Population Ecology Lesson

But first, lets check your bellringers!

Multiple Choice

In an ecosystem, a sudden decrease in the number of bacteria in the soil would most likely result in...

• Increased water pollution in the soil

• Increased precipitation and flooding of the soil

• A reduction in the amount of nitrogen available to the ecosystem

• A decrease in the number of fossils formed in the soil

Multiple Choice

Which of the following descriptions about the organization of an ecosystem is correct
(Remember, sometimes we say 'Species' to represent an individual organism)

• Communities make up species, which make up populations.

• Populations make up species, which make up communities.

• Species make up communities, which make up populations.

• Species make up populations, which make up communities.

Drag and Drop

In the water cycle, water continuously moves between different places on Earth. Water ​

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from liquid water to gas. When it cools, it undergoes ​

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and returns to the earth through ​

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. A special type of evaporation of water from plants is known as ​

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, which also returns water to the atmosphere.

Drag these tiles and drop them in the correct blank above

evaporates

condensation

precipitation

transpiration

Match

Match the following

• A zebra

• A group of zebras

• zebras, elephants, and trees together

• zebras, elephants, trees, temperature, water and air

organism

populations

community

Ecosystem

• organism

• populations

• community

• Ecosystem

Population Density

Population density is a
measurement of the number of
individuals living in a defined space.

Population density is controlled by
biotic and abiotic factors of
an ecosystem.

Population Size Depends on…

Number of births

Number of deaths

Number of individuals who leave a population
(emigrate)

Number of individuals who enter a population
(immigrate)

Emigration

Vs

Immigration

• Emigration: Is the movement of an individual out of a

population (Emigrate = Exit)

• Immigration: Is the movement of an individual into a

population (Immigrate = In)

Exponential Growth

• If a population has unlimited resources, and limited predators and

diseases, the populations will grow exponentially.

• Exponential growth occurs when the individuals of a population

reproduce at fast and constant rate

• The graph has a J-shaped curve

Exponential Growth

•Populations in natural world cannot continue to grow
exponentially because the resources are limited
•Logistic Growth occurs when a population's growth slows
or stops following a period of exponential growth
•This graph has an S-shaped curve

Logistic Growth

Stages of The Logistic Growth

What do you think might cause the decline in the
population size?

Word Cloud

Really, what do you think might cause a steady decline in population size?

Carrying Capacity
•The maximum population size

that the environment can
normally support by providing
all life resources (like food,
water, space, and mates).

Carrying capacity is the factor that levels up the
population growth curve (into a steady state)

Draw

DRAW the carrying capacity onto the graph!

Practice

• What is the approximate

carrying capacity of this
population?

Answer

What is the approximate
carrying capacity of this
population?

80

Limiting Factors

•Biotic and abiotic factors that
affect (limit) the growth of a
population.
•Two types of limiting factors:

1.

Density dependent

2.

Density independent

Density Dependent Limiting Factors

•Depend on the population size
•The larger the population size , the stronger the effect
of density dependent limiting factors
•Examples

•Competition
•Predation
•Diseases
•Parasitism
•Living resources (food, water and space)

What could be a limiting factor for the plants living in the
forest floor?

Word Cloud

What could be a limiting factor for plants living on the forest floor?

Density Independent Limiting Factors

•Affect all populations in similar ways regardless of

population size.

•Examples

•Natural disasters & unusual weather

• Drought/Flooding
• Sever storm/Tornados/lightening
• Volcano/Earthquake
• Temperature & Salinity (amount of salt)

Practice

• Q1: When do a population reaches the carrying capacity?

• Q2: What is a limiting factor?

Answer

• Q1: When do a population reaches the carrying capacity?
• Answer: When the living resources in the population’s

environment become less available (decrease)

• Q2: What is a limiting factor?
• Answer: A factor (biotic or abiotic) that causes population

growth to decrease.

Draw

Mark Density Depending factors with BLUE or GREEN.

Mark Density Independent factors with RED or ORANGE

Answer

The circled ones are density independent limiting
factors, and the rest are density dependent.