Population Growth and regulation

Question 1

What is a regulating factor ?

Answer 1

A factor affecting a population, usually density dependant which helps keep a population at equilibrium.

Question 2

Give an example of a regulating factor.

Answer 2

Food supply,
As a population increases food availability will decrease, leading to more deaths and decreased fecundity
As organisms decline, food availability increases.

Question 3

What are limiting factors ?

Answer 3

Factors affecting population size and and growth

Usually density dependant

Question 4

What is the difference between a regulating and limiting factor ?

Answer 4

Both may limit population size

But a limiting factor does not regulate the population like a regulating factor.

Question 5

Give an example of how regulating and limiting factors interact

Answer 5

Disease
Limits population size (LF)
However animals in a poorer condition may be more vulnerable to disease
Higher prevalence in a low density population. (becomes RF)

Question 6

Give 3 examples of disease affecting population size.

Answer 6

Rabies- Foxes
Myxomatosis- Rabbits
Canine distemper- Lions

Question 7

Describe the outbreak of rabies in foxes.

Answer 7

Disease eradication
High numbers of casualties-
2000 rabid foxes per year.
Limited population size

Question 8

How did the introduction of a rabies vaccine affect fox population size ?

Answer 8

Caused a huge increase in population numbers

Rabies no longer limiting population size

Question 9

Describe the use of Myxomatosis as a means of population control

Answer 9

Introduced in 1953 as biocontrol
Severely impacted population size in the UK
Population remains lower than pre myxo introduction.

Question 10

Describe the impact of canine distemper on lions In the Ngorongoro crater,

Answer 10

Originally limited by food supply- enough for 100.
But had 3 outbreaks of CD in rapid succession
Should see ^ in pop. no as habitat now able to provide for 100+
However pop. are unusually susceptible to CD due to inbreeding (closed population)

Question 11

Describe the processes acting on the population of lions in the Ngorongoro crater

Answer 11

Originally regulated by bottom up (food supply only for 100)

Now regulated by top down (disease- reg, factor)

Question 12

What is the maximum sustainable yield ?

Answer 12

the largest yield that can be taken from a species’ stock over an indefinite period.

(Half the carrying capacity of a population- where largest no. of reproducing offspring found)

Question 13

What is carrying capacity ?

Answer 13

The maximum population size of a species which can sustain the environment indefinitely

Question 14

What is the population growth at carrying capacity ?

Answer 14

Zero, Birth rate= Death rate

Question 15

Birth and death rate are density dependant- True or false ?

Answer 15

True

If the population is above carrying capacity, birth rate will decrease and death rate will increase.

Question 16

Carrying capacity, K remains constant over time - True or false ?

Answer 16

False, carrying capacity changes over time.

Question 17

What does carrying capacity, K depend on ?

Answer 17

Population size
Amount of resources in ecosystem
Amount of resources each individual is consuming
Number of competitors

Question 18

Why are most populations held below the carrying capacity, K ?

Answer 18

Due to competitors.

Question 19

What is human carrying capacity dependant on ?

Answer 19

OIL, Makes up 60% of humanity’s primary energy

Question 20

Give the uses of oil.

Answer 20

Agriculture

pesticides, fertilisers, mechanisation, genetic engineering.

Question 21

Describe the population growth of a K species.

Answer 21

Reach a stable level and sustain their population for an indefinite period
Oscillating around K

Question 22

Describe the population growth of a R species

Answer 22

The population grows to a peak and then collapses

Question 23

How can the human population regain balance with the carrying capacity of its environment.

Answer 23

Decrease in the population size

Decrease in consumption

Question 24

Why is the Irish population at a lower carrying capacity since the 1840’s ?

Answer 24

Potato famine
Potato was staple of the diet, 90% of diet. Potato blight struck
Irish population finally crashed due to death and emigration.

Question 25

What is an overshoot ?

Answer 25

Occurs when a populations consumption exceeds the carrying capacity of its environment.

Question 26

What happens to a population when an overshoot occurs ?

Answer 26

The environment can no longer support the population Will be reduced birth rates and increased mortality Population will decline rapidly.

Question 27

What does the rapidity of decline in a population after an overshoot depend on ?

Answer 27

The degree of the overshoot | Whether carrying capacity continues to be eroded during decline.

Question 28

Why will the population after an overshoot tend to decline rapidly and to a lower level than was sustainable before ?

Answer 28

As the overshoot has degraded the carrying capacity of the environment, Decline can be long lived

Question 29

Describe the population size of the introduced reindeer population on St Matthews island between 1944-1980

Answer 29

29 reindeer introduced (no emigration or predation) increased to 6000, 1963 Completely died out by 1980

Question 30

Why did the overshoot of the St Matthews reindeer population occur ?

Answer 30

No migration Overgrazing of lichen Massive pop. ^ meant excessive no. all competing for limited forage. Led to population crash.

Question 31

What is the aim of maximum sustainable yield ?

Answer 31

to maintain population size at point of maximum growth by harvesting individuals which are being added to the population. = Population will be productive indefinitely.

Question 32

Above maximum sustainable yield (half carrying capacity) what will occur ?

Answer 32

Density dependant factors will limit breeding until the population reaches carrying capacity, Above MSY there are no surplus individuals to harvest

Question 33

List the problems with using maximum sustainable yield as a way to harvest organisms.

Answer 33

``` Impossible to estimate population size Carrying capacity continually changes Ignores several key demographic factors Mating systems are often unknown Irresponsibly used. ```

Question 34

It is not economically beneficial to overharvest a long lived species- True or False ?

Answer 34

False Driving extinction means the no. will decrease Increasing rarity and price.

Question 35

Describe an industry where maximum sustainable yield is irresponsibly used

Answer 35

Fishing industry Ignore size, age and reproductive status- Pop, crash Ignore ecosystem damage, species interaction Bycatch- Unintentional catching of other species

Question 36

What is maximum economic yield ?

Answer 36

The harvesting of organisms that provides the best economic gain.

Question 37

Describe maximum economic yield using elephants.

Answer 37

Meat- 6% can be harvested per year Ivory- 2% can be harvested per year MEY- gained from ivory.

Question 38

Which yields do we want to balance In population ecology ?

Answer 38

Maximum sustainable yield | Maximum Economic yield

Question 39

What is Optimum sustainable yield ?

Answer 39

The level of effort that maximises the difference between total revenue and total cost (lower effort level than MSY)

Question 40

Which is safer fixed effort management or fixed quota management ?

Answer 40

Fixed effort management If population low, less will be found and killed. Self regulating system.

Question 41

What is fixed effort management ?

Answer 41

Specify the number of hunters or length of hunting season

Question 42

What is fixed quota management ?

Answer 42

Specify the number that can be killed.

Question 43

What does Fixed effort management rely on ?

Answer 43

Adaptive harvest management Constant flow of information from hunters on no. & sex killed Use data to know when to close the season.

Question 44

What does maximum sustainable yield rely on ?

Answer 44

Careful observation of the managed population.

Question 45

What is one way that MSY can have a lower impact on populations ?

Answer 45

Compensatory mortality Targeting of age groups, (older) with naturally high rate of mortality.

Question 46

What is additive mortality ?

Answer 46

Reducing the population by more than its natural mortality. | The excess= Additive

Question 47

When applying a population dynamics model to the harvesting of a species What is important ?

Answer 47

An in-depth knowledge of ecology and the species under management.

Question 48

What does ecologically safe harvest management require ?

Answer 48

Adjustment of age of animal harvested (compensatory mortality)