8.4 Effect of Density of Populations

• The formula for population density is Number of Individuals divided by Area Occupied.


  True
• The availability of food, water, shelter, and other essential resources is referred to as resource availability
• Factors like predation, disease, and environmental stresses increase mortality rates.
• Density-dependent factors are environmental influences that increase with population density.


  True
• Disease spreads more easily in dense populations, increasing mortality.


  True
• If there are 50 deer in a 10 square kilometer forest, the population density is 5 deer per square kilometer.


  True
• Order the density-dependent factors from most to least likely to reduce population growth:

  1️⃣ Disease

  2️⃣ Predation

  3️⃣ Competition

  4️⃣ Parasitism

  5️⃣ Territoriality
• What effect does competition have on population growth and survival rates?

  Reduces growth and survival
• How does territoriality limit population density?

  Restricts breeding individuals
• Deer competing for limited grazing lands during a dry season is an example of competition as a density-dependent factor.


  True
• What are density-independent factors?

  Environmental influences affecting populations regardless of density
• How does a wildfire affect a forest population regardless of its density?

  Decimates the entire forest
• Pollution from industrial waste is an example of a human activity that acts as a density-independent factor
• What is the key difference between density-dependent and density-independent factors?

  Density-dependent factors are affected by population density, while density-independent factors are not
• How does resource availability affect population density?

  Supports or limits population numbers
• How does predation act as a density-dependent factor?

  Predators target abundant prey
• Density-dependent factors are environmental influences whose impact intensifies as population density increases.
• Predation controls prey population size as density rises.


  True
• What do parasites thrive in dense host populations reduce?

  Fitness and survival
• Density-dependent factors become more influential as population density rises.


  True
• What is the primary effect of density-dependent factors on populations?

  Regulatory mechanisms
• Severe weather events like storms are examples of density-independent factors.
• Order the following density-independent factors based on their examples:

  1️⃣ Severe Weather

  2️⃣ Natural Disasters

  3️⃣ Climate Change

  4️⃣ Human Activities
• Density-dependent factors can override density-independent effects on populations.

  False
• High population density can lead to increased competition, disease, and predation.
• Increased competition for resources can reduce growth and survival rates
• Low population density allows individuals to thrive due to reduced competition
• Match the population density with its effects:

  High ↔️ Increased competition, disease, predation

  Low ↔️ Reduced competition, disease, predation
• Higher disease transmission rates are associated with high population density.


  True
• Match the population density with its effects:

  High ↔️ Increased competition, disease, predation

  Low ↔️ Reduced competition, disease, predation
• Severe droughts are an example of a density-independent
• What are two density-dependent factors affecting the songbird population in the urban park?

  Territoriality, disease
• Population density is calculated by dividing the number of individuals by the area
• Higher reproduction rates lead to lower population densities.

  False
• Match the factor affecting population density with its effect:

  Resource Availability ↔️ Limits individuals supported

  Reproduction Rates ↔️ Increases population density

  Mortality Rates ↔️ Decreases population density

  Migration ↔️ Impacts local population density

  Habitat Size and Quality ↔️ Constrains maximum density
• Competition for limited resources reduces growth and survival rates.
• Match the density-dependent factor with its example:

  Competition ↔️ Deer competing for grazing lands

  Predation ↔️ Wolves preying on deer

  Disease ↔️ Flu outbreaks in urban areas

  Parasitism ↔️ Ticks infesting deer

  Territoriality ↔️ Songbirds maintaining territories
• Species with higher birth rates and reproductive success achieve higher population densities.
• Density-dependent factors are environmental influences whose impact intensifies as population density
• Disease spreads easily in dense populations, leading to increased mortality