APES Populations unit

What is population size?

Total number of individuals of the same species living in a defined area at a given time

Ex. 500 deer living in a national park

Population Density

Number of individuals per unit area

Population distribution

How individuals are distributed in respect to eachother

Population age structure

How many individuals fit into an age range by sex

Rule of 70

If a population grows at 1% it will take 70 years to double

Exponential growth( Geometric)

Growth at a constant rate of increase

Arithmetic growth

Growth at a constant amount per unit time

Intrinsic growth

Under ideal conditions with unlimited resources it would be a J-shaped curve

Growth Rate

Birth rate - Death rate

What factors increase population size?

• Births ( natality)

• Immigration ( Movement into a population)

Ex. Birds moving into a forest will increase the local bird population

What factors decrease population size?

• Deaths( mortality)

• Emigration ( movement out of a population)

Ex. A drought causes many plants to die, reducing population size

What is a survivorship curve?

A graph showing the production of individuals surviving at each age.

Ex. Humans show hight survival early in life and lower survival at old age.

What is a Type I survivorship curve?

Most individuals survive to old age; death occurs late in life.
Example: Humans, elephants.

What is a Type II survivorship curve?

Individuals have an equal chance of dying at any age.
Example: Birds, squirrels.

What is a Type III survivorship curve?

Many individuals die young; few survive to adulthood.
Example: Fish, insects, plants producing many seeds.

What are density-independent factors?

Factors that affect population size regardless of population density.

Examples:

• Hurricanes

• Fires

• Droughts

What are density-dependent factors?

Factors whose effects increase as population density increases.
Examples:

• Disease

• Competition

• Predation

Why is food availability a density-dependent factor?

As population density increases, food becomes limited, increasing competition.
Example: Too many deer → less grass → starvation.

What are biotic factors?

Living components that affect population growth.
Examples:

• Predators

• Competitors

• Parasites

What are abiotic factors?

Nonliving environmental factors.
Examples:

• Temperature

• Rainfall

• Soil nutrients

What is a metapopulation?

A group of populations separated geographically but connected by migration.
Example: Frog populations living in separate ponds connected by land movement.

What is minimum viable population (MVP)?

The smallest population size needed to survive long-term.
Example: Conservation programs aim to keep endangered species above MVP.

Why is genetic diversity important for population viability?

Low diversity increases extinction risk due to disease or environmental change.
Example: Inbreeding in small populations causes genetic disorders.

What is exponential (Malthusian) growth?

Rapid population growth with unlimited resources.
Shape: J-shaped curve
Example: Bacteria in ideal lab conditions.

What is logistic growth?

Population growth that slows as it reaches carrying capacity.
Shape: S-shaped curve
Example: Deer population stabilizing due to limited food.

What is carrying capacity (K)?

The maximum population size an environment can support sustainably.
Example: A forest can only support 200 deer without ecosystem damage.

What causes overshoot and dieback?

When a population exceeds carrying capacity, resources are depleted, causing a population crash.
Example: Reindeer overgrazing an island and then starving.

What are r-selected species?

Species that reproduce quickly with little parental care.
Examples:

• Insects

• Weeds
  Traits: many offspring, short lifespan.

What are K-selected species?

A: Species that reproduce slowly with high parental investment.
Examples:

• Humans

• Elephants
  Traits: few offspring, long lifespan.

What is the current global human population (as of late 2023)?

About 8.0 billion people.
Example: 8,019,396,121 people worldwide.

Where will most population growth occur in the next 50 years?

Africa and Asia.
Example: Many European countries have stable or declining populations, while African nations grow rapidly.

What factors have reduced human death rates?

• Increased food production and distribution

• Improved medical technology

• Better sanitation

• Access to clean water
  Example: Vaccines dramatically reduce childhood mortality.

What historical events caused major human population surges?

1. Use of tools and fire

2. Agricultural Revolution

3. Industrial & Medical Revolution
   Example: Agriculture allowed permanent settlements and food surpluses.

What is total fertility rate (TFR)?

The average number of children a woman has during her lifetime.
Example: A TFR of 2.1 maintains population size.

What factors affect total fertility rate?

• Cultural traditions

• Government policies

• Female education and job opportunities
  Example: Countries with more educated women tend to have lower TFRs.

Difference between developed and developing countries?

• Developed: High industrialization and income

• Developing: Low industrialization, income often <$3/day
  Example: Germany vs. Niger.

What is Crude Birth Rate (CBR)?

Number of births per 1,000 people per year.
Example: CBR of 20 = 20 births per 1,000 people.

What is Crude Death Rate (CDR)?

A: Number of deaths per 1,000 people per year.
Example: Wealthy countries average ~10; poorer countries ~20.

What is Zero Population Growth (ZPG)?

When births + immigration equal deaths + emigration.
Example: Population size remains stable over time.

What is Infant Mortality Rate (IMR)?

Deaths of children under age 1 per 1,000 live births.
Example: High IMR often indicates poor healthcare access.

What is Child Mortality Rate?

Deaths of children under age 5 per 1,000 live births.
Example: Higher in countries with infectious diseases.

What two indicators best measure quality of life in a country?

• Life expectancy

• Infant mortality rate
  Example: Japan = high life expectancy, low IMR.

Why is immigration controversial?

Job competition

• Strain on social services

• Labor rights issues
  Example: “Guest workers” often do low-paid, dangerous jobs.

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Why is immigration important in population dynamics?

ian significantly increase population size, especially in developed countries.
Example: Developed nations expect ~2 million immigrants per year.