NOTES: CH 5 Populations

Transcription

1 NOTES: CH 5 Populations

2 POPULATION: individuals of a single species occupying the same general area -rely on the same resources -influenced by similar environmental factors

3 -shaped by: Populations are interactions (between individuals and their environment) natural selection (can modify characteristics within a population)

4 Population Characteristics: Geographic Range / Boundaries (may be natural or manmade) Population size Density (# of individ. per unit area/volume) -ex: # of oak trees per km 2 in Clackamas Cty. Dispersion (pattern of spacing among individuals)

5 Measuring Density count individuals directly random sampling / estimation -count individuals in a representative area -count indirect indicators (nests, burrows, droppings, tracks, etc.)

6 Factors Affecting Growth & Decline of a Population increases in pop. size: births immigration decreases in pop. size: deaths (mortality) emigration

7 Calculating Change in Population Size: Change in Population Size = (B D) + (I E)

8 **Consider this. A population of moose had 100 individuals. Over the course of the year, there were 29 births and 34 deaths. Also, 5 moved into the area while 15 left the area. What was the change in the population that year? How many moose are left in the population?

9 B = 29 D = 34 I = 5 E = 15 Remember the equation: (B-D) + (I-E) (29-34) + (5-15) = = -15 So how much of the original population is left? = 85 moose Did the population increase, decrease, or stay the same? decreased

10 What happens to the population size if If more organisms are born than die -Population grows If birthrate = death rate -Population is stable Death rate exceeds birthrate -Population declines

11 Population Growth Models *Exponential Growth vs. Logistic Growth

12 Exponential Growth Model in an ideal, unlimited environment, there will be exponential growth of a population:

13 Exponential Growth: Occurs when there are ideal conditions, unlimited resources -Abundance of food, space -Lack of predators, disease Population size increases Individuals can reproduce at a constant rate

14 if nothing stops a population from growing, it is undergoing exponential growth a natural population cannot continue with exponential growth for long WHY? -- there are limiting factors to continuous growth such as space, food, & competition

15 Exponential Growth

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17 CARRYING CAPACITY CARRYING CAPACITY: # of individuals that the environment can support -property of the environment -varies over space and time with abundance of resources

18 Exponential

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20 Logistic Growth vs. Exponential Growth Exponential growth = J-shaped curve Logistic growth = S-shaped curve Logistic growth occurs when a population s growth stops / slows after a period of exponential growth

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22 Logistic Growth What causes a population growth to stop / slow? -RESOURCES! (a.k.a. LIMITING FACTORS)

23 Population Limiting Factors: Density-dependent factors intensify as pop. size increases -available food -overcrowding -space -nutrients

24 Density-dependent factors (continued) -light (plants) -predation -accumulation of wastes -stress (hormonal changes, aggressiveness, delay in sexual maturation, etc.) -disease -parasitism

25 Density-independent factors: Density-independent factors are unrelated to pop. size -weather & climate -freeze; cooler temps -extreme heat -fires, hurricanes, etc. *Most ecologists agree that a combination of factors limits pop. size

26 5.3: HUMAN POPULATION GROWTH DEMOGRAPHY: study of human population growth characteristics -Growth rate -Age structure -Geographic structure (who lives where?)

27 Human Population Growth is an exception to what we consider a "natural population" the human population, unlike other populations, has increased over the course of time about 500 years ago, the world's population started growing EXPONENTIALLY - WHY? Sanitation, better health care, etc. all led to increased longevity of people

28 as of 2001, the human population is over 6 billion; this is double what it was 40 years ago!!!!

29 It took over 10,000 years for human population to increase to 1 billion people It then took a little over a century to reach 2 billion Then, only 30 years to reach 3 billion!!

30 Since the early 1800 s, the human population on Earth has been growing exponentially. The primary cause -little to do with an increase in birth rate -main cause = decrease in the death rate -improved medicine, agriculture, and living conditions -people have begun to live longer and healthier lives they produce more children that are more likely to survive to adulthood produce even more children EXPONENTIAL GROWTH!

31 On average, each person in the United States uses over 4 times the amount of the world's resources than a person from another country food for thought.

