Environmental Science
A Study of Interrelationships
Thirteenth Edition

Enger & Smith

Chapter 7
Populations: Characterist...
Populations: Characteristics and Issues
7.1 Population Characteristics
 A population is a group of individuals of the same
species inhabiting the same area.
7.1 Population Characteristics

Effect of birthrate and death rate on population size
7.1 Population Characteristics

Age distribution in human populations
Population Density and
Spatial Distribution
 Population density is the number of individuals
per unit area.
• High popula...
7.2 A Population Growth Curve
 Biotic potential is the inherent reproductive
capacity of a species
• (biological ability ...
7.2 Biotic Potential
7.2 A Population Growth Curve
 Population growth follows a pattern:
•
•
•
•

1st
2nd
3rd
4th

lag phase
exponential growt...
7.2 A Population Growth Curve

A typical population growth curve
Population growth curve
 Lag Phase:
 first portion of the curve
 slow population growth
 Few births
Population growth curve
 Exponential Growth Phase (Log Phase):
 More organisms reproducing
 causing accelerated growth
...
7.2 Population Growth Curve
• Deceleration Phase:
– The population growth rate slows
– death rate and birthrate equal one ...
7.2 Population Growth Curve
 Stable Equilibrium Phase:
 The death rate and birth rate become equal
 the population stop...
7.3 Factors That Limit Population Size
 Limiting Factors--prevent unlimited population
growth
• Extrinsic limiting factor...
7.3 Factors That Limit Population Size
 Extrinsic limiting factors
 Come from outside the population
•
•
•
•

Predators
...
7.3 Factors That Limit Population Size
 Intrinsic limiting factors
• factors that originate within the population
• exerc...
Other limiting factors
 Density-dependent limiting factors
• become more effective as the density of the
population incre...
Other limiting factors
 Density-independent limiting factors
• population-controlling influences not related to the
densi...
Density dependent or independent?
 Mutualism between two species.
 A wolf eating rabbits.

 A large fire burns down man...
7.4 Categories of Limiting Factors
 For most populations, limiting factors recognized
as components of environmental resi...
Discussion
 What will we do?
7.5 Carrying Capacity
 Carrying capacity is the maximum sustainable
population for an area.

 It is not an inflexible nu...
7.5 Carrying Capacity
•
•
•
•
•

Successional changes
Climate variations
Disease epidemics
Forest fires, floods, or natura...
7.5 Carrying Capacity
7.6 Reproductive Strategies
and Population Fluctuations
 Species divided into two broad categories based
on their reprodu...
7.6 Reproductive Strategies
 K-strategists: Organisms that typically reach a stable
population as the population reaches ...
7.6 Reproductive Strategies
and Population Fluctuations
 K-strategist characteristics:
• Provide substantial parental car...
K-strategist
7.6 Reproductive Strategies
 r-strategist characteristics include:
•
•
•
•
•

Small, short-lived organisms
Produce many o...
r-strategist
Reproductive strategy
– produce large numbers of offspring to overcome high
mortality.

 r-strategists are c...
r-strategist
Summary
 The birthrate (natality) is the number of individuals
entering the population by reproduction during a
certain p...
Environmental Science
A Study of Interrelationships
Thirteenth Edition

Enger & Smith

Chapter 11
Biodiversity Issues

Cop...
11.3 Invasive Species
 Impact populations (affect population size)

 Some introductions of exotic species are
purposeful...
11.3 Invasive species
 The IUCN estimates about
• 30% of birds and 15% of plants are threatened
• because they are unable...
11.3 Threats to Biodiversity

The Asian long horned beetle
Overview
 http://www.youtube.com/watch?v=Bu6ouKt9zhs
Homework
 4 groups
 Each group answers one question

 Next week (1-29-14), present answers in 5 to 10
minute presentati...
Population principles lecture 5
Population principles lecture 5
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Population principles lecture 5

