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Biology Unit 1 > Measuring Populations > Flashcards

Measuring Populations Flashcards

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1
Q

What is a population?

A

A group of individuals of the same species living in a particular area at the same time.

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2
Q

What are three ways we can measure populations?

A

Using quadrants, transects and capture-recapture.

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3
Q

What types of organisms do each population measuring techniques measure?

A
  • Quadrats and transects are used for sessile or slow-moving organisms.
  • Capture-recapture are used for fast-moving organisms.
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4
Q

How are quadrats used?

A

A quadrat is a frame that is placed onto the ground at random throughout the study area, the number of species in the qudrat is recorded.

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5
Q

How are quadrants used to estimate population size and density?

A
  • Population size (no. of individuals) = no. of individuals in selected quads/no. of selected quads x total no. of quads.
  • Population density (no. of individuals per square meter) = population size/area x total no. of quads.
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6
Q

What are the advantages and disadvantages of using quadrants to measure populations?

A

Advantages:
- Inexpensive
- Easiest method and uses the least amount of time and energy.
- Minimal disturbance to the environment (ethical).

Disadvantages:
- Not accurate (depends on chance)
- Only used for sessile/slow moving organisms.

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7
Q

How are transects used?

A
  • Plan and profile sketches.
  • A line or rope you move along and record which species are located at each point.
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8
Q

What are the advantages and disadvantages of using transects to measure populations?

A

Advantages:
- Minimal disturbance to the environment (ethical).
- Broad view of community land use.
- Can be used on any area
- Can be used to illustrate a particular gradient or linear pattern along which species of plants and animals are living.

Disadvantages:
- Not accurate (only short distances)
- Line can be interfered with
- Cannot be used for a large abundance of plants.
- Only used for sessile/slow moving organisms.

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9
Q

What are the 3 types of distribution?

A

Random, uniform and clumped.

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10
Q

What is random distribution?

A

Spaced irregularly, the location of one organism does not effect the location of another (more common for plants than animals).

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11
Q

What is uniform distribution?

A

Evenly spaced, the presence of one organism determines how close or distant another will be. Common in high density populations of organisms that set up breeding grounds.

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12
Q

What is clumped distribution?

A

A number of individuals grouped together and the groups make up the population. Can result from social behaviour e.g. schools of fish or mini habitats were the abiotic and biotic factors are favourable.

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13
Q

What are population pyramids used for?

A

They show the age distribution and sex ratios of populations.

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14
Q

What is important for future growth of populations?

A

Populations maintain a high level of reproduction aged individuals of both sexes and individuals below reproducing age.

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15
Q

Why is it important for populations to maintain a high level of reproduction aged individuals of both sexes and individuals below reproducing age?

A

For future growth, without individuals of reproducing age no more individuals can be born, which will decrease the chances of the population survival rate.
If there are no individuals of below reproducing age in a population, when the individuals who can reproduce now get older and can’t reproduce anymore, there will be no individuals to reproduce in the future and ensure growth of the population.

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16
Q

What is the formula for population growth rate (word and letters)?

A

Growth rate = (birth rate + immigration rate) - (death rate + emigration rate)

r = (b+i) - (d+e)

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17
Q

How is capture-recapture used?

A
  1. Select a population
  2. Do the first capture and mark individuals captured
  3. Release captured individuals
  4. Do the second capture after organisms have had time to recover
  5. Find the number of marked individuals in the second capture
  6. Release captured individuals.
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18
Q

What is capture-recapture used for?

A

Used to estimate the size of a mobile species.

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19
Q

How is population size estimated in capture-recapture?

A

No. of individuals in the first capture x no. of individuals in the second capture/no. of marked individual in the second capture.

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20
Q

What are the advantages and disadvantages of using capture-recapture to measure populations?

A

Advantages:
- Easy and simple
- Good for determining populations of animals

Disadvantages:
- Inconsistent (most inaccurate)
- Requires a large sample
- Only works for fast moving animals
- Cannot calculate diversity
- Disturbance to the environment
- Time consuming

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21
Q

What assumptions are needed to be valid for capture-recapture to work?

A
  • The marking does not affect the survival rate of the animals.
  • The sampling methods used for the capture-recapture are identical.
  • There is no depth, immigration or emigration (closed populations).
  • All members of the population mix randomly and enough time is given between each captures for the organisms to mix (each member of the population has equal chance of capture each time).
22
Q

What is telementry?

A

Technology used to track individuals of a species, particularly ones that cover large areas.

23
Q

Why is telemetry useful?

A

The data collected by tracking the individuals can be used to model species distribution.

24
Q

What are R-selected species?

A

Species that have a high growth rate but low survivability (“cheap” offspring).

25
Q

What are K-selected species?

A

Species that have a low growth rate but high survivability (“expensive” offspring).

