Ecology Flashcards
What is an ecological niche?
- the sum of the total adaptations of an organismic unit
- a ‘niche’ identifies the role of an organism in its community.
What can information on niches be used for?
- defining the traits that limit a species distribution
- make comparisons of the composition an organisation of communities
- examine shifts in behaviour or ecology of one species in response to another
what are the general dimensions of an organisms niche?
- Foraging strategies and diet
- Reproductive strategies
- social organisation
- defence against predication
- environmental tolarences
- morphology, sensory adaptations, physiology
- competition
What is ecology?
- scientific study of the distribution and abundance or organisms and the interactions that determine their distribution and abundance.
> where do organisms occur?
> How many occur there?
> why are they there?
What are the general components of an animals niche?
- foraging strategies and diet
- reproductive strategies
- social organisation
- defence against predation
- environmental tolerances
- morphology, sensory adaptations, physiology
- competition
What is the lower Sonoran life zone?
- corresponds with the hot deserts of the south-western United States and north west Mexico.
What is the upper Sonoran life zone?
- ranges from 3,500-7000ft in elevation. These include a woodland evergreen oaks, pinyon pine and or juniper.
What is the transition life zone?
An open ponderosa pine forest is characteristic at eve various from 6000 to 9000 ft. Total annual precipitation ranges from 18-26 inches.
What are Grinnells limits for the California thrasher?
- spatially restricted- largely Californian. Due to psychological limitation restricted to a series of enviro tonal conditions.
- closely adheres to the upper Sonoran life zone- the transitional life zone sharply defines its upper range limit.
- occurs on south-facing slopes close to upper I its
- lower limits well fined- may go into lower Sonoran
What does Grinnells niche paper focus on?
- inter-specific exclusion
- Climatic limits
- Habitat and vegetation specificity and the problem of deciding what are limiting factors for a species to occur.
What does Elton define the niche of an animal to be?
- its place in the enviroment
What is the competitive exclusion principle?
- complete competitors cannot co-exist.
- both biotic and abiotic factors determine a species niche
How can one interpret Hutchinson’s ‘hypervolume’ niche models?
- the area in the middle = high fitness
- regions surrounding = region of intermediate fitness.
- outer region = species can survive and reproduce but fitness is low.
> the addition of further variables cuases the hypervolume graph
The hypervolume is good for illustration but what must be remembered?
- not all niches are environmental- some a axes are behavioural
- not all axis can be ordered linearly (e.g. Types of anti-predator behaviour) so they don’t lend themselves to this approach
- different species can hold similar niches and the same species can occupy different niches.
- once a niche is left vacant other organisms can fill the position.
What is the fundamental niche?
- the entire set of conditions under which an animal can survive and reproduce.
What is the realised niche?
- the set of conditions actually used by a given animal, after interactions with other species have been taken into account.
> sometimes fundanmatal niches are termed pre-competitive and post competitive niches reflectiong a traditional focus on interspecific competitions effect on niches.
Why may the realised niche for different populations of the same species differ?
- because of differences in competitors and predators between locations.
What is the niche breath?
- if there is no niche overlap the species diversity is determined by niche breadth.
- if there is constant niche breadth then species diversity is determined by neiche overlap.
> specialist species have narrow niches
generalists have broader ones
What is the problem with using a population for neiche breath?
- unclear whether all the individuals are using almost all of the niche. (Within phenotype component of niche breath is large)
Or whether the individuals are each using a narrow but different part of the niche. ( between component of niche breadth is large)
What are the 3 explanations of how niches arise?
- Current competition (could expand in absence of competitors)
- Evolutionary avoidance of competition
- species have simply evolved in response to natural selection in different ways and independent ways. Do not necessarily compete or have competed in the past.
> to solve which is acting can remove competition and look at results.
What ecological changes can we use the quantified variables of a niche in order to predict effects of?
- Global climate change
- species invasions
- competitive interactions
What is a population?
- Group of interbreeding individuals found within a given area at a given time.
What is population distribution?
- the spatial location of individuals defines the population distribution.
