Week 2-5 Flashcards
What is a population?
A discrete group of individuals from a single species in a relatively self contained space, where there is little immigration and emigration relative to the intentional rates of recruitment and mortality
What increases population isolation (i.e decrease in immigration and emigration)
Geographical barriers such as rivers and mountain ranges, as well as habitat fragmentation cause by deforestation.
Why do populations generally have the same gene pool?
Because populations tend to be isolated and thus can not move breed with other individuals from a different population
What can regulate population size?
Habitat size, quality, fragmentation
predator population
competing species
climate/optimal conditions
What is the difference between population size and population density?
size = total number density = number per unit of space
What is a fundamental niche?
is the combination of environmental conditions and resources where a species COULD survive and reproduce
What is a realised niche?
Is the area of the fundamental niche where a species actually exists after interacting with other species and being out competed from some regions
What determines the limits of the geographic ranges?
Abiotic/biotic factors that prevent further spread
Human transformation of the landscape e.g farming, deforestation
Local population dynamics at the edge of the range
Genetic mechanisms
How can knowledge in population ecology apply to the real world
Conservation of endangered species Harvesting/management of natural resources Invasive species biology Pest control Spread of diseases
Which region hold the highest level of biodiversity
Tropical
What did the Millennium Ecosystem Assessment say about tropical forest
It said that habitat change has placed a very high stress on tropical forest and unless anything is done the impact of this stress will rapidly increase
How much of the Atlantic Forest has been lost`
95%
How much the Mediterranean and temperate did Millennium ecosystem assessment
say are lost
70%
How much semi-natural habitats in the UK have been lost since 1940 on average
70%`
Give an example of a location, with time period, which has suffered fragmentation and a quantified amount of loss
Heathland Dorset: 1759 – 1978 (86% loss)
What is the relationship between landscape structure, population dynamics and ecological processes
Landscape structure can affect the other two
What is the species-are realtionship
It is the positive relationship between the size of an area and the number of species found within it
Why is the species relationship positive
Large areas tend to have more niches which different species can in habit
Isolation is more likely to occur in large areas and so speciation is more likely to occur.
What were the main findings of Ferraz et al. (2003)
A 10-fold decrease in the rate of species loss requires a 1,000-fold increase in area. Fragments of 100 hectares lose one half of their species in <15 years, too short a time for implementing conservation measures.
What is the impact on fragmentation on different species of bird
Different species have different tolerance levels to fragment size e.g blackbirds reached 100% breeding probability in woods less than 1ha but marsh titis needed over 15ha to reach 100% breeding probability
What aspects of population dynamics does landscape structure affect
Dispersal + colonisation Persistence Productivity Synchrony Gene flow Spatial density dependence Buffer effects
Which ecological processes does landscape structure affect
Predation, herbivory, pollination
example of pollinator being affected by fragmentation and by who
Euglossa sp. abundance fell as fragment size decreased Powell and Powell (1987)
example of plant reproductive success being affected by fragmentation and by who
In Sweden the mean number of seeds set per flower of maiden pinks were lower in fragmented habitats than continuous
due to a 2-3 fold decrease in pollinator visitation (Jennersten 1988)
What are the potential consequences of fragment caused changes in pollinators
Fragmentation can restrict pollen flow which may reduce both the genetic variability or progeny and the effective genetic neighbourhood size which in turn increases the risk of inbreeding depression and changes in long term stability of isolated populations
What is the overall change in biodiversity distribution and who stated it
Moving poleward: in Britain 275 out of 329 species have shifted northward. Hickling et al 2006
Define trophic cascade
Trophic Cascade is the theory that food webs are controlled by a top-down process, where top predators affect the abundance or behaviour of their prey, which then has impact on the next lower tropic level.
What is shifting baseline theory
Refers to how, with each generation, the accepted norm for ecological conditions lowers since each generation lacks the historical knowledge of how that environment used to be.
Example of shifting baseline theory and by who
Pauly (1995) observed that there was a gradual accommodation for the disappearance of fish species and how each gen. of fishery and marine scientists assume that the current fish populations are the norm
What is the Hutchinson niche
It is an “n-dimensional hypervolume”, where the dimensions are environmental conditions and resources, that define the requirements an individual/species needs in order to survive. The “hypervolume” defines the multi-dimensional space of resources (e.g., light, nutrients, structure, etc.) available
to be used by the organism under consideration
What’s an advantage to the Hutchinson niche model
niche can be measured, mathematically manipulated and represented in climo-graphs.
What is a meta-analysis
the statistical procedure for combining data from multiple studies
How can a meta-analysis be used
can be used to identify common effects and analyse consistency between studies
5 stages of a systematic review
Defining question Finding the data Summarising relevant data Assessing the quality of the data Analyse and combine the data
Example of the effect fragmentation has on seed predation and by who
Burkey 1993 found seed predation to be lower at than the interior.
What are the consequences of fragmentation affecting seed predation
Seedlings at the edge are less likely to be eaten and thus more likely to survive to germination, however this may be offset by an adverse micro climate.
Also it may lead to changes in spatial heterogeneity and survivor ship of the host plant of the seed predator
Example of how decomposes are affected by fragmentation
Klein 1982 found that as the no. of dung beetle species went down, so did the rate of dung decomposition with increasing fragmentation.
