Populations and Human Impact 1st year Topic 10

Question 1

Define carrying capacity

Answer 1

The maximum population size of a species that the environment can sustain indefinitley,given the food habitat and water and other necessities available in the environment (for an indefinite period of time)

Question 2

What will happen to the population size in terms of natality and immigration?

Answer 2

An increase in population size

Question 3

What will happen to the population size in terms of mortality and emigration?

Answer 3

A decrease in population size

Question 4

True or false

Immigration and emigration are important the size of a population but the most important factors are natality and mortality

Answer 4

True

Question 5

Mention factors which limit population increase

Answer 5

Disease: diseases can spread very quickly through large populations

Overcrowding: This often leads to unhygienic conditions which causes disease and competition

Lack of shelter: animals will compete for shelter in order to avoid predators or harsh weather

Plants compete for light to carry out photosynthesis. + Plants compete for light in dense vegetation

Question 6

What are the main parts of the sigmoid growth curve and what does it represent?

Answer 6

Lag
Log /exponential phase
Transitional phase
Plateau phase

The sigmoid growth curve shows how a population increases overtime with factors such as competition,predation,environmental conditions or resource availability.

Question 7

Explain the lag phase

Answer 7

There is a slow growth of the population size (increases very slowly)

In this phase organisms adapt to the conditions of the new environment and the chances that 2 organisms meet and reproduce sexually is very low

Organism’s will search for food,water,shelter and other resources

Question 8

Explain the log/exponential phase

Answer 8

The population size increases at a fast and constant rate since resources are abundant and there is no or very little competition

This is due to the number of organisms which have increased so the chances of organisms encountering each other and reproducing sexually increases

Question 9

Explain the transitional phase

Answer 9

The rate at which the population size grows slows down

This can be due to factors such as emigration(if the amount of space decreases),or due to overcrowding.

Overcrowding causes organisms to become weaker due to a lack of food(competition) and so diseases spread more rapidly within the population. Or overcrowding can also cause stress to the organisms which affects their rate of reproduction

Question 10

Explain the plateau phase

Answer 10

The population stops growing

Because at this phase the population would have reached the carrying capacity of the environment which is the maximum population size that the environment can sustain indefinitely for an indefinite period of time.

The number of individuls born is the same number of individuals that die off.