Population

Question 1

What is carrying capacity

Answer 1

This is the maximum population size that an environment can support

Question 2

What is phase 1

Answer 2

This is a period of slow growth. The small number of individuals that are initially present reproduce increasing their total population. As the birth rate is higher than the death rate, the population increases in size

Question 3

What is phase 2

Answer 3

A period of rapid growth. As the number of breeding individuals increases, the total population multiplies exponentially.

Question 4

What is phase 3

Answer 4

This is a stable state. Further population growth is prevented by external constraints/limiting factors. During this time, the population size fluctuates, but overall its size remains relatively stable

Question 5

What are limiting factors

Answer 5

Factors that prevent further growth of a population or in some cases, its decline.

Question 6

Examples of limiting factors

Answer 6

Competition between the organisms for resources, the build-up of the toxic by-products of metabolism, or disease

Question 7

What are abiotic factors and state examples

Answer 7

They are non living factors e.g. temperature, water, oxygen, pH, light, humidity

Question 8

What are biotic factors and state examples

Answer 8

These are living factors e.g. predators, disease, competition

Question 9

What is immigration

Answer 9

Movement of organisms into a particular area, increasing population size

Question 10

What is emigration

Answer 10

Movement of organisms away from a particular area, decreasing population size

Question 11

What are density independent factors

Answer 11

These are factors that have an effect on the population regardless of its size. E.g earthquakes, storms, volcanic eruptions, fires etc

Question 12

What is interspecific competition

Answer 12

Competition between two or more different species

Question 13

What is a predator

Answer 13

An organism that kills and eats another organism

Question 14

What is the formula for population growth (%)

Answer 14

Population change during the period/ population at the start of the period x 100

Question 15

What does it mean if the result is positive

Answer 15

The population has grown

Question 16

What does it mean if the result is negative

Answer 16

The population has decreased

Question 17

State factors that affect the birth rate of the human population

Answer 17

Economic conditions, cultural and religious backgrounds, social pressure

Question 18

Factors affecting the death rate in a population

Answer 18

The age profile of the population, the quality of medical care, food availability and quality, the effects of natural disaster, or war

Question 19

What does the future size of a population depend on

Answer 19

The number of women of child-bearing age

Question 20

What is intraspecific competition

Answer 20

This is competition between members of the same species

Question 21

What happens during interspecific competition

Answer 21

This occurs when two or more different species of an organism compete for the same resource. If both species compete for the same food source, there will usually be less available for organisms of each species. As a result of less food, organisms will have less energy for growth and reproduction, resulting in smaller population than if only one of the species had been present

Question 22

What is the competitive exclusion principle

Answer 22

This is if conditions remain the same, the less well adapted species will decline in number until it can no longer exist in the habitat alongside the better adapted idea. This occurs when two species are competing for limited resources

Question 23

What competition occurs between red and grey squirrels for food in the UK

Answer 23

It is an example of interspecific competition. Its population quickly increased in numbers and resulted in the native red squirrel disappearing from many areas. This is primarily because the grey squirrel can eat a wider range of food than the red squirrel and as it is larger it can store more fat. This increases its chances of survival and therefore its ability to reproduce thus increasing its population. An increasing population of grey squirrels further reduces food supply available to the red squirrels, reducing their ability to survive and reproduce.

Question 24

How does availability of resources determine the population size

Answer 24

The greater the availability, the larger the population that can be supported. This results in fluctuations in the number of organisms present in a particular population over time.

Question 25

Stage 1 of population growth

Answer 25

When a resource is plentiful in a habitat, all organisms have enough of the resource to survive and reproduce. This results in an increase in population size

Question 26

Stage 2 of population growth

Answer 26

As a result of the increased population, there are many more individuals that share the food or space available. Resources are now limited, not enough is available for all organisms to survive. The population will decrease in size

Question 27

Stage 3 of population growth

Answer 27

Less competition exists as smaller population means less organisms are competing for the same resources. This means more organisms survive and reproduce, resulting in population grow. The cycle of events will then repeat

Question 28

Stage one of predator-prey relationship

Answer 28

An increase in the prey population provides more food for the predators, allowing more to survive and reproduce. This in turn results in an increase in the predator population

Question 29

Stage 2 of predator-prey relationship

Answer 29

The increased predator population eats more prey organisms, causing a decline in the prey population. The death rate of the prey population is greater than its birth rate

Question 30

Stage 3 of predator-prey relationship

Answer 30

The reduced prey population can no longer support the larger predator population. Intraspecific competition for food increases, resulting in a decrease in the size of the predator population

Question 31

Stage 4 of predator-prey relationship

Answer 31

Reduced predator numbers results in less of the prey population being killed. More prey organisms can survive and reproduce increasing the prey population- the cycle begins again