What are the potential consequences of fragmentation affecting decomposers and who suggested them
Potential implication for habitat productivity and the flow of nutrients through an ecosystem since the rate of decomposition has a positive linear relationship with nitrogen and phosphorus concentrations. Enríquez 1993
What impact has climate had on marine environments and range shifting (cite)
Perry et al 2005 found that the North Sea winter bottom temp. has increased by 1.6 Celsius in 25 years. There has also been poleward shifts in distributional ranges of some marine species with an average rate of 22km per decade
Evidence for climate caused changes in phenology
Parmesan and Yohe 2003 conducted a meta anaylsis on 677 species and found that over a range of 16-132 years, 62% showed trends towards spring advancement e.g earlier frog breeding, bird nesting, first flowering, tree budburst, arrival of migrant birds and
butterflies
How can climate warming change phenologies generally
It can cause earlier springs, later autumns and increased vegetation activity
Describe Keenan et al. 2013 ‘s experiment
Over 20 year they assessed changes in phenology of temperate forest in eastern US
What did Keenan et al. 2013 find after their study
They found that carbon uptake through photosynthesis was more than carbon release through respiration.
What are the implications of Keenan et al 2013
It suggests current and future increase of carbon uptake due to changes in phenology and since this process is a negative feedback loop it could slow down the rate of warming
What is a consequence to changes in phenology
Can lead to trophic mismatch
Example of a trophic cascade
A study conducted by Waser et al 2014 in the Elk Mountains, Colorado found that the coyotes avoided a biological research centre due to the high human activity. Since coyotes often feed on the fawns, the does favour these areas and thus the grazing intensity increased the closer one was to the station. This in term affected the seedling recruitment of blue combine and scarlet gilia flowers, which was significantly lower by the station than away where coyotes activity was higher
Example of trophic mismatch and by who
Doiran at al 2015 studied the effects of warmer springs on greater snow geese. Warmer springs and earlier snow melt caused the peak nitrogen, an index of the nutritive value in plants, to hit earlier. This resulted in a mismatch between peak nitrogen in the plants and the hatch dates of the geese which had not shifted to earlier in the year. Consequently gosling body mass and structural size at fledging were lower when the mismatch was greater, and thus the fitness of geese was negatively affected. One can presume that this will get worse as warming continues
What does the millennium ecosystem assessment say about over exploitation
Overexploitation has a significant impact on biodiversity loss, particularly in marine and tropical biomes
What figures did WWF provide for the wildlife population decline between 1970 and 2010
79% of freshwater, 39% terrestrial species, 39% marine species have declined between 1970 and 2010
What happens carrying capacity of the environment is exceeded
The environment becomes degraded and the final carrying capacity may end up being lower than the original. Also, the loss of species can lead to trophic
cascades that decrease the carrying capacity of the environment for other species
What is the symbol for carrying capacity
K
What characteristics do K-strategist species typically have
Stable environment Large body size Long life expectancy Late maturation High parental care Fewer offspring
What give K-strategists their name
they are species whose population fluctuate at or near the carrying capacity of the environment they live it
What gives r-strategist their name
They are species whose populations are governed by their maximum reproductive capacity.
What characteristics do r-strategist species typically have
- Unstable environment
- High fecundity
- Small body size
- Early maturation
- Short generation time
- Dispersed offspring
Define MSY
Maximum sustainable yield is the number of weight of a species that can be removed from the stock of animals without impacting the long-term stability of the population
Describe the sustainable yield curve (graph)
the x-axis is fishing effort or fishing mortality, y-axis is yield. The sustainable yield curve begins at the origin and increases. However, the rate of increase decreases until it plateaus. This is the MSY and when a stock is fully fished. If effort or mortality continues to increase, the yield decrease at an increasingly faster rate until the stock is depleted
How is the MSY derived from our knowledge of logistic growth
Is a population is assumed to be following logistic growth the MSY will be exactly half of the carrying capacity of the species as this is the stage at which the population growth is the highest
Why is it important to understand population density
It is key to the
management of natural populations (e.g.
conservation or sustainable exploitation)
What is a ‘close’ population
a population with no immigration or emigration
What are the two equations used to represent population density in a close population
Nt= B-D and Nt+1= Nt+B-D
Why are abiotic factors density-independent and give examples
Because they regulate population but aren’t affected by population density.
e.g. Weather and stochastic environmental events (e.g. fire,
flood, drought, habitat destruction, spraying of pesticides)
What is the relationship between population density, mortality rate and fecundity decreases
Usually, the denser a population is, the greater
its mortality rate and fecundity decreases.
When do density-dependent processes occur
when population growth rates are regulated by the density of a population (e.g. competition for mates, competition for resources, diseases, increased predation)
How does low prey density affect predators
Low prey density increases the mortality of its predator because it has more difficulty locating its food source
Examples of different types of density-dependent processes
competition for mates, resources, diseases, increased predation
Describe the relationship between population density, mortality rate and fecundity
As density goes up, mortality rate goes up and fecundity goes down
Describe and explain the relationship between population density and intrinsic rate of increase
As population density increases, the intrinsic rate of increase decrease as the are less resources and disease spread is faster
What age should one focuses on conserving an r-strategy species and why
The focus should be on the older as they produce lots of young since their is a high chance many wont survive
Example of a positive density dependent effect on growth rate
The Allee-effect (Allee 1931) is when population growth rate is very low in a low density population as there is a low chance of finding a mate, which increases as density increases.
Example of positive density dependence other than Allee effect
Insects may be attracted to dense patches of a flowering plant species and pollinate them efficiently, but ignore sparse stands.