32 QUESTION TO PONDER: When will the Earth reach it's carrying capacity for humans and what will happen when it does?

33 NOTES: CH 6 Humans in the Biosphere Humans affect regional and global environments (including soil, water, and the atmosphere) through: -agriculture -development -industry

34 Sustainable Development: RENEWABLE RESOURCES: can be produced or replaced by a healthy ecosystem (i.e. some trees that grow quickly) NONRENEWABLE RESOURCES: natural processes cannot replenish them within a reasonable amt. of time (i.e. fossil fuels, coal, oil, etc.)

35 6.2: Human Impacts on Ecosystems

36 Disruption of nutrient cycling farming and agriculture: remove nutrients from one area; they appear in other areas

37 Disruption of nutrient cycling sewage, factory wastes, livestock runoff, fertilizer leaching all lead to accelerated eutrophication of lakes (excess growth of photosynthetic organisms)

38 toxic chemicals dumped into ecosystems -many cannot be degraded; persist for years -become more concentrated as they are passed up through successive trophic levels

39 Toxic chemicals -top level carnivores most affected -ex: DDT (pesticide); banned in US (1971) BIOLOGICAL MAGNIFICATION

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41 Carbon dioxide emissions / Greenhouse Effect combustion of fossil fuels and burning of wood / deforestation temperature increases w/ increased CO 2

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45 Carbon dioxide emissions / Greenhouse Effect possible scenarios: -melting of polar ice; flooding; warming trend

46 Depletion of Ozone: ozone forms a protective layer in stratosphere that absorbs UV radiation

47 Depletion of Ozone: accumulation of CFC s (used in aerosol propellants and refrigerants) is destroying ozone

48 Depletion of Ozone: possible consequences: -increases in skin cancer -unpredictable effects on crops -unpredictable effects on phytoplankton

49 Exploding Human Population: Where will we all live? HABITAT DESTRUCTION! only 15% of original forest and 1% of original tallgrass prairie remain in US tropical rainforests are cut at a rate of 500,000 km 2 per year; will be gone in approx 20 years

50 Exploding Human Population: development, logging, war, oil spills, etc. The main threat of habitat destruction is the loss of BIODIVERSITY!

51 6.3: BIODIVERSITY BIODIVERSITY: the variety of life in an area

52 BIODIVERSITY How do we measure BIODIVERSITY? -measure / count the # of species in an area Example: 1 acre corn field vs. 1 acre rainforest Corn field: Rainforest: 1 plant species 400 plant species 2 beetle species 5000 beetle species

53 Importance of Biodiversity: The presence of different forms of life make our planet beautiful but why else is biodiversity important?

54 Importance of Biodiversity: Importance to Nature: if a species of lost from an ecosystem, other living things will be affected predator-prey; food web relationships symbiotic relationships change animals can t exist without plants flowering plants can t reproduce without their animal pollinator / partner

55 Importance of Biodiversity: Importance to Nature: EXAMPLE decomposers break down dead material into nutrients the plants can use a rainforest tree grows from nutrients in the soil released by decomposers a sloth eats the leaves of this tree insects live on the sloth **Living things create niches for other living things!!

56 Importance of Biodiversity: Importance to Humans: oxygen is supplied, and CO 2 is removed from the air by diverse species of plants & algae biodiversity gives humans a diverse diet (beef, chicken, tuna, shrimp; multiple & diverse plant products from almonds to zucchini!)

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58 Importance of Biodiversity: Importance to Humans: humans rely on biodiversity for materials used in clothing, furniture, buildings improving human health: most pharmaceuticals are synthesized to mimic naturally occurring chemicals discovered in living things EXAMPLES: penicillin, quinine, aspirin, anti-cancer drugs

59 Loss of Biodiversity: EXTINCTION: the disappearance of a species; when the last of its members dies

60 6.4: Meeting Ecological Challenges ECOLOGICAL FOOTPRINT: describes the total area of land and water ecosystems needed to provide the resources an individual uses and to absorb the wastes that individual generates -includes: the food you eat, the miles you travel, where you live, the electricity / gas you use, etc.

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62 Comparing Footprints: the average American has an ecological footprint over four times larger than the global average. by contrast, the African nation of Zambia has a footprint approx. ¼ the global footprint

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65 A Sustainable Future? We can follow these steps to help us toward a sustainable future: 1) Recognizing a problem in the environment 2) Researching the problem to determine the cause, and then: 3) Using scientific understanding to change our behavior & have a positive impact on the global environment.

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