24 - Population and Sustainability Flashcards
What are 4 examples of environmentally sensitive ecosystems?
- Antarctica 2. Snowdonia 3. Lake District 4. Galapagos Islands
What is a population?
All the organisms of one species in a given area
What is interspecific competition?
Competition for resources between different species
What is intraspecific competition?
Competition for resources between members of the same species
What pattern can intraspecific competition follow and what does this mean?
Can be cyclic, so greater resources mean a larger population
What 2 things can interspecific competition affect?
- Distribution 2. Population of both species (both will usually decrease)
What is carrying capacity?
The maximum stable population size of a species that an ecosystem can support
What is population density?
Number of individuals per unit area of a chosen habitat
What are the 4 most basic factors which affect population density?
- Birth rate 2. Death rate 3. Immigration rate to habitat 4. Emigration rate from habitat
What 2 types of factors can affect population size?
- Density dependent 2. Density independent
What are 3 examples of density dependent factors which affect population size?
- Predation 2. Disease 3. Competition
What are 2 examples of density independent factors which affect population size?
Climate or natural disasters (earthquakes)
What type of feedback are predation cycles an example of?
Negative feedback
What are the 4 phases of a growth curve?
- Lag phase
- Log phase/ exponential phase
- Stationary phase
- Death phase
What happens during the lag phase of a population growth curve?
there is only a very slow increase in population size; this is because little cell division is occurring as the microorganisms are adjusting to their new conditions,
e.g. changing their gene expression, carrying out transcription and
translation to make new carrier proteins and enzymes in order to uptake and metabolise the available nutrients; there will not be much energy available for cell division whilst this phase is occurring;
What happens during the log phase of a population growth curve?
The population growth is increasingly steep
as the highest possible rate of cell division (e.g. binary fission of bacteria) occurs in this phase; there are no significant limiting factors yet: nutrients are still plentiful (so there’s not too much competition in the culture for these) and waste products have not yet built up to toxic levels; the population size may double every 20min (depending on species cultured) and rate of cell division far exceeds the rate of any cell death which may be occurring;
During what phase of a population growth curve is maximum growth rate reached?
Log phase
What happens during the stationary phase of a population growth curve?
The population size appears steady because there is an equal rate
of cell division and cell death; this is because limiting factors have started to have a significant effect (decreasing cell division rate but increasing cell death rate): one or more nutrients may be running low (increasing competition between cells) and waste products may now be at high enough concentration to be toxic to some cells;
;)
:)
During what stage of a population growth curve is carrying capacity reached?
Stationary phase
What normally prevents populations from undergoing uncontrolled exponential growth?
Limiting factors
What happens during the death phase of a population growth curve?
the population size decreases, as cell death rate now far
exceeds rate of cell division; one or more nutrients may have run out and accumulation of toxic waste is killing the cells; pH may have deviated from the optimum for the microorganisms’ enzymes, and heat released by their metabolism may mean that temperature increased so much that enzymes denature; eventually, no cells remain alive.
What causes the death phase of a population growth curve?
A sudden change in the environment which lowers carrying capacity
What is a limiting factor?
A limiting factor is something which stops a process or population increasing
any further.
What is the competitive exclusion principle?
No two species can occupy the same niche in the same habitat at the same time, so the species which uses resources more efficiently will ultimately eliminate the other
What happens when two species are competing for the same food source but one is better adapted than the other?
The less well adapted one is outcompeted and dies off
What is predation?
An interaction in which one organism kills another for food
What are the 3 stages of the effects of intraspecific competition on population size? DRAW GRAPH
- When a resource is plentiful in a habitat, all organisms have enough to survive and reproduce, causing a rise in population size
- Increased population means more organisms have to share available resources. As resources are now limited, the population decreases in size
- Less competition exists due to smaller population, so growth occurs again
What type of competition is almost all predation?
Interspecific
What can happen if a predator or prey species does not evolve?
They could go extinct
Do all predator-prey relationships show the same pattern?
In general yes
What are the stages of a predator-prey relationship?
