Population Growth Population Growth Imagine the following scenario

Population Growth

Population Growth • Imagine the following scenario: – 1 male and 1 female fly in your house – 900 eggs per laying – eggs hatch in one day – 1 month from egg to mature fly – in one month 900 flies in your house – in two months ~400 000 flies – in three months ~180 million flies

Population Growth • population – a group of organisms living in a certain area that belong to the same species • Population growth curve under ideal conditions: population grows very fast after a slow start it picks up speed • more offspring give faster growth

Realistic Population Growth Curves • What really happens?

Realistic Population Growth Curves • Resources decline: food, water • Growth slows until it stabilizes at an amount called the carrying capacity – The level the environment can sustain • Growth is calculated as follows: • population growth = (births + immigrants)(deaths+emigrants) • Population can fluctuate a bit but on average remains close to carrying capacity

Exponential vs Logistic Growth

A. slow population growth – small number of organisms able to reproduce – possibly adjusting to new environment

B Rapid population growth – many organisms capable of reproduction – well adjusted to environment: food, shelter

C. steady population growth – carrying capacity reached and population is constant – deaths equals births (not looking at migration)

catastrophic growth • population grows so fast that it damages environment such that there is a lower carrying capacity afterwards