Populations In Ecosystems

Question 1

Community

Answer 1

All populations of different species in the same area at the same time

Question 2

Ecosystem

Answer 2

A community and the non living components of an environment

Question 3

Niche

Answer 3

An organisms role within the ecosystem. Each species occupies its own niche

Question 4

Biotic factors

Answer 4

Impact of interactions between organisms

Question 5

Abioticfactors

Answer 5

Non living factors in an ecosystem

Question 6

Carrying capacity

Answer 6

Maximum population size an ecosystem can support

Question 7

Abiotic Factors affecting population size

Answer 7

Ph 
Soil quality
Temperature 
Oxygen and carbon dioxide levels
Light intensity

Question 8

… are adapted to abiotic factors which develops through the process of ___

Answer 8

Plants and animals are adapted to abiotic factors which develops through the process of natural selection

Question 9

Species diversity and population size are larger when …

Answer 9

Species diversity and population size are larger when aboitic conditions are less extreme

Question 10

An example of biotic factors include…

Answer 10

Interspecific competition

Question 11

What is interspecific competition

Answer 11

Numbers of different species compete for the same resource which is in limited supply For example light water and food
The better- adopted individual is more likely to survive and reproduce

Question 12

What is intraspecific competition

Answer 12

This is a biotic factor

Members of the same species compete for a resources and a mate

Question 13

Members of the same species of competing for a mate, The more well adapted individuals will be able …

Answer 13

Members of the same species of competing for a mate, The more well adapted individuals will be able to perform a more ‘impressive’ courtship display so will more likely attract a mate and reproduce

Question 14

Predation influences population size

What is predation

Answer 14

Predation influences population size

Predation is Interaction between predator and prey

Question 15

Predator population increases as prey increases as …
Predator decreases cos theres less food
Prey population increases as predator population decreases as ..

Answer 15

Predator population increases as prey increases as there are more food resources increasing survival
And vice versa
Predator decreases cos theres less food
Prey population increases as predator population decreases as they are less likely to b predated on so survive

Question 16

Different ways to measure population size

Answer 16

Quadrats
Belt transects
Mark-release-recature

Question 17

Quadrats r used to sample …

Steps

1) .In quadrats u need to place …
2) .Use a random …
3) .Place quadrat ..
4) . ..

Answer 17

Quadrats r used to sample …

Steps

1) .In quadrats u need to place 2 tape measures at right angles to create a gridded area to take samples from
2) .Use a random number generator to generate coordinates to take samples from
3) .Place quadrat on coordinate and either count abundance of species or calc percentage cover
4) . Repeat at least 30 times

Question 18

Belt transect

This can be used instead of …
1 ). …
2). Quadrat …

Answer 18

Belt transect

This can be used instead of random sampling
One ). Tape Measure is placed thru a non-uniform ecosystem e.g. rocky beach
2). Quadrat is placed at intervals along the transect to measure the impact of changes in the environment

Question 19

Different ways of estimating population size in a quadrat

Answer 19

Frequency : how many squares the species is present in

density : every individual of the species is counted

Percentage cover : estimates the percentage of the whole quadrat that is covered by the species

Question 20

Mark – release – recapture

Used for …

1) .
2) .
3) .

Answer 20

Mark – release – recapture

Used for motile organisms

1) . Animals are trapped and marked with a substance that must b non toxic, weather resistant And not impacted by predation or reproduction
2) . Released and left to redistribute themselves in the population
3) . They’re recaptured a few days later and a second sample is taken. This is repeated at least ten times

Question 21

Mark release recapture equation

Population size = …

Answer 21

Mark release recapture equation

Population size = size of first sample x size of 2nd sample / number of marked recapture

Question 22

Assumptions for mark release recature

Answer 22

Enough time for organisms to redistribute themselves
No migration
No births or death

Question 23

What is succession?

