APES- 12/5Please have out your Rabbit and Wolves activity and your Chapter 9 notes

Permission slips anyone? Remember need them by Friday

Passing back your test! Please save your questions until everyone gets theirs back- Thanks

From the Rabbit and Wolves

1. List 3 things that caused increase in population growth of rabbits, wolves or grass.

2. List 3 things that caused a decrease in population growth of rabbits, wolves or grass.

Population EcologyPopulation Ecology

AP Environmental ScienceAP Environmental Science

Population Dynamics

• What is a population?

• What are Population Dynamics?

how populations change in size over time and how they are spaced in their environment.

Inputs to a population= Birth and immigration

Outputs to a population= Death and emigration

We study 5 population characteristics

1. Population Size• Size (n)• Total number of individuals within an area

2. Population Density

• Population Density (or ecological population density) is the amount of individuals in a population per unit habitat area– Some species exist in high densities - Mice– Some species exist in low densities - Mountain lions100mice / square mile vs 1 moutain lion/ square mile

• Density depends upon– social/population structure– mating relationships– time of year

3.Population Dispersion/Distribution

• How a population occupies the habitat• Depends on interactions of individuals

and availability of resources• There are three main classifications

Fig. 8-2a, p. 162(a) Clumped (elephants)

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Fig. 8-2b, p. 162(b) Uniform (creosote bush)

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Fig. 8-2c, p. 162(c) Random (dandelions)

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4. Sex ration

• Males to females

• Gives and idea of possible population growth due to births

5. Age Structure• The age structure of a population is usually

shown graphically

• The population is usually divided up into prereproductives, reproductives and postreproductives

• The age structure of a population dictates whether is will grow, shrink, or stay the same size

Age Structure DiagramsAge Structure DiagramsPositive Growth Zero Growth Negative Growth (ZPG)Pyramid Shape Vertical Edges Inverted Pyramid

Factors that influence population size

1. Biotic Potential– factors allow a population to increase

under ideal conditions= Growth factors

2. Environmental Resistance – factors that cause a population to

decrease

Biotic PotentialBiotic Potential• Ability of populations of a given species to

increase in size– Abiotic Contributing Factors:

• Favorable light

• Favorable Temperatures

• Favorable chemical environment - nutrients

– Biotic Contributing Factors:• Reproductive rate

• Generalized niche

• Ability to migrate or disperse

• Adequate defense mechanisms

• Ability to cope with adverse conditions

Environmental ResistanceEnvironmental Resistance– Abiotic Contributing Factors:

• Unfavorable light

• Unfavorable Temperatures

• Unfavorable chemical environment - nutrients

– Biotic Contributing Factors:• Low reproductive rate

• Specialized niche

• Inability to migrate or disperse

• Inadequate defense mechanisms

• Inability to cope with adverse conditions

3. Density-independent controls Limiting factor whose effects on a

population are not related to number of individuals (drought, flood, fire)

4. Density-dependent controlsLimiting factors whose effects on a population INCREASE or DECREASE depending on the

population density (competition, predation, disease, parasitism)

APES 12/6

Permission slips?? Have to have them tomorrow!

Please have out your Chapter 9 notes

With your Tablemates1. What is the most common type of

distribution?

2. What is the difference between population size and population density?

Read the Wolf population on Isle Royale Plummets

3. After reading the article what are some density dependent population controls?

4. What are some density independent controls?

Genetic Diversity Problems

• Large populations lots of diversity!

