3.7- Chapter 19- Populations in Ecosystems Flashcards
3.7.4 Populations in ecosystems (110 cards)
1
Q
What is ecology?
A
Study of inter-relationships between organisms and their environment- non-living factors (abiotic) and living factors (biotic).
2
Q
What are ecosystems?
A
dynamic systems made up of a community and non-living factors. e.g. a pond. Can be very large to very small. Contain a number of species.
3
Q
What is the carrying capacity?
A
- The maximum stable population size of a species an ecosystem can support.
- Varies as a result of limiting abiotic and biotic factors.
- Can be sustained over a relatively long period.
4
Q
What is a population?
A
A group of individuals of one species that occupy the same habitat at the same time and can potentially interbreed.
5
Q
What is a community?
A
All the populations of different species living together and interacting at a particular place at the same time.
6
Q
What is a habitat?
A
- The place where an organism normally lives.
- Characterised by physical conditions and other types of organisms present.
- Within an ecosystem there are many habitats.
7
Q
What are microhabitats?
A
- Smaller units within habitats with their own microclimate.
- e.g. mud at the bottom of the stream- microhabitats for bloodworms.
8
Q
Describe the features of ecosystems?
A
- Ecosystems- interacting biotic and abiotic factors in a particular area- number of communities.
- Community of organisms with the non-living (abiotic) conditions in the area in which they live. E.g. a pond/ lake.
- Vary in size- small to large.
9
Q
What conditions are there in ecosystems?
A
- Both biotic and abiotic conditions:
- Biotic conditions- living features of an ecosystem e.g. the presence of predators or food.
- Abiotic conditions- non-living features of an ecosystem- e.g. temperature.
10
Q
What major process occur in ecosystems?
A
- The flow of energy through the system- energy is transferred.
- The recycling of elements within the system.
- There is little to no net loss or gain between natural ecosystems- most energy is transferred and elements are recycled.
11
Q
Describe habitats.
A
- Place where an organism lives within an ecosystem.
- Within each habitat, each species has its own niche.
12
Q
What is an ecological niche?
A
- Within a habitat a species occupies a niche governed by adaptation to both abiotic and biotic conditions- describes how the organism is adapted to its environment to survive reproduce, and maintain a viable population.
- A niche is the role of a species within its habitat- e.g. what it eats, what it does, where it lives.
- Niche includes:
- Biotic interactions- what it eats, what its eaten by, what the organism competes with.
- Abiotic interactions- temperature range it can live in, time of day its active.
- Some species may appear very similar but their behaviour may be different due to different levels of tolerance to environmental factors.
- Each species has it’s unique niche as no niche can be occupied by more than one species- some species appear similar but they have slight differences.
13
Q
What is the competitive exclusion principle?
A
- No two species can occupy the same niche as they will compete with each other- the competition means one will not be able to outcompete the other and will die out.
- Exclusion is based on adaptions- the better adapted species outcompetes the other.
14
Q
Describe adaptions and their relations to niche.
A
- Adaptions- features members of a species have to increase chances of survival and reproduction.
- Can be physiological (processes inside body), behavioural (way an organism acts) or anatomical (structural features). E.g. giraffes have long necks- help them reach vegetation.
- Organisms with better adaptions are more likely to survive, reproduce and pass on advantageous alleles determining adaptions. This increases the frequency of these alleles in the population- adaptions become more common- natural selection.
- Every species- adapted to use an ecosystem like no other species can- unique niche.
- Organisms- better adapted to abiotic conditions (water, temperature etc.) and biotic conditions (predation and competition) within an ecosystem and their niche, are the ones more likely to survive interspecific competition and outcompete the other species.
15
Q
What is population?
A
All the organism of one species in a habitat- make up a community.
16
Q
What is population size?
A
Total number of organisms of one species in a habitat- dynamic- changes over time.
17
Q
How can population sizes and carrying capacity vary.
A
- Populations are dynamic and vary in size and composition over time.
- Population sizes and carrying capacity within ecosystems vary due to many different factors.
