Population Ecology
Populations <ul><li>Groups of organisms of the same species that live within a given area  </li></ul>
Ecologists work at many scales
Ecologists work at many scales
Population Characteristics  <ul><li>We can characterize individual populations in terms of …  </li></ul><ul><li>Variation ...
<ul><li>Members of a population show similarities because they belong to the same species.  </li></ul>
Members of a population also show variation.   Most variation falls in a “normal” distribution  (bell-shaped frequency)
Population Characteristics  <ul><li>We can characterize individual populations in terms of …  </li></ul><ul><li>Variation ...
There are three common patterns of population distribution: Uniform
 
Why Different Types?
Population Characteristics  <ul><li>We can characterize individual populations in terms of …  </li></ul><ul><li>Variation ...
Demographics <ul><li>Characteristics of a population  </li></ul><ul><li>Examples:  </li></ul><ul><ul><li>Average age  </li...
Population Characteristics  <ul><li>We can characterize individual populations in terms of …   </li></ul><ul><li>Variation...
Four Factors Influence the Size of a Population:   <ul><li>Natality:   Birth Rate (offspring produced and added to populat...
Mortality:   Death Rate (individuals that die)
Immigration:   Movement of members of the species into the area
Emigration:  Movement of members of the species out of area to live elsewhere.
Population Change Population Change =  (natality + immigration) – (mortality + emigration))
Exponential Curve  Unlimited Growth   (J-Shaped) Populations tend to grow in size for the simple reason that individuals t...
Can this happen in nature? <ul><li>Yes:  Bacteria </li></ul><ul><ul><li>If there are no factors limiting the growth, their...
Exponential growth of bacteria
Can this happen in nature? <ul><li>Yes:  Invasive species  </li></ul><ul><ul><li>Uniform habitat  </li></ul></ul><ul><ul><...
 
<ul><li>3 Phases:   </li></ul><ul><li>Exponential growth Phase </li></ul><ul><li>Transitional Phase </li></ul><ul><li>Plat...
Exponential Growth Phase <ul><li>Population increases exponentially.  </li></ul><ul><li>Resources are abundant.  </li></ul...
Transitional Phase <ul><li>As a result of intra-specific competition  </li></ul><ul><ul><li>for food, shelter, nesting spa...
Plateau Phase <ul><li>Natality and mortality are equal so population size is constant.  </li></ul><ul><li>When the number ...
Growth of a population of fur seals
Population size oscillates around the carrying capacity (K)  Time N K overshoot oscillations
Population Characteristics  <ul><li>We can characterize individual populations in terms of …  </li></ul><ul><li>Variation ...
<ul><li>Density Dependent Limits  </li></ul><ul><ul><li>Food  </li></ul></ul><ul><ul><li>Water  </li></ul></ul><ul><ul><li...
r-strategies “real lot” <ul><li>An r-strategy involves investing more resources into producing many offspring, having a sh...
Frog Eggs Frogs lay many eggs & leave them in the water to hatch into tadpoles, some get eaten, some become tadpoles.
Tadpole Some tadpoles are eaten, some tadpoles become frogs
Frog Many animals are waiting on shore for frogs: raccoons, foxes, and many other small predators. If 1 frog from a 100 eg...
K-strategies  “caring” <ul><li>A K-strategy involves investing more resources into development and long-term survival. Thi...
K-strategies
K-selected <ul><li>   Elephants are examples of  K-selected  animals. Female elephants have babies about three years apart...
<ul><li>There are organisms that display extreme r- or K-strategies, but most organisms have life histories that are inter...
The environmental conditions that favor either r-strategies or K-strategies <ul><li>In a predictable environment, in order...
Reproductive Strategies
Population Characteristics  <ul><li>We can characterize individual populations in terms of …  </li></ul><ul><li>Variation ...
 
How did we get here? <ul><li>When I graduated  </li></ul><ul><li>high school there were  </li></ul><ul><li>4 billion  peop...
