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APES- 12/5 Please have out your Rabbit and Wolves activity and your Chapter 9 notes Permission slips anyone? Remember need them by Friday Passing back.

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Presentation on theme: "APES- 12/5 Please have out your Rabbit and Wolves activity and your Chapter 9 notes Permission slips anyone? Remember need them by Friday Passing back."— Presentation transcript:


2 APES- 12/5 Please 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

3 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.

4 Population Ecology AP Environmental Science

5 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

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

7 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 lions 100mice / square mile vs 1 moutain lion/ square mile Density depends upon –social/population structure –mating relationships –time of year

8 3.Population Dispersion/Distribution How a population occupies the habitat Depends on interactions of individuals and availability of resources There are three main classifications

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

10 05_12c.jpg

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

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

14 05_12a.jpg

15 4. Sex ration Males to females Gives and idea of possible population growth due to births

16 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

17 Age Structure Diagrams Positive Growth Zero Growth Negative Growth (ZPG) Pyramid Shape Vertical Edges Inverted Pyramid

18 Factors that influence population size


20 1. Biotic Potential –factors allow a population to increase under ideal conditions= Growth factors 2. Environmental Resistance –factors that cause a population to decrease

21 Biotic 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

22 Environmental 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

23 3. Density-independent controls Limiting factor whose effects on a population are not related to number of individuals (drought, flood, fire) 4. Density-dependent controls Limiting factors whose effects on a population INCREASE or DECREASE depending on the population density (competition, predation, disease, parasitism)

24 APES 12/6 Permission slips?? Have to have them tomorrow! Please have out your Chapter 9 notes

25 With your Tablemates 1.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?


27 Genetic Diversity Problems Large populations lots of diversity! Small isolated populations limited diversity that can effect survival Founder effect Demographic bottleneck Genetic drift Interbreeding

28 Population 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)

29 05_17.JPG

30 Figure 8-4




34 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

35 Natural Population Curves Fig. 9-7 p. 168

36 The Role of Predation in Controlling Population Size  Predator-prey cycles  Top-down control  Bottom-up control Fig. 9-8 p. 168

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


39 Exponential Growth One 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!!!

40 Reproductive 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

41 r - Strategists Spend most of their time in exponential growth Maximize reproductive life Minimum life K

42 R 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

43 K - Strategists Maintain population at carrying capacity (K) Maximize lifespan K

44 K- 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

45 Survivorship 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

46 05_14.JPG

47 Eagle Watch

48 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?

49 Habitat 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


51 1949 1964 Habitat fragmentation in northern Alberta 1982 1991


53 Human 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

54 Human Impacts Deliberately or accidentally introducing new species Overharvesting potentially renewable resources Interfering with the normal chemical cycling and energy flows in ecosystem

55 Principles of Sustainability How Nature WorksLessons 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 extinction of species. Reduce births and wasteful resource use to prevent environmental overload and depletion and degradation of resources. Solutions

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