IB Biology, C5 (HL), Population ecology

Explain what it is meant by populations are dynamic

They respond to variations in their environments

What is population measured in terms of?

- Size (number of individuals in a population)

- Density (Number of individuals per unit area)

- Growth rate (Change in number of individuals per unit area / time)

Name a way in which population density can be recorded

Belt transects

Name a method of estimating population size

Capture-mark-recapture

Outline the capture-mark-recapture process

1. Animal are trapped (pitfall trap)

2. Animals marked harmlessly, numbers are recorded, animals released

3. Traps are revisited after a few days

4. Number of marked and unmarked trapped animals are recorded

What is the formula for population size?

(number of individuals in sample 1 - number of individuals in sample 2) / number of individuals in sample 2

What assumption are made during the capture-mark-recapture method?

There are no deaths during time between sample recordings

There is no migration / emigration during time between sample recordings

Identical sample method is used throughout

The marking has no affect in survival rate of samples species

Name the 5 methods of catching commercial fish stocks, which are most and least environmentally friendly and why?

- Purse seine (most sustainable, most selective, less intrusive)

- Bottom Trawling

- Dredging (least sustainable, most destructive, least selective, big bi-catch)

- Gill nets

- Long line

List 5 characteristics of Exponential growth (J curve)

- Could illustrate colonising population in an area for the first time

- Represent rapid exponential J shaped growth

- Food and space limitations slow population growth

- Birth rate outnumbers death rate

- Unsustainable in the long term

Outline the 3 stages of the Exponential growth (J) curve

- Lag phase: Number added per unit population is low

- Deceleration: Population number is limited by environmental factors

- Exponential growth: Number added per unit population is high

List the 5 characteristics of Logistic growth (S curve)

- Illustrates population in equilibrium where birth + immigration = death + emigration

- Represents constant and consistent S shaped growth

- Fluctuations are caused by birth and death rate variations

- Populations fluctuate around carrying capacity constant (K)

- Sustainable in the long terms

Describe the pattern involved in Logistic (S) growth

Populations grows, environmental resistance (food and space limitations) decrease population, more food and space become available, population grows...

Outline the 3 stages of logistic growth

- Lag phase: Exponential growth is seen, number added per unit population is high

- Exponential growth: Population increases above carrying capacity constant K.

- Deceleration: Environmental resistance increases when population > K. Population decreases.

- Stable equilibrium: Population = K

- Population decreases below K. Environmental resistance decreases when population < K. Population increases. Etc.

Name two species that follow the S curve pattern.

Paramecium and daphnia

Name the X and Y axis of J and S curves

X = population number

Y = time

When is an ecosystem in equilibrium?

When birth + immigration = death + emigration

List 7 factors determining population size

- birth

- immigration

- death

- emigration

- fertility

- age structure

- sex ratios

Define fertility

The reproductive rate of the female of a species

Define age structure

the number of organisms of different ages in an ecosystem

Define random distribution

each individual of a species' position is independent from the others

Define uniform (regular) distribution

A species' individuals are more evenly spread / spaced than what would occur by chance

Clumped distribution

Individuals of a species are clumped in groups

Which type of distribution is most common?

Clumped distribution

What do biogeographic factors affect?

Species diversity

What two parts of an ecosystem are important for study?

shape and size

Define biogeography

The study of distribution of a species in an ecosystem in a geographical space through geographical time

Outline the two characteristics of a more diverse space

Large and connected

What edging is best?

Circular

Is it best to have more or less edging?

Less

Which type of reserve preserves biodiversity?

Clustered

List 4 density dependent factors

- number of individuals in a population

- competition for resources

- location by predators / parasites

- vulnerability to infection + disease

these occur as a result of high or low population density

List 2 density independent factors

- abiotic factors (temperature, rainfall, humidity, salinity etc.)

- catastrophic event (floods, tsunamis, fires, drought, earthquakes, eruption)

* These have no direct affect on population density but they do affect density dependent factors (eg. amount of water does not change population density, but it does change competition levels for this water therefore leading to a change in density.)

What sampling method is used to determine zone of tolerance by observing organism number in relation to abiotic factors ?

Line transects

Define the law of tolerance

For each abiotic factor, an organism has a range of tolerances at which it can survive

Define carrying capacity (K)

The maximum population that the environment can indefinitely sustain.