About 5 million years ago Hunter-gathers 1 million people
Neolithic Period (6000 B.C.) No longer a Natural Setting   100 million people
Common area 2000 years ago 300 million people
1800’s (Carbon cycle control) Steam engine 1 billion people
London between 1800 to 1880 <ul><li>1800 pop. 1 million </li></ul><ul><li>1880 pop. 4.5 million </li></ul><ul><li>Improvem...
Life Expectance   <ul><li>Neolithic it was 20 </li></ul><ul><li>1900 it was 30 </li></ul><ul><li>1950 it was 47 </li></ul>...
1800-2000? <ul><li>From 1 billion to 6 billion? How??? </li></ul>
1908 Control of the Nitrogen Cycle <ul><li>Up until 1908 farms were dependent on organic sources for nitrogen (manure) </l...
1944 Plant Breeding <ul><li>Improves yields </li></ul><ul><li>Disease resistance improvements </li></ul><ul><li>Less day-l...
What’s Behind Population Growth   <ul><li>Three Factors  </li></ul><ul><ul><li>Fertility  </li></ul></ul><ul><ul><li>Infan...
Exponential growth of the human population Human population growth  does not currently show  density effects that typicall...
Population Predictions   <ul><li>Most predictions:  9-12B by 2050  10-15B by 2100  </li></ul><ul><li>Large uncertainties <...
Resource Limits <ul><li>Land  </li></ul><ul><ul><li>Deforesting to acquire more arable land  </li></ul></ul><ul><ul><li>Wo...
Populations of organisms <ul><li>Population density is the number of organisms per unit area. </li></ul><ul><li>There are ...
Why monitor populations ? <ul><li>Determine current status of a population  </li></ul><ul><li>Determine habitat requiremen...
Population vs. Sample Sample True Population
RANDOM SAMPLING <ul><li>A sampling procedure that assures that each element in the  population  has an equal chance of bei...
Sample Methods <ul><li>Quadrat </li></ul><ul><li>Mark-Recapture  </li></ul><ul><li>There are  MANY  more… </li></ul>
Quadrat Sampling <ul><li>A square frame is placed in a habitat  </li></ul><ul><li>All the individuals in the quadrat are c...
<ul><li>Useful for small organisms or for organisms that do not move </li></ul>
MARK-RECAPTURE <ul><li>Capture and mark known # of individuals  </li></ul><ul><li>2 nd  round of captures soon after  </li...
where,  N  = population size  M  = number of individuals marked in first trapping  n  = number of individuals captured in ...
After rearranging to solve for  N , this becomes:
Equation: another method:   <ul><li>N = # initially marked x  total 2 nd  catch </li></ul><ul><li># of marked recaptures <...
Mark Recapture Lincoln-Peterson Index M  = 4 n  = 5  R = 2
Survey 1: M = 12 Survey 2: n = 15  R = 4
<ul><li>You capture and mark 150 fish in a lake.  (This must be a random, representative sample.)   </li></ul><ul><li>You ...
<ul><li>M = 150  </li></ul><ul><li>n= 220  </li></ul><ul><li>R= 25  </li></ul><ul><li>N = [(220)(150)] / 25  </li></ul><ul...
Marking methods <ul><li>Paint or dye  </li></ul><ul><li>Color band </li></ul><ul><ul><li>birds  </li></ul></ul><ul><li>Uni...
When would mark-recapture give you a bad estimate of the population size? <ul><li>Marked animals unlikely to be re-trapped...
T-test <ul><li>T-test is used to determine the significance of the difference between two sets of data using values for t....
 
Null Hypothesis <ul><li>The null hypothesis is generally that which is presumed to be true initially. It is rejected only ...
<ul><li>We have all the information we need to complete the </li></ul><ul><li>six step statistical inference process: </li...
Biomes of the World
What is a biome? A BIOME is the largest geographic biotic unit, a major community of plants and animals with similar life ...
How are biomes formed? Biomes are distributed across the Earth based primarily on climate.  Therefore, in areas that are f...