• Small isolated populations limited diversity that can effect survival

Founder effect

Demographic bottleneck

Genetic drift

Interbreeding

Population GrowthPopulation Growth• Growth rate = the change in population over time• Population growth depends upon

– birth rates– death rates- mortality– immigration rates (into area)– emigration rates (exit area)

Population growth= (birth +immigration)-(Deaths+ emigration)

ZPG (b + i) = (d + e)

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Figure 8-4Figure 8-4

http://en.wikipedia.org/wiki/File:S_cerevisiae_under_DIC_microscopy.jpg

today

• At your lab station find a test tube and put your name on it with tape

• Add 15 ml of yeast solution to your test tube• Using your pipette mix solution well • Fill cuvette with yeast solution• Follow directions at your station for colorimeter• Take reading for three cuvettes: water, apple juice and

your yeast solution• Put yeast solution back into test tube and leave in drawer• Figure out who is coming in to make readings

Natural Population Curves

Fig. 9-7 p. 168

The Role of Predation in Controlling Population Size

The Role of Predation in Controlling Population Size

Predator-prey cycles Predator-prey cycles Top-down control Top-down control Bottom-up control Bottom-up control

Fig. 9-8 p. 168

• Which population curve would be density dependent and which would be density independent?

Exponential GrowthExponential GrowthOne female will produce 6 young over her 100 year life span. In a population,

this amounts to a growth rate of 2%

Darwin wondered, how many elephants could result from one male and one

female in 750 years?

19,000,000 elephants!!!19,000,000 elephants!!!

Reproductive StrategiesReproductive Strategies• Goal of every species is to produce as many

offspring as possible• Each individual has a limited amount of

energy to put towards life and reproduction• This leads to a trade-off of long life or high

reproductive rate• Natural Selection has lead to two strategies for

species: r - strategists and K - strategists

r - Strategistsr - Strategists• Spend most of

their time in exponential growth

• Maximize reproductive life

• Minimum life

K

R StrategistsR Strategists• Many small offspring• Little or no parental care and protection of offspring• Early reproductive age• Most offspring die before reaching reproductive age• Small adults• Adapted to unstable climate and environmental

conditions• High population growth rate – (r)• Population size fluctuates wildly above and below

carrying capacity – (K)• Generalist niche• Early successional species

K - StrategistsK - Strategists

• Maintain population at carrying capacity (K)

• Maximize lifespan

K

K- StrategistK- Strategist• Fewer, larger offspring• High parental care and protection of offspring• Later reproductive age• Most offspring survive to reproductive age• Larger adults• Adapted to stable climate and environmental

conditions• Lower population growth rate (r)• Population size fairly stable and usually close to

carrying capacity (K)• Specialist niche• Late successional species

Survivorship CurvesSurvivorship Curves• Late Loss type I: K-strategists that produce few

young and care for them until they reach reproductive age thus reducing juvenile mortality

• Constant Loss type II: typically intermediate reproductive strategies with fairly constant mortality throughout all age classes

• Early Loss type III: r-strategists with many offspring, high infant mortality and high survivorship once a certain size and age

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Eagle Watch

Do humans effect natural populations?

• 83% of land is effected directly by human impact

• Modified, cultivated or degraded

• Do we have a hand in change population size of other species?

Habitat FragmentationHabitat Fragmentation• Process by which human activity

breaks natural ecosystems into smaller and smaller pieces of land

• Greatest impact on populations of species that require large areas of continuous habitat

• Also called habitat islands

1949 1964

Habitat fragmentation

in northern Alberta

1982 1991

Human ImpactsHuman Impacts

• Fragmentation and degrading habitat

• Simplifying natural ecosystems

• Strengthening some populations of pest species and disease-causing bacteria by overuse of pesticides

• Elimination of some predators

Human ImpactsHuman Impacts• Deliberately or accidentally

introducing new species

• Overharvesting potentially renewable resources

• Interfering with the normal chemical cycling and energy flows in ecosystem

Principles of Sustainability

How Nature Works Lessons for Us

Runs on renewable solar energy.

Recycles nutrients and wastes. There is little waste in nature.

Uses biodiversity to maintain itself and adapt to new environmental conditions.

Controls a species population size and resource use by interactions with its environment and other species.

Rely mostly on renewable solar energy.

Prevent and reduce pollution and recycle and reuse resources.

Preserve biodiversity by protecting ecosystem services and preventing premature extinctionof species.

Reduce births and wasteful resource use to prevent environmental overload and depletion anddegradation of resources.

Solutions