1. Environmental Science Chapter 4: Population Ecology
Mr. Manskopf
Notes also available at

2. Population Ecology Big Ideas
In an ecosystem, the biotic and abiotic components interact to form an interconnected system.
Humans classify the diversity of life on Earth in order to better understand their relationships.
Population sizes change according to changes in the environment.

3. Section 1: Studying Ecology
GOALS
Distinguish between biotic and abiotic factors in an ecosystem
Describe how a population, community differ from a species
Explain the importance of habitats

4. What is ecology?
The study of how organisms interact with each other and with their environments

5. What is an ecosystem?

6. Defining an ecosystem
Ecosystem: all the organisms living in an area together
Forest Ecosystem
Pond Ecosystem
Vacant Lot Ecosystem
Desert Ecosystem

7. All Ecosystems are connected
How does your ecosystem impact the Atlantic Ocean?

8. Parts of an ecosystem

9. Parts of an ecosystem
In order for an ecosystem to survive there must be certain basic parts
Energy
Mineral nutrients
Carbon dioxide
Water
Oxygen and more

11. What are some parts of this ecosystem?

12. You will be conducting a study of the interactions of vegetation, animals, mineral composition of the soil, and water levels in a saltmarsh. You are studying the saltmarsh ___.
ECOSYSTEM

13. Biotic vs. Abiotic Biotic: living parts of the ecosystem
Plants, animals, bacteria, etc.
Abiotic: nonliving parts of the ecosystem
Sunlight, soil, air, temperature

14. What are some biotic AND abiotic parts of this ecosystem?

15. Organizing Biotic Parts

17. Smallest Unit
Organism: an individual living thing like you, a tree, a fox, a rose
Species are groups of organisms like red foxes or black widow spiders, or grizzly bears

18. Species
Species: groups of organisms that resemble each other in appearance, behavior, chemistry and genetic makeup…able to reproduce
3.6 to 100 million species (1.4 identified)
Mostly insects/micro
Tropical forests

19. Insects 751,000
Known species 1,412,000
Plants 248,400

20. Population
Population: all the members of the same species that live in the same place at the same time
Field mice living in a corn field, grizzly bears of Yellowstone Park area

22. Community
Community: a group of various species that live in the same place and interact with each other.
Pond Community
Pineland Forest

24. Biosphere
All parts of the Earth where life is found

25. Giraffes, lions, zebras, hyenas, and all the other living things of the Serengeti make up a(n) ___
COMMUNITY

26. Habitat
Habitat: a place where an organism lives Organisms are well suited for their habitat

27. Habitat
Habitats provide an organism with resources—anything an organism needs to survive and reproduce, including food, shelter, and mates.

29. Section 1 Review
Distinguish between biotic and abiotic factors in an ecosystem
Describe how a population, community differ from a species
Explain the importance of habitats

30. Section 2: Describing Populations
Explain the usefulness of tracking population sizes
Define population density
Describe three ways populations can be distributed

31. The Decline of the Passenger Pigeon
How does a species go from having billions to extinct in just one century…The Passenger Pigeon Story.
Extinct in the wild since 1900 and last died in the Cincinnati Zoo 1914.

32. Review: What is a population?
Population: all the members of the same species that live in the same place at the same time
Field mice living in a corn field, grizzly bears of Yellowstone Park area
Wolves in Yellowstone NP

33. Population Size Why care about the size of the population?
How can scientists estimate the population (say of Elephant Seals on a beach in CA)?

34. Population Size
The number of individuals in a population at a given time
Sudden and dramatic decreases in population size can indicate an unhealthy population headed toward extinction.
Ecologists often use sampling techniques to estimate population size.
Did You Know? The passenger pigeon was once North America’s most abundant bird. Hunting drove them to extinction in less than 100 years.

35. Mark and Recapture
Common way of estimating population size

36. Estimating Population
How can you estimate the population of trees in this valley?
WHY NOT COUNT THEM ALL?
WHY IS SAMPLING NEEDED?

37. Population Density What is population density?
What are advantages and disadvantages of high and low density?

38. Population Density Measure of how crowded a population is
Larger organisms generally have lower population densities.
Low population density: More space, resources; finding mates can be difficult
High population density: Finding mates is easier; tends to be more competition; more infectious disease; more vulnerability to predators

39. Population Distribution
How organisms are arranged within an area:
RANDMOM
CLUMPED
UNIFORM
Occurs when individuals hold territory or compete for space. Plants in desert
Occurs where resources needed are found throughout, wildflowers in meadow
Most Common. Occurs where resources are together. Water hole in desert, humans in cities

40. Many bird species are territorial
Many bird species are territorial. In territorial birds species, what kind of population structure would you expect?
UNIFORM

41. Population Distribution
Random distribution: Organisms arranged in no particular pattern
Uniform distribution: Organisms evenly spaced
Clumped distribution: Organisms grouped near resources; most common distribution in nature

42. What type of distribution?
CLUMPED
WHY?

43. Age Structure
Relative number of organisms of each age group within population
Can be used to predict future population growth of a population
HOW?