How many biomes are there? 8
How many biomes are there? <ul><li>Tropical Rainforest </li></ul><ul><li>Tropical Savanna </li></ul><ul><li>Desert </li></...
Tropical Rainforest <ul><li>Typically found near the equator </li></ul><ul><li>Receives more than 200 cm of rain annually ...
Tropical Savanna <ul><li>Grasslands with a few scattered trees </li></ul><ul><li>Experience a wet and dry season </li></ul...
Desert <ul><li>Typically found between 25 o  and 40 o  latitude </li></ul><ul><li>Receives less than 25 cm of rain each ye...
Chaparral <ul><li>Found between 32 o  and 40 o  latitude on the west coast of continents </li></ul><ul><li>Receives betwee...
Grassland <ul><li>Because of the dry climate, trees are found only near water sources such as streams </li></ul><ul><li>Us...
Temperate Deciduous Forest <ul><li>Moderate climate </li></ul><ul><li>Most trees will lose their leaves in the winter </li...
Temperate Boreal Forest <ul><li>Also known as Taiga </li></ul><ul><li>Typically found between 45 o  and 60 o  North latitu...
Tundra <ul><li>Means treeless or marshy plain </li></ul><ul><li>Characterized by permafrost – permanently frozen soil star...
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Ecology Part 2: Population

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  • A biome is a large geographic area containing similar plants and animals. This map shows the locations of some of the major biomes of the world. Each biome can have distinguishing characteristics based on local factors. For example, within the desert biome, there may be hot, cold, and coastal deserts, each with slightly different climates. It is possible to divide the biomes into smaller units that we call biotic communities, ecosystems, or habitats.
  • Climate is a major factor in forming biomes because it is a major factor in controlling which living organisms survive. Most plants that live in cold climates have developed similar adaptations to the cold, and those adaptations are significantly different from the ones required to survive in warm climates. As a result, areas with similar climates (on a global scale) have similar biotic communities and are therefore considered the same biome. Climates change as we move north or south from the equator. As a rule, temperatures drop the farther you get from the equator. Therefore, many biomes are distributed along very distinct lines of latitude. For example, deserts are typically found around 30 degrees North or South latitude. However, climate can also be affected by elevation. Thus, biomes that are typically found closer to the poles may also be found on mountains located near the equator.
  • For purposes of this class, we will consider there to be eight biomes…
  • … However, there is some disagreement among scientists about how many biomes there should be. Some argue that there are as few as five and others that there are as many as thirteen or more. For our purposes, we will focus only on the terrestrial (land) biomes. If we included aquatic, there would be even more. The eight biomes represented here are pretty standard, but they are relatively generic. It is possible to divide these into smaller biomes. For example, we could break the tundra into arctic tundra and alpine tundra.
  • Ecology Part 2: Population

    1. 1. Population Ecology
    2. 2. Populations <ul><li>Groups of organisms of the same species that live within a given area </li></ul>
    3. 3. Ecologists work at many scales
    4. 4. Ecologists work at many scales
    5. 5. Population Characteristics <ul><li>We can characterize individual populations in terms of … </li></ul><ul><li>Variation </li></ul><ul><li>Patterns of Dispersion </li></ul><ul><li>Demographics </li></ul><ul><li>Size and Density </li></ul><ul><li>Limits on population growth </li></ul><ul><li>Human population growth </li></ul>
    6. 6. <ul><li>Members of a population show similarities because they belong to the same species. </li></ul>
    7. 7. Members of a population also show variation. Most variation falls in a “normal” distribution (bell-shaped frequency)
    8. 8. Population Characteristics <ul><li>We can characterize individual populations in terms of … </li></ul><ul><li>Variation </li></ul><ul><li>Patterns of Dispersion </li></ul><ul><li>Demographics </li></ul><ul><li>Size and Density </li></ul><ul><li>Limits on population growth </li></ul><ul><li>Human population growth </li></ul>
    9. 9. There are three common patterns of population distribution: Uniform
    10. 11. Why Different Types?