- Changes in these factors influence the rate of growth and size of the population.
- Populations within communities are affected by, and in turn affect abiotic and biotic factors.
18
Q
Describe how communities affect populations?
A
- Populations of different species live in communities.
- Competition occurs within and between these populations for the means of survival.
- Within a single community, one population is affected by, and may affect, other populations, the biotic factors, in its environment.
- Populations within communities are also affected by, and in turn affect, the abiotic (physicochemical) factors in an ecosystem.
19
Q
What are the factors that impact population sizes and carrying capacities within ecosystems and communities?
A
- Abiotic factors- physiochemical factors e.g. temperature, rainfall.
- Biotic factors- interactions between organisms- affected by other populations- interspecific and intraspecific competition, pathogens and predation.
20
Q
Why is a population often difficult to measure or define?
A
- The boundaries of a population are often difficult to define.
- Populations are dynamic and vary in size and composition over time.
21
Q
How can you plot graphs of population size?
A
- Where a population grows in size slowly- can plot a graph of population against time.
- Large population size difference- exponential e.g. in the growth of bacteria, can be mitigated with a log scale, making it easier to see patterns.
22
Q
Why does no population grow indefinitely?
A
- Factors limit growth- e.g. food, water etc.
- Accumulation of toxic wastes, disease and predators limit growth.
- The population stays within the carrying capacity of its ecosystem.
23
Q
How must you describe factors in relation to the the population size?
A
- Link the birth and death rates of individuals in a population.
- e.g. increase in food- doesn’t mean more individuals just bigger individuals- so have to show what it means e.g. more food= more likely to survive and reproduce so population increases.
- This means effects usually take longer to influence the population size- there is a time lag.
24
Q
Describe the overall growth rate of micro-organisms.
A
With enough food and space- population size of microorganisms grows at a steady rate.
25
Describe how you investigate the growth of micro-organisms.
* Investigated by growing bacteria in liquid broth- broth culture.
* Light passed through sample of broth- scattered because bacteria present- reduces light passing through culture- spectrophotometer measures amount of light passing through- absorbance value- more bacteria present= less light passing through detected by the spectrophotometer- producing higher absorbance value. High absorbance value= high number of bacteria and vice versa.
* Absorbance- proportional to number of bacteria- convert the number to show population of bacteria.
26
How do you plot the graph of bacteria growth?
* Plotted over time- produces an exponential graph- bacteria doubling at regular intervals.
* As numbers increase steeply over a short period of time- it’s hard to draw a scale- logarithm scales can be used to plot the graph instead- results in a straight line graph- need to be able to read log scale to read the graph.
27
How does population size vary in a population growth curve of photosynthetic bacteria.
1. Initially when there are good conditions, the population increases rapidly because all the factors needed for growth are persent and there is no limiting factors.
2. Over time, more nutrients are consumed as the population becomes larger, the population becomes so large the bacteria prevent light reaching those at lower levels, other species may be introduced and compete for the same resources as the bacteria or predate on bacteria, and wintery conditions may bring lower light intensity, making conditions tought.
3. The growth of hte population slows and then stops.
4. The population size sometimes then decreases
5. The population then reaches a constant size until conditions change and factors improve to increase growth again.
28
Name the main abiotic factors that can affect population growth.
* Temperature
* Light
* pH
* Water and humidity
29
Describe the general impact of abiotic conditions on a species.
* When abiotic conditions are ideal for a species, organisms can grow more quickly and reproduce more successfully.
* When abiotic conditions aren’t ideal for a species, organisms can’t grow as fast or reproduce as successfully.
* When abiotic factors are below the optimum- fewer individuals are able to survive if adaptions are not suited to conditions.
* If no individuals have adaptions to survive- the population becomes extinct.
30
How does temperature affect population size in general.
* Each species has a different optimum temperature where it survives best
* Further from optimum= few individuals are able to survive- adaptions further away from optimum- smaller population.
31
How does temperature affect population size of cold-blooded animals.
