1. 5-1 How Populations Grow
A. Characteristics of Populations B. Population Growth C. Exponential Growth D. Logistic Growth

2. Characteristics of a Population
1- Geographical Distribution
2- Density
3- Growth Rate
1- Geographical Distribution
-area inhabited by a population
-could be as small as a few cubic centimeters like a bacteria or as large as millions of kilometers like killer whales

3. 2- Population Density the number of individuals per unit
How organisms are dispersed can be important
Three patterns of dispersal are random, clumped, and uniform

4. 3- Growth Rate - 3 factors that affect a populations size
number of births
number of deaths
number of individuals entering and leaving a population

5. A population will increase or decrease in size depending on the number added or removed from it
A population will grow if: Birth Rate > Death Rate
(# of individuals born) > (# of individuals who die)
A population will stay the same if: Birth Rate = Death Rate
A population will decline if: Birth Rate < Death Rate

6. Individuals entering and leaving the population will also increase or decrease a population’s size
Immigration- movement of individuals into an area (increase population)
Emigration- movement of individuals out of an area (decrease population) exit

7. Initial growth- birth (natality/birth rate) is high Exponential growth
Population Growth 1 2 3 4 5
Initial growth- birth (natality/birth rate) is high
Exponential growth
Carrying capacity- steady state
Decline- increase in death rate
Extinction

8. Exponential Growth
If a population has abundant space and food, protection from predators and disease then the organisms in the population will multiply and the population will increase

9. Exponential Growth
Under ideal conditions with plenty of nutrients, heat, moisture, & light a bacteria can reproduce by splitting in half within 20 minutes producing 2 bacteria
In 20 minutes the population is 2
In 40 minutes the population is 4
In 1 hour: the population is 8
In 2 hours: 64
In 3 hours: 512
In one day: 4,720,000,000,000,000,000,000

10. Exponential Growth
The pattern of growth is a J-shaped curve and the population is undergoing exponential growth
Exponential growth occurs when the individuals in a population reproduce at a constant rate
At first, the number of individuals increases slowly, over time the population becomes larger and larger until it approaches an infinitely large size
Under ideal conditions with unlimited resources, a population will grow exponentially

11. Exponential/Logistic Growth
Exponential growth doesn’t continue in natural populations for very long
If a new species of organism is introduced into a new environment
first the population grows slowly,
then exponentially,
eventually the population growth slows down (the size has not dropped, but the population is growing slower)
As resources become less available, the growth of a population slows or stops forming an S-shaped curve- logistic growth

12. Logistic Growth
Logistic Growth occurs when a population’s growth slows or stops following a period of exponential growth
Birth rate decreases and death rate increases

13. Carrying Capacity When growth levels off the population is not growing
Carrying capacity- the largest number of individuals that an environment can support
When a population overshoots the carrying capacity, then limiting factors may come into effect
A balance between environmental factors must exist for a population to survive
For example:
Producers = consumers
Water use = Rainfall

14. Population Growth Concept Map
can be
represented by
characterized by
which cause a
Exponential
growth
Logistic
Falling
growth rate
S-shaped
curve
Limits on
No limits on
J-shaped
Constant
Unlimited
resources

15. 5–2 Limits to Growth A. Limiting Factors B. Density-Dependent Factors
1. Competition
2. Predation
3. Parasitism and Disease
C. Density-Independent Factors

16. What can limit growth? Limiting Factors
Any factor that causes population growth to decrease

17. What can limit growth? Limiting factors
such as availability of food,
disease,
predators,
or lack of space,
will cause population growth to slow
Under these pressures, the population may stabilize in an S-shaped growth curve

18. Characteristics of Population Growth
J curve
S curve
Carrying capacity
Exponential growth
Time
Population
DISEASE
SPACE
PREDA-TORS
FOOD

19. Density-Dependent Limiting Factors
A limiting factor that depends on population size is a Density-dependent limiting factor
Density-dependent factors include
disease,
competition,
predators,
parasites,
and food.

20. Density-Dependent Limiting Factors
Disease, for example, can spread more quickly in a population with members that live close together.
Example: Black Plague

21. Density-Dependent Limiting Factors
Density dependent factors create an S-shaped curve
Organism Interactions Limit Population Size
Population sizes are limited not only by abiotic factors, but also are controlled by various interactions among organisms that share a community.