    11. 12. Population Characteristics <ul><li>We can characterize individual populations in terms of … </li></ul><ul><li>Variation </li></ul><ul><li>Variationtterns of Dispersion </li></ul><ul><li>Patterns of Dispersion </li></ul><ul><li>Demographics </li></ul><ul><li>Size and Density </li></ul><ul><li>Limits on population growth </li></ul><ul><li>Human population growth </li></ul>
    12. 13. Demographics <ul><li>Characteristics of a population </li></ul><ul><li>Examples: </li></ul><ul><ul><li>Average age </li></ul></ul><ul><ul><li>Average size </li></ul></ul><ul><ul><li>Average number of offspring </li></ul></ul>
    13. 14. Population Characteristics <ul><li>We can characterize individual populations in terms of … </li></ul><ul><li>Variation </li></ul><ul><li>Variationtterns of Dispersion </li></ul><ul><li>Patterns of Dispersion </li></ul><ul><li>Demorgraphics </li></ul><ul><li>Size and Density </li></ul><ul><li>Limits on population growth </li></ul><ul><li>Human population growth </li></ul>
    14. 15. Four Factors Influence the Size of a Population: <ul><li>Natality: Birth Rate (offspring produced and added to population) </li></ul>Babies!
    15. 16. Mortality: Death Rate (individuals that die)
    16. 17. Immigration: Movement of members of the species into the area
    17. 18. Emigration: Movement of members of the species out of area to live elsewhere.
    18. 19. Population Change Population Change = (natality + immigration) – (mortality + emigration))
    19. 20. Exponential Curve Unlimited Growth (J-Shaped) Populations tend to grow in size for the simple reason that individuals tend to have more than one offspring.
    20. 21. Can this happen in nature? <ul><li>Yes: Bacteria </li></ul><ul><ul><li>If there are no factors limiting the growth, their number will increase rapidly. </li></ul></ul>
    21. 22. Exponential growth of bacteria
    22. 23. Can this happen in nature? <ul><li>Yes: Invasive species </li></ul><ul><ul><li>Uniform habitat </li></ul></ul><ul><ul><li>No predators </li></ul></ul><ul><ul><li>No disease </li></ul></ul><ul><ul><li>Unlimited area </li></ul></ul><ul><ul><li>Abundant food </li></ul></ul>
    23. 25. <ul><li>3 Phases: </li></ul><ul><li>Exponential growth Phase </li></ul><ul><li>Transitional Phase </li></ul><ul><li>Plateau Phase </li></ul>Limited Growth Sigmoid (S-Shaped)
    24. 26. Exponential Growth Phase <ul><li>Population increases exponentially. </li></ul><ul><li>Resources are abundant. </li></ul><ul><li>Predators and disease are rare. </li></ul>
    25. 27. Transitional Phase <ul><li>As a result of intra-specific competition </li></ul><ul><ul><li>for food, shelter, nesting space, etc., </li></ul></ul><ul><ul><li>and the build up of waste. </li></ul></ul><ul><li>The growth rate slows down. </li></ul><ul><ul><li>Birth rates decline and death rate increases </li></ul></ul>
    26. 28. Plateau Phase <ul><li>Natality and mortality are equal so population size is constant. </li></ul><ul><li>When the number of individuals in the population have reached the maximum which can be supported by the environment. </li></ul>The number is called the CARRYING CAPACITY
    27. 29. Growth of a population of fur seals
    28. 30. Population size oscillates around the carrying capacity (K) Time N K overshoot oscillations
    29. 31. Population Characteristics <ul><li>We can characterize individual populations in terms of … </li></ul><ul><li>Variation </li></ul><ul><li>Patterns of Dispersion </li></ul><ul><li>Demographics </li></ul><ul><li>Size and Density </li></ul><ul><li>Limits on population growth </li></ul><ul><li>Human population growth </li></ul>
    30. 32. <ul><li>Density Dependent Limits </li></ul><ul><ul><li>Food </li></ul></ul><ul><ul><li>Water </li></ul></ul><ul><ul><li>Shelter </li></ul></ul><ul><ul><li>Disease </li></ul></ul><ul><li>Density Independent Limits </li></ul><ul><ul><li>Natural Disasters </li></ul></ul><ul><ul><li>Humans (logging, mining, farming) </li></ul></ul>Water and shelter are critical limiting factors in the desert. Fire is an example of a Density independent Limiting factor. Limits on Population Growth
    31. 33. r-strategies “real lot” <ul><li>An r-strategy involves investing more resources into producing many offspring, having a short life span, early maturity, reproducing only once and having a small body size. </li></ul>
    32. 34. Frog Eggs Frogs lay many eggs & leave them in the water to hatch into tadpoles, some get eaten, some become tadpoles.
