Factors Affecting Population Growth

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Questions and Answers

What does the rate of growth (r) equal?

Births + Emigration – Deaths + Immigration

Births – Deaths + Immigration + Emigration

Births + Deaths + Immigration – Emigration

Births + Immigration – Deaths – Emigration (correct)

Which of the following statements about mortality is true?

Mortality is connected only to the birth rate.

Mortality can be influenced by an organism's life span. (correct)

Mortality rate is unaffected by environmental factors.

All organisms have the same mortality rate.

Which pair of factors lead to population growth?

Deaths and Emigration

Births and Immigration (correct)

Immigration and Deaths

Births and Emigration

What pattern do many larger mammals follow regarding offspring survival?

High juvenile survival with few offspring. Signup and view all the answers

Which of the following contributes negatively to the rate of growth?

Deaths Signup and view all the answers

What best describes organisms that have equal likelihood of dying at any age after infancy?

Type II survivorship curve Signup and view all the answers

What happens to birth rates when there are food shortages?

Birth rates can decline. Signup and view all the answers

What is the primary effect of high population density on desert locusts?

They group together in swarms and change behavior. Signup and view all the answers

What allows the desert locust to go from solitary to swarming behavior?

Increased food supply leading to quick reproduction. Signup and view all the answers

Which regions are notably affected by swarms of desert locusts?

Northern Africa, the Middle East, and Asia. Signup and view all the answers

How much food can a single swarm of locusts consume in a day?

The equivalent of 500,000 people's needs for a year. Signup and view all the answers

What historical significance do records of locust plagues hold?

They have become part of cultural folklore and religious texts. Signup and view all the answers

What is the typical life cycle behavior of desert locusts during calm periods?

They remain confined to the Sahara Desert. Signup and view all the answers

What is a risk posed by the biotic potential for reproduction in desert locusts?

They can lead to significant agricultural destruction. Signup and view all the answers

What is the average distance that a locust swarm can travel in a single day?

100 km per day. Signup and view all the answers

What happens to locust numbers under typical desert conditions?

They remain under control. Signup and view all the answers

What term describes the curve that illustrates mortality rates being consistent with age?

Survivorship curve Signup and view all the answers

Which type of factors are typically affected by the population size?

Density-dependent factors Signup and view all the answers

What is the effect of abiotic factors on populations?

They can affect populations regardless of size. Signup and view all the answers

What ecological principle explains the oscillation of predator and prey populations?

Lotka–Volterra model Signup and view all the answers

What is a primary consequence of intraspecific competition?

Stronger individuals surviving Signup and view all the answers

Which type of factors could lead to high mortality rates during a population overshoot?

Density-dependent factors Signup and view all the answers

Which of the following best illustrates abiotic factors affecting populations?

Seasonal changes in climate impacting plant growth Signup and view all the answers

How do occasional abiotic disturbances like fire affect ecosystems?

They can rejuvenate plant communities and facilitate seed release. Signup and view all the answers

What might cause stress-related diseases among organisms in high-density populations?

Competition for territory and mating Signup and view all the answers

What is the relationship between seed or egg production and survival rates in many species?

Producing more offspring ensures that some will survive despite predation. Signup and view all the answers

Which factor is NOT a biotic factor affecting populations?

Nutrient availability in soil Signup and view all the answers

How do successful individuals in a species typically contribute to population sustainability?

They secure more resources, increasing their fitness. Signup and view all the answers

What is a common outcome of density-independent factors impacting a population?

Mortality or reproduction unaffected by population size. Signup and view all the answers

What is the potential impact of a hurricane on a population?

It can have devastating or beneficial effects depending on the ecosystem. Signup and view all the answers

Study Notes

Population Growth Factors

Rate of growth is calculated as (Births + Immigration) – (Deaths + Emigration)
This model applies to both human and animal populations.
Birth rates vary between species and can decline due to factors like food shortages or stress.
Emigration is the departure of individuals from a population.
Deaths, or mortality, have patterns influenced by environmental factors and an organism's natural lifespan.
Life spans greatly vary, from minutes for microorganisms to thousands of years for bristlecone pines.

Survivorship Patterns

Different organisms exhibit different survivorship curves.
Some, like whales and elephants, have high juvenile survival and low adult mortality.
Others, like seagulls and mice, have roughly constant mortality rates across their lifespan.
Organisms producing numerous offspring, like fish and trees, often have high initial mortality but high survival past reproduction.

Factors Affecting Population Dynamics

Factors can be intrinsic (within the population) or extrinsic (outside the population), biotic (living) or abiotic (non-living).
Biotic factors include predators, competitors, prey, and their abundance.
Abiotic factors are environmental conditions like climate, soil type, water, and occasional events like fires, floods, and droughts. These can have positive or negative impacts.
Some factors are density-dependent (e.g., predation, competition, spread of disease) affecting populations based on their size.
Other factors are density-independent (e.g., fires, droughts), affecting populations regardless of their size.

Population Interactions

Predation can benefit a population by keeping its numbers in check, eliminating weak members. Predation–prey populations may oscillate.
Intraspecific competition (within a species) drives competition for resources like food, mates, and territory.
Territories regulate access to resources and limit competition within a species.
Stress and crowding can negatively impact reproduction and increase mortality in dense populations.

Case Study: Desert Locust

Desert locusts usually live solitary lives as grasshoppers.
During periods of high rainfall and vegetation growth, locust populations surge, leading to density-dependent changes.
Locusts form enormous swarms, migrate, and cause devastating crop damage.
This cyclical boom-and-bust population dynamics can affect agricultural livelihoods for substantial portions of the global population.
Actions by the Food and Agriculture Organization (FAO) have been taken in recent years to mitigate the impact of these swarms on various regions.

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Description

Explore the various factors influencing population growth and dynamics in both human and animal species. This quiz covers concepts such as birth rates, mortality patterns, survivorship curves, and the impact of environmental factors on populations. Test your understanding of how these elements contribute to the overall population changes.