Answer 23

Change in an ecological community overtime

So when the species change over time

Question 24

Primary succesion

Answer 24

Primary succession

1) . A pioneer species colonises bare rock or sand
2) . Pioneer species r adapted to survive harsh abiotic conditions and change abiotic conditions to become less extreme through their death and decomposition
3) . Moss and smaller plant species can now survive and, and they further increase depth and nutrient density of the soil as they die
4) . This continues and larger plants can survive and further change the environment
5) . Each new species may change the environment in a way that the previous species can no longer survive as they become out competed
6) . These changes result in a less hostile environment and increase bio diversity
7) final stage of succession is a climax community

Question 25

Conservation of habitats

By conserving succession a …
Provides conflict …
E.g. …

Answer 25

Conservation of habitats

To conserve habitats, succession is often managed
By doing this a climax community is prevented so theres a wider variety of habitats and therefore a higher species of diversity
Provides conflicts between human needs and conservation
E.g. tree is coppiced to its base in winter to provide wood for furniture needs but this means that shoots would regrow rapidly conserving species diversity

Question 26

What is a species

Answer 26

Organisms that can interbreed and reproduce fertile offspring

Question 27

What is meant by uniformly distributed?

Answer 27

The organisms are equally spread

Question 28

Ecologists used a method called proportional sampling to estimate the population size of an animal species. This method is based on assumptions. Two of the assumptions are given below.
1. They know the size of the area, A, where the animal population lives.
2. The animals are uniformly distributed in this area.
To carry out the method, the ecologists:
● chose a region of known size, R, inside area A
● counted the number of animals in region R. They called this number S
● assumed that the number, S, would be in proportion to the size of the total population, P,
in area A.

Use the letters a r and s to wrote an equation showing how proportional sampling is used to estimate the total size of a population

Answer 28

Ecologists used a method called proportional sampling to estimate the population size of an animal species. This method is based on assumptions. Two of the assumptions are given below.
1. They know the size of the area, A, where the animal population lives.
2. The animals are uniformly distributed in this area.
To carry out the method, the ecologists:
● chose a region of known size, R, inside area A
● counted the number of animals in region R. They called this number S
● assumed that the number, S, would be in proportion to the size of the total population, P,
in area A.

Use the letters a r and s to wrote an equation showing how proportional sampling is used to estimate the total size of a population

P = a x s / r

Question 29

Population size can be estimated using proportional sampling or mark-release-recapture.
How do the assumptions made in proportional sampling differ from those made in mark-release-recapture?
[2 marks]

Answer 29

Population size can be estimated using proportional sampling or mark-release-recapture.
How do the assumptions made in proportional sampling differ from those made in mark-release-recapture?
[2 marks]

In mark release recapture there is no assumption that organisms r uniformly distributed and that the size of total are isnt required

Question 30

Whats proportional sampling

Answer 30

Assumptions r the animals r uniformly distributed and that they know the size of the area

Question 31

Assumptions in mark release recapture

Answer 31

Size of area isnt required and and no assumption that the animals r uniformly distributed

Question 32

Give one assumption about the animals caught that is in both methods

Answer 32

The animals r all from the same population

Question 33

The graph shows how gross productivity and biomass in an area changed with time in the succession from bare soil to mature woodland.

Suggest appropriate units for gross productivity.

Explain the decrease in gross productivity as the woodland matures.

Answer 33

Unit of energy / mass, per yr

Less light cis more shading so reduced photosynthesis

Question 34

Use your knowledge of succession to explain the increase in biomass during the first 20 years. (3)

Answer 34

Presence of Pioneer species
So change in abiotic conditions to make environment less hostile
This increases diversity of species

Question 35

Suggest one reason for conserving woodlands.

Answer 35

Conserving niches/habitats endangered species

Source of medicines

Question 36

Use the information in the graph and your knowledge of net productivity to explain why biomass shows little increase after 100 yrs

Answer 36

Net productivity = gross productivity - respiratory loss

Decrease in gross productivity

Question 37

On islands in the Caribbean, there are almost 150 species of lizards belonging to the genus Anolis. Scientists believe that these species evolved from two species found on mainland USA. Explain how the Caribbean species could have evolved.
(6)

Answer 37

Geographical isolation 
Separate gene pools so no interbreeding happens
Variation due to mutation
Different selection pressures 
Different reproductive success 
Leads to change in allele frequency

Question 38

Anolis sagrei is a species of lizard that is found on some of the smallest Caribbean islands. Describe how you could use the mark-release-recapture method to estimate the number of Anolis sagrei on one of these islands.

