Midterm #2 Flashcards
Carrying Capacity
Total numbers of individuals of a species that can be sustained in a habitat in the long term.
Normally determined as the average population numbers of the species across multiple years
Ideal Logistic
This is a smooth response
Rapid increase up to carrying capacity then it slowly planes off
Fast replicating species follow this
Damped Oscillations
Rapid increase up to carrying capacity and past it.
Then falls below carrying capacity slight oscillation until it planes out at carrying capacity
More common than ideal logistic
Stable Limit Cycle
Consistent rise and fall above and below carrying capacity
Sin wave
Common in insects
Chaotic
Rapid increase past carrying capacity than a crash eventually rises again but in an unpredictable manner
Caribou of Pribilof Islands
Density-dependant population regulation (limit population growth)
Due to intrinsic factors
Population numbers depend on the activity of individuals (birth rate, death rate, immigration, etc)
Regulation often occurs due to decreased births and increased mortality
Mechanisms for density-dependant effects when populations exceed K (6)
Intraspecific competition: occurs when required resources are in limited supply
(Interference competition and differential ability to secure resources)
Delayed breeding or reduced offspring production: increase agonistic encounters increases the stress of sub-dominant individuals, reduces the birth rate
Larger territories when resources are limiting: Larger territories by dominant individuals leads to reduced access of sub-dominant males, leads to reduction of numbers of non-territorial members
Dispersal (migration): the leaving of individuals from a population as it reaches carrying capacity
Parasites/diseases: become more prevalent in denser populations, effectively culls population numbers
Predators: Predators are a major source of mortality in populations. Increased density of prey allows predators to expand in numbers and distribution
Interference Competition
A form of intraspecific competition
Individuals directly interfere with others for limited resources
Differential Resource Securement
A form of intraspecific competition
Some individuals will be better at getting access to necessary resources for survival
Law of constant final yield
Regardless of the number of seeds planted you should end up with the same final yield under the same conditions
This is because the environment only supports so many individuals
Factors limiting population growth (2)?
Density-dependent population factors and density-independent population regulation
Crepuscular
An animal that is primarily active during twilight (during dusk and dawn)
Cathemeral
Sporadic and random intervals of activity during any time of the day or night
Niche
How an organism makes its living
Resources
Contribute to population growth and whose availability can be reduced as a consequence of being consumed
Substance
Too abundant to be altered by consumption are not included in those involved in competition
Liebigs Law of the Minimum
Population numbers can be regulated by a single resource that has the greatest relative scarcity
Interspecific Competition
This is competition between individuals of different species
Gause’s Law of Competitive Exclusion
Two species with the same niche cannot coexist
Evidence for interspecific competition in nature (4)
Habitat shifts in allopatry and sympatry
Character displacement: the tendency for 2 species to diverge in form when in sympathy
Habitat differences and resource partitioning: the ghost of competition past or competition in the present
Allelopathy: chemical competition in plants and animals (release of chemicals by one species to reduce the growth of others)
Elton’s Niche
The role of a species in a community
Hutchinson’s niche
all biophysical conditions that characterize the life of a species
Fundamental niche
Is the entire multidimensional space that represents the total range of conditions within which an organism can function without limiting factors
Realized niche
The actual multidimensional space that a species can occupy taking into account biotic factors such as predators, competitors and parasites
Quantifying Niche Space
d = distance between two species in average resource use
w = measure of resource spectrum breadth of a species
d/w < 1 means no co-existence
d/w > 1 means full co-existence
Hutchinson’s Concept of Niche Space
The multidimensional niche overlap of species
Helps us understand how 2 species are really interacting
Can be an nth hypervolume – means there could be little overlap in hypervolume
Lotka and Volterra Competition Model
dN/dt = rN [(K-N) - (αN2) / K]
The effect of species 2 on population growth of species 1
Competition Coefficient (α)
This is the competitive overlap
Measure of the inhibitory effect of species 2 on population growth of species 1
Amount of resource one individual of the population uses relative to the other
Functional response curves (FRC)
Rate of food consumption and density of prey
Shows the rate at which food is consumed related to the density of the prey in the population
FRC I
Linear model
As prey density increases so do consumption linearly
Single species
Very rare
Only when the predator has a high metabolism, and food is calorie poor
Single prey species eaten
FRC II
The exponential increase of prey consumption up to a level where it tapers off
Because predator gets satiated or handling time poses a constraint
Single prey species eaten
FRC III
The quadratic increase followed by an inversion to exponential increases up to a flat line
Slow initial increase do threshold of security
Most common model
Multiple prey species eaten
Threshold of security
Minimum density under which no further predation occurs
Predicts that predators would rarely overexploit a prey species
Compensatory predation (4)
At low prey densities: Reduced search efficiency Prey switching Search image Aggregated responses of predators
Relative abundance of predator-prey (2)
Endothermic predators – 1:300
Ectothermic predators – 60:300
Prey defence (8)
Aposematic coloration Crypsis/camouflage Mullerian mimicry Batesian mimicry Protean behaviour Autotomy Structural defence Chemical defence
Aposematic coloration
Brightly coloured individuals to alert predators that they are noxious or poisonous
Mullerian mimicry
many poisonous species in similar areas develop a similar conspicuous colour pattern to mimic each other and reinforce predator avoidance
Batesian mimics
These mimic noxious species in the habitat, but they themselves are not noxious
Plant defence against herbivores
Plant structural defences
Plant chemical defences
Antibrowsing compounds – secondary metabolites (7)
Unpleasant odour Contact irritation Bitter taste Neurotoxins Proteinase inhibitors Growth hormone mimics Psychotropic effects
Animal defence against plant chemical defence (3)
Mixed function oxidase -oxidation, reduction, hydrolysis Concentration of toxins
Selective browsing
Ecological Succession
The sequential change in species composition of the community over time
Primary succession
the initial establishment of plant and animal communities on substrates lacking living organisms
Secondary Succession
Change of an established community
Recolonziation of an already established habitat
Allogenic succession
abiotic disturbance
Autogenic succession
biotic disturbance
Aggregation to the Transition state of biomass following clearcutting
The soil community dies following clear cut, so the detritus builds up. After soil community builds up the detritus begins to be broken down again, reducing the total biomass
What factors are correlated to the rate of succession?
The temperature and rainfall. Faster succession under warmer and wetter conditions
Ecological mechanisms for succession (4)
Stochastic events – largely unpredictable, who gets there first and dictate early seral stages
Facilitation – a species creates conditions favourable for succeeding species but not itself
Inhibition: a species inhibits the colonization of subsequent colonists (slows succession and prolongs a seral stage)
Allelopathy or competitive exclusion
Tolerance: members of the seral stage are those that co-exist due to the use of different resources
Combines facilitation and inhibition into a co-evolutionary view of succession (the ghost of competition past)
Some indices of the food web complexity (3)
Number of producers to top predator
Total number of links (L)
Connectance (C) - number of links in a food web divided by total number of possible links (N)
How to calculate total number of possible links (N)
N = n(n-1) / 2
Umbrella (indicator species)
Species used for conservation decisions
Dominant species
a common species with an effect on the community proportional to its biomass
Keystone species
a species with an effect on the community that is disproportional to its biomass
Nutrient cycling downloading and uploading
Downloading: rivers discharge sediment, trace elements, dissolved organic matter, nitrogen phosphates
Increased primary production in estuaries and adjacent marine waters
Uploading: Movement of marine nutrients back into the terrestrial environment. Normally in the form of carcasses or guano
Increase Nitrogen content of soils
