7 Flashcards

Question

Decomposers

Answer 1

Decomposers such as bacteria and fungi play an important role in ecosystems. They decompose any dead plant or animal material left in an environment. They can do this by secreting (releasing) enzymes that break the dead stuff down into small soluble food molecules. These then diffuse into the microorganisms. This process also releases nutrients into the environment, which the producers need in order to grow.

Answer 2

Food chains show what's eaten by what in an ecosystem. Food chains always start with a producer. Producers make (produce) their own food using energy from the Sun. Producers are usually green plants or algae - they make glucose (a sugar) by photosynthesis. Energy is transferred through living organisms in an ecosystem when organisms eat other organisms. Producers are eaten by primary consumers. Primary consumers are then eaten by secondary consumers and secondary consumers are eaten by tertiary consumers.

Answer 3

Consumers that hunt and kill other animals are called predators, and their prey are what they eat. In a stable community containing prey and predators (as most of them do of course), the population of any species is usually limited by the amount of food available. If the population of the prey increases, then so will the population of the predators. However as the population of predators increases, the number of prey will decrease.

Answer 4

Predator-prey cycles are always out of phase with each other. This is because it takes a while for one population to respond to changes in the other population. E.g. when the number of rabbits goes up, the number of foxes doesn't increase immediately because it takes time for them to reproduce.

Answer 5

Pyramids of biomass show the relative mass of each trophic level. There's less energy and less biomass every time you move up a stage (trophic level) in a food chain. So there are usually fewer organisms every time you move up a level too, as there's less energy available to support them.

Answer 6

One oak tree can feed 2000 caterpillars. These caterpillars are eaten by around 90 bluetits. 1 sparrowhawk can eat around 90 bluetits.

Answer 7

* It can be difficult to catch organisms to calculate their mass * Organisms need to be killed to calculate their dry mass * Biomass varies depending on season etc. * Some organisms feed on multiple trophic levels, e.g. omnivores

Answer 8

Energy from the Sun is the source of energy for nearly all life on Earth. Producers, such as green plants and algae, use energy transferred by light from the Sun to make food (glucose) during photosynthesis. Of the energy that hits these producers, **only about 1% is transferred for photosynthesis**. Some of the glucose is used by the plants and algae to make biological molecules. These biological molecules make up the plant's biomass - the mass of living material. Biomass stores energy. Biomass is transferred through a food chain in an ecosystem when organisms eat other organisms. However, not much biomass gets transferred from one trophic level to the next. In fact, **only about 10% of the biomass is passed on to the next level.**

Answer 9

* Organisms don't always eat every single part of the organism they're consuming. For example, some material that makes up plants and animals is inedible (e.g. bone). This means that not all the biomass can be passed to the next stage of the food chain. * Also some organisms die before they're eaten, so their remains are left to decay and their energy doesn't get passed along the food chain (instead the energy gets passed to the microorganisms that break down the remains).

Answer 10

Organisms don't absorb all of the stuff in the food they ingest (take in). The stuff that they don't absorb is egested (released) as faeces (poo). Some ingested biomass is converted into other substances that are lost as waste. For example, organisms use a lot of glucose (obtained from the biomass) in respiration to provide energy for movement and keeping warm, etc. rather than to make more biomass. This is especially true for mammals and birds, whose bodies must be kept at a constant temperature which is normally higher than their surroundings. This process produces lots of waste carbon dioxide and water as by-products. Urea is another waste substance, which is released in urine with water when the proteins in the biomass are broken down.

Answer 11

You can work out how much biomass has been lost at each level by taking away the biomass that is available at that level from the biomass that was available at the previous level. You can also calculate the efficiency of biomass transfer between trophic levels using this formula:

Answer 12

The distribution of some animal and plant species in the tropics changes between the wet and the dry seasons - i.e. the times of year where there is more or less rainfall, and so more or less water available. Example Each year in Africa, large numbers of giant wildebeest migrate, moving north and then back south as the rainfall patterns change.

Answer 13

The distribution of bird species in Germany is changing because of a rise in average temperature. Example The European bee-eater bird is a Mediterranean species but it's now present in parts of Germany.

Answer 14

The distribution of some species changes in areas where there is more air pollution. Example Some species of lichen can't grow in areas where sulfur dioxide is given out by certain industrial processes.

Answer 15

The water here on planet Earth is constantly recycled. Energy from the Sun makes water evaporate from the land and sea, turning it into water vapour. Water also evaporates from plants - this is known as transpiration. The warm water vapour is carried upwards (as warm air rises). When it gets higher up it cools and condenses to form clouds. Water falls from the clouds as precipitation (usually rain, but sometimes snow or hail) onto land, where it provides fresh water for plants and animals. It then drains into the sea, before the whole process starts again.