Answer 38

Capture mark and release
Make sure method of marking dont harm lizard
Leave sufficient time for lizards to distribute before collecting a second sample
Population = number in first sample x number in second sample / number recaptured

Question 39

The kangaroo rat is found in deserts, it’s kidneys produce extremely concentrated urine

is the production of concentrated urine an adaptation to biotic or abiotic conditions

Suggest how this adaptation helps the kangaroo rat to survive

Answer 39

Abiotic conditions As the kangaroo rat is adapted to a lack of water which is a nonliving feature and so an biotic conditions

By producing Concentrated urine the kangaroo rat is able to conserve water this helps it to survive in deserts where there isn’t much water available

Question 40

The length of proboscis was studied in bees in a mountain habitat in Colorado
The bees were found to b dominated by three species:
One w a long proboscis
One W a medium sized proboscis
And one w a short proboscis
The bees use their proboscis to get nectar from the corolla of flowers
One such flower is shown below
Flowers w a variety of corolla lengths were observed on the mountain

Give one adaptation of the bees to a biotic condition in their habitat

Suggest what would happen if another species of bee w a long proboscis was introduced to the mountain habitat

Answer 40

The length of their proboscis

The new bee species would compete w the current bee species w a long proboscis
One species would out compete the other more successfully until only it is left

Question 41

An investigation looked at the length of beaks in two closely related species of bird living in the same habitat
The birds eat seeds of similar plant species the results r shown below
P 417
Describe the data shown by the graph

Suggest why the two bird species are able to share the same habitat

Answer 41

Species a have a small beak length with most individuals having a beak length of around 5 mm species b has a longer beak w most individuals having a beak length of 15 mm

Cos the two species occupy different niches
Their beaks are diff sizes so they wouldn’t b in competition w each other

Question 42

A team investigated changes in the sizes of a population of owls and a population of mice over 20 years they also monitored changes in temperature the results are shown in the graph below

Give one factor affecting the population of owls which is biotic

Describe how the fall in temperature between years 11 and 12 may have affected the mouse population size and suggest a reason for the change in population size(p 422)

Explain how variation in the mouse population size over the twenty yr period could have caused changes in the owl population size

Answer 42

One biotic factor affecting the population size of owls is the number of mice

As the temperature fell the size of the mouse population decreased this could have been because the cold weather caused the temperature of the surroundings to fall below the body temperature of the mice
if that had happened the mice might have used more energy maintaining their body temperature and this would have meant less energy was available for growth and reproduction causing the population size to decrease

as the mouse population size increased there was more food for the owls and so the owl population grew
As the owl pop increased, more mice were eaten and so the mice population began to fall this meant there was less food for the owls so their population decreased and so the cycle continues

Question 43

What is the population?

what is a community?

Answer 43

Population is all organisms of one species in a habitat

Community is all the populations of different species in a habitat

Question 44

What is carrying capacity

Answer 44

Carrying capacity is the maximum stable population of a species that an ecosystem can support

Question 45

Define interspecific competition and infraspecific competition

Answer 45

Intraspecific competition is when organisms of different species compete with each other for the same resources

intraspecific competition is when organisms of the same species compete with each other for the same resources

Question 46

The student is investigating the abundance of daisies in a field she decides to use a quadrat to measure the percentage cover of daisies in the field described how she could do this

Answer 46

She could place the quadrat on the ground at random locations across the field and count how much of the quadrat is covered by Daisies
A square in the quadrat should be counted if it’s more than half covered by a particular species

Question 47

Describe how the student could take random samples using a quadrat

Answer 47

The student could divide the field into a grid and use a run random number generator to select coordinates
The quadrat could then be placed at these coordinates and the number of daisies in each quadrat counted

