Regulation of Population Growth

Deer Population vs Time

•

Which of these factors depend on the size of the population (Which are density dependant)?

• What are some environmental factors which control population in nature?

Think, Write, Share...

Density Dependent

(size of population matters)

Density Independent

(size of population

doesn’t matter)

Try this...In cooler climates, aphids go through

a huge population increase during the summer months. In autumn, the population ‘crashes’ to much lower numbers. Name a density dependant and a density-independent factor regulating the population

Density dependant:______________Density independant:_____________

Carousel time...

Examples: competition, predation, parasitism, climate extremes, human disturbances

CompetitionOccurs when members of different

species try to utilize a resource (light, space, or nutrients) that is in limited supply.

Competitive Exclusion PrincipleNo two species can occupy the

same ecological niche at the same time

The division of feeding niches =________________________

Chthamalus

Species 1: Chthamalus sp

Species 2: Balanus

Balanus

Area of competition

PredationOccurs when one organism, the

predator, feeds on another, the preyPredators include: ______________________________Predators usually limit the prey

population, although in extreme cases they can_____________________.

What are the reasons why predators rarely kill and eat all of the prey?

Prey species often: --

• Often the predator will _________as the prey species becomes lower in numbers.

Turn to a partner...How can predation help maintain

species diversity? (think top predator)

What causes cycling?

CyclingThe predator population

______________________________and then the predator population declines in number

The prey population ________________________ and suffers the crash, and the predator population follows suit

Less predators to worry about means________________

Parasitism and DiseaseParasites can also limit the growth of

a population (by ______________prey)Range in size from microscopic

disease-causing bacteria to tapeworms 30 cm in length

And now, a bit of practice...

Try this...

Type of curve=______________________a)

b)

c)

d)

e)

Describe what might be happening to the population at:b)

e)

Exponential population growth or Logistic growth?1. A lack of food prevents a certain

population from growing any further ____2. In a steady state, the average growth

rate is zero _____3. The larger a population of bacteria gets,

the faster it grows _____4. A particular environment is limited to a

certain number of rabbits that it can support _____

Density Dependant (DD) or Density Independant (DI)?

1. Freezing weather _____2. Has a greater effect on a larger

population_____3. A volcanic eruption_____4. Predation _____5. Floods ______6. May limit the population before it

even gets close to carrying capacity _____

7. Disease or parasites _____8. Fire ____9. Storms _____10. Intensity of effect no greater for

larger population, no less for smaller population _____

11. Tends to be biotic ______12. Tends to be abiotic ______