    33. 35. Tadpole Some tadpoles are eaten, some tadpoles become frogs
    34. 36. Frog Many animals are waiting on shore for frogs: raccoons, foxes, and many other small predators. If 1 frog from a 100 eggs lives to be a parent, his/her survival is really outstanding
    35. 37. K-strategies “caring” <ul><li>A K-strategy involves investing more resources into development and long-term survival. This involves a longer life span and late maturity, and is more likely to involve parental care, the production of few offspring, and reproducing more than once. </li></ul>
    36. 38. K-strategies
    37. 39. K-selected <ul><li>   Elephants are examples of K-selected animals. Female elephants have babies about three years apart, and they have only one each time. The whole group looks after the youngsters, and protects them through childhood and adolescence </li></ul>
    38. 40. <ul><li>There are organisms that display extreme r- or K-strategies, but most organisms have life histories that are intermediate on the continuum. </li></ul><ul><li>Some organisms such as Drosophila switch strategies depending on environmental conditions. </li></ul>
    39. 41. The environmental conditions that favor either r-strategies or K-strategies <ul><li>In a predictable environment, in order to maximize fitness, it pays to invest resources in long-term development and long life (K-strategy). In an unstable environment, it is better to produce as many offspring as quickly as possible (r-strategy). Of concern is that ecological disruption favors </li></ul><ul><li>r-strategists such as pathogens and pest species. </li></ul>
    40. 42. Reproductive Strategies
    41. 43. Population Characteristics <ul><li>We can characterize individual populations in terms of … </li></ul><ul><li>Variation </li></ul><ul><li>Patterns of Dispersion </li></ul><ul><li>Demographics </li></ul><ul><li>Size and Density </li></ul><ul><li>Limits on population growth </li></ul><ul><li>Human population growth </li></ul>
    42. 45. How did we get here? <ul><li>When I graduated </li></ul><ul><li>high school there were </li></ul><ul><li>4 billion people. </li></ul><ul><li>Today there are </li></ul><ul><li>almost 7 billion people </li></ul>
    43. 46. About 5 million years ago Hunter-gathers 1 million people
    44. 47. Neolithic Period (6000 B.C.) No longer a Natural Setting 100 million people
    45. 48. Common area 2000 years ago 300 million people
    46. 49. 1800’s (Carbon cycle control) Steam engine 1 billion people
    47. 50. London between 1800 to 1880 <ul><li>1800 pop. 1 million </li></ul><ul><li>1880 pop. 4.5 million </li></ul><ul><li>Improvements in medicine and public health </li></ul>
    48. 51. Life Expectance <ul><li>Neolithic it was 20 </li></ul><ul><li>1900 it was 30 </li></ul><ul><li>1950 it was 47 </li></ul><ul><li>Current world average is 67 </li></ul>
    49. 52. 1800-2000? <ul><li>From 1 billion to 6 billion? How??? </li></ul>
