Topic 9 - Ecosystems And Material Cycles Flashcards
What are the different levels of organisation? (4)
Individual - a single organism
Population - all the organisms of one species in a habitat
Community - all the organisms of different species living in a habitat
Ecosystem - a community of organisms along with all the abiotic (non-living) conditions
What non-living (abiotic) conditions affect communities? (4)
> Temperature
Light
Water
Pollutants
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 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.
How does water affect communities?
More people kill houseplants by overwatering than by under-watering them. Many plants cannot survive in waterlogged soils. Their roots are unable to respire, they rot and the plant dies. Other plants, such as pitcher plants, grow best in bogs where the moisture levels are high. Soil moisture meters can accurately determine how wet an area is.
How do pollutants affect communities?
If pollutants such as sulfur dioxide are released from the burning of coal. Lichens cannot survive if the concentration of sulfur dioxide is too high. So lichens are considered to be indicator species for air pollution. If the air is clean there will be lots of lichens so that if the city and countryside are compared, there will be more lichen species further away from the city centre.
What living (biotic) factors affect communities? (2)
> Competition
> Predation
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 predation affect communities?
The arrival of new predators in an ecosystem can have a devastating effect. In balanced ecosystems, predators and prey have evolved together. Predators can catch enough prey to survive, but not so many that they kill all of their food.
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 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.
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.
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 random sampling?
Random sampling using a quadrat involves the placing of quadrats at random coordinates. Regardless of whether you are investigating the number of individual species, the species diversity or the percentage cover in different areas you would use random sampling.
What is systematic sampling?
Systematic sampling can be used if there is a trend or pattern across the habitat, such as distance up a beach, or altitude on a hillside. If you are using the wrong kind of sampling method for your experiment, this can lead to biased results.
How do you use a belt transect? (5)
- Mark out a line in the area you want to study, e.g. from the hedge to the middle of the field.
- Then collect data along the line using quadrats placed next to each other. If your transect is quite long, you could place the quadrats at regular intervals (e.g. every 2 metres) instead. Collect data by counting all the organisms of the species you’re interested in, or by estimating percentage cover. This means estimate percentage area of a quadrat covered by a particular type of organism.
- You could also record other data, such as the mean height of the plants you’re counting or the abiotic factors in each quadrat (e.g. you could use a light meter to measure the light intensity).
- Repeat steps 1 and 2 several times, then find the mean number or mean percentage cover for each quadrat.
- Plot graphs to see if the changing abiotic factor is correlated with a change in the distribution of the species you’re studying.
What do arrows in a food chain or a food web show?
The arrows show the transfer of biomass from one trophic level to another.
Why do you never get a food chain with more than 5 trophic levels?
- Plants convert the light energy into glucose and use the glucose immediately and then store the rest as biomass.
- The rabbit then eats the plant. It uses some of then energy stored in the plant then it stores the rest in its own body. Then a fox eats the rabbit and gets some the energy stored in the rabbit’s biomass.
Energy is not conserved as it is passed onto the next trophic level as it is lost via heat to the surroundings of the animal. The energy is lost when the animal leaves faeces or bones when it is dead.
What is the pyramid of biomass?
It shows how much the creatures at each level would weigh if you put them together. It shows how much energy there is at each level.
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.
How do you work out efficiency of energy transfer?
(Energy transferred to next level ÷ Energy available at previous level) x 100
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 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.
How can the overuse of fertilisers reduce biodiversity?
As the human population increases, we need more food and increased use of fertilisers has impacted on the biodiversity of aquatic environments through eutrophication. Nitrates in the fertilisers run off from fields into rivers and lakes causing the overgrowth of algae. The light is blocked so plants cannot photosynthesise so they die. This causes bacteria to decompose the plants and use up most of the oxygen in the water. Without oxygen, animals such as fish will die. This is a negative impact as the biodiversity of the river or lake will decrease.
How does reforestation increase biodiversity?
This is when land where a forest previously stood is replanted to form a new forest. They will provides and shelter for lots of different animal species. A variety of tree species need to be planted to increase the biodiversity.
How do conservation schemes help protect biodiversity?
- Protecting a species’ natural habitat so that individuals have a place to live.
- Protecting species in safe areas outside of their natural habitat (zoos) and introducing captive breeding programmes to increase numbers
- Seed banks to store and distribute the seeds of rare and endangered plants.
What are the benefits of maintaining biodiversity? (6)
> Protects the human food supply - over-fishing reduced fish numbers; conservation schemes make sure future generations have fish to eat
Minimal damage to food chains - conserving species makes sure none go extinct and affect other organisms that rely on that species.
Providing future medicines - many medicines come from plants; we could miss out on valuable medicines if certain plants go extinct.
Cultural aspects - individual species may be important in a nation’s heritage
Ecotourism - people are drawn to visit beautiful, unspoilt landscapes with a variety of species.
Providing new jobs - conservation schemes, ecotourism and reforestation schemes improve employment opportunities.
What is food security?
Food security is a measure of the availability of food required to support people of a household, region, country or any specified area. It is a measure of how much food there is, if it is of suitable quality and whether people can access it.
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 is intensive farming?
Intensive farming uses machines, fertilisers, man-power and high-yield crops to maximise the amount of food produced. Farmers growing arable crops often specialise in growing only one crop to maximise their profits. This is called monoculture. It can quickly reduce key nutrients in the soil and lowers biodiversity.
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
