Populations In Ecosystems <3 Flashcards
(63 cards)
1
Q
DEFINITIONS - Habitat
A
The place where a community of organisms lives
2
Q
DEFINITIONS - Population
A
All the organisms of one species in a habitat
3
Q
DEFINITIONS - Community
A
Populations of different species in a habitat make up a community
4
Q
DEFINITIONS - Ecosystems
A
- A community, plus all non-living/abiotic conditions in the area in which it lives. Ecosystems can be small or large.
- Made up of all the interacting biotic and abiotic features in an area.
5
Q
DEFINITIONS - Abiotic conditions
A
The non-living features of an ecosystem (e.g. temperature and water availability)
6
Q
DEFINITIONS - Biotic conditions
A
The living features of an ecosystem (e.g. predators and food)
7
Q
DEFINITIONS - Niche
A
The specific role of a species within its habitat (e.g. what it eats, where and when it feeds)
8
Q
DEFINITIONS - Adaptation
A
A feature that members of species have that increases their chance of survival and reproduction (e.g. giraffes have long necks to reach high up food, increasing their chance of survival when food is scarce)
9
Q
What interactions does a niche include within a habitat?
A
- Biotic interactions - such as what the organism eats, and those it’s eaten by
- Abiotic interactions - such as the oxygen the organism breathes in, and the carbon dioxide it breathes out
10
Q
Why can a niche only be occupied by one species?
A
- Every species has its own unique niche
- It could look like two species have the same niche (e.g. they’re both eaten by the same species), but there is always slight differences (for example they themselves may have different diets)
11
Q
What happens when two species occupy the same niche?
A
- They will compete with each other
- One species will be more successful than the other until only one species is left
- The other species must adapt a new niche, otherwise it dies out
12
Q
How would temperature (abiotic factor) affect the distribution and size of an ecosystem?
A
- Enzymes - optimum temperature.
- In plants and cold blooded animals, metabolism slows when moving away from optimum temperature
- In warm blooded animals, energy is wasted keeping warm so there is less energy for growth and reproduction
13
Q
How would light (abiotic factor) affect the distribution and size of an ecosystem?
A
- Rate of photosynthesis increases as light intensity increases
- More photosynthesis means more growth
- Potentially more food sources for wider range of animals and larger populations of animals
14
Q
How would pH (abiotic factor) affect the distribution and size of an ecosystem?
A
- Affect actions of enzymes
- Population will be larger in a pH that is most effective for enzyme action
- When pH is away from the optimum the population will be much smaller
15
Q
How would water and humidity (abiotic factor) affect the distribution and size of an ecosystem?
A
- Humidity affects transpiration rates in plants and evaporation of water from bodies of animals
- In dry conditions, populations of species will need to be able to tolerate low humidity
16
Q
What is population size?
A
The total number of organisms of one species in a habitat
17
Q
What is carrying capacity?
A
The maximum stable population size of a species that an ecosystem can support. It varies as a result of both abiotic and biotic factors.
18
Q
What is a biotic factor?
A
A factor that affects a living organism and is caused by other living organisms.
19
Q
What is interspecific competition?
A
Competition between species for the same resources. When organisms of different species compete with each other for the same resources (e.g. red and grey squirrels compete for the same food sources and habitats in the UK).
20
Q
How is a population reduced by interspecific competition - competing exclusion?
A
- Interspecific competition between two species means that the resources available to both populations are reduced
E.g: - If they share the same source of food, there will be less available to both of them
- This means both populations will be limited by a lower amount of food
- Therefore they’ll have less energy for growth and reproduction, so the population sizes will be lower for both species
21
Q
What happens when one of two competing species is better adapted to its surroundings/niche?
A
- The less well adapted species is likely to be outcompeted, as it won’t be able to exist alongside the better adapted species
E.g: - since the introduction of the grey squirrel into the UK, the native red squirrel has disappeared from large areas
- the grey squirrel has a better chance of survival because it’s larger and can store more fat over winter
- it also has a wider range of foods in its diet
22
Q
What is intraspecific competition?
A
When organisms of the same species compete for the same resources.
23
Q
Give an example of intraspecifc competition - rabbits
A
- The population of a species increases when resources are plentiful. As the population increases, there’ll be more organisms competing for the same amount of space and food.
- Eventually resources such as food and space become limiting as there isn’t enough for all the organisms. The population then begins to decline.
- A smaller population then means that there’s less competition for space and food, which is better for growth and reproduction - so the population starts to grow again.
24
Q
Explain the predator-prey cycle
A
- Predators eat their prey, thereby reducing the population of prey.
- With fewer prey available, the predators are in greater competition with each other for the prey that’s left.
- The predator population is reduced as some individuals are unable to obtain enough food for their survival.
- With fewer predators left, fewer prey are eaten.
- The prey population therefore increases.
- With more prey now available as food, the predator population in turn increases.
25
Why are predator-prey relationships more complex than just the cycle?
Other factors are often involved, such as the food availability for prey.
26
How do you do random sampling?
1. Generate random coordinates such as for example drawing a grid on the map of the area and use a random number generator to generate random coordinates on the map to sample.
2. Use more than 10 quadrats.
3. Count/collect the species within the quadrat.
27
What is a non-motile organism?
An organism that doesn’t move (e.g. a plant).
28
What is a line transect used for?
