LEC 23 Flashcards
Population Dynamics
Biosphere
All of the ecosystems on earth
Levels of organization in human biology (SMALLEST TO LARGEST )
Atom/Molecule
Cell
Tissue
Organ
Organ System
Organism
Population
Community
Ecosystem
Biosphere
Ecosystem
consists of a community of organisms and the physical environment in which they live (living and non-living components combined)
Community
groups (populations) of different species that occupy the same geographic area and interact
Population
Groups of individuals of the same species occupying the same geographic area who interact with each other
- groups within a community
Characteristics of Populations - Distribution (3)
The area where we can find a particular population
Also known as its “range”
Found here because the area is suitable to growth & survival
Characteristics of Populations - Population Density (2)
The number of individuals per unit area or volume
Tends to be higher in areas with plentiful resources
Characteristics of Populations - Population Density Trends (2)
- Larger body size of the organism, population density declines
- Smaller body size of the organism, population density increases
Growth
a population will grow when the number of births exceeds the number of deaths
Growth rates
Growth rate = ((# births - # deaths) x 100)) / total population
Biotic Potential
The maximum rate of growth of any population, under ideal conditions
Biotic Potential influenced by:
abundance of resources
(Enough food, water, habitat etc.)
Biotic Potential related to characteristics of the species (4)
- Usual number of offspring per reproduction cycle
- How often each individual reproduces
- Age when reproduction begins
- Ratio of males to females
Doubling Time of a Population
If you know the percent of change (for a period of time) in a population, you can calculate the time for that population to double in size
Doubling Time of a Population equation
Doubling Time = 72 / rate of change
Exponential Growth Also known as
theoretical growth
Exponential Growth Characteristics (4)
Occurs in ideal conditions (no limiting factors)
Population will double in size over a given time
Will continue to grow “unchecked” as long a resources are available
As population grows, the competition increases, may slow down rate of growth
Exponential Growth Graph
“J” shaped
Exponential Growth 2 phases
- Lag phase (slower rate of growth because number of individuals is small)
- Exponential phase (growth is accelerating)
population growth will slow as conditions in the area change
environmental resistance
Environmental resistance
- Finite resources & competition exist
- Anything that limits a species ability to consistently realize biotic potential
- Things that kill organisms
- Prevents them from reproducing
Realized Growth AKA
logistic growth
Realized Growth graph
“S” shaped curve
Realized Growth 4 phases
- Lag
- Exponential
- Deceleration – rate slows due to increased competition for resources
- Stable equilibrium – little if any growth occurs
Stable Equilibrium
population finds balance between its biotic potential and environmental resistance
Carrying Capacity
population size the ecosystem can support indefinitely
Population size is _______ constant but rather hovers around _______ _________ over time
- not
- carrying capacity
Density-Independent Factors (3)
- Cause sudden & catastrophic reduction in population size
- Examples include weather and natural disasters
- Effect is not influenced by the number of individuals in the population
Density-Dependent Factors (2)
- The percentage of the population affected increases as the density increases
- Examples include competition and predation
Competition (2)
- Members of same species try to use same resources, which are limited in supply
- Not all members of the population will have access to the resources to ensure survival
Predation
- One organism (predator) eats another organism (prey)
- Effect of predation increases as prey population increases (easier to find as there are less hiding spots)
Factors Regulating Growth
- Density-Independent Factors
- Density-Dependent Factors
- Competition
- Predation
Patterns in Ecology
1.Opportunistic species
2.Equilibrium species
3. Extinction
Opportunistic species
- Tend to exhibit exponential growth
- Members are small in size, mature early, short life spans and provide limited parental care
- Density-independent factors limit population size
Equilibrium species (3)
- Exhibit logistic growth
- Members are larger in size, are slow to mature, have longer lives and invest in raising young
- Population size affected mostly by density-dependent factors
Extinction (2)
- Total loss of a species
- Equilibrium species are often at higher risk
Human Population Growth - 4,000 years ago
population began to rise due to agriculture & domestication of animals
Human Population Growth - 1700’s
rapid growth with Industrial Revolution
Human Population Growth - Now
explosive growth with little (if any) environmental resistance
Some believe that the concept of _______ _______ doesn’t apply to humans because we can ______ our environment to suit our needs
- carrying capacity
- alter
Zero population growth
When the number of births in a population EQUAL the number of deaths
To reach Zero population growth, we need to either: (2)
Decrease birth rate
Increase death rate
Fertility Rates
of children born to each woman during her lifetime
To reach zero population growth, the average fertility rate required is a ________ ___________ _____ of 2.1 children per woman
replacement fertility rate
Growth in More Developed Countries (MDC’s)
North America and Europe included in this group
Populations grew rapidly between 1850 - 1950
Improved sanitation, medicine and overall socioeconomic conditions led to lower death rates
Birth rates also lowered resulting in modest growth since 1950’s
Growth in Less Developed Countries (LDC’s)
Latin America, Asia and Africa
Dramatic population growth, however, many individuals living in poverty
Death rates dropped significantly after WWII due to modern medicine
Birth rates remained high
Still represents the majority of global population growth
