 group of organisms of the  same species  live in a specific area  can interbreed

Population Density and Dispersion via YouTube Populations Distribution

 Births  deaths Growth Rate – can be +, -, or 0

 Populations usually stay about the same size from year to year because various factors kill many individuals before they can reproduce.  These factors control the sizes of populations.  In the long run, the factors also determine how the population evolves.

 maximum number of offspring that an organism can produce  increases when individuals — produce more offspring at a time — reproduce more often — reproduce earlier in life – greatest effect

 small organisms (bacteria and insects) reproduce when they are only a few hours or a few days old — populations can grow quickly  large organisms (elephants and humans) become sexually mature after many years and have a much lower RP than insects

 a large number of individuals is added to the population in each succeeding time period  occurs when there’s — plenty of food and space — no competition or predators  ex. pop explosions occur when bacteria or molds grow on a new source of food

 conditions are neither ideal nor constant  populations cannot grow forever  resources are used up or the environment changes  deaths increase or births decrease  only some members of any pop will survive and reproduce so the properties of a pop may change over time

 the largest pop that an environment can support  may increase beyond this number but cannot stay at this increased size  CC is met when a resource is used faster than ecosystem can replace it  difficult to predict but can be estimated by looking at average pop sizes or by observing a pop crash after CC has been exceeded Serious Science: Biological Carrying Capacity

1) sampling – org in a small area are counted and projected to the entire area select any 4 random blocks count the number of "snakes" in the 4 blocks (develop a set of counting rules for snakes that span 2 or more boxes) estimate the snakes in the entire grid - multiply the total number you counted by four

2) mark and recapture  a portion of the pop is trapped, marked and returned  after a period of time, another portion is captured and the # marked is recorded  mathematical formula used to estimate pop size