- When predator numbers are low, the prey population increases as few are eaten by predators. Most prey offspring survive to breed themselves. Birth rate of prey is higher than death rate.
- However, the increasing prey population now means there is more readily available food for predators. If the prey population has increased beyond its carrying capacity, some prey individuals may be weakened by lack of food (as intraspecific competition for limited food may lead to starvation) or by the increased presence of disease or pathogens spreading through the crowded population. These factors plus the high prey density mean that predators can catch prey more easily, with low energy expenditure themselves.
- Predators therefore now have increased growth rates (enabling them to breed sooner), higher fertility and more offspring that survive to breed themselves. Hence, after a time delay, the previous increase in prey population is now followed by an increase in the predator population. The delay between the two will be longer in species where the predators are slow to reach maturity and have long gestation periods: it could then take several years before an increase in prey actually translates to bigger predator population.
- Now the predator population is increasing (with their birth rate higher than their death rate), they will be killing and feeding on more prey. This results in the prey population declining. Death rate has now exceeded birth rate in the prey.
- However, if the prey population is falling, this means food is less readily available to the predators. The predators may have to expend more energy to catch the increasingly scarce prey. The prey may be stronger (less weak) and so better at evading capture as they have less intraspecific competition for their own food sources (hence they are better nourished); they may have fewer diseases and parasites (as these don’t spread readily in a sparse population).
- The predator population may now fall as the predators struggle to get enough food: they may reach breeding age later due to poor nutrition and fewer offspring may survive to breed themselves. If the predator population has exceeded carrying capacity, its numbers may also be declining due to increased disease or parasite transmission. Death rate of predators now exceeds birth rate.
- As the predator population falls, there are fewer predators killing prey. Hence the prey population has the opportunity to increase again: the above sequence of events will restart and repeat. Both populations will oscillate over time, but the changes in the predator population always lag behind those in the prey population.
Why are predator-prey relationships rarely as simple as the model?
There are other biotic and abiotic factors to consider
What is conservation?
Conservation is the active management of a habitat/ecosystem (by humans)
with the aim of maintaining or increasing its biodiversity.
What is preservation?
Preservation is the prevention of any human activity in a pristine ecosystem,
in order to avoid its damage or modification.
What type of process is conservation and why?
A dynamic one, as it needs constant adaptation to changes within the ecosystem
What is reclamation?
Restoring ecosystems which have been damaged or destroyed
What does pristene mean?
By pristine, we mean that there has not already been any significant human impact
What are 3 examples of commonly preserved ecosystems?
- Marine conservation zones 2. Nature reserves 3. Newly discovered caves
What things are maintained in conservation?
genetitc, habitat and species biodiversity
What are 3 classes of reasons for the importance of maintaining biodiversity?
- Economic
- Ethical
- Social
What are 5 techniques used as part of conservation?
- Managing land
- Taking steps to encourage new habitats
- Removing animals to captivity
- Growing plants in cultivation
- Reclamation
What is a technique humans can use to encourage new habitats?
Controlled habitats
Is anything removed from a preserved area?
No
What are 3 threats to biodiversity?
- Habitat loss 2. Invasive species 3. Overexploitation
What are 3 reasons wild populations may be overexploited by humans?
- For food 2. For sport 3. For commerce
What are 3 reasons habitats may be disrupted by humans?
- Intensive agricultural practices 2. Increased pollution 3. Building
What is a sustainable resource?
Renewable resource that is being economically exploited in such a way that it will not diminish or run out.
What are 5 methods used for conservation?
- National parks
- Green belts (areas of green land)
- SSSIs (Sites of Special Scientific Interest)
- Legal protection
- Ex Situ conservation
What is sustainable management of the environment necessary for?
Conservation of natural resources for future generations
What are the 5 aims of sustainability?
- Preserve the environment
- Ensure resources are available for future generations
- Allow humans in all societies to live comfortably
- Enable LEDCs to develop through exploiting their natural resources
- Create even balance in consumption of resources between LEDCs (less economically developed countries) and MEDCs (more economically developed countries)