Question 48

A student is investigating how the abundance limpets on a rocky shore changes with distance from the sea
describe a suitable method he could use to investigate this at low tide

Answer 48

The scientist could place a tape measure in a straight line from the sea to the top of the shore to form a transect line
He could then place a quadrat at regular intervals along the transect and count the number of limpets present in the quadrat

Question 49

The mark release recapture method was used to estimate the size of a black beetle population in two different locations
on day one the Beatles were marked using white paint and then released
the second sample was captured the following day

Size of the first sample
Location a = 19
Location b = 17

Size of second sample
Location a = 14
Location b = 21

Number of marked beetles in second sample
Location a = 3
Location b = 6

Use the data in the table to estimate the total population size of beetles at
Location a = (19 x 14) / 3 = 89 beetles
Location b = (17 x 21) / 6 = 60 beetles

Are the estimates for these locations accurate? Explain your answer.

Answer 49

Use the data in the table to estimate the total population size of beetles at
Location a = (19 x 14) / 3 = 89 beetles
Location b = (17 x 21) / 6 = 60 beetles

Are the estimates for these locations accurate? Explain your answer.
No because the two samples were only taking a day apart which may not be long enough for them to mix back in with a population also the Beatles were marked with white paint which might have affected the chances of survival

Question 50

The scientist has been investigating the effect of salt spray from a road adjacent to an inland field the results are shown below
P 429

Describe the data shown in the kite diagram and the graph

One of the plant species is normally found in coastal areas which species is this likely to be, A B or C. explain your answer?

The scientist is unable to prove that salt spray from the road is responsible for the absence of species b between zero and 20 m from the road using the data shown above explain why

Answer 50

1)The kite diagram shows that species a is present between 20 and 45 m from the road with a low percentage Also present between 80 and 140 m and is most abundant between 130 and 140 m.
Species b is present between 55 and 130 m from the road and is most abundant between 60 and 85 m
Species c present between zero and 50 m from the road and theyre most abundant between 0 to 35 m
The graph shows that soil salinity is high between 0 to 30 m from the road close shopping between 30 and 40 m continues to fall until around 50 m and then remains low

2). Salinity is high in coastal areas, so Plants that grows here must be able to tolerate for these conditions. species c is present between 0-50m from the road boundry and this overlaps w where salinity is the highest ( 0-30m) this suggests that species c is adapted to higher salinity conditions.

3). The data shows that at a high soil salinity there is an absence of species b but it doesn’t prove that salt spray from the road is the cause
Species might b absent for other reasons e.g. cos its outcompeted by species b

Question 51

What is meant by the term abundance and distribution

Name and describe two measures of abundance

What is a quadrat, and a belt transect

Answer 51

The number of individuals of one species in a given area

Where a particular species is within the area u r investigating

Frequency which is the number of samples a species is recorded in
Percentage cover, is which how much area u r investigating is covered by a species

A quadrat is a square frame divided into a grid of a hundreds smaller squares by strings attached to a frame

A belt transect is when quadrats r placed next to eachother along a transect to work out species frequency and percentage cover across an area/along the transect

Question 52

Population size equation

Answer 52

Pop size = number caught in 1st sample x number in 2nd sample / number marked in 2nd sample

Question 53

A team analyse data on ecological changes in part of a national park
Their results r shown in the graph below

P 433

What type of succession is shown on the graph
Explain

Describe the characteristics of the dominant plant community between 1800 and 1860

Describe and suggest an explanation for the change shown in the average length of time dominant plant seeds remain viable for.

