Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
A population is a group of organisms of one species, living in the same area at the same time.
The Sigmoid Growth Curve describes the growth of a population in an environment with limited resources. It consists of four main phases: the lag phase (slow initial growth), the log (exponential) phase (rapid growth where birth rate exceeds death rate), the stationary phase (birth rate equals death rate due to limiting factors), and the death phase (death rate exceeds birth rate).
Limiting factors are components of an ecosystem that restrict the growth of a population. These are categorized into abiotic factors (e.g., temperature, availability, light intensity, ) and biotic factors (e.g., predation, competition for food, and spread of disease).
The carrying capacity, denoted as , is the maximum number of individuals of a particular species that a specific environment can support sustainably without degrading the resource base.
Community refers to all the populations of different species living and interacting in the same ecosystem.
Human population growth has followed an exponential pattern due to technological advances in agriculture and medicine, leading to increased emissions and habitat destruction.
Biodiversity is the range of different species living in an ecosystem. High biodiversity contributes to ecosystem stability and resilience.
📐Formulae
💡Examples
Problem 1:
At the start of , a nature reserve had a population of golden eagles. During the year, chicks were hatched, eagles died, eagles flew into the reserve from outside, and eagles left the reserve. Calculate the total population at the end of the year and the percentage growth rate.
Solution:
Final Population: . Percentage Growth Rate: .
Explanation:
First, the net change is calculated by adding births and immigration and subtracting deaths and emigration. Then, the percentage increase is found by dividing the change () by the original population () and multiplying by .
Problem 2:
Explain why a population of bacteria in a closed flask enters the 'Stationary Phase' after a period of exponential growth.
Solution:
In a closed system, the population reaches a point where the birth rate equals the death rate. This is caused by limiting factors such as the depletion of nutrients (e.g., glucose), the accumulation of toxic metabolic waste (e.g., or ethanol), and competition for physical space.
Explanation:
Growth is limited because the environment reaches its carrying capacity (), where resources are no longer sufficient to support more individuals than are currently dying.