Succesion and conservation
Suggest one explanation for this ecological succession.
Action of species changes abiotic conditions. Making habitat suitable for later species.
The species that are present change during succession. Explain why.
Species change the environment so that it becomes less hostile for other species.
What does biodiversity encompass
Species diversity, habitat diversity and genetic diversity
Faeces from cows contain large amounts of dead plant material and are called cow pats. Students investigated changes in cow pats with time. They recorded the insect species present on cow pats of different ages. The table shows the resultsThese results illustrate ecological succession. Describe how.
Species of insect (community) changes with time;
How are forests managed?
A forest can be managed by coppicing and pollarding, which allow timber to be harvested, while conserving the forest
Explain the increase in the diversity of birds as the woodland developed.
As the woodland developed there would be an increase in the variety of plants which means more varieties of food and therefore more niches.
Explain how human activities have contributed to global warming.
Carbon dioxide is a greenhouse gas. Deforestation also contributes to global warming because if trees are removed less carbon dioxide is removed by photosynthesis. Combustion also contributes because it produces carbon dioxide. Methane produced by cattle is a greenhouse gas.
Plants that colonise bare soil usually produce large numbers of seeds, which are dispersed over large distances. Explain the advantages of these adaptations.
Chance of finding areas of bare soil is low chance of survival is also low due to hostile conditions
Last stage in succession
Climax community
Why is the climax community the most stable community?
Climax community has a much more complex food web. There's competition as there are more habitats and more types of species with different niches.
Some scientists reviewing this investigation were concerned about the validity of the results because of the use of concrete blocks. Suggest one reason why these scientists were concerned about using concrete blocks for the growth of algae.
Concrete is man-made so the nutrients in it will be different and this may affect the growth rate of algae.
Some scientists reviewing this investigation were concerned about the validity of the results because of the use of concrete blocks. Suggest one reason why these scientists were concerned about using concrete blocks for the growth of algae
Concrete is man-made so the nutrients in it will be different than the nutrients in natural rock and so this may affect the growth of the algae.
What is conservation?
Conservation is the protection and management of the ecosystem in a sustainable way
What does conservation involve
Conservation of habitats frequently involves management of succession.
5 aims of conservation
Conserve niches Protect endangered species Maintain biodiversity Reduces global warming as woodlands remove CO2 Reduce eutrophication/erosion
How does coppicing increase biodiversity
Coppicing allows more light and heat to reach the forest floor. This gives opportunity for woodland flowers to become established, making the area more suitable for many butterfly species and other woodland pollinators and thus increases biodiversity of woodland
What is coppicing?
Coppicing is the practice of cutting trees and shrubs to ground level, promoting vigorous re-growth.
Table 2 shows the results of a soil analysis carried out on samples collected from positions A and C along the transect. Using information in Table 2 and your own knowledge, explain why the nitrate concentration is greater at position C than at position A.
Dead plant material (humus) is converted to nitrate by soil bacteria. Plant material decomposed by saprobionts. Organic molecules containing nitrogen are converted to ammonia and this process involves ammonifying bacteria. Ammonia to nitrite and then nitrite to nitrate involving nitrifying bacteria.
A student investigated an area of moorland where succession was occurring. She used quadrats to measure the percentage cover of plant species, bare ground and surface water every 10 metres along a transect. She also recorded the depth of soil at each quadrat. Her results are shown in the table. Explain how these data suggest that succession has occurred from points A to E along the transect.
Decrease in of bare ground linked to more plant species. Change in diversity of plant species as abiotic conditions altered due to competition. Increase in depth of soil as plants die and humus forms as a result.
Why do numbers of pioneer species increase after new land has been erected?
Due to lack of competition they rapidly colonise the empty land.
True or False Conservation is just leaving the enviornment untouched
FALSE Conservation involves active intervention to manage succession and maintain a wide variety of different plagioclimaxes
The rate at which a heather plant produced new biomass was measured in g per kg of heather plant per year. This rate decreased as the plant aged. Give three reasons why.
Fewer leaves so less photosynthesis to produce new glucose. Competition with other species for nitrates so reduced synthesis of protein. Ratio of leaves to woody parts and roots decreases as plant ages so higher respiration rate to photosynthesis rate
Climax community
Final, stable community. No further succession after this stage. This community contains dominant animal and plant species. All climax communities determined by main abiotic factor.