    50. 53. 1908 Control of the Nitrogen Cycle <ul><li>Up until 1908 farms were dependent on organic sources for nitrogen (manure) </li></ul><ul><li>Haber figured out how to convert N 2 into NH 3 and then into NH 4 + of NO 3 - </li></ul><ul><li>Commercial fertilizers are born </li></ul>Fritz Haber
    51. 54. 1944 Plant Breeding <ul><li>Improves yields </li></ul><ul><li>Disease resistance improvements </li></ul><ul><li>Less day-length sensitive </li></ul><ul><li>Improve sharing of ideas on plant breeding </li></ul>
    52. 55. What’s Behind Population Growth <ul><li>Three Factors </li></ul><ul><ul><li>Fertility </li></ul></ul><ul><ul><li>Infant Mortality </li></ul></ul><ul><ul><li>Longevity </li></ul></ul><ul><li>Animal Domestication and Agriculture </li></ul><ul><ul><li>Provided for a few to feed many </li></ul></ul><ul><li>Industrial Revolution </li></ul><ul><ul><li>Growth of Cities and Infrastructure </li></ul></ul><ul><ul><ul><li>Water </li></ul></ul></ul><ul><ul><ul><li>Energy </li></ul></ul></ul><ul><ul><ul><li>Transportation </li></ul></ul></ul><ul><ul><li>Increased Productivity </li></ul></ul><ul><ul><li>Nutrition </li></ul></ul><ul><ul><li>Sanitation </li></ul></ul><ul><ul><li>Medicine </li></ul></ul>
    53. 56. Exponential growth of the human population Human population growth does not currently show density effects that typically characterize natural populations. Limited resources eventually will cause human population growth to slow, but global human carrying capacity is not known.
    54. 57. Population Predictions <ul><li>Most predictions: 9-12B by 2050 10-15B by 2100 </li></ul><ul><li>Large uncertainties </li></ul>
    55. 58. Resource Limits <ul><li>Land </li></ul><ul><ul><li>Deforesting to acquire more arable land </li></ul></ul><ul><ul><li>Would run out in next century at current yields </li></ul></ul><ul><li>Water </li></ul><ul><ul><li>In 1950 people used half of accessible water </li></ul></ul><ul><ul><li>Are now dependent on dams </li></ul></ul><ul><ul><li>Pollution loses 33% of potential water </li></ul></ul><ul><ul><li>Getting close to limits </li></ul></ul><ul><li>Energy </li></ul><ul><ul><li>growth very high last fifty years </li></ul></ul><ul><ul><li>Mostly hydrocarbon fuels </li></ul></ul><ul><ul><li>Nonrenewable resource consumption </li></ul></ul><ul><ul><li>Climate change issues </li></ul></ul>
    56. 59. Populations of organisms <ul><li>Population density is the number of organisms per unit area. </li></ul><ul><li>There are advantages and disadvantages to both high and low densities. </li></ul><ul><li>Examples? </li></ul>
    57. 60. Why monitor populations ? <ul><li>Determine current status of a population </li></ul><ul><li>Determine habitat requirements of a species </li></ul><ul><li>Evaluate effects of management </li></ul>Population Sampling *Complete “census” of natural populations is often very difficult!
