population dynamics
what is the carrying capacity
the maximum population size of a species that can be sustained by a specific environment
is dynamic - can change over time as the accessibility of food and resources changes
what influences the carrying capacity
the availability of various resources (the competition with other species for limited resources)
is also influenced by the combination of various limiting factors
what does the density of a population mean
it means the number of individuals per unit area or volume
provides a measure of how closely packed individuals are within a certain space
what are density-dependent factors
factors that influence population dynamics, and their impact can vary depending on the population density
have a greater impact on population size as there is an increase in population density
examples of these factors - predation, disease, competition for resources
what happens as the population size increases
increase of population size = limited availability of resources = competition between organisms
competition = decreased/reduced reproductive success, decreased growth rates & higher mortality
higher population density also = allows the spread of disease & risk of predation = decrease in population growth
what is negative feedback
a mechanism where a system responds to changes in its internal or external environment by reversing the direction of change, which maintains homeostasis
do density-dependent factors act as negative feedback?
yes, they do act as negative feedback, as they help regulate population size, & keep it closer to the carrying capacity of the environment
populations typically increase due to reproduction, but density-dependent factors help to reduce the population & keep it closer to the carrying capacity
what’re density-independent factors
factors that influence populations regardless of their density or size
they’re external to the population & can cause unexpected changes
ex: natural disasters, such as floods or earthquakes
can destroy habitats, which affects the survival rate of individuals
anthropogenic factors (are caused by humans) are also an example of density-independent factors
why do density-independent factors have such a strong influence or effect on the ecosystem
they affect the availability of resources, which changes the carrying capacity of an ecosystem
when does exponential growth occur
it occurs in populations under ideal conditions, where there is unlimited access to resources & abiotic factors are favourable
this pattern is often seen in bacterial populations grown under lab settings
bacteria can reproduce continuously & rapidly under the right conditions
what are some factors that limit exponential growth
basically limiting factors
the amount of nutrients, competition for resources, parasitism & predation
when does the Sigmoid population growth occur
in environments with limited access to resources
when there is abundance of resources & low competition, there is exponential growth
when the population size increases, density-dependent factors become involved & limit the population growth
decrease in availability of resources = gradual decrease in growth rate
what happens over time in the Sigmoid population growth
the population reaches a steady-state equilibrium around carrying capacity of environment
at this point, birth rate=death rate & population stabilises
S-shaped curve represents transition from rapid exponential growth to a gradual increase until reaching carrying capacity
info on graphing population growth
recommended to use a logarithmic scale for the population size on y-axis
allows for better visualisation of changes in population size (compresses data=easy to observe patterns & trends)
non-logarithmic scale for time on x-axis
maintains a linear representation of time, ensuring accurate understanding of data
what may deviations from the population graph indicate
it may indicate that other factors are influencing population dynamics (ex: density-dependent limitations or environmental limitations)