POPULATIONS- individuals of the same species that live together in the same place.

Population Features Size- How many of one type of organism that exist. Density- How many of an organism that live in a given area. Dispersion- how a certain organism is arranged in that given area.

Patterns of Dispersion Clumped distribution Even distribution Random distribution

DEMOGRAPHICS – The statistical study of the characteristics and composition of the population.

4 factors determining the Population Birth rate or Natality Emigration POPULATION Immigration Death Rate or Mortality

Modeling Population Growth A population model is a hypothetical graph used to show how a specific population could react to specific factors that are manipulated by those that make the graphs.

Types of Population Models Exponential Growth Curve Model- this is a graph that shows steady growth of a population which would go unchecked. Size x rate of growth

The Carrying Capacity = K The largest population an environment can support at any given time.

Populations do not go unchecked and are normally limited to the resources in a given area so populations will eventually reach their carrying capacity . This is called logistical growth because it’s logical.

Graphic Analysis Mean – (The average) …the sum of the data divided by the total possible. 2,4,6,8,= mean-5 Median- This is the midpoint in a series of numbers. 1……….7………….14 Mode – The most frequently occurring value. Range – The difference between the largest and smallest value.

Density Independent Factors Environmental conditions like climate or weather that dictate the growth or decrease a population.

Density Dependent Factors These are factors that are limited to an area and their amounts are dictated by the size of populations within that area. Best examples are food and water.

Examples of limiting factors… Predation Disease Food limits Water Temperature Mating availability Shelter

Effects of Factors Some organisms only thrive during certain times of the day or year because of the temperature and climate of the area. Also others can only breed when conditions are right Dependent factors create the limiting line that makes populations have a carrying capacity. Go past that line and food runs out!

R strategists These organisms breed in high numbers and create huge populations, but they don’t live long and must reproduce often. Growing and developing is quick so these organisms are small and simple. They also drop in numbers when conditions start to worsen.

In past information You could use R strategist as a good example of exponential growth, but as time continues that growth is followed by exponential death. These organisms also has no parental involvement other than to have the offspring and have them often.

K-strategists These organisms are like us. We live long lives and have few children. We care for them for long periods of time and our development is very slow. They also tend to live in stable environments. Population grows more logistically than exponentially.                               

Hardy – Weinberg Principle The frequency of alleles in a population does not change unless evolutionary forces act on the population. ** When climate changes populations will change or adapt..***

Evolutionary forces acting on a Population Mutations – changes in the genes Non-random mating – inbreeding Gene flow- Immigration / Emigration Natural selection – competition /struggle Genetic drift – Isolation of small populations (high mortality)

Population Change - EVOLVE Phenotype- physical appearance changes Genotype- actual genes in the population change Alleles – expression of genes– mutation Change in DNA=mutation