During what time period would u expect to see a high percentage of plants whose seeds would require high light intensity for germination. Explain

Describe and suggest an explanation for the change in the soil moisture content shown on the graph

Answer 53

Primary succession because there is no soil present in 1800

The dominant plants would been adapted to survive without much water content and fluctuating ground temperatures they would have had seeds that would remain viable for long periods of time they would have been species of small pants (not have been tree species)

The average length of time dominant plant seeds remained viable for was relatively high between 1800 and 1860
This might have been because seeds that remained viable for a long time could lie dormant until conditions were favourable enough to germinate
between about 1860 and 1880 the average length of time fell sharply and then continued to fall more slowly until levelling off at around 1960
This may have been because the plants that were dominant between 1800 and 1860 were succeeded by other plant species which were better adapted to the changed conditions
E.g. a higher soil moisture content so they no longer need to be viable for longer periods of time

Between 1800 and 1920 cos there was no tree species present during this time so there was less shade cast by the trees

The soil moisture content is zero between 1800
And 1820 cos theres no soil
The soil moisture content increased gradually from 1820 until 1940 as the soil developed, then it increased more rapidly between 1940 and 2000 because the addition of decomposed organic material helped to increase soil moisture content and the deeper soil was able to retain more water

Question 54

Why are ecosystems described as dynamic?

Whats succession

Answer 54

They are dynamic because ecosystems are constantly changing

Succession is the process by which an ecosystem system changes over time

Question 55

Which type of succession happens in areas with no soil

Answer 55

Primary succession

Question 56

Given example of a pioneer species

Answer 56

Marram grass,

lichens

Question 57

Succession in an area of steppe (grassland) can result in a forest.
A nature reserve wishes to conserve the steppe landscape by managing succession
grazing, mowing and fire were used on three areas that were last for a set amount of time the results were compared to control area which was left undisturbed for the same length of time. The data is shown on the bar chart below

describe what the results show about the effectiveness of the three methods of managing succession

Suggest two advantages of controlling succession by grazing rather than by fire

Answer 57

(A)The areas of steppe in which succession was controlled by grazing and fire had the highest percentage cover of grasses compared to the control
The area of steppe controlled by fire also have the lowest percentage cover of treesThis would suggest that Mayar was the most effective method this would suggest that the fire was the most effective method of controlling succession
mowing was the least successful method
The area of steppe in which succession was controlled by mowing had the lowest percentage cover of grasses and the highest percentage cover of trees after the control

(B)grazing is less dangerous than fire

Question 58

The saiga antelope is an endangered species living in the area
a major cause of the population decline of this saga has been hunting by local people for meat and also for its horns which are sold for use in traditional medicine
suggest why education programs on developing alternative livlihoods for local people could b a useful part of the effort to conserve the saiga antelope

Answer 58

There is also a conflict between the needs of local people for food and income and the conservation and of protecting the saiga by educating local people about importance of not hunting the saiga at unsustainable levels and providing alternative sources of income and food this can contribute towards less saiga being killed and therefore the conservation of the species

Question 59

What is conservation

Answer 59

The protection and management of species and habitats

Question 60

Just one reason why people don’t always agree with conservation measures

Answer 60

Cos theres often a conflict between human needs and conservation

Question 61

Describe how a managed fire can be used to prevent succession in order to preserve an ecosystem in its current stage

Answer 61

A managed fire is lit
After the fire, secondary succession will occur — the plant species that grow back first ( pioneer species) are the species that are being conserved
Larger plant species will take longer to grow back and will b removed again the next time the area is burnt

Question 62

Give an example of a method of conservation other than the management of succession

Answer 62

Seed banks, captive breeding, fishing quotas, protected areas

Question 63

A team of scientists is investigating the distribution of Marsh marigolds across a field that is directly next to a stream
suggest and describe a method that scientists could use to do investigate the distribution of Marsh marigolds

[2 marks]

Answer 63

They could set up a belt transect

The transect could extend across the width of the field and the abundance of marsh marigolds recorded in each quadrat

Question 64

The team decided they want to record the percentage cover of marsh marigolds describe how they could measure the percentage cover and given advantage of measuring species abundance this way

Answer 64

They could count how many squares of each quadrat are covered by marsh marigolds by counting a square if its more than half covered
The number if squares covered can b converted into a percentage

Measuring percentage cover is a quick way to investigate the abundance of marsh marigolds as they wouldn’t have to count all the individual marsh marigolds

Question 65

Biotic factors were investigated at each place where data on Marsh marigolds was recorded.explain what is meant by the term ‘abiotic conditions’

