SB9: Ecosystems and material cycles

Describe the different levels of organisation

Explain how communities can be affected by abiotic factors

temperature, light, water, pollutants

Explain how communities can be affected by biotic factors

competition, predation

What is interdependence and why is it important in a community

All organisms in an ecosystem depend upon each other- if the population of one organism rises or falls, then this can affect the rest of the ecosystem

Survival of one species being dependent on another species can be…

* Parasites live in or on another organism- it takes what it needs from the host but the host receives nothing in return and often suffers as a result (toxic relationship!!) \n
* Mutualism is a type of relationship between two species where both benefit

Quadrats are square frames of wire placed on the ground to look at the plants or slow-moving animals found within them \n we can use this to measure: \n - the number of individuals in a specific species \n - species richness (the number of different species) \n - percentage covered by one species \n


1. random sampling places quadrats at random coordinates \n
2. systematic sampling (belt sampling, in the picture) can be used if there is a trend across the habitat- eg. distance up a beach or distance from a large tree that shades the ground

How to determine the number of organisms in a given area using raw data from field-work techniques, including quadrats and belt transects

Estimated population size = total of organisms counted in samples x (total area size/quadrants area)

What occurs in energy release between trophic levels?

Some energy is not useful and affects the number of organisms at each trophic level, limits the length of a food chain and determines the shape of a pyramid of biomass in an ecosystem.

What do arrows in a food web represent?

the stages in a food chain or web are called trophic levels \n - the arrows show the transfer of biomass from one trophic level to another

Positive and negative human interactions within ecosystems and their impacts on biodiversity for fish farming?

Humans consume fish for increased nutrients, this increases the human population, we need more of it. Overfishing wild fish stocks has damaged some water ecosystems, however fish farming aims to produce more fish and so reduce overfishing of wild fish \n \n problems caused as so many fish kept in a relatively small space. uneaten food and feces sinks to the bottom of the water, which can change conditions. this may harm wild organisms, and also mean parasites and disease spread more easily between fish in pens

Positive and negative human interactions within ecosystems and their impacts on biodiversity for introduction of non indigenous species?

POSITIVE:some species are introduced in order to affect an ecosystem, such as reduce the numbers of another species that has got out of control (often happens when humans have changed the ecosystem, affecting the food web). \n \n NEGATIVE:can affect the indigenous or native species. for example, cane toads from south america were introduced to australia to control the numbers of cane beetle which ate sugar cane crops. however, these toads are poisonous and kill native animals, which is a problem

Positive and negative human interactions within ecosystems and their impacts on biodiversity for eutrophication?

POSITIVE:

addition of more nutrients to an ecosystem than it normally has. for example, when too much too much fertiliser is added to a field

\
NEGATIVE:

1\. fertilisers from farming run off into water bodies, providing lots of nutrients \n 2. this causes algae to grow rapidly (blooming) \n 3. this prevents sunlight from reaching other plants \n 4. the plants die and are decomposed, depleting oxygen \n 5. lack of oxygen causes the animals to die

Explain the benefits of maintaining local and global biodiversity

conservation of animal species stops them becoming extinct, increases biodiversity,

the impact of reforestation-reduces global warming as carbon is absorbed so less CO2 in atmosphere

areas with greater biodiversity can recover faster from natural disasters such as flooding, we can use plants and animals for food and a source of medicine

Describe the biological factors affecting levels of food security:

* increasing population


* changing diets (increased meat and fish consumption)
* new pests and pathogens
* climate change
* increased costs of farming
* sustainability issues like the cost of agricultural inputs

What is the carbon cycle?

1. plants remove carbon dioxide from the atmosphere by photosynthesis
2. plants, the animals that eat them, and the decomposers that feed on their waste return carbon dioxide to the atmosphere by respiration
3. carbon dioxide is also released into the air by combustion, particularly of fossil fuels

What is the water cycle?

water evaporates from oceans, lakes and rivers to form water vapour. as air rises it cools, so water vapour in it condenses to form clouds. as water droplets get too large and heavy they fall as rain or snow in rivers and lakes. this eventually returns to the ocean \n \n to make water portable (safe to drink), it must be treated with chemicals and filtered, to remove dirt, pathogens and any toxic substances (eg metal ions). also may be treated to improve taste, by removing other non toxic substances

What is the nitrogen cycle?

1. **Nitrogen gas** from the air is converted to **nitrate** compounds by **nitrogen-fixing bacteria** in soil or **root nodules**. Lightning also converts nitrogen gas to nitrate compounds. The **Haber process** is a man-made process where nitrogen gas is converted into ammonia which is used to make fertilisers. Farmers use fertilisers like ammonium nitrate to help crops to grow and increase yields.
2. **Ammonia** is converted to nitrates by **nitrifying bacteria** in the soil.
3. **Plants absorb nitrates** from the soil and use these to build up **proteins**. The plant may be eaten by an animal, and its biomass used to produce **animal protein**.
4. **Decomposers** break down the bodies of dead organisms, urine and faeces resulting in nitrogen being returned to the soil as **ammonia**. This **ammonia** is converted to nitrates by nitrifying bacteria.
5. In some conditions denitrifying bacteria in the soil break down nitrates and return **nitrogen** back to the air. This is usually in waterlogged soil. Improving drainage reduces this effect, making the soil more fertile by retaining more **nitrates**.

Describe the use of indicator species for air quality?

Lichen are very sensitive to the concentration of sulfur dioxide. \n - The air is clean if there are lots of lichen, especially bushy lichen (which require cleaner air than crusty lichen) \n \n The presence of blackspot fungus found on rose leaves indicate that the air is clean. \n - Blackspot fungus is also sensitive to the level of sulfur dioxide.

Describe the use of indicator species for clean water

Describe the use of indicator species for clean water and polluted water

water polluted by raw sewage or fertilisers has low oxygen levels; this can be indicated by: \n - stonefly larvae and freshwater shrimp are very sensitive to oxygen levels, so their presence in a river indicates that the river is clean, and their sudden absence indicates water pollution \n - blood worms and sludge worms can suvive in low oxygen concentrations, so their presence indicates high levels of water pollution

Explain the effects of temperature, water content and oxygen availability on the rate of decomposition in food preservation

temperature-

water content-

oxygen availability-