Environmental Science 4.3-Population Growth

Chapter 4.3-Population Growth

Multiple Choice

Which is the simplest level of organization within the environment?

• cell

• organism

• population

• community

Multiple Choice

Which term refers to the study of organisms and their interactions within the environment?

• biosphere
• niche
• ecology
• habitat

Multiple Choice

Which term refers to the place where an organism obtains everything they need to survive?

• biosphere
• habitat
• niche
• ecology

Multiple Choice

Similar organisms that can reproduce with each other are considered to be members of the same _______________.

• community

• species

• biosphere

• ecosystem

Multiple Choice

All the alligators in the same area are an example of a(n) _______________.

• organism

• community

• population

• group

Multiple Choice

Study of populations in relation to environment, including environmental influences on density and distribution, age structure, and population size.

• population ecology

• community ecology

• ecosystem ecology

• biosphere ecology

Multiple Choice

Number of individuals per unit area or volume.

• denisty

• dispersion

• survivorship

• immigration

Lesson Objectives

• Describe the factors that influence a population's growth rate

• Explain Exponential growth and logistic growth

• Explain how limiting factors and biotic potential affect population growth

Open Ended

Bacteria can reproduce once in about four minutes. A whale can reproduce once in a year. Why do you think there is such a large time difference between the two organisms?

Population Growth

• A population increases in size when more individuals enter the population than leave it

  • Entering includes births and immigration

• A population decreases in size when more individuals leave the population than enter it

  • Leaving includes death and emigration

Birth and Death Rates

• Natality: the rate at which individuals are born

• Mortality: The rate at which individuals die

• Both Values are expressed as a number per 1000 individuals over a given time

Survivorship Curves

• Individuals of different ages have different probabilities of dying

• Survivorship Curve: a graph that shows how the likelihood of death varies with age

  • Three types of curve

    • Type I

    • Type II

    • Type III

Type I: Survivorship Curve

• Type I: Most individuals survive young and die old

  • Example: Humans- More 80 year old people die than 10 year old

Type II: Survivorship Curve

• Type II: An Individual's age does not affect the probability of their death

  • Example: Most bird species

Type III: Survivorship Curve

• Type III: Most Individuals die young and adults are more likely to survive

  • Examples: Many plants and amphibians

Multiple Choice

A graphic way of representing the data in a life table.

• survivorship curve

• exponential growth curve

• logistic growth curve

• lag phase

Multiple Choice

If the number of births in a population is the same as the number of deaths in a population, what will happen to the growth of the population?

• It will increase.
• It will decrease.
• It will stay the same.
• It will fluctuate.

Multiple Choice

Which Survivorship Curve describes populations whose mortality is highest at young ages

• Type I

• Type II

• Type III

Immigration and Emmigration

• Individuals in an animal population move around and can leave the population and join another one

  • Immigration: the arrival of individuals from outside the population

  • Emigration: The departure of individuals from a given area

Migration

• Sometimes animals leave an area as part of a seasonal routine

• Migration: The Seasonal Movement into and out of an area

  • This can lead to large population growth for limited periods of time that eventually return to normal

Calculating Population Growth

• We can show the population growth with the following equation

  • A positive growth is an increase,

  • A Negative growth is a decrease

Calculating Population Growth Example Problem

• A population's birthrate is 18 per 1000 and its death rate is 10 per 1000. In the same year, 5 individuals joined the population and 7 emigrated. What is the population growth?

Calculating Population Growth Example Problem

• A population's birthrate is 18 per 1000 and its death rate is 10 per 1000. In the same year, 5 individuals joined the population and 7 emigrated. What is the population growth?

Fill in the Blank

• A population's birthrate is 18 per 1000 and its death rate is 10 per 1000. In the same year, 5 individuals joined the population and 7 emigrated. What is the population growth rate per 1000 individuals?

Calculating Population Growth Example Problem

• We can turn the Growth rate into a percentage that can be used to predict changes over time

  • Example: the growth 6/1000 individuals

How populations Grow

• Growth rates are not a static measurement and can change depending on conditions at any given time

• There are two main modes of population growth

  • Exponential Growth

  • Logistic Growth

Exponential Growth

• Exponential growth: When a population increases by a fixed percentage each year

  • Let's say we have a population of 1,000 individuals that has a growth rate of 10%

    • After the first year, they will increase by 10% (100) and have a total of 1100 in the population

    • After the 2nd year, they will increase by another 10% (110) and have a total of 1210

Exponential Growth

• Exponential Growth occurs when the starting population is small and conditions are ideal

• Makes a J-shaped graph

Limiting Factors

• Exponential growth can only last a short time

  • Eventually, some resources run out

• Limiting Factors: Characteristics of the environment that limit a population growth

• Carrying Capacity: The Largest population size an environment can support

Logistic Growth

• Logistic growth: A population grows exponentially until it comes close to the carrying capacity, and then slows/stops

  • If Carrying capacity is exceeded, the population will decrease back down to the carrying capacity

Population Growth in Nature

• In reality, both curves are very simplified models of populations

• Carrying capacities can fluctuate depending on the circumstances

Multiple Choice

The Largest number of individuals of a population that the environment can support is called the ___________

• carrying capacity

• population

• biome

• mutualism

Multiple Choice

What type of growth is shown in the diagram?

• exponential growth

• logistic growth

• predator-prey cycle

• boom-bust curve

Multiple Choice

When a population grows past the ecosystem's carrying capacity, what most likley happens to the population?

• Continues to grow

• The population starts to die off to return to carrying capcity

• The population will go completely extinct due to lack of resources

Multiple Choice

What is the carrying capacity for this sheep population?

• 2.0 million

• 1.0 million

• 1.6 million

• 0.5 million

Limiting Factors

• Limiting Factors can slow population growth

  • can be sorted into two categories

    • Density Dependent

    • Density Independent

Density-Dependent Factors

• Density-Dependent Factors: factors whose influence changes depending on how large the population is

  • The more individuals, the more competition for resources

    • Food, water, shelter

  • Larger populations have more chance for disease to spread and predators to attack

Density-Independent Factors

• Density-Independent Factors: Factors whose influence is not affected by the size of the population

  • Includes factors like catastrophic events and severe weather

Biotic Potential

• Individuals in a population affect how a population grows just as much as the environment they exist in.

• Biotic Potential: The maximum ability of individuals to reproduce in ideal conditions

Factors that influence Biotic Potential

• Gestation Time: How long it takes for offspring to develop before birth

• Generation time: How long it takes for an individual to reach reproductive age

• Number of Offspring Produced

Categorize

Options (8)

disease

Available Water

Available Food

Predators

Heavy Rain

Low Sunlight

Late Winter

An Earthquake

Organize the following factors into Density-Dependent and Density-Independent

Density Dependent

Density-Independent