> may remain fairly stationary (sessile organism) to may constantly vary (migratory organisms).
How can we calculate population density?
- divide population size by its area
Why calculate population density?
- strongly effects important ecological processes of interest > brith and death rates.
what are life tables?
- used to summarise or infer patterns of births and deaths.
2 approaches - over time follow cohort follow the group you’ve branded this is best method.
- record structure of a ovulation at some point in time a ‘snapshot’.
What are population dynamics caused by?
- births
- deaths
- immigration
- emigration
how can populations be estimated?
> Total counts of individuals time consuming often impossible
sampling methods - count proportion and sue this to estimate a total.
What are the 3 critical assumptions made by capture recapture methods?
Marked and unmarked animals are captured randomly
Marked animals have the same mortality rate as unmarked
Marked animals are neither lost nor overlooked
What is the simplest way to model population regulation?.
To assume the net reproductive rate decreases linearly with N.
N is population size
When N is very small dN/dt is approximately rN and population grows exponentially
When N = K/2 growth rate is at its highest
If N> K then dN/dt is negative and population declines
What are the 5 main intra-specific interactions?
Competition (mutual negative effects both harmed)
Predatation or parasitism (one organism benefits the other is harmed)
Mutualism (both benefit)
Amensalism (one organism is harmed the other is unaffected.
Commensalism (one organism benefits the other is unaffected)
What defines 2 organisms being competitors ?
If they both use the same resources and those resources are insufficient to supply their combined needs.
What is the definition of predication?
- Commonly used to describe the situation where one organism consumes all or part of another organism (herbivore is a form of prediction)
What is Parasitism?
Like preditisitms it is also a form of +/- relationship
> parasites live in close association with their hosts.
- feed on host tissue
what is Amenalsim?
-/0
> e.g. Water holes mammals are unaffected by plants surrounding water in holes however the plants get trampled.
What is commensalism?
+/0
Cattle egret capture more insects when foraging with large grazing animals such as Cape buffalo
describe a typical predator prey cycle
- Low predator population allows increase in prey
- increase in prey allows increase in predictors
- increasing preditors cuases decrease in prey
- decrease in prey cuases decrease in preditors
STARTS again
What is the gross primary productivity?
- the RATE energy is incorporated into the bodies of photosynthetic organisms
What is gross primary production? What to plants use it for?
- the amount of accumulated energy used for: > metabolism > Growth > reproduction
What sis the net primary productions?
The energy available to the organisms that eat plants
What affects primary productivity?
Tempratrue and moisture affect the amount of energ plants assimilate by photosynthesis
How does primary production impact biodiversity?
- increasing pp increases energy available, whcih increases population densities resulting in lower extinctions and higher levels of biodiversity.
- at very high pp competition is intense and only few species can exist (competitive exclusion).
What are organisms divided into trophi pic levels for?
- based on how they obtain their energy.
> photosynthetic organism gain enery from sun- primary producers
heterotrophs (non photosynthetic organisms) consume either directly or indirectly the energy rich organic molecules = primary consumers
What is the assimilation efficiency?
- The ratio of assimilation to ingestion
What is the production efficiency?
- the ratio of production to assimilation
what is consumption efficiency?
- The ratio of ingestion to production.
What is a food chain?
- Sequence of interactions describing the feeding interactions
What is a food web?
Interconnected food chains
What are keystone species?
- Have very strong influence on ecosystems despite having relatively low abundance
E.g beavers create new habitats by cutting down trees and creating dams.
What is a trophic cascade?
- When a change in the species community at one trophi level affects the species community at a trophi level that is not directly above or below the altered trophic level.
what are the features of a stable community?
- many interactions, including competition and predication
- Processes operating in a density dependant manner to regulate population sizes.
- species saturation (no scope for invaders)
- Rare catastrophic environmental events
What does the energetic hypothesis suggest?
- food chain lengths are relatively short due to the inefficiency of energy transfer along the chain.
What are 4 food web generalisations?
- More species results in more linkages
- chain lengths are generally short
- the proportion of species at each level is approximately constant
- omnivore tends to be common in food webs