* If fall below optimum- enzymes work more slowly- metablic rate reduced- smaller carrying capacity.
* Above optimum- enzymes work less efficiently and denature- carrying capacity and population size reduced
32
How do changes in temperature affect warm-blooded animals?
* Warm blooded animals- birds and mammals- maintain constant body temperature regardless of external temperature.
* Extreme temperature changes from the optimum- mean more energy expended trying to maintain normal body temperature.
* Less energy for growth and reproduction.
* Carrying capacity and population size reduced.
33
How does light impact population size?
* Light is the main source of energy for most ecosystems- basic necessity of life.
* Rate of photosynthesis increases as light intensity increases.
* Faster photosynthesis= faster plant growth and more seeds.
* Carrying capacity greater and carrying capacity of animals that feed on the plants greater.
34
How does pH impact population size?
* Affects the action of enzymes.
* Enzymes- have optimum pH where work most effectively.
* Population of organisms larger where the right pH exists and smaller where pH is different from the optumum.
35
How does water and humidity impact population size?
* Low water= small population- only species adapted to dry conditions
* Humidity- affects transpiration rates of plants and evaporation rates of water from animals.
* Dry condidtions- populations adapted to tolerate low humidity large than those with no adaptions.
* Carrying capacity of adapted populations greater.
36
What biotic factors affect the population size and carrying capacity.
* Interspecific and Intraspecific competition
* Predation
* Pathogens
37
What is competition?
* Two or more individuals share a resource that is in insufficient quantity to satisfy all their needs.
* Competition occurs within and between populations for means of survival.
* Leads to evolution of the species and adaptions.
38
What are the two types of competition and describe them.
* Intraspecific competition- competition between members of the same species
* Interspecific competition- competition between members of different species.
39
Describe intraspecific competition.
* Individuals of the same species compete for **resources and mates to survive and reproduce.**
* The availability of resources determines population size and competition- more= larger population and less competition and v.v.
* Can cause cyclical change in population size around the carrying capacity- population grows, shrinks, then grows again:
* The population increases when resources are plentiful.
* As the population increases, there’s more organisms competing for the same amount of space and food- resources become limiting.
* If population grows beyond carrying capacity- not enough resources for all the organisms- population declines.
* Smaller population- less competition for space and food- better for growth and reproduction- population grows again- cyclical.
40
Draw a graph to represent the cyclical nature of intraspecific competition.
Answer on revision card.
41
Describe interspecific competion.
* Different species compete with each other for the same resources.
* The resources available to both populations are reduced so both have less energy for growth and reproduction and both population sizes will be lowered.
* If one species has a competitive advantage- this population becomes larger than the other population- it **out-competes it.** The other population may **become extinct.**
42
Describe the competitive exclusion principle.
* In interspecific competition, species usually has a competitive advantage- this population increases while the other population decreases.
* If conditions remain the same and the species occupy the same ecological niche (habitat, food etc.)- this will lead to the complete removal of one species.
* In competition for limited resources- the species that uses these resources most effectively will ultimately eliminate the other- **it out-competes it**.
* If species occupy different niches e.g. similar but eat different foods- competitive exclusion can’t happen.
* No two species can occupy the same niche for a long time without one species eliminating the other- it **becomes extinct** e.g. Grey squirrels and red squirrels.
43
Describe the predator- prey relationship
Interspecific- their population sizes are interlinked- the population of one changing causes the population of the other to change.
44
What is predation?
When one organism is consumed by another.
45
What is a predator?
An animal that feeds on another animal.
46
What is prey?
Animals that are fed on by other animals.
47
Why is evolution important for predators and prey?
* Predators and prey evolve together- as predators have become more evolved and better adapted at catching prey, prey have evolved to become better at escaping predators.
* If predators and prey do not adapt one may become extinct, which may lead to the extinction of the other.
48
Why are habitats important for predator- prey relationships?
* If prey and predator are brought together in a lab, they prey exterminates the predator- demonstrating habitats are important for survival of prey.