Answer 16

The whole carbon cycle is "powered" by photosynthesis. CO2 (carbon dioxide) is removed from the atmosphere by green plants and algae, and the carbon is used to make glucose, which can be turned into carbohydrates, fats and proteins that make up the bodies of the plants and algae.

Answer 17

Some of the carbon becomes part of the fats and proteins in animals when the plants and algae are eaten. The carbon then moves through the food chain. The energy that green plants and algae get from photosynthesis is transferred up the food chain. When plants, algae and animals die, other animals (called detritus feeders) and microorganisms feed on their remains. Animals also produce waste, and this too is broken down by detritus feeders and microorganisms.

Answer 18

Some carbon is returned to the atmosphere as CO2 when the plants, algae, animals (including detritus feeders) and microorganisms respire. Also CO2 is released back into the air when some useful plant and animal products, e.g. wood and fossil fuels, are burnt (combustion).

Answer 19

Where an organism is found is affected by environmental factors. An organism might be more common in one area than another due to differences in environmental factors between the two areas. Example - In a playing field, you might find that daisies are more common in the open than under trees, because there's more light available in the open and daisies need light to survive (they use it for photosynthesis - see page 165). There are a couple of ways to study the distribution of an organism: 1. You can measure how common an organism is in two or more sample areas using quadrats and compare them. 2. You can study how the distribution changes across an area, by placing quadrats along a transect (see pages 343-344). Both of these methods give quantitative data (numbers) about the distribution. The data you collect can be used to provide evidence for environmental change. For instance, if the distribution of organisms across an area changes over time, this could be due to changes in the environment.

Answer 20

* At warmer temperatures, enzymes involved in decomposition can work at a faster rate, increasing the rate of decay. * If the temperature is too high, these enzymes will denature and the rate of decay will decrease. * At low temperatures, the enzymes involved in decomposition work slowly, decreasing the rate of decay - this is why we keep food in a fridge.

Answer 21

* Oxygen is needed by many decomposers for aerobic respiration - without oxygen, they cannot survive. For these decomposers, the rate of decay decreases as oxygen availability decreases. * However, some microorganisms can respire anderobically (they don't require oxygen to survive), resul ting in anderobic decay (such as in biogas generators).

Answer 22

Decomposers require water to survive (water being essential for certain biological processes) - Many decomposers also function by secreting enzymes onto decaying biological matter and absorbing the products of this chemical digestion - without water these reactions cannot occur. Therefore, as water availability decreases, so does the rate of decay.

Answer 23

The more microorganisms and detritus feeders there are, the faster decomposition happens.

Answer 24

Compost is decomposed organic matter (e.g. food waste) that is used as a natural fertiliser for crops and garden plants. It recycles nutrients back into the soil giving you a lovely garden and improving crop growth. Farmers and gardeners try to provide the ideal conditions for quick decay to make compost. Compost bins recreate the ideal conditions for decay

Answer 25

Biogas is mainly made up of methane, which can be burned as a fuel. Lots of different microorganisms are used to produce biogas. They decay plant material and animal waste (e.g. faeces) anaerobically (without oxygen). This type of decay produces methane gas. Sludge waste from sewage works is used to make biogas on a large scale. Biogas is made in a simple fermenter called a digester or generator. Biogas generators need to be kept at a constant temperature to keep the microorganisms respiring away. Biogas can't be stored as a liquid (it needs too high a pressure), so it has to be used straight away for heating, cooking, lighting, or to power a turbine to generate electricity.

Answer 26

There are two main types of biogas generator - batch generators and continuous generators.

Answer 27

Batch generators make biogas in small batches. They're manually loaded up with waste, which is left to digest, and the by-products are cleared away at the end of each session. They don't have to be filled up as often as continuous generators, but they don't produce biogas at a steady rate.

Answer 28

Continuous generators make biogas all the time. Waste is continuously fed in, and biogas is produced at a steady rate. Continuous generators are more suited to large-scale biogas projects.

Answer 29

Whether a generator is big or small, or for batch or continuous use, it needs to have the following: * an inlet for waste material to be put in, * an outlet for the digested material to be removed through, * an outlet so that the biogas can be piped to where it is needed.

Answer 30

measure of the variety of all different species of organisms on Earth, or within a particular ecosystem Biodiversity ensures stability – reduces dependence on one species. If the number of one species reduces, it is less likely to have a huge impact on another

Answer 31

The increase in human population has had an enormous effect on our environment. The future for species on Earth depends on maintaining good biodiversity. Any human activities are reducing biodiversity. * More land is needed for building houses, shops, roads etc. This destroys habitats and reduces biodiversity * More land needs to be cleared (deforestation) for farming to produce food. This destroys habitats and reduces biodiversity of plant and animal species * We dig up land to make quarries to obtain rocks and metal ores. This reduces land available for organisms * Human waste pollutes the environment

Answer 32

As we make more and more things we produce more and more waste, including waste chemicals. And unless this waste is properly handled, more harmful pollution will be caused. Pollution affects water, land and air and kills plants and animals, reducing biodiversity.

