Population Dynamics Essential Standards: and 2.1.4

Essential Standards 2.1 – Analyze the interdependence of organisms within their environment ▫2.1.3 – Explain various ways organisms interact with each other (including parasitism, competition, parasitism, mutualism) and with their environments resulting in stability within ecosystems ▫2.1.4 – explain why ecosystems can be relatively stable over hundreds or thousands of years, even though populations may fluctuate (emphasizing the availability of food, availability of shelter, number of predators and disease)

Abiotic factors Non living components of an organisms environment ▫Sunlight ▫Temperature ▫Precipitation ▫Soil type ▫Salinity ▫Water ▫Nitrogen ▫oxygen

Biotic factors Living things in the environment ▫Other interacting organisms ▫Bacteria, fungi, plants, animals, protista (5 kingdoms) ▫Organisms that another organism eats or that try to eat it ▫Symbiotic relations

Population Made up of all organisms of a species that live in an area at the same time Affected by births, deaths, immigration and emmigration Population = births+immigration – (deaths+emmigration)

Immigration Movement of organisms into an area ▫Increases population size ▫Births + immigration = population increase

Emigration Movement of organisms out of an area ▫Deaths + emigration = population decrease What happens to the population when births + immigration is greater than deaths + emigration? What happens to the population when deaths + emigration is greater than births + immigration? Population increases Population decreases

R growth Think R-think roach Many offspring born, but die off quickly due to high predation Which type do you think is R selection?

K growth Think k- think kangaroo Few offspring born, more live to adulthood Which type do you think is K selection? r and k selection

Factors of birth and death rates Underdeveloped countries have higher birth rates than developed countries ▫Need for more people to do jobs such as farming Death rates also tend to be higher in underdeveloped countries ▫Lack of food and water  Droughts ▫Lack of medical care and sanitation

Changes in birth and death rates Death rates in developed countries have declined since 1900… why? Birth rates have also declined… why? Changes in limiting factors can greatly affect population size in natural environments

Limiting Factors Most population stabilize rather than grow endlessly- why? Anything that can limit the population size is a limiting factor – can be biotic or abiotic ▫Food ▫Water ▫Oxygen ▫Sunlight ▫Relationships with other organisms 2 main types of limiting factors ▫Density dependent ▫Density independent population change

Abiotic factors Biotic factors SunlightPathogens SoilPredators WaterFood Natural disasters (earthquakes, wildfires, floods, tsunamis) Symbiotic organisms

Population Density Measure of the number of organisms per unit of area

California Red woods Population density difference in penguins

Density-dependent Limiting Factors Limiting factor that depends on the size of a population living in a certain amount of space ▫Depends on population density Have more effect when population is high rather than low Includes: ▫Competition ▫Predation ▫Parasitism ▫disease

Disease Density dependent factor Example - Dutch elm disease ▫Fungus ▫Spreads through close contact ▫Elms were once close together ▫Closeness provided habitat for beetles that spread the fungus ▫Disease can spread by roots

More diseases Tuberculosis – once the leading cause of death in the US ▫Caused by a bacteria affecting lungs ▫Many do not become infected who come in contact with TB, but can carry the disease ▫Spreads rapidly in dense populations malaria

Density-Independent Limiting Factors Limit population growth regardless of density Abiotic factors ▫Weather ▫Natural disasters  Forest fires, drought, tsunamis Can sharply reduce or wipe out populations ▫Forest fire can wipe out a plant species Pollution caused by humans

Carrying capacity Largest population an environment can support over a long period ▫What kind of curve do you see with this? Different for each species ▫Habitats and resource needs are different S!!!

Population change at carrying capacity Stops growing Population size stabilizes or levels off ▫Initially, resources are plentiful and population is small.  Death rate low  Birth rate high  Population grows rapidly ▫Resources are used up  Not enough to support growth  Overshoot possible  Too many organisms

Carrying Capacity depends on: Number of organisms living there Ecosystem size Available resources Humans need: ▫Energy ▫Water ▫Oxygen ▫Food ▫Medical care ▫Sanitary living conditions

Effects of resource use on the environment Growing population increases demand for resources ▫Can cause changes in other abiotic factors Humans need energy ▫Burning fossil fuels for energy plays a key role in what cycle? How?

Greenhouse effect CO 2 is a greenhouse gas- from pollution and natural activity like volcanoes Traps solar energy (heat) and prevents it from being reflected into space Helps keep Earth’s temperatures livable Too much warmth causes global issues

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