* In habitats, the area a population can travel is greater and the variety of environment is more diverse- more potential refuges- prey can escape predation because they are harder to find and catch and rarely become extinct.
49
Why is it hard to study predator-prey relationships?
* Can't be studied in a lab as doesn't reflect what happens in the wild.
* Not possible to count all individuals in a population- population can only be estimated- no guarantee of accuracy- data must be treated with caution.
* It is hard to reflect predator-prey relationships with data- other factors, such as the preys food supply, disease and climatic factors may be affecting results. Predators eat a range of foods so the predator and prey aren’t directly linked
50
How does the predator-prey relationship affect population size cyclically?
* Prey population increases- more food for predators- predator population grows.
* Predators eat prey, reducing prey population.
* With fewer prey, the predators have greater competition.
* The predator population is reduced as some are unable to obtain enough prey to survive and reproduce.
* With few predators left, fewer prey are eaten and more survive and reproduce so the prey population increases.
* With more prey for food, the predator population increases.
51
Describe how the predator prey population changes graphically?
Predator and prey populations cyclically fluctuate
52
How does the predator prey relationship influence evolution?
* Population crashes are important for evolution
* Fluctuations create selection pressues- individuals who escape predators,, catch prey, or withstand disease/ bad climate- more likely to survive and reproduce.
* The population becomes better adapted to conditions
53
What measures are used surrounding populations?
Populations of organisms are investigated by looking at distribution and abundance of a species in a particular area.
54
What is distribution?
Where a particular species is within the area you’re investigating.
55
What is abundance.
Number of individuals within a species within a given area.
56
How can abundance be measured?
* Frequency- the number of samples a species is recorded in (e.g. in a quadrat). Useful if species are hard to count. Quick and easy. Doesn’t provide detailed information on distribution and density.
* Percentage cover- estimate of area that a species covers- useful when a species is abundant. Data can be collected rapidly and individual plants don’t need to be counted but less useful when organisms overlap. Only works for non-motile or slow-moving species.
* Measurements depend on whether species are motile.
57
Why is abundance and distribution hard to measure.
* It's impossible to count every organism
* Counting organisms is time-consuming and can damage habitats.
58
How can abundance and distribution be estimated?
* Small samples studied in detail.
* Samples should be representative of the wholoe habitat so conclusions are reliable.
59
What factors must be considered when taking samples?
* Choose an area to sample- small area within area investigated.
* Random to avoid bias- e.g. using random number generator.
* Use appropriate techniques to measure the sample.
* Repeat taking as many samples as possible- reduces likelihood results due to chance.
* Number of individuals in the whole area can be estimated taking the mean of the data collected and multiplying it by the size of the whole area.
60
What sampling techniques can be used to study habitats?
* Random sampling using frame/ point quadrats- abundance of slow moving or non-motile organisms.
* Systematic sampling along a belt transect- distribution- abundance of slow moving or non-motile organisms.
* Sampling motile organisms using mark-release-recapture.
61
How can abundance of slow-moving or non-motile organisms be measured?
* Measured using random sampling involving quadrats.
* Quadrats are placed on the ground at random points within the area you’re investigating.
62
How can abundance be measured (numerically)?
* Frequency- whether a species is encountered in a quadrat and how many it occurs in- then put over the total amount of quadrats e.g. 5/10 is 50%.
* Percentage cover- estimate of area in a quadrat that a plant species covers.
63
Describe the different types of quadrats.
* Frame quadrat- square frame- divided into equally sized subdivisions. Placed in different locations in the area and the abundance of each species is recorded- sometimes individually or sometimes as percentage cover.
* A point quadrat- horizontal bar with two legs- holes at set interviews where pins dropped- what pin touches is recorded.
64
What factors must be considered when using quadrats?
* Size of quadrat- depends on size of plant/ animals counted and distribution- larger= larger quadrats. If species not evently distributed- large number of small quadrats- more representative than small number of large quadrats.
* Number of quadrats- more= more reliable. Balance needs to be reached with time constraints. Greater number of species- greater number of quadrats for reliable results.
