1.5.1

# Population Growth

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## Growth

Growth can be thought of as when something gets larger over time. This might be the population of a particular species, the amount of money in a bank account or the number of people using Seneca.

### Linear growth

• Linear growth is when something increases by a steady amount over set time periods.
• E.g. a cinema gets 100 extra visitors each month.
• If they have 200 visitors in month 1, they will get 300 visitors in month 2, 400 visitors in month 3, 500 visitors in month 4, etc.

### Exponential growth

• Exponential growth is when something increases by a multiplier (or percentage) over set time periods.
• E.g. the number of people playing Fortnite increases by 2× each month.
• If they have 200 users in month 1, they will get 400 users in month 2, 800 users in month 3, 1,600 users in month 4, etc.

### Exponential growth in bacteria

• Populations of bacteria can grow exponentially.
• This means the number of bacteria increases by a set multiplier over a given time period.

### Exponential growth in bacteria 2

• The population of an example colony of bacteria starts at one.
• If the population of bacteria doubles every hour you'd get the exponential growth seen above.