Populations

Multiple Choice

Which of the following is a biotic factor that could affect an ecosystem?

• Geological formations
• Weather patterns
• Landslide

• Predator species growing in size

Multiple Choice

Which example of an abiotic factor could affect an ecosystem?

• Low precipitation

• Herbivores

• Bacteria
• Predators

Labeling

Label the water cycle

Drag labels to their correct position on the image

Evaporation

Condensation

Run off

Precipitation

Labeling

Place the labels

Drag labels to their correct position on the image

Tertiary Consumer

Secondary consumer

Primary consumer

Producer

Labeling

Who is an autotroph and who is a heterotroph

Drag labels to their correct position on the image

Heterotroph

Heterotroph

Heterotroph

Autotroph

Multiple Choice

What is an invasive species?

• A native species that benefits the environment
• A species that is not harmful to the ecosystem
• A species that does not compete with local wildlife
• A non-native species that causes harm to the environment, economy, or human health.

Multiple Choice

What is a non-native species?

• A non-native species is a species that is not originally from a specific area or region, but has been introduced there by human activity.
• A non-native species is a species that is only found in one specific region.
• A non-native species is a species that is introduced to an area by natural means.
• A non-native species is a species that is originally from a specific area or region.

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UNIT 7

ECOLOGY

OBJECTIVES FOR TODAY

(a) Understand population dynamics, carrying

capacity, & limiting factors for population

growth.

(b) Explain the effects of uncontrolled
population growth on the Earth’s resources.

Take out
your
guided
notes.

Population

3

All the members of a particular species in
geographic area.

Examples:

- All the HUMANS in Charlotte
- All the DEER in Blue Ridge Mountains
- All the BACTERIA in a human gut.

Population Characteristics

4

1. Geographic Distribution – The area

inhabited by a population

2. Density - the number of individuals per

unit area

3. Growth Rate – how fast the population

grows

Population Size & Growth

5

Three factors can affect population size:

1. The number of births (nacimientos)
2. The number of deaths (muertes)
3. How fast the population numbers grow

How Populations Grow

6

Populations grow when the birth rate is HIGHER
than the death rate!

A formula to calculate population growth is:

If your outcome is a POSITIVE number, then your
population is GROWING.

​

(# Births – # Deaths)/Total Population

​

Other Growth Factors
(Otros factores de crecimiento)

7

Immigration🡪 organisms move into an area.

Populations can also grow or decline depending
on how many individuals move to or away from
an area.

​

Emigration🡪 organisms move out of (or exit)
an area

Types of Population Growth
(Tipos de crecimiento de la población)

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There are two types of population growth:

- Exponential Growth

(Crecimiento exponencial)

- Logistic Growth

(Crecimiento logístico)

Exponential Growth
(Exponencial)

10

- Looks like a J Curve
- Under ideal conditions with unlimited

resources, a population will grow
exponentially.

- This occurs when individuals in a

population reproduce at a constant rate.

- Population doubles regularly.

11

Exponential Growth

12

The IDEAL conditions for

Exponential Growth are rare

!!!

Logistic Growth
(Logístico)

13

- Looks like an S curve.
- Occurs when population growth slows or

stops AFTER a period of exponential
growth

Q: Why does this happen?
A: LACK OF RESOURCES and LACK OF
SPACE

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Logistic Growth

16

DO YOU THINK THE
HUMAN POPULATION
GROWS
EXPONENTIALLY OR
LOGISTICALLY?
Why or why not?

17

Logistic or
exponential?
Why or why

not?

Multiple Choice

How does the increasing human population affect the natural resources we use?

• It increases the supply of resources

• 1. It decreases the amount of resources. 

• 1. It results in less demand for resources. 

• 1. It improves the quality of the resources.

Carrying Capacity
(Capacidad de carga)

20

When a population is in logistic growth, we
say it has met its carrying capacity

Carrying Capacity → the largest number of
individuals that a population can support

Q: What is the growth rate when population is
at carrying capacity?→A:ZERO

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Carrying Capacity

22

What are some
ABIOTIC & BIOTIC
factors affect
carrying capacity
(i.e., how big a
population can
grow)?

Multiple Choice

What are abiotic factors?

• Abiotic factors are non-living components of an ecosystem.
• Abiotic factors are responsible for photosynthesis in plants.
• Abiotic factors are only found in aquatic environments.
• Abiotic factors are living components of an ecosystem.

Multiple Choice

What are biotic factors?

• Inanimate objects in nature
• Non-living components of an ecosystem
• Living components of an ecosystem
• Artificial elements in the environment

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BIOTIC FACTORS

ABIOTIC FACTORS

- Amount of food
- Amount of

organisms
competing for food

- Space
- Water
- Climate

Limiting Factors

24

Any biotic or abiotic factor in an ecosystem that
causes population growth to stop.

Examples:
- Parasitism
- Disease
- Drought
- extreme weather

Two Types of Limiting Factors

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1. Density-Dependent

2. Density-Independent

Density-Dependent Factors

26

The effect on the population depends on
population size.

Become limiting only when the population
density reaches a certain level

These factors operate most strongly when a
population is large and dense.

Density-Independent

28

Affect all populations in similar ways, no
matter the population size.

Most density-independent factors are
abiotic, or nonliving.