospheric CO2?
- increasing atmospheric CO2 has short-term effects on individual plants by increasing rate of photosynthesis due to increased diffusion into the leaf and stomata partially close, reduces water loss (transpiration)
- long-term effects on individuals plants is less rubisco produced, reduces photosynthetic rates, less carbon is allocated to production of leaves (increases roots), fewer stomata are produced on leaf surface (decreased growth)
- do not know how these effects translate into changes in the net primary productivity of terrestrial ecosystems
What is consistent throughout all the predictions made about global climate change?
1) increase in the average global temperature and global precipitation (temperature 2-6 degrees celsius in next 100 years)
2) changes will not be evenly distributed over Earth’s surface (warming is expected to be greatest during the winter months in northern latitudes, felt more on land mass and not in oceans)
3) increased variability in climate (more severe storms and hurricanes, greater snowfall, increasing variability in rainfall)
What will directly impact ecological systems?
changes in temperature and water availability
What will be the impacts of global climate change?
- physiological behavioural responses of individuals
- b,d,r of populations, shifts distributional patterns (geographic ranges) of species
- community structure, changes in regional patterns of biodiversity and species interactions
- secondary production, influenced by altered rates of primary production (photosynthesis) and internal cycling of nutrients
- ultimately influence the distribution and productivity of ecosystems around the globe
Understanding global climate change requires the study of _______ at all levels of ________ on a global scale.
ecology
organization
_______: flow of all nutrients from the nonliving to the living and back to the nonliving components of the ecosystem in a more or less cyclic path
Biogeochemical cycle
_________ and the ________ are the two major types of cycles based on the primary source of nutrient input.
Gaseous cycles
Sedimentary cycles
The processes of _____ and _______ of nutrients during biogeochemical cycles link different ecosystems.
inputs
outputs
Historically, exchanges of CO2 between terrestrial and atmosphere were thought to be in equilibrium but recently, _____________
CO2 in the atmosphere has increased
Chemical compounds in the Earth’s atmosphere (________) trap thermal energy, which warms the earth’s surface and lower atmosphere = ____________
greenhouse gases
greenhouse effect
Can the ocean absorb the increasing Co2 in the atmosphere?
probably not
Will increased CO2 concentrations increase photosynthesis (primary production), reducing the amount of atmospheric CO2?
probably not
