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ENVIRO & ECOLOGY > Population Growth > Flashcards

Population Growth Flashcards

1
Q

Why is the study of population growth important? (3)

A

For conservation management
Food supply (i.e: fish stocks)
Understanding causes of population changes
To make predictions about future growth/ decline

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2
Q

When will exponential growth occur? Give an example

A

Occurs when there are optimal conditions and an unlimited environment
- When individuals colonise new habitats with lots of resources
e.g. introduced species
- When populations recover
E.g. over hunted species are allowed to recover
- Bacteria in a petri dish!

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3
Q

How do bacteria reproduce?

A

Binary fission

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4
Q

What is exponential growth?

A

Rapid population growth

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5
Q

What is binary fission an example of?

A

Exponential growth

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6
Q

Why do populations not generally demonstrate exponential growth for long? (3)

A

Resources usually limited
Conditions vary and may not be optimal
Effected by interactions with other organisms and the environment

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7
Q

Give two case study examples of exponential growth

A

Whopping cranes - only 15 existed in 1941 but by 2004 population reached over 300

American Bison in Yellow Stone National Park - 21 individuals in 1902, 250 by 1915

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8
Q

Why were the growth of American Bison in Yellow Stone National Park so successful

A
  • hunting band = few predators
  • plenty of food availability
  • they were isolated (= no migration)
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9
Q

What does an exponential growth curve look like?

A

a J shape (hockey stick)

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10
Q

What is the difference between exponential growth and linear growth?

A

Exponential = constant growth by number of individuals added increases (multiplies) - i.e: population doubles, then triples etc

Linear = population growth is consistent over time - i.e: population grows by 2 individuals each year

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11
Q

When does geometric population growth occur?

A

When populations reproduce periodically (i.e: at the same time each year)

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12
Q

Gave an example of an animal that has geometric population growth

A

Bison - only give birth in spring to early summer time each year (when the population grows)

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13
Q

Give 5 limiting factors of bison population growth

A 
Diseases
Predation
Habitat loss and fragmentation
Human intervention
Harsh winters/ climatic conditions
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14
Q

Before the 1800s, how many bison existed?

A

15-100 million

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15
Q

How did human intervention control bison population growth?

A

Herd management - individuals were removed from population

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16
Q

Which 4 factors define population size

A

Birth rates (natality)
Death rates (mortality)
Immigration (new individuals)
Emigration (removing individuals

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17
Q

How do you calculate the change in population?

A

(Births + Immigration) - (Deaths + Emigration)

Total individuals added) take away (total individuals removed

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18
Q

What does the symbol for population change over time look like?

A

triangle N over triangle t

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19
Q

Which letter represents the population size in equations?

A

N

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20
Q

Which letter represents the growth rate in equations?

A

r

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21
Q

What does the triangle represent in equations?

A

‘Change’ - i.e: change in t / population size etc

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22
Q

How do you calculate growth rate of a population?

A

Change in population size divided by change in time

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23
Q

If growth rate is consistent, why does the growth curve get steeper?

A

Because there are more individuals per unit time

24
Q

what does r represent?

A

Growth rate

25
Q

What does N represent

A

Population size

26
Q

What does a triangle represent?

A

Change

27
Q

What does ‘r max’ mean

A

The maximum per capita rate of population growth

28
Q

How do you calculate the maximum population growth rate?

A

Change in population size / change in time = maximum population growth rate

29
Q

what is the range of r max?

A

1 - 0

30
Q

What is the max rate of population growth for a species?

A

1

31
Q

What can a triangle symbol also be represented by?

A

d - for delta

32
Q

What does an r maxN rate more than 0 mean?

A

there will be fast exponential growth

33
Q

What conditions are needed for exponential growth

A

unlimited resources

34
Q

What is the carrying capacity (K)

A

The maximum population size that a habitat can sustain

35
Q

What is the name for the maximum population size that a habitat can sustain

A

Carrying capacity (K)

36
Q

What factors limit carrying capacity (3)

A

Space
Food
Water

37
Q

Which letter represents carrying capacity

A

K

38
Q

What affect does carrying capacity have on a population

A

it can limit the number of individuals

39
Q

What 2 main types factors can affect population size

A

Density-DEPENDENT factors

Density INDEPENDENT factors

40
Q

Name 3 density dependent factors

A

Increased predation
Disease
Competition

41
Q

Name 3 density independent factors

A

Pollution
Natural disasters
Extreme weather/ climatic conditions
(Stochastic events)

42
Q

Which factors affect a population more as it approaches the carrying capacity

A

Density-dependent factors - because the population becomes more dense

43
Q

What happens to birth rates if resources decrease

A

Birth rates decrease

44
Q

What happens to death rates if disease increases

A

Death rates increase

45
Q

What does a logistic growth curve show?

A

Natural population changes

46
Q

What is a logistic growth curve also called? And which shape is it

A

Sigmoidal curve

S shape

47
Q

What does an S shape curve show?

A

logistic growth of a natural population

48
Q

In a logistic growth curve, what does the levelling off indicate?

A

That carrying capacity has been reached - has limiting factors restricting population growth

49
Q

What are the 5 stages of sigmoidal population growth curves

A 
The establishment stage
The increase stage, 
The inflection stage, 
The deceleration stage 
The maximum sustained density stage.
50
Q

Which stage comes just before the levelling off in a sigmoidal curve?

A

The deceleration stage

51
Q

Which stage shows the most growth in a sigmoidal curve?

A

The inflection stage (Middle, steepest part of the S shape)

52
Q

What happens to population size when is it nearing carrying capacity?

A

It fluctuates

53
Q

Why do populations fluctuate near the carrying capacity ?

A

Because seasonal or environmental cycles can cause changes - plus other density dependent factors

54
Q

What is the difference between an exponential growth curve and a logistical growth curve?

A

Exponential = J shaped curve

Logistical = S shaped curve

55
Q

What is the equation for exponential growth?

A

dN / dt = rN

Change in population size / change in time = growth rate of population

56
Q

If the r is more than 0 what happens to the population?

A

it grows

57
Q

What is the equation for logistic growth?

A

dN/ dt = rN (K-N / K)

K= carrying capacity

ENVIRO & ECOLOGY (24 decks)

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