1. Population Ecology SNC1L Science

2. 11/18/20152 Populations Change A Population is all of the members of a single species living in an area. The various populations of different species in one area are called a community. Population size depends on four factors: Births, Deaths, Immigration, and Emigration. (migrating in) (migrating out) P = (N+I) – (M+E)

3. 11/18/20153 Populations are limited A limiting factor is any biotic or abiotic factor that affects growth of a population. Too much or too little of any one is not good! Populations will grow or decline depending on their Biotic Potential This depends on: Birth Potential Capacity for Survival Procreation Reproductive Lifespan BIOTICABIOTIC Food resources Predation Disease Competition Level of light Temperature Chemicals Water Resources

4. 11/18/20154 Birth Potential Maximum Number of offspring per birth Humans have a much lower birth potential than ducks, or salmon. Whooping Cranes only lay two eggs a year.

5. 11/18/20155 Number of offspring that survive to reproductive age Humans have a better chance at this than many other species... Female Clams release five million eggs at a time, but only 50 may survive. Sea Turtles lay 50 – 100 eggs, but few reach maturity. Parenting is not universal in nature! Capacity for Survival

6. 11/18/20156 Procreation Number of times a species reproduces each year. Humans can only procreate once in a given year. Mice can have a litter of 10 – 14 pups every 6 to 8 weeks. Sparrows produce up to 3 broods of chicks annually.

7. 11/18/20157 Reproductive Lifespan Age of sexual maturity & how many years reproduction is possible. Humans need more than a decade to reach sexual maturity. African elephants need 15 years to mature, but may reproduce to 90! Dogs are mature at 1 year; they can reproduce for the rest of their lives.

8. Population sizes go up and down, but like to be stable Stability = when the population is in balance Carrying Capacity = max # of individuals that the ecosystem can support Populations can exceed their environment’s carrying capacity, but not for long. 11/18/20158 Carrying Capacity

9. 11/18/20159 Carrying Capacity Example: Fluctuations in Elk & Wolf populations in Banff, Alberta

10. 11/18/201510 Carrying Capacity Example: Fluctuations in Snowshoe Hare & Lynx populations, British Columbia

11. 11/18/201511 Carrying Capacity Example: Human population from prehistory to modern day

12. 11/18/201512 Population Density Population size per unit area of habitat Dense Populations = when there are a lot of organisms in a limited area Density determines population change, also. Density Dependent Factors Density Independent Factors Food shortage Competition Disease Invasive species Predation Flood, fire… Pesticide use Climate change Drought Habitat loss