Human Impacts on Environment Population

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Human Impacts on Environment- Population

• Earths Human Population is over 6 billion
• Growing exponentially
• Expected to add several billion more people in
  21st century
• Increase will adversely affect living conditions
  in many areas of the world

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Ecology

• Ecology
• eco house logy study of
• The study of interactions among and between
  organisms in their abiotic environment
• Broadest field in biology
• Biotic- living environment
• Includes all organisms
• Abiotic- non living or physical environment
• Includes living space, sunlight, soil,
  precipitation, etc.

3
Food Chains- The Path of Energy Flow

• Energy from food passes from one organisms to
  another
• Each link is called a trophic level

4
Evolution

• The cumulative genetic changes that occur in a
  population of organisms over time
• Current theories were proposed by Charles Darwin,
  a 19th century naturalist
• Evolution occurs through natural selection
• Natural Selection
• Individuals with more favorable genetic traits
  are more likely to survive and reproduce
• Frequency of favorable traits increase in
  subsequent generations

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Natural Selection

• Based on four observations about the natural
  world
• Overproduction
• Each species produces more offspring than will
  survive to maturity
• Variation
• Individuals in a population exhibit variation
• Limits on Population Growth
• Resource limitations will keep population in
  check
• Differential Reproductive Success
• Individuals with most favorable traits are more
  likely to reproduce

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The Water (Hydrologic) Cycle
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Temperature Changes with Latitude

• Solar energy does not hit earth uniformly
• Due to earths spherical shape and tilt

Equator (a) High concentration Little Reflection
High Temperature
Closer to Poles (c) Low concentration Higher
Reflection Low Temperature
From (a) to (c)
In diagram below
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Temperature Changes with Season

• Seasons determined by earths tilt (23.5)
• Causes each hemisphere to tilt toward the sun for
  half the year

• Northern Hemisphere tilts towards the sun from
  March 21- September 22 (warm season)

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Biomagnification

• The increased concentration of toxic chemicals in
  the tissues of organisms that are at higher
  levels in food webs
• Diagram is example of biomagnification of DDT

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Toxicity

• Toxicity measured by dose and response
• Dose amount that enters that body of an exposed
  organism
• Response the amount of damage caused by a
  specific dose
• LD50
• Lethal dose to 50 of the test organisms
• Smaller the LD50, the more lethal the chemical
• Determined for all new synthetic chemicals

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Dose-Response Curve
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