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How Populations Grow
Photo Credit: © Frans Lanting/Minden Pictures, Inc.
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2. Characteristics of Populations
Group of the same organisms living in the same place at the same time.
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3. Characteristics of Populations
-The area a population Lives in is called geographic distribution
-Population density is the number of individuals in the area.
-The increase OR decrease of the population size is its growth rate.
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Population Growth
Population Growth
Four 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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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
(team 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,
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A Density Independent Factor reduces 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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16. Density-Dependent Factors
The size of a population determines if the factor will cause the population to grow or decrease. An individuals chance of surviving depends on the number of individuals in the same area.
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17. Density-Independent Factors
Affect all populations in similar ways regardless of size. The population reduces by the same proportions no matter what size the population is. LUCK!!!
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18. Density Independent or Dependent?
Will small and large populations be affected the same way? independent, Dependent
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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20. 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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Predator Prey Video
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23. Community Interactions
Symbiosis is
When 2 different organisms/species live in a close/long term relationship (sounds like what?) .
Includes: 3 types
mutualism
commensalism
parasitism
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SYMBIOSIS (CONT)
Mutualism- Both species benefit from the relationship
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SYMBIOSIS (CONT)
Commensalism- one organism is helped, the other is not harmed/helped.
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Parasitism- relationship where one organism harms another for its own benefit
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27. Copyright Pearson Prentice HallB D A
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28. Ecological Succession
Ecological succession is the gradual and sequential regrowth of a community in an area .
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29. Ecological Succession Video
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Video “mini quiz”
Explain to your face partner what ecological succession is.
Tell you shoulder what the difference is between primary and secondary succession.
With your shoulder partner come up with one example of each type of succession
Define a pioneer species with your whole team
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31. 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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32. 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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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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34. Draw/Label Primary Succession and be ready to present
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35. 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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36. 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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37. 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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38. 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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