24. Predation affects population size
Predation is a density-dependent factor
When a predator consumes prey on a large enough scale, it can have a drastic effect on the size of the prey population
Populations of predators and their prey are known to experience cycles or changes in their numbers over periods of time

25. Competition within a population
Competition is a density-dependent factor
When only a few individuals compete for resources, no problem arises
When a population increases to the point at which demand for resources exceeds the supply, the population size decreases
Competition can also occur between members of different species- this creates evolutionary change
The two species competing are under stress to change in way that decrease competition- eventually evolving to occupy separate niches

26. Predation affects population size
The data in this graph reflect the number of hare and lynx pelts sold to the Hudson’s Bay Company in northern Canada from 1845 through 1935.
Lynx and Hare Pets Sold to the Hudson’s Bay Company
Lynx
Hare
Number of organisms in thousands)
Times (in years)

27. Isle Royale
Moose
Wolves
The periodic increase in the moose population is quickly followed by a rise in the number of wolves.
This increase in the number of wolves increases the number of moose captured by their predator and the moose population drops.
The wolf population will then decrease after the moose numbers drop because the wolves are less able to find food.
The predator prey cycle can be repeated indefinitely.

28. Parasitism and Disease
Parasites can also limit a population’s size-density-dependent
As the # of individuals , parasites which then causes the # of individuals to
Parasites are similar to a predator in that they take nourishment at the expense of their host
As a population increases in size, disease is more common because individuals are in closer contact with one another

29. Density-independent limiting factors and population growth
Density-independent factors can affect all populations, regardless of their size
Most density-independent factors are abiotic factors,
such as temperature,
storms,
floods,
drought, and
major habitat disruption

30. Density-Independent Factors
Density-independent factors create a boom-and bust curve (exponential growth followed by a sudden collapse)
Examples:
Weather- a drought kills grass
Human activity: deforestation- destroys habitat
Seasons: a severe winter regulates insect population

31. Boom-and-Bust Curve
Time
Population
Density

32. Limitations on Population Growth

33. Reproduction Patterns
In nature, animal and plant populations change in size.
Biologists study the factor that determines population growth—an organism’s reproductive pattern, also called its life-history pattern
A variety of population growth patterns are possible in nature- R strategists and K-strategists

34. Rapid life-history patterns- R Strategists
rapid life-history patterns are common among organisms from changeable or unpredictable environments
rapid life-history organisms have a small body size, mature rapidly, reproduce early, and have a short life span

35. Slow life-history patterns – K-strategists
large species that live in more stable environments usually have slow life-history patterns.
reproduce and mature slowly, and are long-lived. They maintain population sizes at or near carrying capacity

36. 5–3 Human Population Growth
A. Historical Overview
B. Patterns of Population Growth
1. The Demographic Transition
2. Age Structure
C. Future Population Growth

37. Demography
Demography, the study of human population size, density and distribution, movement, and its birth and death rates
Demography examines the characteristics of human populations and attempts to explain how those populations will change over time
Demographic transition- a change in a population from high birth and death rates to low birth and death rates; Examples- United States and Japan

38. Human Population Growth
Industrial Revolution Begins
Industrial
Revolution
begins
Agriculture
begins
Agriculture
begins
Bubonic plague
Plowing and irrigation
Bubonic
plague
Plowing
and
irrigation
Until about 500 years ago, the population grew slowly. Agriculture and industry made life easier and safer.

39. We are growing exponentially
Human Population
We are growing exponentially
Due to technological advances: medicines, a dependable food supply, and sanitation
The death rate is decreasing and the life expectancy is increasing
The human population will eventually reach its carrying capacity

40. Age Structure
Population Distribution Per Age Range for Several Countries
Stable growth
Rapid growth
Slow growth
Male
Reproductive years
Female
Age
Population (percent of total for each country)
Population growth depends on how many people of different ages make up a given population
Demographers can predict future growth using age-structure diagrams
Age-structure diagrams graph the number of people in each age group

41. Age Structure
U.S. Population
Rwandan Population

42. Ch.6-2: Human Impact on the Environment
Air
Greenhouse effect
Trapping of heat by gases in the Earth’s atmosphere (carbon dioxide)
This may lead to global warming- increase in the Earth’s temperature from the rapid buildup of carbon dioxide and other greenhouse gases
Acid Rain
Burning of fossil fuels release nitrogen and sulfur into the atmosphere which combined with water form nitric and sulfuric acid
Acid Rain kills plants
Smog
Mix of chemicals in the air from automobile exhaust
Affects the respiratory system especially those with asthma

