chapter 5 populations. what is a population? a population is a group of one kind of organism....
TRANSCRIPT
CHAPTER 5
Populations
What is a population?
A population is a group of ONE kind of organism.
Examples: Herd of cattle Pack of geese
Population Density
Population Density describes how many individuals live in a given area.
Formula Pop. Den. = # Individuals
Area
Population Density Word Problems
• Example 1:– There are 60 flowers in a garden that is 3 feet by 4
feet. What is the population density per square foot?
• Example 2:– Given that the population density of a neighborhood is
10 people per square mile, how many people would live in a city with an area of 10 square miles?
Population Growth
Populations can change in size for any of the following reasons: Reproduction Death Immigration = moves TO location Emigration = moves AWAY from location Other Circumstances
Exponential Growth Curve
• When organisms reproduce very quickly, and there seems to be NO limits on population growth, the graph is said to be exponential.
• Sometimes this is called a J-curve because it looks like a J.
Logistic Growth Curve
• When organisms reproduce very quickly, and there seems to be limits on population growth, the graph is said to be logistic.
• Sometimes this is called an S-curve because it looks like a sideways S.
Logistic Growth (cont)
• The level that the graph plateaus at is called the carrying capacity.
• Carrying capacity describes the maximum number of individuals the environment can sustain given limited resources / factors.
Density-Independent Factors
Density-Independent Factors are factors that affect all populations in similar ways.
Examples: Weather / Seasonal Cycles Natural Disasters Human Activities
Density-Dependent Factors
Density-Dependent Factors usually affect populations with high population densities.
Examples: Competition Predation Disease Parasitism
Are these density-independent or density-dependent?
• Example 1:– A flu outbreak is spreading through a
large high school. Over 200 students become ill.
• Example 2:– A tornado funnel touches down in a
small farming community. The tornado destroys a third of the homes and businesses.
• Example 3:– Several lions and hyenas gather near a
small watering hole. There is limited water, so the lions and hyenas fight each other.
Human Population Growth
• Human population growth increased very slowly until the Industrial Revolution in the 1800s.
• It has since skyrocketed to over 7 billion people on Earth.
Patterns of Human Population Growth
Demography is the study of human populations.
Birth rate is the number of births per 1000 people.
Death rate is the number of deaths per 1000 people.
Demographic Transition
Stage 1 = High birth and death rates
Stage 2 = High birth rate, slowing death rate
Demographic Transition
Stage 3 = Slowing birth rate, low death rate
Stage 4 = Low birth and death rates
Age-Structure Diagrams
Age-structure diagrams (aka p0pulation pyramids) are modified histograms (bar graphs) that display the subgroups of a country based off of gender and age group.
The youngest individuals are on the bottom, and the oldest individuals are on the top.
Males are on the left, and females are on the right.
Age-Structure Diagrams
Depending on how well-developed a country is, the age-structure pyramid may have a different shape. Rapidly growing countries (developing) have a
very triangularly shaped pyramid with a very side base and narrow top.
Slowly growing countries (moderately developing) have a triangular shape, but the bottom is not as wide and the top is wider.
Negatively growing countries (well developed) have a small base and may seem almost uniform throughout the pyramid
Age-Structure Diagrams
CHAPTER 6
Human Impact on the Environment
Human Activities throughout History
Hunter-Gatherers
Agriculture
Industrial Growth & Urban Development
Biodiversity
Biodiversity describes the range of differences in living things in terms of ecosystems, species, and genetics.
Renewable resources are materials that can be reused and replenished whereas nonrenewable resources cannot.
Extinction & EndangermentExtinction & Endangerment Habitat FragmentationHabitat Fragmentation
Threats to Biodiversity & Natural Resources
Invasive SpeciesInvasive Species Soil ErosionSoil Erosion
Threats to Biodiversity & Natural Resources
DesertificationDesertification Pollution & Biological MagnificationPollution & Biological Magnification
Threats to Biodiversity & Natural Resources
DeforestationDeforestation OverfishingOverfishing
Threats to Biodiversity & Natural Resources
Controlled AquacultureControlled Aquaculture Air Pollution (smog, acid rain, etc)Air Pollution (smog, acid rain, etc)
Threats to Biodiversity & Natural Resources
Ozone DepletionOzone Depletion Global WarmingGlobal Warming
Threats to Biodiversity & Natural Resources
Current Solutions
Conservation efforts are underway to preserve ecosystems as they currently are.
Many businesses and governments are seeking ecological sustainability, meaning they will function in a way that will be able to help the environment while they run efficiently.