Answer 33

* Farmers add fertilisers to their soils to make sure it is fertile year after year. These fertilisers have high mineral content, particularly nitrates. * These minerals are easily washed into streams, rivers or ponds. * These nitrates stimulate growth of algae and aquatic plants. They rapidly grow. * There is too much competition for light and many plants die. Any other plants trapped below the algal bloom can also die due to lack of light. * Microorganisms feed on the dead and decaying plants. * Microorganisms respire – using up a lot of oxygen * Larger organisms, e.g. some fish, do not have enough oxygen to respire so die * Microorganisms feed on the decaying animals – respire, use up more oxygen etc. * It is a vicious cycle until all aerobic organisms die.

Answer 34

* Toxic chemicals can be washed into waterways. These chemicals can bioaccumulate in food chains. Large organisms at the top of the food chain may die or fail to breed because of toxic build-up.

Answer 35

* Litter and waste can be dumped on the land. This can reduce the area within which an organism can live, or directly harm/kill a species * Landfill takes up room and destroys natural habitats * Toxic or hazardous chemicals from household or industrial waste can spread into the soil. E.g. post-Chernobyl nuclear accident, nuclear waste spread for thousands of miles. Lambs in Wales could not be sold for food as they had consumed radioactive grass. * Farmers increasingly use chemicals on their crops (pesticides, herbicides etc.). This can get into the soils and affect other plant life. These toxic chemicals can pass up a food chain. Higher trophic levels eat lots of ‘contaminated’ lower trophic levels so toxins can accumulate (bioaccumulation)

Answer 36

* Any sulphur impurities in the fossil fuels react with oxygen when they burn to form sulphur dioxide. * Sulphur dioxide can cause breathing problems if concentrations are too high. Sulphur dioxide and nitrogen oxides can dissolve in rain water and react with oxygen to form acid rain * Acid rain can kill leaves, buds etc. or soak into soil and destroy roots. * Acid rain can make water more acidic which can mean aquatic plants and animals cannot survive. * Acid rain travels – the effects are often experienced by the countries who do not produce it. * Many countries are using low-sulphur fuels e.g. gas (instead of coal) to reduce sulphur oxide emissions.

Answer 37

* Increases the amount of tiny solid particles (particulates) in the air. They reflect sunlight so less light hits the Earth – could lead to cooling effect, but also could limit photosynthesis * Particulates can damage the lungs/cardiovascular system if breathed in

Answer 38

The temperature of the Earth is a balance between the energy it gets from the Sun and the energy it radiates back out into space. Gases in the atmosphere naturally act like an insulating layer. They absorb most of the energy that would normally be radiated out into space, and re-radiate it in all directions (including back towards the Earth). This increases the temperature of the planet. It's called the greenhouse effect. If this didn't happen, then at night there'd be nothing to keep any energy in, and we'd quickly get very cold

Answer 39

There are several different gases in the atmosphere which help keep the energy in. They're called "greenhouse gases", and the main ones whose levels we worry about are carbon dioxide (CO₂) and methane - because the levels of these two gases are rising quite sharply. The Earth is gradually heating up because of the increasing levels of greenhouse gases this is global warming. Global warming is a type of climate change and causes other types of climate change, e.g. changing rainfall patterns.

Answer 40

glaciers are melting, sea levels are rising, habitats are being flood and destroyed, reducing biodiversity

Answer 41

as temperatures increase and rainfall patterns change, some animals may be able to extend their ranges. Others may find their range shrinks. They must migrate or die. Immigration f new species into new places could disrupt species interactions in the new habitat.

Answer 42

seasons will change due to change in climate, which could alter when/if some species migrate, e.g. birds. They may not be able to tell when the ‘right’ time to migrate is. This could alter breeding seasons etc.

Answer 43

Biodiversity could be reduced if some species are unable to adapt to a change in the climate, then they won't survive and the species will become extinct. For example, if it's too hot for them where they usually live but they can't survive in other habitats because there isn't the right food source, then they might die out.

