Populations and Sustainability

Question 1

Explain the population growth curve as 3 phases

Answer 1

Phase 1 - A period of slow growth, initially few numbers present but birth rate is higher than death rate so size
increases slowly

Phase 2 - A period of rapid growth. As breeding increases the population multiplies exponentially. No limiting factors
present as of yet

Phase 3 - A stable state. There are fluctuations above and below the maximum capacity which is known as the
carrying capacity. This is due to limiting factors

Question 2

What is the definition of limiting factors

Answer 2

Factors whose magnitude slows down the rate of a natural process

Question 3

Name the two types of limiting factors

Answer 3

Biotic

Abiotic

Question 4

What are abiotic factors

Answer 4

Non living factors that include
Temperature
Light intensity 
pH
Water availability
Soil quality 
Oxygen availability

Question 5

What are biotic factors

Answer 5

These are living factors and include
Predators
Disease
Competition

Question 6

How can migration affect populations size explain both types

Answer 6

Immigration - Movement of individual organisms to a particular area increasing population size

Emigration - Movement of individual organisms away from a particular area decreasing population size

Question 7

What are density independent factors

Answer 7

Factors that have an effect on the whole population regardless of it size dramatically changing the population size
e.g. earthquakes, fires , volcanic eruptions and storms
In some obscene scenarios a whole population can be removed from a region

Question 8

Name the two types of competition

Answer 8

Inter
Intra
Specific competition

Question 9

What is interspecific competition and give an example

Answer 9

Competition between different species

An example being the red and grey squirrels

The grey squirrels were introduced from America to England and its numbers began to increase whilst the native red squirrel population began to decrease.

The grey squirrel can eat a wider range of food increasing its survival rate and therefore reducing the red squirrels food supply reducing their ability to survive and reproduce

Question 10

What is intraspecific competition and give an example

Explain in 3 stages

Answer 10

Competition within a species that compete for the same resource
Typically those best adapted survive
e.g. robins compete for breeding territory

Stage 1 - There are plentiful resources so there are enough of the resource for all of organisms to survive and
reproduce resulting in an increase in population size

Stage 2 - Resources are now limited so only those best adapted survive decreasing the population size

Stage 3 - Resources are now plentiful again due to less completion so more organisms survive and reproduce
increasing population size again
Cycle will repeat

Question 11

Explain the predator-prey relationship

Answer 11

Both act as limiting factors for each population size

Stage 1 - Increase in prey population provides more food for the predators so its population increases

Stage 2 - Due to being eaten the prey population falls (death rate>birth rate )

Stage 3 - This reduced prey population sees predator population decline due to intraspecific competition

Stage 4 - Reduced predator numbers means more prey organisms can survive and reproduce so their population increases

Cycle repeats again