* Position of quadrats- must be random.
65
Why is random sampling important?
Avoids bias which ensures the data is reliable.
66
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How do you obtain a random sample with quadrats?
* Random number generators-** divide area into a grid** with tape measures and **use random number generators to select coordinates** to sample from. **Place quadrats at these coordinates.**
* Running means- work out all of the mean of the data for each sample- once the mean no longer changes by a large amount- you should have a realistic estimate of the whole area.
67
Describe how an estimate for abundance is achieved through quadrats.
* **Divide area into a grid** with tape measures and **use random number generators to select coordinates** to sample from.
* **Place quadrats at these coordinates. **
* Once a sample is selected, **count the frequency/ percentage cover of the species in each quadrat and multiply the mean by the number of squares in the grid** to find an estimate for the whole area.
68
How can a reliable result be achieved from quadrats.
* To achieve a reliable result **a large sample size is used with many quadrats selected at random- mean of all samples obtained.**
* The larger the number of samples= more representative of the community.
69
When is systematic sampling used?
Systematic sampling is used to measure distribution- achieved using transects which show how organisms are distributed over an area.
70
What can systematic sampling show?
* Gradual changes in ecosystems.
* Lines of succession- shows the stages of succession across an area.
* Effects of abiotic factors on populations.
71
How is systematic sampling achieved in habitats.
* Transects.
* Laying a tape measure straight across the ground.
* A quadrat is laid along the line at equal intervals adn the species within it is recorded.
72
What are the two types of transect?
* Belt transects- quadrats are placed next to each other along the transect to work out species frequency and percentage cover along the transect.
* Interrupted belt transects- take measurements using a quadrat placed at regular intervals e.g. every two metres. Makes it easier to cover a large distance.
73
Describe required practical 12- Investigation into the effect of a named environmental factor on the distribution of a given species.
Distribution changes depending on abiotic factors- e.g. shade-loving plants may be closer to trees than to in full sunlight. This can be investigated.
74
Give an example method for investigation into the effect of a named environmental factor on the distribution of a given species.
* Marram grass and soil pH.
* Place a tape measure in a straight line from the shore to inland.
* Take a 1m2 quadrat divided into 100 squares.
* Starting from the shore, place the quadrat near the tape measure.
* Count the squares containing marram grass and record the result as percentage cover. Take repeat quadrat samples next to your initial quadrat and take a mean.
* At each sample point measure pH using a pH probe and record results.
* Repeat every 10m along the transect.
75
How do you process results when investigating into the effect of a named environmental factor on the distribution of a given species.
* Sketch a with two lines- distance from the shore should be on the x-axis. Then one line should be the variable and the other should be percentage cover.
* Think of explanations for the variable and also the percentage cover. Remember, that even if there is a correlation, it may not be a causation, as there could be many other factors affecting results- biotic and abiotic.
76
What issues should be considered when completing fieldwork?
* Ethical issues- when carrying out fieldwork be careful to make the smallest impact on the environment as possible- e.g. avoid stepping on plants and too much trampling, minimise stress to animals.
* Safety issues- should plan ahead with a risk assessment- assess risk of uneven ground, stings, bites, and weather.
77
Why can quadrats and transects not be used to measure the abundance of all organisms?
* Quadrats and transects are good to measure plants and non-moving or slow moving animals.
* Can't measure motile organisms as move away when approached, are often hidden and are difficult to find and identify.
78
What method is used to measure the abundance of motile organisms?
Mark-release-recapture
79
How does mark release recapture work?
* **Capture a sample** of animals in a set amount of time using a set amount of people.
* **Mark** the animals- **ensure marking in a harmless way so that it does not affect survival.**
* **Release** the animals back into the community.
* Wait a set amount of **time**, e.g. a week **for the organisms to randomly distribute before collecting a second sample** from the same population in the same amount of time using a same amount of people.
* Count how many individuals are marked and unmarked and use the equation to estimate the population size.
* **Population= number in first sample × number in second sample divided by number of marked in second sample/number recaptured- always mention the equation in these questions.**
80
What is the equation for mark-release-recapture?
