Populations

Populations Population- A group of organisms of the same species that live in a particular area. Three important characteristics of a population are its geographic distribution, density, and growth rate.

POPULATIONS Population Growth- the change in the size of a population with time. Population Density- is the number of individuals per unit area. Geographic Density is how the population is distributed.

POPULATION SIZE Three factors can affect population size. Number of births Number of deaths Number of organisms that enter or exit the population

POPULATION SIZE Immigration- The movement of organisms into a population. Emigration- The movement of organisms out of a population.

POPULATION GROWTH Exponential growth- occurs when the individuals in a population reproduce at an ever increasing rate.

POPULATION GROWTH Linear Growth- increase of a population at a constant rate.

Maintaining a Balance For a population to survive, a balance must exist between producers/consumers, predator/prey, growth and decay, water use and rainfall…etc.

Limiting Factors Limiting Factors- Any condition of the environment that limits the size of a population. Some can happen naturally and some are caused by humans. Ex: Food, water, shelter and space availability, Predation, Climate, Disease, Pollution, Competition,….

HUMAN IMPACT Humans have disrupted this balance through…. Building of roads, industry, homes Pollution Hunting/poaching Global Warming, Excess CO2

Carrying Capacity The number of organisms a given ecosystem can support. S-shaped curve

Predicting Carrying Capacity Because ecosystems change, carrying capacity is difficult to predict and calculate However, islands are the ideal place to study (clear boundaries)

Rabbits in Australia no rabbits in native ecosystems of Australia introduced in 1859 number increased rapidly plenty of vegetation; no predators; no competition disease and starvation caused the rabbit pop. to crash over time, vegetation recovered and rabbit pop. increased again continues to increase and decrease, but less dramatically

Rabbits reduced Phillip Island to a wasteland Rabbits reduced Phillip Island to a wasteland. Photos: Department of the Environment and Heritage Recovery was spectacular after the rabbits were eradicated Photos: Department of the Environment and Heritage

Reindeer near Alaska 25 reindeer introduced to one of Pribilof Islands near Alaska in 1911 by 1938, herd had grown to 2,000 reindeer ate mostly lichens, which grow back very slowly by 1950, only 8 reindeer alive on the island

Predator/Prey This is an example of a predator/prey relationship. As one increases the other will as a result decrease.….which in turns causes the other to decrease. A normal cycle

Two Types of Population Regulation Cause of death may be density dependent or density independent

Density Dependent Factors Density Dependent Factors have an increasing effect as populations increases deaths are caused due to density (population too many)

Density Dependent Factors Competition, Predation Parasitism Disease Crowding

Population is growing rapidly and there are limited resources, predation, or disease

Density Independent Factors Density Independent Factors are factors that affect a population or cause death regardless of density. Severe weather, natural disasters, etc. cause death that did not result due to density.

DEMOGRAPHY DEMOGRAPHY- The study of population. You can study charts of the age structure of a population and determine if it is growing or not.

Human Population

HUMAN POPULATION Currently at 6.5 Billion People Growing Exponentially Industrial Revolution and Agriculture advancements are the reason for the drastic increase since the 1800’s The population trends differ depending on Developing and Developed Countries.

Developed Countries Higher Average Incomes Slower Population Growth Diverse Industrial Economies Stronger social support Uses a large % of available resources Ex: US, Canada, Japan, and countries of Western Europe

Developing Countries Lower Average Incomes Simpler and agriculture-based economies Rapid Population Growth Uses small % of available resources Ex: Indonesia and countries in Africa.