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Population Dynamics Chapter 4.1
How fast do populations grow? <ul><li>Populations of organisms do not experience linear growth </li></ul><ul><ul><li>They ...
Human Population Growth <ul><li>Human population growth is different from bacteria population growth in that we can consci...
Is growth unlimited? <ul><li>Exponential Growth:  As a population gets larger, it grows at a faster rate </li></ul>
What can limit growth? <ul><li>Population growth has limits </li></ul><ul><li>Limiting factors:  food, disease, predators,...
Carrying Capacity <ul><li>Carrying Capacity:  The number of organisms of one species that an environment can support indef...
Carrying Capacity Cont. <ul><li>When a population overshoots the carrying capacity </li></ul><ul><ul><li>Then limiting fac...
Reproduction Patterns <ul><li>Life-history pattern:  an organisms reproductive pattern </li></ul><ul><li>Example #1 = mosq...
Rapid life-history patterns <ul><ul><li>Common among organisms that live in changeable or unpredictable environments </li>...
Slow life history patterns   <ul><ul><li>Large species that live in a more stable environment  </li></ul></ul><ul><ul><li>...
Density factors and population growth <ul><ul><li>Limiting factors are both biotic and abiotic </li></ul></ul><ul><ul><ul>...
Density factors and population growth continued <ul><ul><li>2 kinds of limiting factors that are related to dispersal = de...
Organisms Interactions Limit Population Size
Predation affects population size <ul><li>Predation can affect population sizes in both minor and major ways </li></ul><ul...
Predation affects population size continued <ul><li>Populations of predators and their prey are known to experience cycles...
Competition within a population <ul><li>When a population is small, resources can build up and become plentiful </li></ul>...
The effects of crowding and stress <ul><li>When populations = crowded, individuals exhibit stress </li></ul><ul><ul><li>St...
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Chapter 4.1

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Transcript of "Chapter 4.1"

  1. 1. Population Dynamics Chapter 4.1
  2. 2. How fast do populations grow? <ul><li>Populations of organisms do not experience linear growth </li></ul><ul><ul><li>They start out slowly </li></ul></ul><ul><ul><li>It begins to resemble a J-shape curve </li></ul></ul><ul><li>The initial increase in the number of organisms is slow because the number of reproducing individuals is small </li></ul><ul><li>The rate of population growth soon increases because the total number of individuals that are able to reproduce has increased </li></ul>
  3. 3. Human Population Growth <ul><li>Human population growth is different from bacteria population growth in that we can consciously change our environment </li></ul><ul><ul><li>ex: we eradicated smallpox </li></ul></ul><ul><ul><li>ex: developed methods for producing more food </li></ul></ul><ul><ul><li>ex: infant mortality rate has decreased </li></ul></ul><ul><ul><li>ex: technological developments improved water quality </li></ul></ul><ul><li>Result = live longer and produce more offspring that live long enough to produce more offspring </li></ul>
  4. 4. Is growth unlimited? <ul><li>Exponential Growth: As a population gets larger, it grows at a faster rate </li></ul>
  5. 5. What can limit growth? <ul><li>Population growth has limits </li></ul><ul><li>Limiting factors: food, disease, predators, or lack of space </li></ul><ul><ul><li>All cause population growth to slow </li></ul></ul><ul><li>Under these pressures, the population may stabilize in an S-shaped growth curve </li></ul>
  6. 6. Carrying Capacity <ul><li>Carrying Capacity: The number of organisms of one species that an environment can support indefinitely </li></ul><ul><li>When a population is developing in an environment with resources… </li></ul><ul><ul><li>There are more births than deaths </li></ul></ul><ul><ul><li>And the population increases until the carrying capacity is reached or passed </li></ul></ul>
  7. 7. Carrying Capacity Cont. <ul><li>When a population overshoots the carrying capacity </li></ul><ul><ul><li>Then limiting factors may come into effect </li></ul></ul><ul><ul><li>Deaths being to exceed births </li></ul></ul><ul><ul><li>And the population falls below carrying capacity </li></ul></ul><ul><li>Many organisms in nature show a graph that has a line below the carrying capacity </li></ul>
  8. 8. Reproduction Patterns <ul><li>Life-history pattern: an organisms reproductive pattern </li></ul><ul><li>Example #1 = mosquitoes (rapid life history pattern) </li></ul><ul><ul><li>Reproduce very rapidly </li></ul></ul><ul><ul><li>Produce many offspring in a short period of time </li></ul></ul><ul><li>Example #2 = elephants (slow life history pattern) </li></ul><ul><ul><li>Slow rate of reproduction </li></ul></ul><ul><ul><li>Produce relatively few young over their lifetime </li></ul></ul>
