Definition Population • A population consists of all the individuals of the same kind, or species, that live in a given area. Species • A species consists of the organisms so similar that they can mate and produce fertile offspring.
Question… • Which of the following does not represent a population? • A. all the robins in Toronto • B .all the grass frogs in the pond of Brampton • C. all the birds in Ontario • D. all the black footed ferrets in Saskatoon • Answer: • C. all the birds in Ontario
Something to Consider Today: 7 Billion People 2040: 9 Billion People
Population size in a community can change due to 4 factors. Natality - number of births in one year Mortality - number of deaths in one year Immigration - number of individuals of moving into an existing population Emigration - number of individuals of moving out of an existing population Population Growth
Population growth is the change in population over time. It can be calculated using the following formula: Population Growth = births + immigration – deaths – emigration Population Growth
Other Population Factors • All other population factors and events lead back to one of the four basic factors. • E.g. Plagues and Disease • Deaths Mortality (death rate) • E.g. Natural Disasters (Hurricanes, Earthquakes, etc.) • Homelessness Immigration, Emigration • E.g. Better Medicine & Healthcare • Less Disease Natality (birth rate)
Exponential Growth • Without limits population growth of a species will accelerate!
Limiting Factors • All population growth is limited! • Limitingfactor: a factor that stops the growth of a population in an ecosystem • Light • Temperature • Food • Predators • diseases
POPULATION SIZE GROWTH FACTORS Decrease factors Abiotic Abiotic Favorable light Favorable temperature Favorable chemicalenvironment Too much or too little light Temperature too high or too low Unfavorable chemical environment Biotic Biotic Adequate foodsupply Suitable habitat Ability to compete for resources Ability to defend against predators Ability to resistdiseases & parasites Inadequate food supply Unsuitable or destroyed habitat Too many competitors Insufficient ability to hide from or Defend against predators Inability to resist diseases and parasites
Limited Growth • Growth is slowed by limiting factors. • Growth levels off when factors are in balance.
Carrying Capacity • Carryingcapacity is the largest population of a species that an ecosystem can support • when a population is maintained at its carrying capacity, the size of the population is at an equilibrium • Births + Immigration = Deaths + Emigration
Limited Growth Carrying Capacity.