Populations & Sustainability Flashcards
Name each of the phases
A = lab phase
B = log phase / exponential
C = stationary phase
D = death
What’s happening at a
The lag phase:
Organisms are acclimatising to the new environment
There’s a low rate of reproduction
Population growth is slow
What’s happening at b
Log phase / exponential
There are plentiful resources & no competition:
Reproduction»_space;> Mortality
As there a good conditions, there is high population growth
What’s happening at c
The stationary phase
This is when reproduction = mortality
- carrying capacity has been reached
Resources / the habitat cannot support a larger population
What is carrying capacity
The maximum population size which can be supported & maintained over a particular period by the habitat
What happens at d
Death phase
There isn’t enough resources to support the population
What are density independent factors and are they linked to abiotic or biotic factors
These are factors that act just as strongly regardless of population size
For example: abiotic (non-living) factors, like light availability, space, soil pH etc
Abiotic factors that affect population size
Temperature
Water mineral content
Natural disasters
Light availability
Space
Water supply
Soil pH
What are density dependent factors and are they linked to abiotic or biotic factors
As population size increases, the factor is more influential
Therefore more linked to biotic (living!) factors (e.g. interactions between organisms)
Examples of factors that affect population size
Predation
Parasitism
Food
Water
Light
Immigration & emigration
What’s a K strategist species
A species whose population size is determined by carrying capacity
C.C. Reached -> population growth slows -> limiting factors = more influence
Features of K strategists
Low reproductive rates
Late reproductive age
Large body mass
Slow development (longer lifespans)
E.g. large mammals & birds
What’s an R strategist
A species that has a rapid increase in population size until they exceed carry capacity & limiting factors begin to have an affect & population growth & level falls
Features of R strategists
- faster reproductive growth
High reproductive rate
Quick development
Small body mass
E.g. mice / insects
3 main interactions between populations
Intraspecific competition
Interspecific competition
Competitive exclusion
What’s intraspecific competition
Between individuals of the SAME specifies
How does intraspecific competition keep the population size relatively stable
Plentiful resources = increased population = more individuals compete for same resources = carrying capacity reached
-> resources become limiting
This keeps the population size relative stable
What is interspecific competition
Between individuals of different species
Intensity of competition = no resources = decreases reproduction rate, increases mortality rate
What is competitive exclusion
The idea that 2 organisms can’t occupy the same niche
What happens in competitive exclusion
2 organisms occupy the same / similar niches
One organism is slightly better adapted
The other organism is outcompeted & dies out in that habitat
This may not always apply in natural ecosystems, as other variables may be acting as limiting factors
Explain this predator population graph
Initially predator population size increases, as more prey are available, so more predators can survive & reproduce
More prey are eaten
Less prey survive & reproduce
Prey population size decreases
Less prey avaibke
Predator population size decreases, as less can survive and reproduce
Prey population size increases
& so on
What’s the difference between conservation & preservation
Conservation is maintains biodiversity THROUGH sustainable, human activity: its an active process whereas Preservation is a way of protecting the biodiversity of an environmentally sensitive area by restricting human activity
What are the reasons for conservation
- Economic (e.g. ecotourism provides income & resources like medicines, wood & food)
- Ethical (e.g. all have a right to exist & our responsibility is to ensure that)
- Social (aesthetic value from which we derive pleasure & relaxation)
What are the aims of sustainability (sustainable resource management)
To ensure that there are enough resources for current & future generations
To preserve the environment
To enable development of lower income countries by balancing resource consumption
What is the process coppicing
Tree trunk close to ground level
Several new shoots grow from cut surface
Protect young shoots from grasses
Process repeated after certain time / rotational coppicing
What is pollarding
Repeatedly cutting tree stems HIGH up
This helps trees avoid being eaten by certain herbivores like deer
Aim of coppicing & pollarding
For new shoots to grow out of the stump
What’s rotational coppicing
When the stems of each section mature & grow larger before they are recur
-> so more light is let into diff habitats in the woodland
- maintains specifies biodiversity
= basically when trees are cut by section each year
Issues with large scale timber production versus how to reduce the issues
What are edge habits
Replanting trees @ optimal distance apart
- to avoid competition
What is selective cutting
Removing only larger / better trees from the habitat, so the rest are largely unaffected
Sustainable fishing methods
What is clear felling & how can it be improved
It’s cutting all the trees down in an area
Improved by:
- replant all the trees after
- only do it so often
- limit the area felled
Markscheme reasons why something would be conservation
- local people there
- sustainable use e.g. if an areas used for logging or farming
- active measures to maintain biodiversity or the habitat
Why can controlled grazing be better than normal
Normal overgrazing can disrupt the food chain
Peat bogs need high levels of moisture: what implementations can you do make sure of this
No planting of trees as they’ll remove water from the bog
No ditch as it will drain water from the bog
No ‘controlled burning’ etc - may lead to death in rare species organisms
Reasons why something may be preservation (ms)
E.g. no visitors allowed, or restricting human interference e.g. tree planting
How to make clear felling SUSTAINABLY
limit the size of the area felled,
Replant the trees that have been felled after
Limit the soil erosion after felling by limiting the area felled too
Benefits of coppicing
- fewer large trees = more light for smaller plants
- prevents succession
- provides variety of light levels
- large machinery not needed
- maintains soil quality
Other measures of sustainable fishing (ms) and difficulties with implementing them
- fishing quotas (area too large?)
- monitoring & surveillance after implementing restrictions (expensive to monitor & hampered by weather / seasons)
- penalties & sanctions (people could false report their fishing)
