ecology 1 ppt
TRANSCRIPT
Populations• Defined by
– Size– Density– Dispersion.
• Size: Total number of individuals present– Limited by
• Birth – increases size• Death – decreases size• Immigration – increases size (moving INTO population)
• Emigration – decreases size(moving OUTof population)
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Practice Problem:
• An initial population of axolotls is 42. • 4 of the axolotls die of natural causes. 8 axolotls immigrate into the population. 2 axolotls emigrate from the population. 17 axolotls are born.
• What is the size of the new population?• Did the population grow or shrink in size?
• Density: number of individuals per unit area or volume.
• Sampling techniques are used to estimate population sizes– Mark and Recapture:
• Some organisms are captured, marked and released.
• Later, organisms are captured again.• The frequency of marked organisms that were recaptured can be used to determine density of population.
Population Size
Area/Volume
HONORS
• Dispersion: describes how the individuals within a population are spaced out.
Clumped: Random: Uniform:
most common
Population Growth• Biotic Potential: maximum rate at which a population could increase under ideal conditions– Different populations have different biotic potentials– Affected by several factors:
• Length of time before reproductive period begins• Length of time reproductive period lasts • Number of reproductive periods in lifetime• Number of offspring produced at a time.
HONORS
Exponential population growth pattern:
• Exponential growth = rate of growth keeps increasing.– No predation– No parasitism– No competition– No immigration/emmigration– Unlimited resources
Doesn’t last in nature.
Seen in: • Bacteria grown in lab• Humans for the past
300 years.
Logistic population growth pattern:
– Initial period of slow growth– Period of exponential population growth– Population reaches carrying capacity: maximum number of individuals the environment can support
– Population crashes or oscillates (goes up and down) around the carrying capacity.
– When the population becomes stable we can say it is in equilibrium
Popu
latio
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Time
Carrying Capacity
Exponential Growth
Stable Population
• Carrying capacity = K• Each environment has its own K• K can change as environmental conditions change.
K‐Strategists• Keep population size constant, near the carrying capacity (K)
• Produce a few, large offspring who take a long time to develop
• Intensive parenting• Reproduce many times• Mammals
r‐Strategists• Population size grows whenever environment is uncrowded/rich in resources.
• Produce many small offspring who quickly develop.
• Little to no parenting• Reproduce once• Insects
HONORS
HONORS
Oh Deer! Game
• Each person is either a deer or a resource• The 3 resources are:Blue = water Green = food Brown = shelter• For each round, on the count of 3 – everyone holds up ONE resource card
• The “resources” must then pick a deer with the same card to match with.. They then become a deer
• If you are a deer and are NOT chosen – you switch lines and become a “resource”
Oh Deer! Questions
• Would it ever be possible for the entire class to become deer?
• What real life scenarios could result in SIGNIFICANTLY less available water? Food?
• How can we describe the graph that resulted from our class data?
Limits to Population Growth
• Limiting factors: limit population growth.–2 Types:
• Density‐dependent factors: factors that increase as population density increases.
–Competition for food, waste buildup, predation, disease, etc.
• Density‐independent factors: factors that are unrelated to population density.
–Natural disasters
• Bikini Bottom is found on the bottom of the ocean floor. What is a likely limiting factor for the PLANTS living there?
• OH NO!A tornado hit bikini bottom.• Would this be considered a density dependent or density independent factor?
• Hungry “MEEP” fish have invaded the Krusty Krab !!!!
density dependent or density independent limiting factor?
MEEP!
MEEP!
MEEP!
MEEP!
MEEP!MEEP!
• There is only one tub of bubbles left but all the Spongebob characters want to use them!
• density dependent or density independent limiting factor?