  1. 1. Environmental Science A Study of Interrelationships Thirteenth Edition Enger & Smith Chapter 7 Populations: Characteristics and Issues Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
  2. 2. Populations: Characteristics and Issues
  3. 3. 7.1 Population Characteristics  A population is a group of individuals of the same species inhabiting the same area.
  4. 4. 7.1 Population Characteristics Effect of birthrate and death rate on population size
  5. 5. 7.1 Population Characteristics Age distribution in human populations
  6. 6. Population Density and Spatial Distribution  Population density is the number of individuals per unit area. • High population density – injures all individuals within the population – because they compete for resources
  7. 7. 7.2 A Population Growth Curve  Biotic potential is the inherent reproductive capacity of a species • (biological ability to produce offspring).  biotic potential is much above replacement level. • natural tendency for increase
  8. 8. 7.2 Biotic Potential
  9. 9. 7.2 A Population Growth Curve  Population growth follows a pattern: • • • • 1st 2nd 3rd 4th lag phase exponential growth phase deceleration phase stable equilibrium phase
  10. 10. 7.2 A Population Growth Curve A typical population growth curve
  11. 11. Population growth curve  Lag Phase:  first portion of the curve  slow population growth  Few births
  12. 12. Population growth curve  Exponential Growth Phase (Log Phase):  More organisms reproducing  causing accelerated growth  continues if birth rate exceeds death rate
  13. 13. 7.2 Population Growth Curve • Deceleration Phase: – The population growth rate slows – death rate and birthrate equal one another
  14. 14. 7.2 Population Growth Curve  Stable Equilibrium Phase:  The death rate and birth rate become equal  the population stops growing
  15. 15. 7.3 Factors That Limit Population Size  Limiting Factors--prevent unlimited population growth • Extrinsic limiting factors • Intrinsic limiting factors • Density-dependent factors • Density-independent factors
  16. 16. 7.3 Factors That Limit Population Size  Extrinsic limiting factors  Come from outside the population • • • • Predators Loss of food source Lack of sunlight Accidents of nature
  17. 17. 7.3 Factors That Limit Population Size  Intrinsic limiting factors • factors that originate within the population • exercise control over it • Behavioral changes amongst the population cause lower birthrates and higher death rates.
  18. 18. Other limiting factors  Density-dependent limiting factors • become more effective as the density of the population increases. • Denser population – Predators more effective
  19. 19. Other limiting factors  Density-independent limiting factors • population-controlling influences not related to the density of the population. • Accidental • Extrinsic factors
  20. 20. Density dependent or independent?  Mutualism between two species.  A wolf eating rabbits.  A large fire burns down many of the trees in a forest.  A disease kills all the mice in a local radius and the foxes have nothing to eat.
  21. 21. 7.4 Categories of Limiting Factors  For most populations, limiting factors recognized as components of environmental resistance • • • • Raw material availability Energy availability Accumulation of waste products Interactions among organisms
  22. 22. Discussion  What will we do?
  23. 23. 7.5 Carrying Capacity  Carrying capacity is the maximum sustainable population for an area.  It is not an inflexible number; it can be influenced by environmental differences
  24. 24. 7.5 Carrying Capacity • • • • • Successional changes Climate variations Disease epidemics Forest fires, floods, or natural disasters Nutrient levels in aquatic ecosystems
  25. 25. 7.5 Carrying Capacity
  26. 26. 7.6 Reproductive Strategies and Population Fluctuations  Species divided into two broad categories based on their reproductive strategies: • K-strategists • r-strategists
  27. 27. 7.6 Reproductive Strategies  K-strategists: Organisms that typically reach a stable population as the population reaches the carrying capacity.  K-strategist characteristics:  Usually occupy relatively stable environments • Large organisms • Long-lived • Produce few offspring
  28. 28. 7.6 Reproductive Strategies and Population Fluctuations  K-strategist characteristics: • Provide substantial parental care • Reproductive strategy – invest a great deal of energy in producing a few offspring that have a good chance of living to reproduce.  K-strategists • controlled by density-dependent limiting factors.
  29. 29. K-strategist
  30. 30. 7.6 Reproductive Strategies  r-strategist characteristics include: • • • • • Small, short-lived organisms Produce many offspring Little if any parental care Exploit unstable environments Usually do not reach carrying capacity (boom-bust cycles)
  31. 31. r-strategist Reproductive strategy – produce large numbers of offspring to overcome high mortality.  r-strategists are controlled by densityindependent limiting factors.
  32. 32. r-strategist
  33. 33. Summary  The birthrate (natality) is the number of individuals entering the population by reproduction during a certain period.  The death rate is the number of deaths in a population in a certain period.  A typical population growth curve shows a lag phase followed by an exponential growth phase, a deceleration phase, and a stable equilibrium phase at the carrying capacity.
  34. 34. Environmental Science A Study of Interrelationships Thirteenth Edition Enger & Smith Chapter 11 Biodiversity Issues Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
  35. 35. 11.3 Invasive Species  Impact populations (affect population size)  Some introductions of exotic species are purposeful, while others are accidental.  Globalization is responsible for spreading thousands of invasive alien species around the world.
  36. 36. 11.3 Invasive species  The IUCN estimates about • 30% of birds and 15% of plants are threatened • because they are unable to successfully compete against invasive exotic species.  Various insects have had an effect on ecosystem structure. • Asian long horned beetle  Freshwater ecosystems have been greatly affected. • Zebra mussel
  37. 37. 11.3 Threats to Biodiversity The Asian long horned beetle
  38. 38. Overview  http://www.youtube.com/watch?v=Bu6ouKt9zhs
  39. 39. Homework  4 groups  Each group answers one question  Next week (1-29-14), present answers in 5 to 10 minute presentation

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