Population= number in first sample × number in second sample divided by number of marked in second sample / number recaptured
81
What assumptions are made in mark- release- recapture?
* The proportion of marked to unmarked individuals in the 2nd sample is the same as the proportion of marked to unmarked individuals in the population as a whole- the population size doesn’t change due to:
* Emigration or immigration.
* Births.
* Deaths.
* The marked **individuals distribute themselves evenly** amongst the rest of the population- if the conditions are unfavourable this will not happen.
* The method of marking doesn’t affect the individuals chance of survival e.g. it isn’t toxic or doesn’t make the individual less camouflaged.
* The mark isn’t rubbed off during investigation.
82
How should motile organisms be captured?
* Nets and traps are used.
* These should be designed to avoid causing animals unnecessary stress, as it could reduce it’s chance of survive or influence it to avoid the trap, interfering with the accuracy of the estimate.
83
What is succession?
* Ecosystems- dynamic- constantly change as populations fluctuate- changes can be slow or rapid.
* Succession- describes changes in an ecosystem over time.
84
How does succession work?
* Has stages- at each stage in succession, certain species change the environment so that it becomes:
* Less suitable for the existing species- the new species may out-compete the existing one and take over.
* More suitable for other species with different adaptions- the species may be out-competed by the better adapted new species.
* This leads to a series of successional changes- biotic conditions alter the abiotic conditions which in turn alter the biotic conditions- this causes one community of organisms to be succeeded (replaced) by another.
* Changes that organisms produce in their abiotic environment during succession can result in a less hostile environment, making it easier for other species to survive, enabling new communities to form and changing biodiversity.
85
What are hte different types of succession?
Primary and secondary.
86
What is primary succession?
* Primary succession- occurs on newly formed/ exposed barren land where there are no organic materials or soil present. Has stages from colonisation by pioneer species to climax community.
* Barren land can result from many factors e.g. volcanoes erupting, sand piled into a dune, sea level falling.
87
Describe pioneer species.
* * The first stage of primary succession is colonisation by a pioneer species (the first species to settle an area) of barren land:
* Settle their seeds and spores blown in by the wind e.g. marram grass, lichen.
* Have adapted features to make them suitable for colonisation of hostile abiotic conditions- limited water, few minerals and nutrients, high light intensity, exposure to wind and rain, fluctuating temperature.
88
Give some example adaptions of pioneer species.
* Asexual reproduction- can rapidly multiply to build up a population.
* Production of large quantities of wind-dispersed seeds/ spores- easily reach isolated areas.
* Rapid germination of seeds- don’t require a period of dormancy.
* Ability to photosynthesis- light available but not other food.
* Ability to fix nitrogen from the atmosphere- as soil has few/ no nutrients.
* Tolerance to extreme conditions
89
Describe primary sucession.
* The first stage of primary succession is **colonisation by a pioneer species** (the first species to settle an area) of barren land.
* **Pioneer species change the abiotic conditions**- die and microorganisms decompose dead organic material- forms a thin soil as able to e.g. fix nitrogen, soil helps to retain water. Makes **conditions less hostile and more suitable to new species** with different adaptions which can move in and grow.
* New organisms- die and decompose- add more organic material- make the soil deeper and richer in minerals e.g. nitrates.
* Nitrogen-fixing bacteria form in deeper soil- turn nitrogen from the atmosphere into ammonia- used by plants. Larger plants e.g. shrubs can grow- retains more water and contains more nutrients.
* New species- change the environment so it becomes less suitable for the previous species.
* At each stage, different plants and animals better adapted for the changing conditions, move in, out-compete plants and animals that are already there and become the dominant species. The dominant species- one which causes the most change to the abiotic environment- makes it more suitable for other species. During this time **changes occur to biodiversity.**
* Succession continues- ecosystem becomes more complex- new species move in alongside existing ones- biodiversity increases.
* Plants- create more habitats for animals- abiotic conditions become less hostile and biomass increases.
