Ecology Flashcards
why is ecology important?
human dominated time period - impact on lots of environments globally so want to understand the impact we’re having on different populations
what is the LPI?
living planet index
what does LPI tell us?
- indicator of the state of the world’s biodiversity
- measures trends in populations of vertebrate species living interrestrial, freshwater and marine ecosystems
describe the state of the worlds biodiversity.
- global decline of 27%
why are albatross endangered?
Eats a lot fish → at the moment we are overfishing → taking away part of its food source
Long line fishing → long lines, get tangled in the lines and then they can drown
why do ecologists need to understand why populations change in size?
to reverse the declines
what is a population?
a group of individuals of the same species living in a given area at a given time
what can we look at to understand how our populations are changing?
- Size → number of individuals
- Range → area they’re covering
- Density → number of individuals in a given area
what are the different types of population?
closed population. metapopulation. open population.
what are the different types of populations based on?
based on importance of birth/death rates and dispersal
what is a closed population?
Numbers of individuals is driven by the number of births and deaths in these populations
Limit of dispersal is pretty short
what is an example of a closed population?
Example → Northern brown argus (butterfly), see in scotland and durham in disused quarries, quarries are quite distant so we don’t see much movement between them
what is a metapopulation?
Some movement
what is an open population?
Limit of dispersal encompasses a lot of patches so can have a lot of movement between them
Size of population is going to be driven mainly by dispersal
what is an example of an open population?
Small tortoiseshell (butterfly) → lives around patches of nettles, so there is a lot more movement
what are the different patterns of spatial distribution?
- Clumped - When you find one individual have a high probability of finding another individual
- Uniform - Regular pattern
- Random
what are patterns of temporal distribution?
- Species are distributed in time as well as in space
- Seasonal/daily changes in distribution eg migration
- Life cycles
what are the 2 different types of life cycles?
- Semelparous
2. Iteroparous
what is semelparous?
annual, overlapping eg insects, reproduce once then die
what is iteroparous?
continuous, overlapping eg tree, once they reach maturity can reproduce many times
what are the features of population dynamics?
- rates of reproduction
- death
- migration
what are life tables?
- all populations contain individuals of different ages
- looking at patterns of mortality
what are the assumptions of life tables?
Assume population changes are due only to changes in birth and death rates (no migration) → limitation
Assume a closed population
what are the 2 types of life tables?
- cohort life tables (semelparous)
2. static life tables (long lived iteroparous species)
what can we find out from a cohort life table?
- tell us the number of organisms that an individual is having in its life cycle
- can figure out if the population is increasing, stable or declining
- find out how much reproduction is happening
what does the little x mean?
age class or life stage
what is ax?
total number of individuals observed at each stage or class (in a closed population)
what is Nx?
the standardized number of individuals in each age/stage x
what is Ix?
proportion of original number of individuals surviving to the next stage or class; survivorship
what is dx?
proprtion of original number of individuals dying during each stage or class; mortality
what is qx?
mortality rate for each stage or class
what is Fx?
total fecundity or reproductive output of entire population, for each stage or class
what is mx?
individual fecundity or mean reproductive output for each stage or class
what is lxmx?
number of offspring produced per original individual during each stage or class; product of survival and reproduction
what is R0?
basic reproductive rate average number of offspring that a female produces during her lifetime, consider if organism is semelparous or iterparous
what does the study of populations involve?
- description of population charactersitics
- exploration of factors determining population size
- use models to predict growth of populations
what are the limits to population growth?
- physical environment
- intrasepcific interactions
- interactions with other species
(biotic and abiotic)
how can we use the information from a life table?
population age structure. population growth rate. population survivorship patterns
what can we find out from a static life table?
Use the data to figure out if the young are reproducing and plot survivorship curves
what does R0 represent?
Net reproductive rate - average number of offspring produced by a female in her lifetime
what does R0 = 1 represent?
replacement rate - steady and stable
what does R0 < 1 represent?
a declining population
R0 > 1 represent?
an increasing population
what is little r?
per capita rate of increase
- intrinsic rate of natural increase
- instantaneous rate
what is the equation for r?
r = ln(R)
why do ecologists usually use r?
easier to see if the population is increasing or decreasing
why should we use data to make a model?
Shed light on what’s happening in the natural world
Desire to formulate general rules in ecology
Graphical or mathematical
Help us figure out the shared properties of different populations and compare
what is the intrinsic rate determined by?
how quickly individuals reproduce and how long they live
what is the carrying capacity?
the maximum number of individuals a habitat can support
how does growth differ in relation to life history?