To sample species/individuals along a line.
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What is a belt transect used for?
To sample species/individuals within quadrats placed along the line at regular intervals.
30
What can be investigated with a transect?
- Changes in species/individuals present (e.g. how species change from a hedge towards the middle of a field)
- This is done by using a tape measure as a transect and every two metres/at regular intervals placing a quadrat. Frequency or % cover is measured
31
What is an interrupted belt transect?
When quadrats are placed at intervals down the transect.
32
What are the potential drawbacks of transects?
- May not be representative, as it may avoid certain areas.
- This can be counteracted by a carrying out a larger number of transects for the same study.
33
What is the method for sampling motile organisms called?
Mark-release-capture
34
What is the method for mark-release-capture?
1. Capture a large sample of organisms in a set amount of time.
2. Mark each animal in a way that will not harm it or attract predators.
3. Release and allow time for them to mix with the remaining population.
4. Catch a second sample in the same as used for the first sample.
5. Number in sample 1 x number in sample 2/number in sample two that are marked
35
What assumptions do we make when doing mark-release-recapture?
- Large initial sample size
- No immigration or emigration during study
- No births or deaths during study
- Marked animals are no more likely to die than unmarked animals
- Marked animals mix fully and randomly through the population
36
PS - What is a pioneer species?
A species that colonises a new land surface.
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PS - FEATURES OF PIONEER SPECIES - Asexual reproduction
A single organism can rapidly multiply to build up a population
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PS - FEATURES OF PIONEER SPECIES - Vast quantities of wind dispersed seeds and spores
So that they can reach isolated areas such as volcanic islands.
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PS - FEATURES OF PIONEER SPECIES - Rapid germination of seeds
So that they do not require a period of dormancy.
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PS - FEATURES OF PIONEER SPECIES - Ability to photosynthesise
As light is normally available but other food is not. They are not dependent on any animal species.
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PS - FEATURES OF PIONEER SPECIES - Ability to fix nitrogen
As soil likely has few or no nutrients.
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PS - FEATURES OF PIONEER SPECIES - Tolerance to extreme conditions
As this environment is likely to be inhospitable to most organisms.
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PRIMARY SUCCESSION - How do pioneer species change the abiotic conditions of an environment?
- They die and decompose
- The dead organic matter forms a basic soil called humus
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PRIMARY SUCCESSION - What does humus do to an environment?
- The conditions of this new environment are therefore less hostile
- The basic soil can retain water, allowing for other species to grow
- Then, when these new species die, they will also decompose and add to the organic matter.
- The soil will become deeper and more rich in minerals.
45
SECONDARY SUCCESSION - when does secondary succession occur?
When land supporting life is cleared by an event such as a fire.
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SECONDARY SUCCESSION - what are the key differences between primary and secondary succession?
- Secondary succession happens in the same way, BUT there is already a layer of soil, so succession occurs quicker.
- Pioneer species tend to be larger such as shrubs.
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SECONDARY SUCCESSION - how do we get a new dominant species?
As the stages of succession continue, different plants and animals that are better adapted for the improved conditions move in, out-compete plants and animals already there and become the new dominant species.
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SECONDARY SUCCESSION - what happens to the ecosystem?
The new ecosystem becomes more and more complex as new species move in alongside existing species, which increases biodiversity.
49
What is the final stage of succession called?
Climax community
50
What is climax community?
- When the ecosystem is supporting the largest and most complex community of plants and animals that it can.
- This is a steady state, and little change will occur over time. A change in one species will have little effect on the other species.
51
What is conservation?
The process of maintaining biodiversity.
It frequently involves preventing succesion from occurring or managing succession.
52
What is plagioclimax?
When human activities prevent succession, stopping a climax community from developing.
53
What would happen without plagioclimax?
- Many habitats would simple turn into woodland.
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Why do we want to prevent succession?
- There is generally more diversity leading up to the climax community than there is in the final stage.
- This is because there are more niches for the different species to occupy.
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PREVENTING SUCCESSION - how can we use grazing animals?
Animals like sheep or cattle can be used to graze an area of land, preventing growth of larger plants like shrubs and trees.
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PREVENTING SUCCESSION - how can clearing shrub help?
Larger woody plants can be cleared to make way for smaller plant growth.
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PREVENTING SUCCESSION - how can mowing help?
Prevents the growth of larger plants and encourages growth of fast growing plants with short life cycles.
58
PREVENTING SUCCESSION - how can we use managed fires?
- Controlled fires can be used to clear areas of woodland.
- The ash from the burned trees makes the soil more fertile.
- Secondary succession can begin.
59
What is a problem with conservation methods?
Not everyone always agrees, and conflict between human needs and conservation can arise.
60
Mark scheme answer for primary succession?
1. Colonisation by pioneer species.
2. Pioneers change the environment by forming humus.
3. These makes it less hostile for other new species.
4. Change/increase in biodiversity.
5. To climax community.
61
What causes a population size to vary?
- Effect of abiotic factors.
- Interactions between organisms such as interspecific and intraspecific competition.
62
Why are the crashes in the predator prey cycle important?
They create a selection pressure.
63
In what ways may pioneer species alter an environment?
- Make it less suitable for existing species, as the new species may outcompete the previous ones.
- Make it more suitable for the other species with better adaptations. As a result, this species may be outcompeted by older species.
