ecosystems module 6

What is an ecosystem?

All living organisms & non living components & their interactions

What is a population?

Number of individuals of the same species living in the same place at the same time

What is a community?

All the organisms, of all the different species living in a habitat

What is a habitat?

Place where an organism lives

What is a niche?

The role of an organism in the ecosystem

What are biotic factors?

Living factors that effect other living organisms E.G predation, herbivores eating plants & competition

What are abiotic factors?

Non-living factors of the environment that affect organisms e.g. temperature, pH, light intensity, wind speed, humidity, H2O supply & CO2 concentration

How does light affect the ecosystem?

Needed in photosynthesis, more light means a higher success of a species. Strategies made by plants are formed to cope with different light intensities e.g low light have bigger leaves

How does temperature affect the environment?

Affects enzymes controlling metabolic reactions. Plants develop more in warmer temperatures. Changes in temperature of an ecosystem can cause migration in animal species

How does water availability affect the environment?

Lack of water causes stress which can lead to death. Can lead to plant wilting as water is needed to keep cells turgid. Needed for photosynthesis

How does oxygen availability affect the environment?

In aquatic ecosystems, it's beneficial to have a fast-flowing cold water because it has a high concentration of O2. Rate lowers with warmer H2O

How does Edaphic factors affect the environment?

Different soil types have different particle sizes, this effects organisms that survive in them. Clay has fine particles & clumps when wet. Sandy is course, well seperated particles that allow free draining

How does biomass transfer occur?

All organisms in an ecosystem need an energy source to survive, mainly the sun. Light energy is converted to chemical energy in plants, which is then transferred to other non-photosynthetic organisms as food

What are trophic levels & the food chain?

Position of an organism in the food chain. Producer fix carbon using sunlight. Primary consumer eats producer, secondary consumer eats primary consumer.

What is biomass?

Mass of living material in a food chain. Found by multiplying number of organisms by their dry mass.

What is an advantage of using dry mass in a pyramid of mass?

Removing water will allow for comparisons to be made between different organisms, different organisms have different water contents which affect the whole biomass

What is a disadvantage of using dry mass in a pyramid of mass?

Organism dies during the process with no water involved

How is the energy content of dry mass obtained?

Using a bomb calorimeter, burn the sample in a high pressure of oxygen, rise in the temperature of the water is measured

By what factor does the biomass decrease between each trophic level?

By a power of 10

Why does the biomass in each trophic level nearly always less than the tropic level below?

Not all biomass is eaten e.g bones & roots. Some is transferred in the environment as heat, some is excreted & some is indigestible

What is net primary production?

energy available at each trophic level, measured in kj/m2 per year. This allows us to see photosynthetic production & consuming feeding patterns in the year

What factors increase net primary production?

High temperature & increase in sunlight, more photosynthesis occurs so there's more storage of biomass

Why do producers only convert 1-3% of the sunlight they receive into chemical energy?

Not all light hits chlorophyll, not all light hitting leaves is absorbed, can be reflected, transmitted through the leaf or of the wrong wavelength

What is productivity?

the rate of production of new biomass by producers

What is gross primary productivity?

Total quantity of energy converted by plants in this way

What is net primary productivity?

Energy which remains as chemical energy after plants supplied their own needs in respiration

Why do consumers at each trophic level convert at most 10% of the biomass in their food to their own organic tissue?

Not all biomass is eaten, some lost as heat to the environment through respiration, excreted via urine & some biomass is of previous level but is not digestible

How do you measure ecological efficiency?

Energy available after transfer/ energy available before transfer x 100

How can humans manipulate transfer of energy in animals?

Reduce movement to keep high mass, feed high protein diet for muscle mass, slaughter just before maturity

Why is it important that nitrogen is recycled?

Vital for making amino acids in plants & animals. Nitrogen gas in the atmosphere can't be taken up by plants - it must be combined with other elements.

What is nitrogen fixation?

the chemical processes by which atmospheric nitrogen is combined (using nitrogenase) with H2 to form NH3 which can be absorbed by plants.

How can nitrogen gas in the air get recycled?

Non-living processes through Lighting & Haber process & living organisms in nitrogen fixing bacteria

What are the 2 nitrogen fixing bacteria?

Rhizobium & Azotobacter, both have nitrogenase. Azotobacter is a free-living soil bacterium, Rhizobium live in root nodules

How is ammonia converted into nitrates? (Nitrification process)

Ammonia (NH3) is made into nitrites (NO2-) using nitrosomonas which is then converted to nitrates (NO3-) through nitrification using nitrobacter. Nitrates are soluble so they enter plants

What is ammonification?