Conservation of grassland habitats involves management of succession. Explain why.
Grassland consists of annual plants will be outcompeted by woody plants so these woody plants must be removed.
The diversity of animal species is higher at E than A. Explain why
Greater variety of food so more variety of niches.
State 2 benefits of coppicing
Helps prevent the manifestation of dead or diseased wood in the tree, by renewing constant fresh growth and the removal of old wood, allowing the tree to live for a lot longer than if it were left un-coppice Provides a sustainable supply of timber for future generations.
Why is the concept of ecological successions used in conservation?
Its used because living systems maintain some degree of stability through constant change in response to changing environmental conditions. Management of succession causes environment changes which increases the sustainability of many communities and results in a greater success with conservation practices.
What does conservation try to find the balance between
Keeping the land as a productive resource whilst still sustaining biodiversity.
The foxglove is a biennial plant, which means that it lives for two years. In the first year it produces leaves but no flowers. In the second year it flowers and each plant releases about 300 000 very small seeds. Suggest how being a biennial enables a foxglove plant to produce very large numbers of seeds.
Long period for growth/photosynthesis/more leaves/early start in second year. More food reserves for seed production;
Species found in coloniser communities do not grow well below trees in a tree community. Use the graph to explain why.
Low light intensity under tree canopy For the coloniser plant, the rate of photosynthesis is low when the light intensity is low
How is grassland maintained
Maintained by grazing animals which prevents the growth of shrubs and trees, but allows grasses to grow. Grazing by sheep and rabbits leaves grass particularly short and creates unique environments.
Use the results of this investigation to describe and explain the process of succession
Pioneer species increases then decreases. Pioneer species make the abiotic conditions less hostile. The pioneer species are outcompeted by new species.'Named species' increases and other species decrease
The student used the mark-release-recapture technique to estimate the size of the population of sand lizards on an area of moorland. She collected 17 lizards and marked them before releasing them back into the same area. Later, she collected 20 lizards, 10 of which were marked. Give 5 conditions for results from mark-release-recapture investigations to be valid.
Marking is not removed nor does it affect survival of lizards. No immigration Sufficient time for marked individuals to mix within the population No births or deaths Sampling method is the same
Marram grass is a pioneer species that grows on sand dunes. It has long roots and a vertically growing stem that grows up through the sand. Sand dunes are easily damaged by visitors and are blown by the wind. Planting marram grass is useful in helping sand dune ecosystems to recover from damage Use your knowledge of succession to explain how.
Marram grass stabilises and stops sand shifting. It makes abiotic conditions less hostile by Adding nutrients and improving water retention of soil
Explain the decrease in gross productivity as the woodland matures
More competition for light results in reduced photosynthesis.
Hydrilla is an aquatic plant which has become a major pest of waterways in parts of the USA. Hydrilla is not a native species of the USA. It was introduced into natural habitats from aquariums. In many freshwater habitats it has rapidly become the dominant plant species.In many freshwater habitats Hydrilla has rapidly become the dominant plant species. Suggest thee reasons why
More resistance to disease Few consumers and pathogens Outcompetes other species for resources and abiotic factors
Why is climax community more stable?
More species present in a climax communtiy More complex food webs Change in one species will have little effect on others as alternate food sources available
Use the information in Figure 3 and your knowledge of net productivity to explain why biomass shows little increase after 100 years.
Net productivity= Gross productivity - respiratory losses The graph shows a decrease in gross productivity
The foxglove is a biennial plant, which means that it lives for two years. In the first year it produces leaves but no flowers. In the second year it flowers and each plant releases about 300 000 very small seeds. Suggest how producing large numbers of very small seeds adapts the foxglove for colonising woodland clearings.
Not many will reach suitable conditions so producing many seeds means there is a better chance of some reaching a clearing. Small so more easily and widely dispersed by wind.
The pine trees in the forest have leaves all year. Explain how this results in a low species diversity of plants in the forest.
Only plants which can photosynthesise with less light remain.
The pine trees in the forest have leaves all year. Explain how this results in a low species diversity of plants in the forest.
