Posts Tagged ‘Carrying capacity’

  • Explain the concepts of limiting factors and carrying capacity in the context of population growth.
Carrying  capacity is the maximum number of organisms that an area or ecosystem can sustainably support over a long period of time.
There are however limiting factors including temperatures, water and nutrient availability. The main factors are temperature and water availability.
Limiting factors are factors that limit the distribution or numbers of a particular population. Limiting factors are environmental factors which slow down population growth.
Temperature:
There are many ways the temperature can affect species. For example some seeds only grow in extremely high temperatures as it enriches the soil with nutrients and kills competition. However some are damaged if they are too warm or too cold. Some are able to survive low temperature. Animals adapt to the hot/ cold temperature either by burrowing under the ground to avoid heat or having cold blood in the heat.
Water:
All plants/animals need water to survive, for plants have no water could cause the plant to not germinate or seeds to die. No water = Death.
  • Describe and explain S and J populations curves.
S-curve (Sigmoidal) : population growth curve that shows a rapid growth at the beginning then a slow down as the carrying capacity is reached.
J-curve:
A population curve which shows only exponential growth. It starts slow the becomes increasingly fast.
  • Describe the role of density-dependent and density-independent factors, and internal and external factors, in the regulation of populations.
Density-dependent factors:
Factors that lower the birth rate or raise the death rate as a population grows in size. They are negative feedback mechanisms leading to the stability or regulation of the population.
When prey increases so does the predator, but when this occurs the prey decreases and then again the predators decrease too causing the prey to increase again.
Density-independent factors:
Factors that affect a population irrespective of population density notably environmental change. Abiotic factors are density-independent factors, the most important ones are the extremes of weather (droughts, fires and hurricane) and long-term climate change.
These factors have an impact that can increase the death rate and reduce the birth rate, it all depends on how severe the event was.
Factors which regulate population size can be divided into either INTERNAL or EXTERNAL.
Internal:  fertility rates, territory sizes
External: predation, pressure, parasitism
The major cause of population regulation are in the environments, these can be physical or biological.
The physical class of environmental factors are water availability, nutrient availability anf so on.
Biological factors include predators, and competition.
Ways humans can cause population growth:
  • increase available resources
  • reduce competition
  • reduce pressure from predators
  • introduce animals to new areas
Ways to decline population:
  • change environment, cause habitat disruption
  • change the biological environment by introducing new species
  • cause secondary extinctions
  • overkill
  • Describe the principles associated with survivorship curves including, K and r strategists.
Survivorship curves and r and k strategists:
K-strategists are slow growing and produce few, large offspring that mature slowly.
R-strategists, slow and mature quickly and produce many, small offspring.
K= carrying capacity
R= growth rate
K-strategist:
  • low reproductivity
  • large investment in parental care
  • late maturity/longer living
  • slow growth
  • larger size
  • require stable environment
R-straegists:
  • high reproductivity
  • short life
  • low investment in parental care
  • early maturity
  • rapid growth
  • small organisms
  • highly adaptable
  • large number of few species
Survivorship rates:
What influences survivorship rates:
  • competition for resources
  • adverse environmental conditions
  • predator-prey relationships
Example of survivorship curve:
  • curve for species where individuals survive for their potential life span, and die at the same time. Salmons/humans (K-strategists)
  • curve for species where individuals die young but who survives lives very long life turtles/ oysters. (r-strategists)
  • Describe the concept and processes of succession in a named habitat.
Succession: Change in the community structure of a particular area over time.
Primary succession: colonization of newly created land by organisms (rock).
Secondary succession: occurs in places where a previous community has been destroyed. (forest/fire) It is faster than primary succession because of the presence of soil and a seed bank.
Pioneer= earliest community of the succession.
Climax community= the last and final community.
The change from pioneer to climax is called a sere.
Succession is the process of change over time in a community changes in the community of organisms frequently cause changes in the physical environment that allow another community to become established and replace the former through competition. They get more complex at the end.
Zonation:
The arrangement or patterning of plant communities or ecosystems into bands in response to change, over a distance, in some environmental factor.
The main biomes display zonation with altitude on a mountain, or around the edge of a pond in relation to soil moisture.
  • Explain the changes in energy flow, gross and net productivity, diversity and mineral cycling in different stage of succession. 
GP, NP and diversity will change over time as a ecosystem goes through succession. GP is low in early stages then increases as soils become more structured. As food webs become more structured NPP and diversity stabilize as the ecosystem reach climax population.
  • Describe factors affecting the nature of climax communities. 
Climax community:
  • greater biomass
  • higher levels of species diversity
  • more favourable soil condition
  • better soil structure
  • lower pH
  • taller and longer living plant species
  • more k-strategies or fewer r-strategist
  • greater habitat diversity
  • steady state equilibrium
Climate and edaphic factors determine the nature of a climax community. Human factors frequently affect this process through, for example; fire, agricultures, grazing and/or habitat destruction.
  • Explain difficulties in applying the concept of carrying capacity to local human populations.

If one were to examine the needs of a given species and the resources available, it could be possible to estimate the carrying capacity of that environment for the species. This is problematic when it comes to the human population for many reasons like:

  • Resources used by humans are much more than any other species and when this source becomes limited humans begin to substitute one resource for another. The use of resources change from person to person, lifestyle to lifestyle, time to time and population to population.
  • Developments in technology increase the changes of the resource consumption.
  • The human population also import resources very often which come from outside their environment, which makes the grow beyond the boundaries set by their local resources and lets their carrying capacity increase. This however does not affect the global carrying capacity.

These variables make it almost impossible to make reliable estimates of carrying capacities for the human populations.

*Carrying capacity: The maximum number of a species or ”load” that can be sustainably supported by a given environment.

Here we can see 3 models of a population growing and approaching carrying capacity.

*Optimum population: the number of people which when working with all the available resources, will make the highest per capita economic return. it shows the point at which the population has the highest standard of living and quality of life.

Standard of living is the result of the interaction between physical and human resources and can be expressed as:

Standard of living: (natural resources X technology) / population

*Over-population: this happens when there are too many people compared to the resources and technology available for the standard of living. They suffer from natural disasters such as droughts and famine, low incomes, poverty, poor living conditions and a lot of emigration.

*Under-population: this happens when there are too many resources in one area that is too much for the people living there. Countries like this could export their surplus food, energy and mineral resources.

  • Explain how absolute reductions in energy and material use, reuse and recycling can affect human carrying capacity.

Human carrying capacity is determined by the rate of energy and material consumption, the level of pollution and the extent of human interference in global life-support systems. While reuse and recycling reduce these impacts, they can also increase the human carrying capacity.

*Recycle: when a household or industrial waste is reused and made into another product, like plastic, metals and paper.

*Re-use: when a product is used more than once by returning it to the manufacturer or processor each time. This is very energy efficient and more efficient than recycling.

*Reduce: this is when energy use is decrease for example turning off the lights when not needed or using the amount of water needed in a kettle.

*Substitution: when using one resource over the other, the use of renewable source over a non-renewable source is a major benefit to the environment.