Populations

Question 1

Habitat

Answer 1

The place where an organism lives e.g. a pond

Question 2

Population

Answer 2

All the individuals of one species in a habitat
e.g. dragonflies in a pond

Question 3

Biodiversity

Answer 3

The variety of living organisms in an area – e.g. this can be a single habitat or globally

Question 4

Abiotic factors

Answer 4

An ecological factor that makes up part of the non-biological environment of an organism (physical/chemical factors) e.g. temperature, pH, rainfall, humidity

Question 5

Community

Answer 5

All the populations of different species in a habitat e.g. dragonflies, newts, beetles in a pond

Question 6

Species

Answer 6

A group of similar organisms that can interbreed, successfully reproducing to produce fertile offspring

Question 7

Biotic factors

Answer 7

An ecological factor that makes up part of the living environment of an organism e.g. food availability, competition, predation

Question 8

A niche

Answer 8

Every species occupies its own niche (the role it plays) within its habitat, this includes:
• Its biotic interactions – what it eats, what its eaten by
• Its abiotic interactions – e.g. the oxygen it breathes in, and the carbon dioxide it
breathes out
• Every species has its own unique niche – a niche can only be occupied by ONE SPECIES

Question 9

Carrying capacity

Answer 9

•Carrying capacity is the maximum stable population size of a species that an ecosystem can support.
Population size is affected by:
• Abiotic factors (non-living) • Biotic factors (living)

Question 10

Limiting factors

Answer 10

A factor that limits further growth of a population.
-migration
-density independent factors eg earthquake

Question 11

• Three typical types of populations pyramids are:

Answer 11

1. Stable population: birth rate = death rate
2. Increasing population: birth rate > death rate 3. Decreasing population: birth rate < death rate

Question 12

Intraspecific variation

Answer 12

• Intraspecific variation–variation within a species e.g. antibiotic resistance in a species of bacteria

Question 13

Inter specific variation

Answer 13

Inter specific variation–variation between different species e.g. thickness of blubber in seals and sea lions

Question 14

Random and systematic sampling

Answer 14

• Random: Sampling method in which all members of a community have an equal and independent chance of being selected
– E.g.quadrat
• Systematic: Sampling method in which data is gathered according to a system, usually at fixed intervals from a fixed point

Question 15

Method for random sampling

Answer 15

• Createagridusingtwotapemeasures
• Create random coordinates using a random number generator
• Take samples where two random coordinates intersect
• Repeattocalculateamean

Question 16

Representative sampling

Answer 16

Representative sampling
• The sample gives a fair and accurate representation of the whole species. There is no impact of bias or chance on the results.

Question 17

Sampling bias

Answer 17

Sampling bias
• occurs if the sample is unrepresentative due to bias sampling technique

Question 18

Sampling errors

Answer 18

• Selection bias: Actual selection probabilities differ from assumed selection probabilities
• Random sampling error: Variation due to randomness
• Non-sampling error: – Over-coverage
– Under-coverage
– Measurement error – Processing error
– Non-response

Question 19

Quadrat(random)

Answer 19

-Squares of a fixed size randomly placed on ground to be sampled
-Estimating the population of sessile (stationary) or slow-moving organisms
-Simple, quick to repeat, suitable for flat ground
-Difficult on uneven terrain, cannot sample fast-moving animals

Question 20

Line transect (systematic)

Answer 20

-Line or strip laid across area to be studied. Organisms at fixed intervals along it are counted
-Measuring the distribution of organisms along a gradient (e.g. altitude, light intensity, moisture)
-Simple, can sample across a range of habitats in an ecosystem, shows change in abiotic factors too
-Can be time- consuming, distance from transect must be maintained, cannot sample fast-moving animals

Question 21

Mark and recapture

Answer 21

-Members of a population are caught, counted, marked, and released
-Estimating the population of fast- moving or difficult- to-see animals
-Can be used for fast-moving animals
-Very time- consuming, difficult not to just catch sick/weak specimens

Question 22

What does skewed mean

Answer 22

If median, mode, and mean are not equal, distribution is said to be skewed

Question 23

Why scientists use sampling techniques

Answer 23

• Too many organisms to count
• Cannot find all organisms
• Area too large to study
• Too time consuming

Question 24

Why might we want to sample an area

Answer 24

• Curiosity/scientific endeavour • Conservation
• Sustainability

Question 25

Mark release recapture method

Answer 25

1. Capture a sample of the animal, using an appropriate technique
2. Mark them in a harmless way (count how many you have caught)
3. Release them back into their habitat
4. Wait a week, and resample the same population
5. Count how many of the second sample are marked
6. Use the Lincoln Index to estimate the total population

Question 26

Lincoln index

Answer 26

(n1 ×n2)÷n3 =total population
-n1 first capture
-n2 second capture
-n3 recaptures

Question 27

What are the limitations of a capture- mark-recapture system?

Answer 27

• Accuracy depends on capturing a fairly large proportion of the population.1
• Many study populations arenot geographically closed because only a part of a population’s range is included in the study area.
• Animals can move into and out of some study areas, and the number of animals present at a given time may be less than the population estimated

Question 28

What assumptions do we have to make about our sampling technique and the population we are sampling for the Mark- release-recapture method?

Answer 28

1. During the study period, births, deaths and migration rates have remained stable (Why can’t we say NO BIRTHS/DEATHS?)
2. The mark doesn’t affect how well the individual survives – make it stand out to predators/toxic
3. The mark doesn’t rub off
4. The marked individuals have enough time to mix back into the population

Question 29

Ecosystem

Answer 29

More or less self contained unit in ecology made up or biotic and abiotc factors

Question 30

Community

Answer 30

All the populations of different species living and interacting together in a particular area

Question 31

Primary succession

Answer 31

Primary succession – on land that is newly formed or exposed. No organic material or soil there at the start.

Question 32

Secondary succession

Answer 32

• Secondary succession – soil is present but no plants or animals.

Question 33

Deflected succession

Answer 33

• A community that remains stable only because human activity prevents succession from running its course.
• This happens all the time, for example, sheep grazing prevents grassland from developing into woodland.
• Many places need to be actively managed in the battle against succession, for example, golf courses need to be mowed all the time
• It is called a plagioclimax as succession is stopped artificially

Question 34

2 types of competition

Answer 34

Intraspecific – between individuals of same species
Interspecific – between individuals of different species

Question 35

Competition

Answer 35

• Competition is:
– a struggle between individuals for
resources (like food & water) that are in limited supply
• Competition decreases reproduction rate (fewer resources to support reproduction) but increases death rate (fewer resources to support survival)

Question 36

Interspecific competition

Answer 36

• When the population size of one species changes so does the other.
• Generally has a pattern of 4 stages:
1. Increase in prey – more food for predators
2. Increase in predator – means decline in prey population
3. Less food available for predators – competition leads to a reduction in predator population size
4. Less predators – more prey are able to survive, increase in prey