Nitrogen compounds from dead organisms are turned into NH3 by decomposers which forms NH4+ ions. Waste contains nitrogen compounds which is turned into NH3 by decomposers to form NH4+

What is the role of Saprobionts?

Fungi & bacteria that secrete enzymes onto food which hydrolyses polymers, allowing monomers to be absorbed

What is the Haber process?

a method used to produce ammonia by combining nitrogen from the air with H2 from natural gas e.g methane. N2 + 3H2

What is the carbon cycle when decomposers are present?

1. CO2 is absorbed by plants in photosynthesis, to form carbon compounds in tissues. 2. Carbon is passed on each consumer when each consumer is eaten. 3. Organisms die & carbon compounds are digested by decomposers. 4. Carbon is returned to air & H2O as all organisms carry out respiration which forms CO2

What if dead matter ends up in areas with no decomposers?

1.Carbon compounds are turned into fossil fuels over millions of years. 2. Carbon is released when fossil fuels are burnt. 3. Other rocks are formed from dead matter made up of CaCO3 e.g limestone & chalk.

How does the movement of tectonic plates allow for CO2 to be released into the atmosphere?

Chemical changes occur which release CO2 which is released via volcanoes.

How does CO2 become released in land?

Rocks become land which is weathered via chemicals & rainwater & by plant roots. Chemical weathering causes mineral ions & HCO3- ions to be released from rock & enter groundwater which is transported in oceans.

What is succession?

Process where an ecosystem changes over time. Occurs due to changes in the environment (abiotic factors) causing plant & animal species present to change

What is primary succession?

succession that occurs on land that's newly formed, no soil or organic material to start with e.g where a volcano erupted to form new rock surface

What is secondary succession?

Succession that occurs on land with soil but that's been cleared of all the plants & animals e.g after a forest fire

What happens in each succession stage?

Key species can be identified that change the abiotic factors, especially the soil to make it more suitable for the existence of the next species

What is the pioneer community?

First species to colonise an area. arrives before climax, subject to greater change, lower biodiversity, less stable & have a low biomass e.g mosses

Why is the pioneer community so important?

Fixes nitrogen, can cope with harsh conditions due to being specialised to cope with them. Makes environment less hostile by retaining water in the soil

What is the intermediate community?

pioneer species die & they add to the soil which can support grasses & flowers which outcompete the pioneer species e.g grasses

What is the climax comunity?

When the intermediate species die they add to the soil which supports larger shrubs & trees. They outcompete grasses & flowering plants for light, space & nutrients e.g oak & hickory

What is deflected succession?

Human activity stops the natural flow of succession & stops it from reaching it's climax community. e.g mowing the lawn. Artificial halting of succession is plagioclimax

Why do we carry out sampling?

Measure diversity of species in a habitat, which is further calculated by simpson's index of diversity. Too hard to count all organism so we find a small area to represent the whole area

How do you carry out a random sample?

Choose a habitat to find a population e.g field, measure out the field on 2 axis', then use a random number generator or dice to find X & Y co ordinates of where to place quadrat

Why is randomisation important?

Avoids bias. Can be done by taking samples at regular distances in the habitat e.g every 5 metres or a random number generator for co ordinates

How many samples should be tested?

Many samples must be found to find the mean. Sample at different times of the day & avoid recounting the same plant

How are quadrats used when sampling plants?

Used to find the % cover of the number of each species or count species in the quadrat, quanative method - statistical tests can be done

What is the DACFOR scale?

A qualitative scale which measures what organisms are present e.g grass is Rare, can't be used in statistical analysis

Dominant

Abundant

Common

Frequent

Occasional

Rare

What is a belt transect?

Set 2 transect lines Using a quadrat, at equal distances count the organisms of each species, use an identification key & a method to avoid recounting, find a mean & repeat at different times of the year

What is a line transect?

Marking a line along the ground between two poles & marking samples at specified points, organisms touching the line are counted. Not as detailed as the belt transect

How to measure a field?

Use 2 tape measures to make a grid, use number generator to get random coordinates, use a quadrat to count the members of each species, use an identification key, a method to avoid recounting & sample at different times of the year

What is stratified sampling?

Population is split into mutually exclusive strata & a random sample is taken from each strata & repeated so it represents the area. Use an identification key, a method to avoid recounting & sample at different times of the year

What are the role of keys?

Used to identify both plants & animal species

How can we sample animals?

Wait to see what large animals appear in their habitat - opporunistic. For smaller animals use, sweep net, collect from trees, pitfall trap, tullgreen funnel, light trap