    58. 61. Population vs. Sample Sample True Population
    59. 62. RANDOM SAMPLING <ul><li>A sampling procedure that assures that each element in the population has an equal chance of being selected </li></ul><ul><li>Sampled population should be representative of target population </li></ul>
    60. 63. Sample Methods <ul><li>Quadrat </li></ul><ul><li>Mark-Recapture </li></ul><ul><li>There are MANY more… </li></ul>
    61. 64. Quadrat Sampling <ul><li>A square frame is placed in a habitat </li></ul><ul><li>All the individuals in the quadrat are counted </li></ul><ul><li>The process is repeated until the sample size is large enough </li></ul>
    62. 65. <ul><li>Useful for small organisms or for organisms that do not move </li></ul>
    63. 66. MARK-RECAPTURE <ul><li>Capture and mark known # of individuals </li></ul><ul><li>2 nd round of captures soon after </li></ul><ul><ul><li>Time for mixing, but not mortality </li></ul></ul><ul><li>Fraction of marked individuals in recapture sample is estimate of the proportion of population marked in first capture </li></ul>
    64. 67. where, N = population size M = number of individuals marked in first trapping n = number of individuals captured in second trapping R = number of marked individuals recaptured Lincoln-Peterson Index Using mark-recapture sampling to estimate animal populations This is known as the &quot;Lincoln Index&quot;
    65. 68. After rearranging to solve for N , this becomes:
    66. 69. Equation: another method: <ul><li>N = # initially marked x total 2 nd catch </li></ul><ul><li># of marked recaptures </li></ul><ul><li>Or </li></ul><ul><li>N 1 x N 2 </li></ul><ul><li>N 3 </li></ul>
    67. 70. Mark Recapture Lincoln-Peterson Index M = 4 n = 5 R = 2
    68. 71. Survey 1: M = 12 Survey 2: n = 15 R = 4
    69. 72. <ul><li>You capture and mark 150 fish in a lake. (This must be a random, representative sample.) </li></ul><ul><li>You release them back into the lake, allowing enough time for them to remix with the population. </li></ul><ul><li>You trap another 220 fish, of which 25 are recaptures (i.e., marked from the initial trapping. </li></ul><ul><li>What is your estimate of the total population of fish in the lake? </li></ul>Example:
    70. 73. <ul><li>M = 150 </li></ul><ul><li>n= 220 </li></ul><ul><li>R= 25 </li></ul><ul><li>N = [(220)(150)] / 25 </li></ul><ul><ul><ul><li>= 1320 FISH </li></ul></ul></ul>Example:
    71. 74. Marking methods <ul><li>Paint or dye </li></ul><ul><li>Color band </li></ul><ul><ul><li>birds </li></ul></ul><ul><li>Unique markings </li></ul><ul><ul><li>Large mammals; keep photo record </li></ul></ul><ul><li>Toe clipping </li></ul><ul><ul><li>Reptiles, amphibians, rodents </li></ul></ul><ul><li>Radio Collars </li></ul><ul><li>Micro chips </li></ul>(NPS 2000)
    72. 75. When would mark-recapture give you a bad estimate of the population size? <ul><li>Marked animals unlikely to be re-trapped </li></ul><ul><li>Marked animals likely to die </li></ul><ul><li>Marks fall off </li></ul>
    73. 76. T-test <ul><li>T-test is used to determine the significance of the difference between two sets of data using values for t. </li></ul><ul><li>The t-test can be used to compare two sets of data and measure the amount of overlap. </li></ul><ul><li>A review of t-test </li></ul>
    74. 78. Null Hypothesis <ul><li>The null hypothesis is generally that which is presumed to be true initially. It is rejected only when it becomes evidently false, that is, when the researcher is 90%, 98%, or 99% confident that the data does not support it. </li></ul><ul><li>For example </li></ul><ul><li>if we want to compare the test scores of two random samples of men and women, a null hypothesis would be that the mean score of the male population was the same as the mean score of the female population: </li></ul><ul><li>H 0  : μ 1 = μ 2 where: H 0 = the null hypothesis μ 1 = the mean of population 1, and μ 2 = the mean of population 2. </li></ul>
    75. 79. <ul><li>We have all the information we need to complete the </li></ul><ul><li>six step statistical inference process: </li></ul><ul><li>1.State the null hypothesis and the alternative hypothesis based on your research question . </li></ul><ul><li>2. Set the alpha level . </li></ul><ul><li>= .05 </li></ul><ul><li>3. Calculate the value of the appropriate statistic. Also indicate the degrees of freedom for the statistical test if necessary. </li></ul><ul><li>t = 2.252 </li></ul><ul><li>df = n 1 + n 2 - 2 = 5 + 5 - 2 = 8 </li></ul><ul><li>4. Write the decision rule for rejecting the null hypothesis. Reject H 0 if t is >= 1.860 </li></ul>
    76. 80. Biomes of the World
    77. 81. What is a biome? A BIOME is the largest geographic biotic unit, a major community of plants and animals with similar life forms and environmental conditions.