44. Sex Ratios Proportion of males to females
Age structure diagrams give information about sex ratios.
For a monogamous species, the ideal sex ratio is 50:50.
Why is 50/50 not as important in non-monogamous populations?

45. Section 2: Describing Populations Review
Explain the usefulness of tracking population sizes
Define population density
Describe three ways populations can be distributed
TERMS: Population Size, Population Density, Population Distribution, Age Structure, Sex Ratios

47. Section 3: Population Growth
Describe the factors that influence population’s growth rate
Explain exponential and logistic growth
Explain how limiting factors and biotic potential affect population growth
TERMS: survivorship curve, immigration, emigration, exponential growth, carrying capacity, logistic growth, biotic potential

48. What does this graph show?

49. Population Growth?
Why are there so few whales, but so many bacteria?

50. Factors the Determine Population Growth
A population’s relative birth and death rates (mortality and natality) affect how it grows.
More births than deaths = population increase
More deaths than births = population decrease

51. Survivorship
Individuals of different ages have different probabilities of dying
Survivorship curves show how the likelihood of death varies with age.

52. Type I survivorship curves are for species that have a high survival rate of the young, live out most of their expected life span and die in old age. Humans are a good example of a species with a Type I survivorship curve
Type II survivorship curves are for species that have a relatively constant death rate throughout their life span. Death could be due to hunting or diseases. Examples of species exhibiting a Type II survivorship curve are coral, squirrels, honey bees and many reptiles.

53. Type III survivorship curves are found in species that have many young, most of which die very early in their life. Plants, oysters and sea urchins are examples of species that have Type III survivorship curves.

54. If a tree wants to successfully reproduce, how many seeds should it spread?
If a couple in India knows for sure there child will survive to adulthood, will they decide to have more or less children do you think?

55. Immigration/Emigration
In addition to births and deaths, population growth is affected by immigration and emigration—individuals moving into and out of a population.
Migration, seasonal movement into and out of an area, can temporarily change population size.

56. Population Calculations
Net population Change = (births + immigration) – (deaths + emigration)
There are 300 people living in a village, 50 children are born, 20 people die, 10 immigrate and 2 emigrate. What is the new population?

57. Calculating Growth Rate
Determined by the following equation: (birthrate + immigration rate) – (death rate + emigration rate)
Growing populations have a positive growth rate; shrinking populations have a negative growth rate.
Usually expressed in terms of individuals per 1000
Current human growth rate 1.25% down from 2.2% in 1963

58. Every spring, many species of bird travel north to the Arctic to breed, and in the fall travel south again for the winter. This is an example of _____
MIGRATION

59. How Populations Grow
What resources are available to the population?

60. Patterns of Growth EXPONETIAL GROWTH
Population increases by a fixed percentage every year.
Normally occurs only when small populations are introduced to an area with ideal environmental conditions
Rarely lasts long
WHAT SHAPE DOES EXPONENTIAL GROWTH LOOK LIKE?
Starts slowly, then takes off – “J-Shaped Curve”

62. Why doesn’t exponential growth last long?

63. Limiting Factors
Limiting Factor Principle: too much or too little of any abiotic factor can limit or prevent growth of a population, even if all other factors are near or above optimum.
Why are there no citrus fruit growing in NJ?
Why do trees grow toward the sky?

64. What Might Be Some Limiting Factors in the Ocean?
may include:
Salinity Ph
Sunlight
Dissolved oxygen
Temperature

66. Carrying Capacity
Limiting Factors lead to Carrying Capacity: the largest population an environment can sustain.
What is the maximum amount of wolves that can be sustained in Yellowstone?

67. Logistic Growth
Carrying Capacities are NOT fixed

68. A population of wolves is reintroduced into Yellowstone National Park
A population of wolves is reintroduced into Yellowstone National Park. For the first decade, the wolf population grows exponentially. Then, the population growth slows. The new pattern is known as ___
LOGISTIC GROWTH
In the example above, where wolves are reintroduced to Yellowstone National Park, the number of elk and other prey species within the park are _____
Limiting Factors

69. Biotic Potential
An organism’s maximum ability to produce offspring in ideal conditions
Many factors influence biotic potential, including gestation time and generation time.
Organisms with high biotic potential can recover more quickly from population declines than organisms with low biotic potential.

70. Biotic Potential Scorpion Fish Mature 3-5 years
Release 50,000 to 100,000 eggs
Once fertilized take days to hatch
HIGH BIOTIC POTENTIAL
Orangutans
Females Mature 10 years
Birth to single babies once every eight years
LOW BIOTIC POTENTIAL

71. Section 3 Population Growth Review
Describe the factors that influence population’s growth rate
Explain exponential and logistic growth
Explain how limiting factors and biotic potential affect population growth
TERMS: survivorship curve, immigration, emigration, exponential growth, carrying capacity, logistic growth, biotic potential

72. Chapter 4 Big Ideas
In an ecosystem, the biotic and abiotic components interact to form an interconnected system.
Humans classify the diversity of life on Earth in order to better understand their relationships.
Population sizes change according to changes in the environment.

73. Think About: Essays
Explain how limiting factors and biotic potential interact to regulate the population growth of a species.
What are some of the benefits for humans of keeping track of the population sizes of wild species?