43. The Formation of Acid Rain
Section 6-2
Chemical Transformation
Nitric acid
Sulfuric acid
Condensation
Emissions to Atmosphere
Nitrogen oxides
Sulfur dioxide
Dry Fallout
Precipitation
Acid rain, fog,
snow, and mist
particulates, gases
Industry
Transportation
Ore smelting
Power generation

44. Human Impact of the Environment
Water
Excessive nutrients can cause an increase in algae growth and depletion of oxygen for other organisms
Over harvesting of fish has reduced the number of fish

45. Human Impact of the Environment
Land
Erosion
The wearing away of surface soil by water and wind
Desertification
The combination of farming, overgrazing, and drought in dry climates which turn productive areas into deserts
Deforestation
The loss of forests which leading to severe erosion and changes in soil properties
Deforestation erosion water pollution and desertification

46. Humans need to learn to be a part of nature not apart from nature!
Consequences
If humans continue to alter the environment, they will have to deal with the results
Examples: fossil fuels combustion, habitat destruction, deforestation, ozone layer destruction, global warming
Human Overpopulation results in:
Worldwide malnutrition
Increased disease
Increased pollution
Humans need to learn to be a part of nature not apart from nature!

47. Ch. 6-3: Biological Diversity
Ecosystem diversity- variety of habitats, communities, and ecological processes in the living world
Species diversity- the number of different species
Genetic diversity- sum total of all the different forms of genetic information carried by all organisms living on Earth today
Biodiversity increases as you move toward the equator.
Areas around the world differ in biodiversity
Biodiversity can bring stability to an ecosystem.
Biodiversity is one of the world’s greatest resources

48. Variations within a species also helps protect against disease or parasite
Genetically different individuals within a species have a better chance of resisting disease
Example: world cheetah population reduced by a single virus
Tree plantation has same type of trees (single species) vulnerable to disease, etc..- spread easily
Diversity among individuals in a population is important to resistance of population as a whole (genetically different)
Biological diversity causes ecological stability

49. Adaptations- changes in response to factors in the environment (physical and behavioral changes)
Slow process that takes place over many generations
Organisms can be specialized to occupy a specific niche
Advantages
The more specialized an organism’s method of obtaining food and life requirements are (NICHE), the less competition they will have with other species (they have a better chance of surviving)
Example: anteater with long snout can reach into ant hills
Disadvantages
If there are changes in the environment, organisms may not be able to adapt fast enough in response
Example: Koala bears eat only Eucalyptus trees

50. Species Diversity Insects Protists Other Animals Plants Bacteria Fungi
54.4%
Protists
Other Animals
4.2%
19.7%
Plants
18%
Bacteria
Fungi
0.3%
3.4%

51. Loss of Biodiversity
Extinction is the disappearance of a species when the last of its members dies
Extinction is a natural process and Earth has experienced several mass extinctions during its history
A species is considered to be an endangered species when its numbers become so low that extinction is possible

52. Threats to Biodiversity
Complex interactions among species make each ecosystem unique
Changes to habitats can therefore threaten organisms with extinction
Human activity can reduce biodiversity by altering habitats, hunting species to extinction, introducing toxic substances into food webs, and introducing invasive species
Habitat loss-One of the biggest reasons for decline in biodiversity

53. Threats to Biodiversity: Habitat fragmentation
Habitat fragmentation is the separation of wilderness areas from other wilderness areas
Habitat fragmentation creates “islands” of habitat that are isolated from each other

54. Threats to Biodiversity: Demand for wildlife products
Hunting has caused many animals to go extinct
For example: passenger pigeon and Stellar sea cow
Humans hunt for food, fur, hides, and body parts thought to have medicinal properties
In the United States animals are protected from hunting if they are endangered

55. Threats to Biodiversity: Biological Magnification
Fish-Eating Birds
Magnification of
DDT Concentration
Threats to Biodiversity: Biological Magnification
10,000,000
Increasing concentrations of a harmful substance in organisms at higher trophic levels in a food chain or web
Example: DDT
Large
Fish
1,000,000
Small Fish
100,000
Zooplankton
10,000
1000
Producers 1
Water

56. Threats to Biodiversity: Introduced Species
Introduced species threaten biodiversity
Introduced species are organisms that have been introduced into new habitats and often become invasive, reproduce rapidly
Invasive species lack density-dependent limiting factors to keep their populations in check and take over areas and out compete existing species
Native to South America, nutrias have become pests in coastal areas of se US. These furry rodents eat water plants that protect fragile shorelines from erosion. This destroys the habitats of species native to those ecosystems.