Topic 9 - Ecosystems And Material Cycles Flashcards
How are fertilisers used?
Natural fertilisers such as manure or compost are used by farmers to provide a source of nitrate to increase crop yield. Expensive artificial fertilisers such as ammonium nitrate can be applied to the fields.
How does light affect communities?
Some plants have evolved for optimum growth in bright sunlight. An example of this is a cactus houseplant. Cacti originally come from deserts where they grow in bright sunlight. Other plants have evolved to grow in shade.
What happens each time you go up a trophic level?
The mass of the organism goes down because most of the biomass (energy) is lost and so doesn’t become biomass in the next level up.
What is stage three of the carbon cycle?
Animals feed on plants, passing the carbon compounds along the food chain. Most carbon they consume is exhaled as carbon dioxide during respiration. The animals and plants eventually die.
Why is nitrogen important and how is it useful?
Nitrogen is essential for the formation of amino acids which form proteins. The nitrogen cycle is a model that explains how nitrogen is recycled.
There’s lot of nitrogen in the air – about 78% of the air is nitrogen. Because nitrogen is so unreactive, it cannot be used directly by plants to make protein. Only nitrates are useful to plants, so we are dependent on other processes to convert nitrogen to nitrates in the soil.
How do you use quadrats?
Quadrats are square frames of wire usually 0.25 m2. These are placed on the ground to look at the plants or slow-moving animals within them. When looking at plants in a quadrat the following sampling can be used:
- Number of an individual species: the total number of individuals of one species (eg daisies) is recorded.
- Species richness: the number of different plant or animal species is recorded but not the number of individuals within a species.
- Percentage cover: the percentage of the quadrat area that is covered by one species (eg grass). This is easier to estimate if a quadrat has wires making smaller sections. Percentage cover rather than number of individuals is used when estimating plant frequencies if it is difficult to identify individual plants, such as grasses or moss.
What is transpiration in the water cycle?
Plants need to maintain a constant stream of water to their leaves for transport and support. They allow some water to evaporate as water vapour from their leaves so it is continually ‘pulled’ to their leaves from the soil.
What are the advantages and disadvantages of intensive farming? (8)
Advantages:
- Higher yields
- Cheaper food for the consumers
- More efficient use of food
- Quality control easier
Disadvantages:
- Reduction in biodiversity
- Creates pollution
- Risk of antibiotic resistance
- Considered unethical by some people
What is interdependence and why is it important?
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.
If the foxes in the food chain were killed, the population of rabbits would increase because they are no longer prey to the foxes. As a result the amount of grass would decrease because the increased population of rabbits would be eating it.
Often very small changes to ecosystems have large consequences, which can be difficult to predict. This means that all the organisms in an ecosystem are dependent upon each other. We call this interdependenc
How does competition affect communities?
The introduction of a new species into an ecosystem can result in it out-competing another native species. Several hundred years ago grey squirrels were brought over from North America by wealthy people and let free in their grounds. Our smaller native red squirrel couldn’t compete with the newer, larger grey squirrel. Because grey squirrels are larger they can store more fat and survive harsher winters. So the numbers of red squirrels and the places they live has reduced dramatically.
How does fish farming can reduce biodiversity?
Fish are farmed in large nets or tanks within lakes or in the sea.
Farm waste, chemicals, pathogens and parasites are released into the surrounding water, harming other marine life.
Carnivorous species of farmed fish, such as salmon, need high amounts of protein in their diet. They are often fed on wild fish, reducing their populations.
Sometimes fish can escape and compete with indigenous wild species and compete for resources, resulting in reduced biodiversity. Predators of the fish such as sea lions can become trapped in the nets and die.
How does temperature affect the rate of decay?
A warm temperature speeds up enzyme-controlled reactions ion microbes, so decay happens faster.
What is stage four of the carbon cycle?
Dead organisms are eaten by decomposers and carbon in their bodies is returned to the atmosphere as carbon dioxide. In some conditions decomposition is blocked. The plant and animal material may then be available as fossil fuel in the future for combustion.
What is crop rotation?
