Monday, January 23, 2012

• Homework: Short Checkup on Population Growth on block day.

• Semester test review due Friday (January 27)

(yes, it counts as a grade)

• Make up missed food web checkup if missed.

• Make a new logbook entry-

Limiting Factors and Carrying Capacity- 1/17/12

Get a sheet in plastic (1 per person) from the front counter

• Read the information about carrying capacity and limiting factors and answer questions 1, 2, and 3 in your logbook.

1. Define carrying capacity.

The maximum population of a particular species that the habitat can support.

The carrying capacity of an ecosystem can change as environmental conditions change.

2. List two biotic factors and two abiotic factor and describe how they can be limiting factors.

**The abundance of or the lack of certain plants then translates into an abundant or a limited food supply for a chain of other organisms.

** When the population of insects drops, the population of organisms that feeds on mosquitoes Is affected

BIOTIC LIMITING FACTORS– FOOD, PREDATORS, MATES, BIRTH AND DEATHRATE

ABIOTIC LIMITING FACTORS– LIGHT, SPACE, WATER, WEATHER, …**Climate and particular weather conditions can affect the population size directly by presenting the best conditions for the growth and reproduction or by presenting conditions that make growth and reproduction difficult.**Water is a requirement of all living organisms, and thus it is a limiting factor

3. Use the terms limiting factors and carrying capacity to describe the difference between exponential (J-curve) and logistic (S-curve) population growth.

3. Use the terms limiting factors and carrying capacity to describe the difference between exponential (J-curve) and logistic (S-curve) population growth.

EXPONENTIAL GROWTH DOESN’T ACCOUNT FOR OR ISN’T LIMITED BY LIMITING FACTORS. THE POPULATION INCREASES VERY QUICKLY.

POPULATIONS EVENTUALLY REACH THEIR CARRYING CAPACITY AS SOME LIMITING FACTOR KEEPS THE POPULATION FROM GROWING TOO LARGE. EX. FOOD RUNS OUT, TOO MUCH COMPETITION FOR FOOD OR MATES, TOO LITTLE SPACE, DISEASE, ETC

Exponential Model of Population Growth• Population increases rapidly with no limit• What will a graph look like?• Rare in nature. Why?

“J” shaped curve

Limit on the amount of resources (food / space)

• unlimitedresources-with plot.html

Logistic Model of Population Growth

• Accounts for influence of limiting factors

• What will the graph look like?

Stretched out “S”When population is small,

birth rate is higher

than death rate

As population reaches

carrying capacity,

death rate increases

When at carrying capacity,

birth rate is equal to

death rate

• Populations can’t grow exponentially forever because of limiting factors

• Limiting factors can be: biotic– predators, food, disease, competition from their own or other species

• Abiotic– space, water, shelter, soil, salinity, temperature

• carrying capacity2.html

• Make an entry titled- Population Growth Notes- 1/23/12

• It is a “see attached” entry

INCREASE size• Births• Immigration (coming in)

DECREASE size• Deaths (mortality)• Emigration

(going out/leaving)

Growth rate =

(births + immigration) – (deaths + emigration)

•If (births + immigration) > (deaths + emigration), population INCREASES

•If (births + immigration) < (deaths + emigration), population DECREASES

•If (births + immigration) = (deaths + emigration), population STAYS SAME SIZE

Time

Po

pu

lati

on

A B C D E F G

Sample population graph

Different time periods on the graph are labeled A-G. Identify which time periods show the following:

1. Increasing population2. Decreasing population3. The highest population4. The fastest growth rate5. (births + immigration) < (deaths + emigration)6. (births + immigration) = (deaths + emigration)

Interpreting population graphs

Time

Po

pu

lati

on

A B C D E F G

Sample population graph

2. Decrease

5. B+I < D+E

Time

Po

pu

lati

on

A B C D E F G

Sample population graph

6. B+I = D+E

Time

Po

pu

lati

on

A B C D E F G

Sample population graph

1. Increase

4. Fastest Growth

Time

Po

pu

lati

on

A B C D E F G

Sample population graph

1. Increase

Time

Po

pu

lati

on

A B C D E F G

Sample population graph

6. B+I = D+E

3. Highest Pop

Time

Po

pu

lati

on

A B C D E F G

Sample population graph

2. Decrease

5. B+I < D+E

Time

Po

pu

lati

on

A B C D E F G

Sample population graph

6. B+I = D+E

1. C and D show increasing population

2. A and F show decreasing population

3. E shows the highest population

4. C is the fastest growth rate

5. A and F show

(births + immigration) < (deaths + emigration)

6. B, G and E show

(births + immigration) = (deaths + emigration)

• Changes in Carrying Capacity

• Carrying capacity- the maximum size of a population that can be supported by an ecosystem

• The carrying capacity of an ecosystem can change as environmental conditions change.

• Limiting factors- any factor that controls the growth of a population

(e.g., food, space, disease, predators)

The graph below shows the growth of a population over time—a population that has increased and reached a balance due to limiting factors. (REACHED CARRYING CAPACITY)

Time

Population

Original population graph

1) The birth rate DOES NOT change, but the amount of food and other resources increases

Time

Population

Original population graph

2) The birth rate increases but the amount of food And other resources DOES NOT increase

Time

Population

Original population graph

3) A population quickly increases but exceeds the amount of resources and the population crashes

Time

Population

Original population graph