    78. 82. How are biomes formed? Biomes are distributed across the Earth based primarily on climate. Therefore, in areas that are far apart, you will sometimes find similar plants and animals because the climate is similar. One factor affecting climate is latitude. Typically, the farther you move north or south of the equator, the colder the temperature gets. Another factor affecting climate is elevation. The higher you go in elevation, the colder the temperature gets. Biomes usually found at cold latitudes far from the equator are sometimes also found on high mountains at low latitudes. Typically, a climb of 100 feet in elevation is equivalent to traveling 600 miles northward.
    79. 83. How many biomes are there? 8
    80. 84. How many biomes are there? <ul><li>Tropical Rainforest </li></ul><ul><li>Tropical Savanna </li></ul><ul><li>Desert </li></ul><ul><li>Chaparral </li></ul><ul><li>Grassland </li></ul><ul><li>Temperate Deciduous Forest </li></ul><ul><li>Temperate Boreal Forest </li></ul><ul><li>Tundra </li></ul>Although there is some disagreement among scientists on how to divide up the Earth’s biomes, most can agree on the following eight:
    81. 85. Tropical Rainforest <ul><li>Typically found near the equator </li></ul><ul><li>Receives more than 200 cm of rain annually </li></ul><ul><li>Temperatures typically fall between 20 o C and 25 o C for the entire year </li></ul><ul><li>As many as 50% of all the world’s animal species may be found here </li></ul>
    82. 86. Tropical Savanna <ul><li>Grasslands with a few scattered trees </li></ul><ul><li>Experience a wet and dry season </li></ul><ul><li>Hot temperatures </li></ul><ul><li>Annual rainfall is between 50 and 127 cm </li></ul><ul><li>More species of grazing mammals than any other biome </li></ul>
    83. 87. Desert <ul><li>Typically found between 25 o and 40 o latitude </li></ul><ul><li>Receives less than 25 cm of rain each year </li></ul><ul><li>Temperatures typically range between 20 o C and 25 o C but some extreme deserts can reach temperatures higher than 38 o C and lower than –15 o C </li></ul>
    84. 88. Chaparral <ul><li>Found between 32 o and 40 o latitude on the west coast of continents </li></ul><ul><li>Receives between 35 and 70 cm of rain, usually in the winter </li></ul><ul><li>Extremely resistant to drought and weather events </li></ul>
    85. 89. Grassland <ul><li>Because of the dry climate, trees are found only near water sources such as streams </li></ul><ul><li>Usually receives between 50 and 90 cm of rainfall each year </li></ul><ul><li>Summer temperatures can reach up to 38 o C, and winter temperatures can fall to –40 o C </li></ul>
    86. 90. Temperate Deciduous Forest <ul><li>Moderate climate </li></ul><ul><li>Most trees will lose their leaves in the winter </li></ul><ul><li>Temperatures range between –30 o C and 30 o C </li></ul><ul><li>Averages from 75 to 150 cm of precipitation </li></ul><ul><li>Well developed understory </li></ul>
    87. 91. Temperate Boreal Forest <ul><li>Also known as Taiga </li></ul><ul><li>Typically found between 45 o and 60 o North latitude </li></ul><ul><li>Cold climate with summer rains </li></ul><ul><li>Very few reptiles </li></ul><ul><li>Limited understory </li></ul><ul><li>Snow is primary form of precipitation (40 – 100 cm annually) </li></ul>
    88. 92. Tundra <ul><li>Means treeless or marshy plain </li></ul><ul><li>Characterized by permafrost – permanently frozen soil starting as high as a few centimeters below the surface – which severely limits plant growth </li></ul><ul><li>Winter temperatures average –34 o C while summer temperatures usually average below 10 o C </li></ul><ul><li>Low precipitation (15–25 cm per year) but ground is usually wet because of low evaporation </li></ul>

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