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Section 7 - Populations in ecosystems Flashcards

1
Q

What is population size?

A

Number of individuals in a population at a given time

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2
Q

What is exponential population growth?

A

When resources are unlimited, populations exhibit exponential growth.
(J-shaped curve)

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3
Q

What is logistic population growth?

A

When resources are limited, populations exhibit logistic growth.

Population expansion decreases as resources become scarce.

Levels when carrying capacity of the environment is reached.
(S-shaped curve)

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4
Q

How does temperature affect population growth?

A

Lower temperatures lower metabolic rate so enzymes work more slowly.

Higher temperatures could denature enzymes

Low and high temperatures affect carrying capacity of a population

As more energy is being used to maintain bodies optimum temperature, less energy for growth and reproduction so carry capacity is reduced

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5
Q

What is the carrying capacity?

A

Each population has a certain size that can be sustained over a long period of time and this is determined by limiting factors.

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6
Q

How does light affect population growth?

A

Source of energy, rate of photosynthesis increases as light intensity increases.

Carry capacity is increases
(plants grow faster, more source for animals)

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7
Q

How does pH affect population growth?

A

Affects action of enzymes

Higher pH may denature enzymes, lower pH may decrease rate so enzymes work more slowly

Decreases carrying capacity of a population

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8
Q

How does water and humidity affect population growth?

A

Lower water, populations are small and only species that have adapted to dry conditions will exist

Humidity affects transpiration rates in plants and evaporation rates from animals

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9
Q

What is a habitat?

A

Place in an ecosystem where a particular population is found

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10
Q

What is ecology?

A

Study of inter-relationships between organisms and their environment

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11
Q

What is a microhabitat?

A

Small units within a habitat

mud at bottom of a stream

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12
Q

What is a niche?

A

Description of how a species functions within a habitat due to its adaptations

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13
Q

What is a biotic factor?

A

Living factors in an environment

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14
Q

What is an abiotic factor?

A

Non-living factors in an environment

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15
Q

What is an ecosystem?

A

How the community interacts with each other and the physical environment including abiotic factors

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16
Q

What is a community?

A

The sum of all the organisms in an ecosystem

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17
Q

What is a species?

A

Group of interbreeding organisms that produce viable and fertile offspring

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18
Q

What is intraspecific competition?

A

Competition between members of the same species

Availability of resources will determine size of population

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19
Q

What is interspecific competition?

A

Competition between members of a different species

Species will compete, dominant species will increase in population

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20
Q

What is the competitive exclusion principle?

A

Where 2 species are competing for limited resources, the one that uses the resources most effectively will eliminate the other

No 2 species can occupy the same niche definitively when resources are limited

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21
Q

What is the pattern of a typical predator-prey relationship in terms of population change?

A

Prey is eaten by predator
Predator population increases, prey decreases

Fewer prey means increases competition for food, so predator population decreases

Fewer predators means more prey survive, cycle begins again

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22
Q

What are reasons against counting every individual?

A

Time consuming

Damages habitat

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23
Q

What are methods of studying habitats?

A 
Bell transect
Frame quadrat
Pitfall trap
Light trap
Pooter
Sweep net
Drift net
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24
Q

What are the 2 types of quadrat?