* Eventually these **changes result in a climax community**.
90
Describe a climax community.
* Ecosystem supporting the largest and most complex community of plants and animals it can.
* Remains in a largely steady state.
* Same species present- stable community.
* Abiotic factors remain more or less constant.
* Populations are stable around the carrying capacity.
* Abiotic factors of the ecosystem, largely climate, determine the species of the climax community.
91
What is the climax community for a set climate called?
The climatic climax.
92
Describe the process ofsuccession of lichen.
* Lichens survive on bare rock with little moisture. They weather the rock producing sand/ soil. When the lichens die and decompose they release nutrients into the soil which support small plants. Therefore, the lichens change the abiotic environment by creating soil and nutrients for organisms that follow.
* Mosses and ferns follow. The continued erosion of the rock and increased amounts of organic matter from the death of plants makes they layer of soil thicker. The Organic material holds water making it easier for other plants to grow. These species change the abiotic environment, making it less hostile and more suitable for organisms to follow e.g. small flowering plants and grasses, then shrubs, then trees.
* These species provide sources of food for animals, leading to food chains that develop into complex food webs and communities of plants and animals.
* The climax community then forms- this is deciduous oak woodland in the UK. The climax community has a stable state over a long period of time with a balanced equilibrium io species, with few, if any, new species replacing those that are established. Many species flourish and there is more biodiversity.
93
Describe how animals undergo succession.
* Animals undergo similar series of succession but their succession is determined by plant types available for food and habitats.
* In the lichen example:
* Dead lichens- provide food for small animals- e.g. mites.
* Mosses and grasses- provide foods and habitats for insects, millipedes and worms.
* These are followed by secondary consumers e.g. centipede- feed on these organisms.
* Development of flowing plants- helps to support communities of butterflies and moths.
* Development of trees- supports larger organisms e.g. reptiles, mammals and birds.
94
Describe secondary succession.
* Occurs when land already sustaining life is altered e.g. land clearance for agriculture or a forest fire, however, the soil remains.
* Occurs during any stage after the pioneer stage.
* The established community of species is destroyed usually without too much disturbance to the soil.
* Process very similar to primary succession but because of existing soil layer- starts at a later stage- pioneer species are larger plants e.g. shrubs.
* The ecosystem returns to its climax community through succession but more rapidly as soil already exists with spores and seeds that are still alive.
* There is an influx of animals and plants through dispersal and migration from surrounding areas.
* Because the land has been altered some of the species become different.
95
Describe the common features of succession.
* **Pioneer species colonise the area and cause a change in the environment e.g. food for other species.**
* Abiotic environment becomes **less hostile and more suitable to other species**- soil forms helping to retain water, nutrients are more plentiful, plants provide shelter from the wind. **New species can then colonise the area.**
* This leads to a greater number and variety of habitats and niches- **overall increase in species diversity/richness**.
* This results in increased biodiversity- different species occupy these habitats- evident in the early stages.
* Increased biodiversity leads to increasingly complex food-webs and increased biomass.
* Biodiversity peaks mid-succession- after decreases and the **climax community is reached**. Decrease due to **new species out-competing pioneer and other species as succession continues**- leads to their elimination from the community.
96
How can humans influence succession?
* Humans can prevent succession, stopping a climax community from developing.
* When succession is stopped artificially the resulting climax community is called the plagioclimax e.g. mowing the lawn, grazing.
* This enables some species that may not survive in the climax community to survive and can be a form of conservation.
97
What is conservation?
Protection and management of species and habitats (ecosystems) in a sustainable way- so that enough resources are taken to meet the needs of today without reducing the ability of those in the future to meet their own needs.
98
What does conservation involve?
* Involves active intervention by humans to maintain ecosystems and biodiversity- involves management of existing resources and reclamation of damaged areas.
* Conservation- dynamic- methods need to be adapted to constant changes within ecosystem.
99
What conflict is there with regards to conservation.
Conflict between human needs and conservation- management is needed to find a balance of human needs and conservation to maintain the sustainability of natural resources.