  9. 9. Rapid life-history patterns <ul><ul><li>Common among organisms that live in changeable or unpredictable environments </li></ul></ul><ul><ul><li>Characteristics: </li></ul></ul><ul><ul><ul><li>small body size </li></ul></ul></ul><ul><ul><ul><li>mature rapidly </li></ul></ul></ul><ul><ul><ul><li>reproduce early </li></ul></ul></ul><ul><ul><ul><li>and have a short life span </li></ul></ul></ul><ul><ul><ul><li>Populations increase rapidly  then decline when environmental changes occur suddenly </li></ul></ul></ul><ul><ul><ul><ul><li>The small surviving population will reproduce exponentially </li></ul></ul></ul></ul>
  10. 10. Slow life history patterns <ul><ul><li>Large species that live in a more stable environment </li></ul></ul><ul><ul><li>Ex: bears, elephants, whales, humans, and trees </li></ul></ul><ul><ul><li>Characteristics: </li></ul></ul><ul><ul><ul><li>reproduce and mature slowly </li></ul></ul></ul><ul><ul><ul><li>long lived </li></ul></ul></ul><ul><ul><ul><li>maintain populations at or near carrying capacity </li></ul></ul></ul>
  11. 11. Density factors and population growth <ul><ul><li>Limiting factors are both biotic and abiotic </li></ul></ul><ul><ul><ul><li>They determine whether or not an organism can live in a particular environment </li></ul></ul></ul><ul><ul><ul><li>Ex: limited food supply, space, chemicals (produced by plants themselves), extreme temperature, storms </li></ul></ul></ul><ul><ul><li>Organisms disperse in 3 patterns </li></ul></ul><ul><ul><ul><li>random </li></ul></ul></ul><ul><ul><ul><li>clumped </li></ul></ul></ul><ul><ul><ul><li>uniform </li></ul></ul></ul>
  12. 12. Density factors and population growth continued <ul><ul><li>2 kinds of limiting factors that are related to dispersal = density-dependent and density-independent. </li></ul></ul><ul><ul><ul><li>Density-dependent factor </li></ul></ul></ul><ul><ul><ul><ul><li>ex: disease, competition, predators, parasites, food </li></ul></ul></ul></ul><ul><ul><ul><ul><li>These factors have an increasing effect as the population increases </li></ul></ul></ul></ul><ul><ul><ul><li>Density-independent factor </li></ul></ul></ul><ul><ul><ul><ul><li>Affects populations, regardless of their density </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Often abiotic factors </li></ul></ul></ul></ul><ul><ul><ul><ul><li>ex: volcanic eruptions, temperature, storms, flood, drought, chemical pesticides </li></ul></ul></ul></ul>
  13. 13. Organisms Interactions Limit Population Size
  14. 14. Predation affects population size <ul><li>Predation can affect population sizes in both minor and major ways </li></ul><ul><ul><li>ex: owl kills and eats a mouse </li></ul></ul><ul><ul><li>ex: swarm of locusts eats and destroys acres of lettuce </li></ul></ul><ul><ul><li>ex: brown snake introduced to Guam (no native predators)  drastic effect on prey population </li></ul></ul>
  15. 15. Predation affects population size continued <ul><li>Populations of predators and their prey are known to experience cycles or changes in their numbers over period of time </li></ul><ul><li>Graph: the number of hair increases  then the number of lynx increases </li></ul><ul><li>Predation increases the chance that resources will be available for the remaining individuals in a prey population </li></ul>
  16. 16. Competition within a population <ul><li>When a population is small, resources can build up and become plentiful </li></ul><ul><ul><li> Then as these resources are used, the population increases in size </li></ul></ul><ul><ul><li> Competition for resources (food, water, and territory) increase significantly </li></ul></ul><ul><li>Competition is a density dependent factor </li></ul><ul><li>If few individuals are present  Then there is little competition for resources </li></ul><ul><li>When a population increases to the point where demand exceeds supply  the population size decreases </li></ul>
  17. 17. The effects of crowding and stress <ul><li>When populations = crowded, individuals exhibit stress </li></ul><ul><ul><li>Stress is shown via </li></ul></ul><ul><ul><ul><li>aggression </li></ul></ul></ul><ul><ul><ul><li>decrease in parental care </li></ul></ul></ul><ul><ul><ul><li>decreased fertility </li></ul></ul></ul><ul><ul><ul><li>decreased resistance to disease </li></ul></ul></ul><ul><ul><li>All have negative effects on populations </li></ul></ul><ul><li>They become limiting factors for growth and keep populations below carrying capacity </li></ul>
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