A

Point quadrat- bar with 10 holes where a pin could be dropped

Frame quadrat

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25
What are 3 factors to consider when using quadrats?
The size of the quadrat to use The number of sample quadrats to record within the study area The position of each quadrat within the study area
26
What does mark-release-recapture do?
Generates an estimate of the population size
27
What is the equation for mark-release-recapture?
Number in 1st sample X number in 2nd second sample / Number of marked animals recaptured in 2nd sample
28
What are the assumptions made for mark-release-recapture?
Only used for animals which are randomly distributed Enough time must be allowed for the released animals to mingle Method of capture must not alter the habitat Marking method doesn't harm animals, reduce chance of survival or affect behaviour patterns Must be no migration or immigration
29
What is the mark-release-recapture method?
1. Capture sample of species 2. Mark in harmless way 3. Release back into habitat 4. Wait a week then take second sample 5. Count how many are marked 6. Use equation to estimate size
30
Why would an animal be marked on their underneath and not back in mark-release-recapture?
Does not make them less camouflage so their chance of being prey is not reduced
31
What is an effective method of random sampling?
1. Lay 2 tape measures at right angles along study area 2. Obtain coordinates by random generator 3. Place quadrat at intersection of each pair and record species
32
How would you use systematic sampling to find population size?
Using bell transect Place string across ground in straight line Move frame quadrat alongside line at regular intervals and record species within
33
What is abundance?
Number of individuals of a species within a given area
34
What are 2 ways of finding the abundance of a species that doesn't move?
Frequency- likelihood in area Percentage cover- estimate of area that species covers
35
What is the advantage and limitation of percentage cover?
Useful where a species is hard to count Data collected rapidly Less useful where organisms occur in several overlapping layers
36
What is the advantage and limitation of frequency?
Useful where species is hard to count Gives quick idea of species present Doesn't provide information on density and detailed distribution
37
Why are ecosystems described as being dynamic?
Populations constantly rise and fall Any small change can have a large effect Biotic and abiotic factors may alter conditions of ecosystem
38
What is succession?
A change in a community over time
39
What is primary succession?
Where an area previously without life is colonised by a community of organisms
40
What is the pioneer species?
First species to colonise an area Able to rapidly exploit sudden change in conditions Grow quickly and usually short-lived
41
What is the climax community?
Achieved once succession has gone as far as conditions will allow
42
What is the process of primary succession?
Pioneer species colonise area Change abiotic factors of environment Allows more complex organisms to survive
43
What effect does death and decay of the pioneer species have?
Adds organic matter creating basic soil.
44
What are harsh abiotic conditions?
Decreased fresh water Increases salt Strong winds No proper soil
45
Why does plant diversity decrease at the climax?
Climax community organism takes light and stops other species growing
46
What is a seral stage?
Each stage in succession
47
What do successful pioneer species have?
Rapid growth Rapid reproduction Efficient seed dispersal Tolerant to harsh conditions
48
Why would species at earlier conditions at early stages disappear?
Shading by larger plants Eaten by herbivores Unable to compete
49
What is secondary succession?
Succession when soil or vegetation is already present
50
What common features emerge during succession?
Abiotic environment becomes less hostile Greater number of habitats Increased biodiversity More complex food webs Increased biomass
51
What is the general name given to the first organisms to colonise bare land?
Pioneer species
52
How do changes in the environment lead to increased biodiversity during succession?
Pioneer species die and form a soil with nutrients Further colonisers can survive in soil Environment is less hostile More habitats and food sources available Other species survive Increased biodiversity
53
What is the name of the stable, final stage of any succession?
Climax community
54
What is an example of a plagioclimax community?
Intensive grazing by sheep can deflect succession from a forest climax community to grassland
55
How might succession be managed in order to aid conservation?
Succession is prevented in order to preserve ecosystem
56
What are the main reasons for conservation?
Personal- maintains our planet Ethical- respect for living things Economical- animals can make substances which can prove valuable Cultural & aesthetic- variety adds interest to everyday life
57
How might succession be managed in order to aid conservation?
Succession is prevented in order to preserve ecosystem
58
What measures could be taken to prevent succession?
Cut back reeds to prevent them becoming dominant Remove dead vegetation
59
What is a niche?
The role and space that an organism fills within its habitat
60
What is plagioclimax?
The climax community produced when succession is artificially stopped by human intervention
61
Why would a student measure percentage cover of each species rather than counting individual plants?
To allow comparisons as plant sizes may vary
62
A student carrier out a belt transect in an identical area at an identical time as another student but results were not the same. Why?
There is a chance that one transect doesn't represent the full habitat or community
63
What are the abiotic factors that affect population growth?
Temperature Light intensity (for photosynthesis) pH (impact on enzyme action) Water and humidity
64
How should plants be chosen to get a representative sampling site?
Large sample area
65
What is the role of the pioneer plants?
Make conditions less hostile Soil development Increase nitrogen Provide shelter Sustainable environment
66
How could deflected succession be caused?
Grazing Burning Exposure to wind
67
How does biomass change during primary sucession?
Increases Plants at later stages are large
68
How is stability maintained in a population with a high reproduction rate?
Limited food Disease Competition
69
What are 2 limitations of the mark-release-recapture method?
Assumes no emigration Assumes there is no death or birth Assumes marking doesn't affect survival Assumes marked organisms don't loose their mark
70
Why is genetic drift more likely to affect an endangered species?
Endangered species so found in lower numbers Genetic drift due to chance fluctuations in allele frequencies More likely to affect smaller frequencies

Biology (25 decks)

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