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Population Ecology (chapter 14 -- sect 3 and 4) Intro to Chapter 16 – Human pops Each population has A Density A Dispersion A Reproductive Strategy.

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Presentation on theme: "Population Ecology (chapter 14 -- sect 3 and 4) Intro to Chapter 16 – Human pops Each population has A Density A Dispersion A Reproductive Strategy."— Presentation transcript:

1 Population Ecology (chapter 14 -- sect 3 and 4) Intro to Chapter 16 – Human pops Each population has A Density A Dispersion A Reproductive Strategy

2 Population A group of the same species of organism living in the same place Understand food chains and food webs What might effect the survival of THIS group of dolphins?

3 Characteristics of Populations 4 Major Characteristics of Populations: –Geographic Distribution –Density –Growth Rate –Age Structure

4 –Area inhabited by a population *remember, there are also ecological equivalents in similar ecosystems around the planet, but if they are not in the same habitat, they are NOT the same population! 1. Geographic Distribution

5 Population dispersion Way in which individuals of a population are spread in an area or a volume 3 types: Dispersion patternsDispersion patterns -- page 437 in textbook Clumped Uniform Random



8 # of individuals in population per unit area –(# individuals) / (area) –Varies depending on species in ecosystem –Increase density = increase crowdedness 2. Population Density

9 Example: 150 bullfrogs live in a pond that covers an area of 3 square kilometers. What is the bullfrog’s population density?

10 Answer: 50 bullfrogs per square kilometer

11 How fast a population is growing/shrinking 3. Growth Rate

12 Negative & Positive Growth Positive growth: net increase –Total penguin population was 1200 at the beginning of the year, now is 1600. Negative growth: net decrease –250 penguin chicks died during the year.

13 Biotic Potential The maximum rate at which the population of a given species can increase when there are no limits on its growth. The maximum rate at which the population of a given species can increase when there are no limits on its growth. “living” potential It is not possible for a population to increase FOREVER – there are limitations!

14 1.Immigration: movement into an area 2.Emigration: movement out of an area ***approach maturity & move out ***shortage of resources 3.Birth Rate Change in # births 4.Death Rate 1.Change in # deaths ***increase/decrease birth & death rates ***birth = death? Factors affecting population growth

15 Types of Population Growth Exponential Growth Logistic Growth

16 J-shaped curve reproduce at a constant rate –Slowly at first, then larger until approaches infinitely large size. ideal conditions unlimited resources 1. Exponential Growth

17 S-shaped curve –Slow increase, larger increase when large number of resources, then slows when resources become less available, growth slows/stops, oscillates around carrying capacity. Carrying Capacity- –largest # individuals environment can support –Tells size of population when average growth rate reaches zero. How could growth slow or stop? 2. Logistic Growth

18 How population growth may slow: –Birth rate decreases –Death Rate Increases –Both occur at the same rate Reason why these change  Limiting factors

19 causes population growth to decrease Limiting Factors

20 1. Density Independent Factors Do not depend on population size Ex: Unusual weather natural disasters seasonal cycles damming rivers clear-cutting forests

21 2. Density-Dependent Factors depends on population size. Competition Predation Parasites Diseases Competition Predation Parasites Diseases larger populations are more affected by density-dependent factors (orgs are closer together)

22 Q1: Think about the black racer snake populations in Georgia. Once a pair of mice start reproducing, what would happen to the black racer snake populations, and why? Application


24 Answer They will increase because there will be more mice to feed them. Q2: If the mice population dies off, what would happen to the snake populations, and why?

25 Answer: The snake populations would decrease, because there would be fewer mice to eat. GRAPH this senario! What is the GENERAL shape and height of each curve shown…

26 Below is called a TRACKING GRAPH – because the peaks of the predators always follow the peaks of the prey

27 2a. Competition compete for resources when population becomes overcrowded. I only have 5 bottles left

28 Types of Competition InterspecificIntraspecific

29 Interspecific Competition Competition between different species for the same resources. wildebeast and rhinovultures and hyenas

30 Intraspecific Competition Competition between members of same species for similar resources. lions Bunchgrass in Mojave Desert – roots compete herons

31 1b. Parasitism and Disease Parasite or disease-causing organism takes nourishment from host, weakens/kills host spreads quicker w/ greater density. Wasp Cocoons This larval sphinx moth has been attacked by a parasitic wasp. The wasp inserted its eggs beneath the moth’s skin. After hatching, the wasp larvae fed on their host internally until they appeared as white cocoons on its back.

32 1c. Predation Predator-prey interactions Increase prey, increase predator


34 Demography Study of human population growth characteristics Looks at growth rate, age structure, geographic distribution Can tell if pop is growing by looking at the difference between the birth rate and the death rate In US, death rate is declining, life expectancy is increasing, fertility rate is decreasing – WHY?

35 Age-Structure diagrams or Population Pyramids Describes how many individuals of different ages make up a population Population Pyramids, or Age-Structure Diagrams, show age structure in a population. Populations with large numbers of young offspring have greater potential for rapid growth


37 Comparing Human Populations… Expansive ConstrictiveNear Stationary

38 Patterns of Population Growth… The Demographic transition- A change in a population from high birth and death rates to low birth and death rates.

39 Human Population on Earth Thomas Malthus – economist, late 1700’s *wrote an essay that stated that human population was growing faster than the Earth’s resource could support Today’s human population exceeds 6 billion…

40 Human Population -- predictions

41 Carrying capacity and humans Carrying capacity for human pop has changed due to technology Due to improvements in: Agriculture, transportation, medicine, sanitation

42 Nonrenewable vs. renewable resources Nonrewable – used faster than they form ex. Coal and oil Renewable – cannot be used up or can replentish themselves over time ex. Wind energy If not used carefully, renewable COULD become nonrenewable Ex. Water – pollution often makes it unusable

43 U.S. uses more resources and produces more waste…. Than any other country on the planet ex. 230 million tons of garbage/year (4.2 lbs per person per day) Ecological footprint: The amount of land necessary to produce and maintain enough food and water, shelter, energy, and waste Depends on: amount and efficiency of resource use, and the amount and toxicity of waste produced See textbook page 487 for world view

44 Calculate YOUR ecological footprint

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