26
Q

Can species change their selection strategy?

A

Some species can change their selection strategy according to environmental conditions.

27
Q

What strategies do most organisms typically demonstrate?

A

Most organisms typically demonstrate an intermediate strategy somewhere along the spectrum.

28
Q

What does an ecosystems carrying capacity refer to?

A

The maximum population size of a species that an environment can sustain.

29
Q

What is an ecosystems carrying capacity determined by?

A

The amount of available resources (water, habitat, food etc.).

30
Q

Draw a graph illustrating the reach of a populations carrying capacity.

A

Refer to book

31
Q

Draw a graph illustrating the population growth of a population reaching carrying capacity.

A

Refer to book

32
Q

What is a population overshoot?

A

A population is in overshoot when it exceeds available carrying capacity.

33
Q

How does a population overshoot affect a population?

A

A population in overshoot may permanently impair the long-term productive potential of its habitat, reducing future carrying capacity. It may survive temporarily but will eventually crash as it depletes vital natural capital (resource) stocks.

34
Q

What are limiting factors?

A

Anything that has the ability to constrain a population’s size and slow or stop it from growing.

35
Q

What are density-dependent factors?

A

Limiting factors that affect an individual of a population influenced by the population density.

36
Q

What are density-independent factors?

A

Limiting factors that affect an individuals of a population to the same extent regardless of population density.

37
Q

What are some examples of density-dependent factors?

A
  • Competition
  • Food supply
  • Disease
  • Parasites
  • Predation
38
Q

What are some examples of density-independent factors?

A

Physical:
- Acidity
- Rainfall
- Humidity
- Temperature
- Salinity

Catastrophic events:
- Volcanic eruption
- Tsunami
- Fire
- Drought
- Earthquake
- Flood

39
Q

Why is competition (e.g. for food supply) dependent on the population density?

A

The more individuals in a population, the more food needed. If there is limited food and too big of a population some individuals will outcompete the other.

40
Q

Why is predation dependent on the population density?

A

The more individuals in a population, the easier it is for predators to spot.

41
Q

Why is disease/parasites dependent on the population density?

A

The more individuals in an area the easier it is for disease and parasites to spread.

42
Q

Describe r-selction, hint: offspring, environment and population size. (4 marks)

A
  • Occurs in unstable environments where there are ecological disruptions and resources are used for maximising reproduction.
  • There are usually many offspring per brood, which require little parental care and have a high rate of mortality
  • The body size of offspring is typically small and they have an early onset of maturity (short developmental span)
  • Population size is typically variable (highly fluctuating) and an example of a r-selected organism is a pioneer species
43
Q

Describe k-selction, hint: offspring, environment and population size. (4 marks)

A
  • Predominates in stable or predictable environments where resources are used for maximising long-term survival
  • There are usually very few offspring per brood, each requiring high levels of parental care (resulting in low mortality)
  • The body size of offspring is typically larger and they have a late onset of maturity (long developmental span)
  • Population size is typically stable (reaches carrying capacity) and an example of K-selection is a climax species
44
Q

What scale are transects used for and how?

A
  • Spatial scale
  • Shows how population density changes with distance from a point or between two points.
45
Q

What scales are quadrats used for and how?

A

Spatial scale
- Compare 2 different areas

Temporal scale
- Compare the same area at different times

46
Q

How can you cover a large area with transects?

A

Use multiple

47
Q

Give two reasons an ecologist would need to measure the number of individuals in an animal or plant population.

A
  • See the stability of the population.
  • Showing whether conservation efforts are helping an endangered species increase in numbers.
48
Q

Why do ecologists use sampling techniques when measuring populations?

A

Because it is less time consuming and easier to do.

49
Q

What factors should be considered when deciding on a sampling technique to estimate population size or density?

A

Wether the organisms are sessile, fast-moving or slow-moving.

50
Q

Describe what is meant by population growth curve and carrying capacity and discuss a minimum of four factors that impact the growth of a specific population and the carrying capacity within that ecosystem. (10 marks)

A
  • Lagging phase: slow growth, due to the low numbers of reproducing individuals.
  • Exponential growth phase: rapid increase in population due to the birth rate exceeding the death rate (abundance of resources that allows for optimum growth and survival).
  • Transitional phase: resources start to limit for the population, decrease in birth rate, increase in death rate.
  • Stationary phase/plateau: equilibrium is reached, the fluctuations in the population are minimal. Stable population.
  • Carrying capacity: the maximum population size of a species that an environment can sustain.
  • Graph drawn
    Biotic:
  • Soil composition (% of nutrients in the soil).
  • Food resources
  • Disease presence (density-dependent)
    Abiotic
  • Oxygen levels (low levels = potentially low population).
  • Water quality (components dissolved in the water)

Biology Unit 1 (13 decks)

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