100
What are the reasons for conservation.
* Sustainability- maintain our planet and support our life system.
* Ethical- respect for other species who also occupy the Earth.
* Economic- gene pools that create valuable substances, provides ecosystem services that enable productivity.
* Cultural and aesthetic- inspire writers, places of cultural/spiritual significance, areas of recreation.
101
What is the most frequent method of conservation?
The management of succession.
102
How does conservation thruogh the management of succession work?
* Many species that existed in earlier stages of succession are no longer present in the climax community due to habitats disappearing after being out-competed.
* To conserve these habitats- human activities manage succession by preventing the next stage- interrupt so that the ecosystem stays in its current stage of succession.
* This conserves species who would otherwise not survive in the climax community, ensuring increased biodiversity- makes it more likely species will survive if conditions change to become more harsh.
* E.g. moorlands conserved by grazing and burning heather- destroy young tree saplings so prevent succession to woodland.
* Heaths/ grasslands are the result of human activities converting oak woodland to grazing land- e.g. sheep eat saplings- prevent them from developing into trees.
* If the factor preventing succession is removed- the ecosystem develops into climax community e.g. farmland abandoned- shrubs take over then woodland.
103
Give example methods of conservation.
* Managing succession.
* Seed banks.
* Captive breeding.
* Fishing quotas.
* Protected areas.
* Managing livestock.
104
Describe how seed banks aid conservation and the benefits and drawbacks.
* Store of seeds from different plant species- if they become extinct or are lost from a particular habitat- seeds can be used to reintroduce species.
* Large numbers of species conserved in small space- seeds are small.
* Can be stored for long periods of time- as long as the area is cool and dry.
* Seeds need to be regularly tested to see if they’re viable- expensive and time-consuming.
105
Describe how captive breeding aids conservation and the benefits and drawbacks.
* Breeding animals in controlled environments- usually species that are endangered or extinct in the wild- bred to increase their numbers.
* Can involve problems for animals as they do not breed easily outside their natural habitat or are not kept in their natural conditions.
* Animals can be reintroduced to the wild- increases numbers in the wild- conserve numbers and restore species after extinction.
* Reintroduction- cause problems e.g. carrying diseases, preventing evolution.
106
Describe how fishing quotas aid conservation and the benefits and drawbacks.
* Limits to the amount of fish species fishermen are allowed to catch- conserve fish species to prevent the species reaching low levels of extinction.
* Can be unpopular with fishermen- limit income.
* Leads to discards- ships catching more fish than they are allowed to then throwing back fish so don’t exceed quota- wasteful.
* International cooperation- problem in areas with international fishing.
107
Describe how protected areas aid conservation and the benefits and drawbacks.
* e.g. nature reserves- protect habitats and species by restricting urban and industrial development and farming.
* Habitats- managed to conserve them.
* Protected areas- may be used as tourist attractions to raise money- however can lead to conflict with conservation.
108
Describe how livestock can be managed to aid conservation.
* Ensure **livestock numbers remain small so their populations do not grow large enough to cause competition.**
* Choose livestock that do not directly compete against the species.
* **Keep livestock in enclosed/ separate areas to the habitat.**
* Choose to **grow crops so there is no competition.**
109
How do you assess data with regards to conservation.
* You may need to evaluate evidence and data concerning issues relating to the conservation of species and habitats and consider conflicting evidence.
* Describe the data- changes over time, using numerical values. Compare to controls.
* Draw conclusions- what the data suggests from the description.
* Evaluate the method- whether effects of other variables were factored into the control/ the study, the size of the sample (bigger= more accuracy), random sampling to remove bias and increases accuracy.
* If repeat studies have occurred and draw the same conclusion- enables it to be increasingly accepted.
110
How do you assess conflicting data with regards to conservation.
* Describe the data- use statistics from the graph.
* Draw conclusions- state that they conflict with the previous study.
* Evaluate the method in comparison with the previous study- whether control variables were the same or other factors were at play, the sample size, statistical test.