- Discrete individuals eg grasshoppers
2. Continuous breeding eg humans
describe discrete intervals
Geometric growth
Individuals added to population in events
Suppose each individual gives rise to 2 new individuals
Factor by which population increases = reproductive rate = finite rate of increase R = 2
At time point N1 we have twice as many individuals at time point N0
Nt+1 = RNt → general equation
This pattern of population growth can also be written as Nt = N0Rt
This equation has some irritating mathematical properties
The model describes a population with no competition, R is constant and if R>1 the population will continue to increase
describe continuous breeding
Nt = N0e(^rt)
R = intrinsic rate of reproduction
e = base of natural log
Therefore R = e(^r) → r = ln(R)
why are pests spreading?
the climate
describe the invasion of the harlequin ladybird
Introduced from Asia and feeds on our native species
The impacts - Detrimental impacts on native UK ladybird populations
The evidence - Measure the population growth rate of the invader, AND rate of population decline in native ladybird species
describe logistic growth
equation assumes resource (or prey) affects carrying capacity
what are the 2 types of competition that individuals will face in the real world?
intra and interspecific competition
what is competition?
interaction between two individuals that both need the same resource which is in limited supply - leads to a reduction in survivor-ship
what are the features of competition?
- decreased contribution to the next generation
- resources must be in limited supply
- density dependence
what is intraspecific competition?
between individuals of the same species
what is interspecific competition?
between individuals of different species
what is scramble (exploitation) competition?
- no direct interaction
- interspecific - one species would be coming away with more
what is contest (direct or interference) competition?
some type of confrontation
what are the 3 features of intraspecific competition?
- decreased contribution to the next generation
- resources must be limited supply
- density dependence - if competitiros increase then competition increases
describe density dependent factors on population growth
- impact of the factor increases as we get more individuals in our population
- regulating factors become more effective as population density increases
- causes an increase or decrease in growth rate
- drives the population towards carrying capacity
what are some examples of density dependent factors?
Competition for resources → food Predation → to be eaten Disease → to catch a disease Toxic waste build-up → eg by products build up Intrinsic factors Territoriality → hormones and aggression
describe density independent factors on population growth
- effectiveness of limiting factors is independent of population density
- graphically shows an instantaneous drop in population size
- can occur at different starting densities
what are some examples of density independent factors?
Environmental factors that check N or distribution (floods, fires, droughts, earthquakes, etc.)
what are some features of interspecific interactions?
- similar potential to regulate populations
- generally less intense
- often very asymmetric
- occurs when individuals of one species suffer a reduction in growth, survival or fecundity as a result of activities of another species
- species from distant taxa compete
what is competitive exclusion?
not all species occur everywhere
what is coexistence
when competition does not lead to exclusion - differ in the way they use a resource - specialisation
what is a niche?
combination of a conditions and resources which allow a species to maintain viable populations
what is a fundamental niche?
the set of conditions and resources that a species could occupy in the absence of competition
what is a realised niche?
the set of conditions and resources that a species actually occupies
what is the competitive exclusion principle?
- two competing species coesxit
- if there is no differentiation between them one species will exclude the other
what happens to predators in the absence of prey?
predators decline exponentially
what does predator-prey interaction depend on
- rate at which food is consumed
- the predators efficiency at turning food into offspring
- predator birth rate
what are coupled oscillations?
- large food source for predators
- predators eats the food source so it declines
- predator population then declines as there’s not enough prey
what is habitat fragmentation?
patch of habitat surrounded by an environment that isn’t ideal for species living in the patch of habitat
what are the challenges of habitat fragmentation?
- reduced biodiversity
- reduced area of habitat size
- not enough resources and/or mates
what are the 3 principles of island biogeography?
- effect of area and isolation
- dynamic equilibrium
- faunal collapse
why does GB have more species than Ireland?
- bigger surface area, more oppurtunity for habitat
- many terrestrial animals came across from mainland europe
- ireland is more isolated
what is the importance of island area for species richness?
as island area increases so does our number of species
why is isolation important?
if an island is closer to the mainland and may therefore have more species than that island should for its size
what is Darlington’s rule of thumb?
- Relationship between area and number of species is remarkably constant
- As you move from one area to another 1/10th the size the number of species in a particular group will be halved
- Can reverse this and use it to predict the impact on species
what is the equation that links the area and the number of species?