Answer 44

The expanding human population means that we need more development. More development means that we need to use more land. Sometimes, the way we use land has a bad effect on the environment for example, if it requires deforestation or the destruction of habitats like peat bogs and other areas of peat. The four main human activities that do this are: * Building * Quarrying * Farming * Dumping waste

Answer 45

Deforestation is the cutting down of forests. This causes big problems when it's done on a large-scale, such as cutting down rainforests in tropical areas. It's done for various reasons, including:

Answer 46

1. Clear land to grow foods e.g. rice, palm oil 2. To rear more cattle, particularly beef 3. To grow crops that can be used to make biofuels based on ethanol, e.g. sugarcane or maize which can be fermented

Answer 47

* Burning trees to clear the land releases carbon dioxide directly. Any dead vegetation is then decomposed by decomposers that respire to release more carbon dioxide into the atmosphere * Trees can no longer remove carbon dioxide from the air by photosynthesis * Deforestation can directly kill animals/plants during the process or destroy their habitat, eventually leading to their extinction. This reduces biodiversity * Many undiscovered plants/animals may become extinct. We could be destroying sources of new medicine or food.

Answer 48

material made of plant material that cannot decay completely because conditions are very acidic and lack oxygen. They are huge stores of carbon.

Answer 49

Bogs are areas of land that are acidic and waterlogged. Plants that live in bogs don't fully decay when they die, because there's not enough oxygen. The partly-rotted plants gradually build up to form peat (a brown, soil-like material). So the carbon in the plants is stored in the peat instead of being released into the atmosphere.

Answer 50

Peat is often burnt as a fuel – releasing carbon dioxide into the air. Peat is also often removed to be used as fertiliser in gardens. This destroys it as a habitat in its natural environment. This becomes difficult because we need cheap and effective compost for food production, but the creation of it can destroy habitats Destruction of the peat bog contributes to global warming, but also destroys the habitat. Peat is formed very slowly, so the habitat is being destroyed far quicker than it can be generated.

Answer 51

Organisms that can tell us about the levels of pollution in an area by their presence or absence

Answer 52

Breeding programmes Protection and reintegration of rare habitats Reintroduction of field margins and hedgerows Reduction in deforestation and carbon emissions Recycling

Answer 53

Species are bred to increase numbers to avoid extinction They are then reintroduced into the wild

Answer 54

Rare and threatened habitats, e.g. coral reefs are becoming protected This prevents additional destruction and gives them time to regenerate Can charge a fee to enter protected areas – money can go towards conservation

Answer 55

Often cleared to make more land to grow crops, raise cattle etc. This destroys ‘green bridges’ / pathways between habitats Replanting them provides habitats and allows animals to move around the habitat Laws being put in place to prevent their removal. Farmers are being paid to replant

Answer 56

Quotas for home much deforestations can happen per year or how much carbon dioxide can be released by businesses per year. E.g. new car emissions policies

Answer 57

Reduce amount of waste going to landfill Reduces land pollution and protects habitats from being turned into landfill. Reusing rather than buying new also stops habitats being used for brand new resources

Answer 58

EXPENSIVE For our current standard of living, we need to exploit natural resources, e.g. mine for metals to make mobile phones Some developing countries rely on the environment more, e.g. cutting down trees for cooking on a fire. Reducing ‘deforestation’ could make their lives impossible

Answer 59

* Biological factors which are threatening food security include: * the increasing birth rate has threatened food security in some countries * changing diets in developed countries means scarce food resources are transported around the world * new pests and pathogens that affect farming * environmental changes that affect food production, such as widespread famine occurring in some countries if rains fail * the cost of agricultural inputs * conflicts that have arisen in some parts of the world which affect the availability of water or food.

Answer 60

* Reduces movement – kept in a restricted environment so less energy spent on movement so more biomass available for growth * Controlled temperature – less energy from respiration spent on thermoregulation so leaves more biomass for growth (need to burn fossil fuels for this?) * Direct provision of food – less energy spent moving to find food / ‘hunting’ so leaves more biomass for growth * Generation of ‘bigger’ (more muscle) organisms so can sell for a greater profit * Keep more individuals in a smaller space * Given high protein diet (to increase growth) – but can be more expensive

Answer 61

* Issue of spread of disease if all closely packed – need to use antibiotics. Could lead to resistance or accumulate in the food chain * Ethical issues!

Answer 62

Overfishing (catching too many fish) is reducing fish stocks in the oceans. This means there's less fish for us to eat, the ocean's food chains are affected and some species of fish may disappear altogether in some areas - for example, cod are at risk of disappearing from the north west Atlantic. To tackle this problem, we need to maintain fish stocks at a level where the fish continue to breed. This is sustainable food production. Fish stocks can be maintained (conserved) in several ways.

Answer 63

There are limits on the number and size of fish that can be caught in certain areas. This prevents certain species from being overfished.

Answer 64

There are different limits of the mesh size of the fish net, depending what's being fished. This is to reduce the number of 'unwanted' and discarded fish - the ones that are accidently caught, e.g. shrimp caught along with cod. Using a bigger mesh size will let the 'unwanted' species escape. It also means that younger fish will slip through the net, allowing them to reach breeding age.