Only the plants which could photosynthesise at low light intensities would be present.
How is moorland maintained?
Periodic burning. Fire kills tree saplings but not heather, which is fire resistant and re-grows after a few weeks.
Why must succession begin with a pioneer species?
Pioneer species are the only type of species that are specially adapted to survive in hostile conditions
Main role of pioneer species in speciation
Pioneer species grows, dies and forms humus
Explain how the change in species composition occurs in a succession.
Present species make the abiotic conditions less hostile. This change in habitat allows for other species to colonise and these new species are better competitors.
Succession
Process by which an ecosystem changes over time because of abiotic factors and the presence of species
The rate of uptake of carbon dioxide is a measure of the rate of photosynthesis. At high light intensities, the coloniser had the highest rate of photosynthesis of all the plant species shown. Suggest the advantage of this high rate of photosynthesis.
Rapid growth means that they are able to reproduce more quickly. It also means they have energy to produce more seeds.
Clover plants are able to reproduce by vegetative propagation. Suggest four advantages of this form of reproduction when clover colonises a new habitat.
Rapid process Large number produced Only one plant required because its asexual reproduction No variation as new plant is genetically identical to the parent plant
The rate of uptake of carbon dioxide is a measure of the rate of photosynthesis. At high light intensities, the coloniser had the highest rate of photosynthesis of all the plant species shown. Explain why carbon dioxide was released at low light intensities
Rate of respiration is greater than rate of photosynthesis.
State the effect of removing invasive species
Reduces inter-specific competition
Explain three ways in which farming practices prevent the formation of woodland
Regular grazing prevents succession; Using Herbicides kills herbaceous plants Burning destroys plants
Many species in the pioneer community are xerophytes. Suggest and explain how having sunken stomata is an advantage to these plants.
Sand has a low water retention. Sunken stomata reduces water loss by transpiration as pocket of saturated air trapped near stomatal pore. This reduces water potential gradient and therefore reduces diffusion rate
The leaves of foxgloves contain a poisonous substance, called digitalis. In high concentrations, digitalis slows down the rate at which impulses pass across the atria of the heart. Explain how the presence of digitalis may protect foxgloves from being eaten by mammals.
Slows conduction from SAN to AVN. Slows down contraction of ventricles so heart rate decreases This means that less blood is pumped around the body so less oxygen is taken up by the respiring cells. Mammals that eat them become less active. Selection favours those that do not eat foxgloves.
Marram grass is a pioneer species that grows on sand dunes. It has long roots and a vertically growing stem that grows up through the sand. Sand dunes are easily damaged by visitors and are blown by the wind. Planting marram grass is useful in helping sand dune ecosystems to recover from damage. Use your knowledge of succession to explain how.
Stabilises sand (stops sand shifting) makes conditions less hostile by adding nutrients, improving water retention and forming soil.
Plagioclimax
The climax stage of a community, influenced by man or some other outside factor.
Use your knowledge of succession to explain the increase in biomass during the first 20 years
The pioneer species die and decay making the abiotic conditions less hostile by forming humus and enabling new species to colonise. This causes an Increase in number and diversity of species.
The species that are present change during succession. Explain why.
The species present changed the environment. making the habitat less hostile. New species outcompete species already present.
Explain why it would be more appropriate to use a transect rather than random quadrats when investigating this succession.
There's a series of changes over a distance so it ensures sampling of each community;
Why are pioneer species eventually succeeded?
They are out competed by new species
Why are some people against conservation?
They believe that it is harming wildlife and damaging the environment.
How does conservation link with maintaining a gene pool?
To maintain the gene pool we need to preserve species diversity and to conserve species diversity we must provide suitable niches for all species by preserving habitat diversity. This can only be done through conservation.
The scientist used percentage cover rather than frequency to record the abundance of algae present. Suggest 3 reasons why.
Too many to count Individual organisms not identifiable Grows in clumps
How are woodlands maintained?
Woodland is maintained by replacing non-native conifer plantations with native broad-leaved trees and reducing density by thinning. Thinning allows more light to reach the ground layer, encouraging the growth of shrubs and wildflowers.
Give a reason why people would want to conserve woodland
Woodlands are a source of medicine