Population is the group of organisms of same species living in in the particular habitat. forces that controlling the growth of a population are biotic potential (ability to reproduce at given rate and inherent the characteristic of a populations), environmental resistance (opposite to the growth (limited resources, pest, predators).
Limiting factors
population growth will be slower than their intrinsic rate of population.
- Density independent limiting factors – not related to size of the populations. E.g – flood, tsunami, volcanic activities
- Density dependent limiting factors – related to the size of the populations – E.g – predation, diseases, pests
Carrying capacity
Carrying capacity is the maximum number of individuals of a species that can be supported be their environment over sustained time period.
Different strategies of survival – r selection and K – selection.
R – selection Vs K – selection
| R – selected species | K – selected species |
| Population size usually fluctuates below the carrying capacity due to environmental disturbances | population size relatively stable, near the carrying capacity due to density dependent regulation. |
| short life span, die in young age | long life span, die older |
| body size relatively small | large body size |
| mature early | mature later |
| many offsprings | few offsprings |
| little parental care | extensive parental care |
| type 3; survivorship curve | type 1; survivorship curve |
Survivorship curves
Type 1 – low mortality rate at early ages and high mortality rate at old ages.
Type 2 – constant mortality throughout the lifespan.
Type 3 – high mortality rate at early ages and low mortality rate at old ages.
Population growth curves
J-shaped curve – the growth rate of the population is accelerated. (Human population growth)
S-shaped curve – first growth rate accelerated and reach to the maximum rate the rate slow down (sheep population in tasmania)
Boom – crash patten curve – exponential rapid growth of the population and rapid decline of the population. (Predator prey interactions)
Changes of the population size is influenced by fertility, mortality, migration.
Human population
Human carrying capacity is influenced by the various factors such as resources availability, technology, environmental impacts…, however the carrying capacity can not expand forever because
- Some resources are finite and non-renewable, e.g. fossil fuels and minerals.
- Some environmental impacts are irreversible e.g. such as biodiversity loss and climate change, pollution, some technologies give unintentional problems e.g. human settlement displacements.
Problems of the over populations
- Resource depletions – food, water, energy, ana other renewable and non renewable resources are depleting rapidly.
- Environmental degradation due to pollution, deforestation, climate changes,loss of biodiversity, reduce the water quality due to fertilizers, chemicals, sewage…
- Collapse the infrastructures – transportation, public services… are strain due to overcrowding
- Diseases are spread faster causing new pandemics and epidermis
- Risk of unemployment
References:
- Survivorship curve – Wikipedia. (n.d.). Survivorship Curve – Wikipedia. https://en.wikipedia.org/wiki/Survivorship_curve
- Biological exponential growth – Wikipedia. (2022, January 15). Biological Exponential Growth – Wikipedia. https://en.wikipedia.org/wiki/Biological_exponential_growth
- File:Logistic Carrying Capacity.svg – Wikimedia Commons. (2019, May 21). File:Logistic Carrying Capacity.svg – Wikimedia Commons. https://commons.wikimedia.org/wiki/File:Logistic_Carrying_Capacity.svg
- Lotka–Volterra equations – Wikipedia. (2010, March 22). Lotka–Volterra Equations – Wikipedia. https://en.wikipedia.org/wiki/Lotka%E2%80%93Volterra_equations