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How Populations Grow
Photo Credit: © Frans Lanting/Minden Pictures, Inc.
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2. Characteristics of Populations
A population is a group of the same organisms living in the same place at the same time.?
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3. Characteristics of Populations
-The increase OR decrease of the population size is its growth rate.
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Population Growth
Population Growth
3 factors can affect population size:
# of births
# of deaths
Immigration/Emigration
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# Births = population
# Deaths = population
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Population Growth
Immigration- the movement of individuals into an area,
(I=into=immigration)
Animals Immigrate in search of mates/food.
Population=
Emigration- the movement of individuals out of an area
(E=Exit=Emigration)
Caused by: leaving to find mate, food
Population =
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7. Copyright Pearson Prentice HallB D A C
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A=increase
B=decrease
C=stay the same A B C
Immigration Greater than emigration A B C
Emigration greater than immigration A B C A B C
#Births=#deaths
# Immigration= # emigration A B C A B C
# births greater than # deaths
#deaths greater than # births
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Africa: World’s best series: amazing swarms
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Exponential Growth
What are exponential growth and logistic growth?
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2 Types of Growth Rates
Types of Growth Rates
1.Exponential growth- occurs when the population grows at a constant rate
Required Conditions:
Unlimited resources
Ideal conditions-
Plenty of food, water, land, mates
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Exponential Growth
Exponential Growth
In the presence of unlimited resources and in the absence of predation and disease, a population will grow exponentially. Both hypothetical graphs show the characteristic J-shape of exponential population growth.
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Logistic Growth
Types of Growth Rates
2.Logistics growth – occurs when a population’s growth slows or stops due to limited resources because of increased competition.
(With shoulder partner, find 3 things that can stop Exponential Growth)
Required Conditions:
Resources become less available
Increased competition
Carrying Capacity is reached
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Logistic Growth
Carrying Capacity of the environment is
-the maximum # of individuals an environment can support over a long period of time.
When a population reaches the carrying capacity of its environment, growth levels off. (The average growth rate is zero.)
This graph shows the S-shaped curve of logistic growth. As resources become less available, the population growth rate slows or stops. The growth of this population has leveled off at its carrying capacity.
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Limits to Growth
Limits to Growth
Limiting Factor- ANYTHING that causes population growth to decrease
(face partners list-try to get 10 limiting factors in 2 minutes)
Share your list w/your whole team and add their items to your list
(T-chart)
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Limits to Growth
A Density-dependant limiting factor is based on the size of the population. The size of the population determines if the factor causes the population to grow or decrease.
(EX: Disease-The more dense the population is the close they are and the more chance of spreading)
With your team come up with an example for each one below.
Competition, Predation, Parasitism, Competition
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A Density Independent Factor affect all populations the same(equally) regardless of their size. Their population is reduced by the same proportion
(Ex: if a dam stops flow of river water, population of fish downstream will die regardless of 1 or 1000 fish).
Natural disasters
Unusual weather
Human activities – clear cutting; damming rivers
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19. Density Independent or Dependent?
Will small and large populations be affected the same way? Yes/No…….Dependent/Independent
Examples:
Competition
Food shortage
Disease
Human activities
Parasitism
Predation
Natural Disasters (fire, flood, hurricane)
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Community
A community is a group of populations living in the same place at the same time.
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21. Community Interactions
Predator/Prey)
-Predation is when one organism captures and feeds on another organism
Predator-does the killing/eating
Prey-killed/eaten
#Predators __ then #Prey _____
#Predators ___ then #Prey _____
Competition is when 2 or more members of the same or different populations fight over the same limited resources such as
Land, food, and mates
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Limited mates
Loss of land to human activity
Limited water due to drought
Increased death rate caused by disease
Increased birth rate due to lack of predators
Which can cause a change in Carrying Capacity B D A C
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Killer whales fighting over a sea lion
Hurricane Katrina flooding Louisiana
A great white hunting seals
Tapeworms in the intestines of a wolf population
The bird flu killing dense populations of birds
Density dependent vs Density Independent B D A C
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25. Copyright Pearson Prentice HallB D A
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26. Ecological Succession
Ecological succession is the gradual and sequential regrowth of a community in an area .
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27. Ecological Succession
Ecological Succession (READ ONLY-IMPORTANT)
Ecosystems are constantly changing in response to natural and human disturbances.
As an ecosystem changes, older inhabitants gradually die out and new organisms move in, causing further changes in the community.
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28. Ecological Succession
Primary succession is when a community develops in an area where no life had been before.
EX: Hardened lava, sand dunes, bare rock
ORDER OF SUCCESSION:
Lichens, grasses, shrubs, trees
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29. Draw/Label Primary Succession and be ready to present
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Pioneer species-----
-The first species to populate a new area where there was no life before are lichens.
(fungus/alga-break apart rock and become soil as they die)
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31. Ecological Succession
In this example, a volcanic eruption has destroyed the previous ecosystem.
Primary succession occurs on newly exposed surfaces, such as this newly deposited volcanic rock and ash.
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32. Ecological Succession
The first organisms to appear are lichens.
Primary succession occurs on newly exposed surfaces, such as this newly deposited volcanic rock and ash.
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33. Ecological Succession
Mosses soon appear, and grasses take root in the thin layer of soil.
Primary succession occurs on newly exposed surfaces, such as this newly deposited volcanic rock and ash.
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34. Ecological Succession
Eventually, tree seedlings and shrubs sprout among the plant community.
Primary succession occurs on newly exposed surfaces, such as this newly deposited volcanic rock and ash.
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In your notes (w/shoulder partner) explain why the population of predators will increase/decrease along with the population of its prey. P Does this make the predator/prey relationship a good method of population control?
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36. Copyright Pearson Prentice HallB D A C
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5-1
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5-1
Population density is the number of individuals
that are born each year.
per unit area.
that immigrate.
that emigrate.
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5-1
When the birthrate of a population exceeds its death rate, the population
decreases.
increases.
stays the same.
increases then decreases.
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5-1
An S-shaped curve on a graph of population growth is characteristic of
exponential growth.
logistic growth.
carrying capacity.
delayed growth.
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5-1
Exponential growth in a population slows down or stops as
resources become limited.
rate of immigration increases.
rate of emigration decreases.
birth rate increases.
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5-1
Exponential growth rate means that each new generation of a population
adds the same number of new individuals as the previous generation did.
increases at the same rate as the previous generation.
is the same size as the generation before.
increases by a varying amount.
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Exponential Growth
Exponential Growth
Ideal conditions/unlimited resources, a population will grow exponentially.
Individuals in a population reproduce at a constant/non-stop rate.
The population becomes larger and larger until it approaches an infinitely large size.
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Logistic Growth
Logistic Growth
In nature, exponential growth does not continue in a population for very long.
-W/shoulder partner, find 3 things that can stop Exponential Growth
As resources become less available, the growth of a population slows or stops.
Logistic growth occurs when a population's growth slows or stops following a period of exponential growth
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45. “I Want to be a billionaire so freakin bad!”
Would you take a job where they paid you .01/day?
What if they doubled it each day?
W/your shoulder partner try to figure out what the pay would be at the end of each week and graph it. (Use a a line graph like the one you just saw-units of time will go on horizontal axis, amount of money/pay will go on vertical axis)
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46. Ecological Succession
-Series of predictable changes that occur in a community
-Ecosystems can change due to natural disasters, or human disasters
-Can be sudden, or gradual
ecological succession---
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