One year the farmer will grow one of crops that have nitrogen-fixing bacteria in its roots. This will increase the nitrate content and fertility of the soil. Then the following years, the farmer will plant another crop in the nitrate rich soil. Growing different crops each year in a cycle is called crop rotation.
What is food security affected by? (5)
Food security is reduced by:
- The increase in human population, as birth rates are increasing and many people have better access to medical care.
- Changing diets eg people starting to eat more meat in newly developed countries like China. This means that food resources are transported to be sold from areas which need them, especially meat and fish.
- New pests and pathogens that attack crops and farm animals.
- Environmental changes such as global warming could affect growth of crops, therefore reducing yields.
- Increased costs of farming may put off farmers and producing food.
Armed conflicts.
What living (biotic) factors affect communities? (2)
> Competition
> Predation
Describe reverse osmosis. (3)
- salt water is forced at high pressure into a vessel with a partially permeable membrane
- the pressure causes water molecules to move in the opposite direction to osmosis from a concentrated salt solution (low water concentration) to a lower salt concentration (higher water concentration)
- water molecules pass across the membrane leaving the salt behind, so pure water is available for drinking
How does the introduction of non-indigenous species reduce biodiversity?
A non-indigenous species does not live in an area and may be introduced by humans for a particular purpose such as removal of pest species or for hunting. However, the new species may out-compete or kill indigenous or naturally occurring species. These may be reduced in number, resulting in reduced biodiversity or maybe extinction.
What is organic farming?
Organic farmers do not use machines to the same extent as intensive farming. They do not apply pesticides to their crops and use natural fertilisers such as compost and manure. They rotate their crops to avoid monoculture. Crop rotation increases yield, promotes biodiversity and helps to keep soils heathy. Organic food is often more expensive than intensively farmed food, and many people are willing to pay more for the perceived benefits.
What is condensation in the water cycle?
After evaporation water can cool and convert from gas to liquid, often forming clouds.
What are the negative impacts of new pests and pathogens?
Pathogens including bacteria, fungi and viruses may infect the crops or farm animals and will reduce the yield of crops and reduce the food availability for the human population. New pathogens may reduce yields dramatically as the crops or animals may not be resistant. New diseases may lead to crop failure and reduced food production. Also new pests such as insects may damage the growth of crops, reducing yield and food security.
How is the survival of some organisms dependent on other species for mutualism?
Mutualism is another type of relationship between two species, where both species benefit. For example bees and flowering plants have a mutualistic relationship. Bees obtain nectar for food and spread the flower pollen from one flower to another, which helps reproduction in plants.
What is stage two of the nitrogen cycle?
Ammonia is converted to nitrates by nitrifying bacteria in the soil.
What is stage four of the nitrogen cycle?
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.
What is stage three of the nitrogen cycle?
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.
Why is decomposition important?
Decomposition is crucial to the cycling of elements, such as carbon from one living organism to another.
How does temperature affect communities?
Both animals and plants have evolved to grow healthily at their optimum temperatures. If you planted either your cactus or orchid houseplants outside in cold temperatures, they would die. Similarly, animals that have evolved to live at the North Pole, such as the polar bear, could not survive in warmer conditions.
How can water be polluted?
If water is polluted by raw sewage or fertilisers, eutrophication can happen, which decreases the oxygen concentration in the river or lake.
What is stage five of the nitrogen cycle?
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.
How is the survival of some organisms dependent on other species for parasitism?
Parasites live in or on another organism, which is called the host. The parasite takes what it needs from the host but the host receives nothing in return and often suffers as a result. An example of parasitism is the relationship between fleas and dogs. Fleas live on dogs and feed on their blood. The dog receives no benefit but the fleas are provided with food and a habitat. Fleas attach themselves to hairs and can spread from one host to another by jumping huge distances.
What is the carbon cycle and why is it important?
The carbon cycle shows how atoms of this element can exist within different compounds at different times.
All cells - whether animal, plant or bacteria - contain carbon, because they all contain proteins, fats and carbohydrates. Plant cell walls, for example, are made of cellulose - a carbohydrate.
Carbon is passed from the atmosphere, as carbon dioxide, to living things, passed from one organism to the next in complex molecules, and returned to the atmosphere as carbon dioxide again. This is known as the carbon cycle.