S = CA^z (to get a stratightline: Log S = Z log A + log C)
use the florida mangrove to give an example of area and isolation
The Florida Mangroves - Dan Simberloff
Test: experimental manipulation of size → impact of changing the size of the island on arthropods
Saw: changes in the number of arthropod species on mangrove islands
As area decreases so does the species richness
what is dyanmic equilibrium?
dynamic equilibrium between colonisation and extinction - island species diversity
what happens to the rate of new species arriving on an island over time?
drops as species accumulate
what happens to the rate of extinction on an island over time?
increases - compete for resources
describe dynamic equilibrium on larger islands
have more colonists and lower rates of extinction compared to smaller islands (assumes there is no difference in isolation of islands)
describe dynamic equilibrium in isolated islands
Isolated islands have lower rates of colonisation compared to near islands and thus fewer species at equilibrium (assumes size is the same)
what is faunal collapse?
how long does it take to lose species after fragmentation
what is relaxation time?
how quickly we lose species
how can calculate relaxation time?
- look at continental land bridge islands
what are continental bridge islands?
formed after the last ice age
how was separation determined?
- sea depth around the islands
- deep sea = longer ago
- longer ago = fewer species
what is extinction debt?
more species than an area can support because not all species have died off yet when there has been a reduction in size
which species will be lost?
- species living at low population densities
- those with large range requirements
- those higher up the trophic ladder
- those that depend on rare habitats or require scarce resources
why doesn’t everything live everywhere?
physical constraints
what is meant by physical constraints?
- dictate the range of environmental variables an organism can survive in eg temperature
what is the fundamental niche?
The full range of environmental conditions that a viable population of species can occupy and use
Changeable (move alter with climate change) → will change over time
All the places where the species could live
what is the realised niche?
The set of conditions which are actually occupied
More restricted than the fundamental niche
All the places where the species actually live
why isn’t everything everywhere that is physically suitable?
- can’t get there - LIMITED DISPERSAL
2. INTERACTIONS with other species
what is a niche?
a multidimensional habitat that allows a species to practise its way of life
what are some examples of interspecific interactions?
antagonism
mutualism
commensalism
amensalism
what is antagonism?
where at least one participant loses more than it gains by the interaction
what is mutualism?
where interactions enhance the reproduction and population growth of both species
how are interactions dynamic?
Interactions may be costly or beneficial
Natural selection may cause adaptations (to reduce cost or maximise benefit)
May lead to coevolution and speciation
what is competition?
Competition for limited resources (food, mates, shelter, light, space) is a lose-lose situation (with one competitor likely to lose more)
what is resource partitioning?
Evolutionary pressure to minimize overlap species’ niches
what are two features of predation?
- coevolution
- prey switching
what is coevolution?
adaptation and counter adaptation
what is pprey switching?
preference for the most common type of prey
describe paratism in cuckoos
social parasties - lay their eggs in the nests of other species
what are mutualistic interactions?
These are win-win situations - both participants have greater than cost
how are benefits of mutualistic interactions measured?
Benefit is measured in terms of increased reproductive output and survival
what are the benefits of mutualistic interactions?
Benefits include access to nutrients, shelter, reproductive facilitation
what are the costs of mutualistic interactions?
Costs include energy-consumption, loss of food resources, investment in protein/fat/carbohydrate structures and specialised tissue
what is obligate?
If one or both sides of mutualism cannot survive without the other
what is facultative?
If one or both sides can survive without the other
how do obligate relationships begin?
start out as facultative and were reinforced over time by nautral selection
what is an example of coevolution?
flowers evolved in response to pollinators - who in turn adapted in response to availability
how can mutualisms become antagonisms?
if one partner begins to cheat
use tubualr flowers and bees as an example of mutualisms becoming antagonsims?
Tubular flowers → bees must go past the anthers or stigma increasing population but slowing down the bee
If bees nip the flower base from the outside they can drink the nectar without pollinating the flower → saving time
what is commensalism?
An interaction in which one party benefits with no cost of benefit to the other
what is amensalism?
An interaction in which one party is harmed with no cost or benefit to the other
What is necessary in order for natural selection to occur, according to Darwin and Wallace?
Reproduction. Heritability. Variation. Differential survival and reproduction.
What benefits from infanticide in lions?
Genes for infanticide, individual lions committing infanticide
What benefits from the suicidal stinging of honeybee species?
Genes for stinging, bee colonies, honeybee species
What type of model is the IFD model?
- optimisation model (each animal behaves to maximise its own fitness)
- ESS model (best behaviour depends on the rest of the population)