Answer 65

the nonliving features of an ecosystem

Question 66

The results of the investigation are recorded in figure 1 and figure 2
the team conclude that marsh marigolds will grow better in waterlogged ground how far does the data support this conclusion explain your answer

Answer 66

The graph shows that there is a positive correlation between the moisture of the soil and the abundance of Marshe marigolds
there is also a positive correlation between the soil ph and the abundance of marsh marigolds
but you can’t conclude from this data that all marshe marigolds will grow better in waterlogged grounds cos the results r only taken from an investigation looking at one field
The results don’t show a casual relationship cos its not clear whether soil moisture or soil ph has the biggest effect on marshe marigold growth, also there may b other factors involved that increase marshe marigold growth e.g. fewer herbivores that consume plant near stream

Question 67

The stream is prone to flooding and the land around it is often boggy

Describe two risks that the scientists should b aware of and and suggest the appropriate course of action they should take to reduce their risk

Answer 67

Theres a risk of flooding so they should check the weather forecast before carrying out their experiment

Risk for falling on the boggy ground so should wear suitable footwear such as wellies w good grip

Question 68

A student is investigating the population of a particular species of centipede
He decides to use the mark release capture method

Describe how the student could use the mrc method to estimate the pop size of the species in his garden

Answer 68

He could use a method to capture and count a sample of centipedes
The species z centipedes caught should b marked in a harmless way and released back into their habitat
After a week the same method should b used to collect a second sample of centipedes from the same population
The number of species z centipedes in the second sample and the number in thr second sample marked should b counted
The pop size can b estimated using the equation
Total pop size= number caught in second sample x number caught in first sample / number marked in second sample

Question 69

An area of heathland in a national par is home to an endangered plant species which needs high light intensity and acidic souls to grow successfully
The park managers have decided to halt succession on the health and are exploring ways in which to do this
They are considering burning the heathland every fifty years

Whys burning the heathland every 50 yrs not helping to conserve the endangered plant species (2 points)

Answer 69

Over 50 yrs succession might lead to plants growing tall enough to decrease light intensity to a level too low for the endangered species to grow
The process of burning the heathland might also alter soil ph so its less suitable for the endangered species

Question 70

The managers have found data from another heathland which halted succession by burning every 20 years
the data is shown in figure 3

Describe and explain the changes in the population sizes of heather shrubs and insects between 1991 and 2000

Answer 70

Between 1991 and mid 1992 the population size of heather and shrubs dramatically because they were burnt by the fire
and the population size of insects falls because the loss of Heather and shrubs causes them to lose their source of food / habitat
From mid 1992 until 2000 the population size of heather and shrubs starts to rise as secondary succession occurs and the growth of shrubs and heather provides a habitat for insects and their population also gradually increases

Question 71

What’s a pioneer species

Answer 71

The first species to colonise an area during succession

Question 72

Describe the changes in the population size of herb species X shown in figure 3 over the 20 yr period
suggest explanations for the changes seen

Answer 72

Herb species x wasnt present before 1992, before the fire. perhaps because the abiotic conditions weren’t favourable
between 1992 and 1994 population size of herb species X increased dramatically so it must be better adapted than the other species to the changed abiotic conditions created by the fire the increase in population size of herb species x slowed down and then levelled off between 1994 and 2003
Perhaps because it was outcompeted by another species or because it wasn’t adapted to the changed abiotic conditions created by the increasing population size of other plant species

Question 73

The managers have met opposition against the use of fire to halt succession
Some campaigners against the use of fire have used the data shown above to argue that insect populations dont recover following a fire

Suggest and explain two reasons why the date doesn’t support this conclusion

Answer 73

Graph only shows data over a 19 year period after a fire
The graph only shows data for one year before the fire and the insect population size was decreasing so the data in 1990 might mot b representative of the normal population size of insects

Question 74

Explain an alternate way in which the plant species could b conserved

Answer 74

Animals could b allowed to graze the land and eat the growing points of the shrubs and heather stopping from establishing themselves this would help to keep vegetation low and so increase the amount of light for the endangered species
Controlling the soil ph would help to keep the soil acidic for the plant