biology paper 2 advanced information Flashcards
need to do: 4.7.2 organisation of an ecosystem, 4.7.3 Biodiversity and the effect of human interaction on an ecosystem, required practical)
what do food chains always start with?
a producer - producers make their own food using energy from the Sun. Producers are usually green plants or algae - they make glucose by photosynthesis
what is the biomass of the plant?
the mass of living material - biomass can be thought of as energy stored in a plant
what is glucose used for after a green plant produces it?
some of it is used to make other biological molecules in the plant. These biological molecules are the plant’s biomass - the mass of living material
what will happen in a stable community containing prey and predators?
- 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, which therefore eventually causes the population of the predator to decrease
- However this allows the population of the prey to increase, and the cycle starts again
- 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 other populations. 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
how is energy transferred through living organisms?
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
what is the distribution of an organism? What is it affected by?
where an organism is found - this 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
give two ways to study the distribution of an organism. What kind of data do these methods give?
- by measuring how common an organism is in two sample areas (e.g. using quadrats) and compare them
- by studying how the distribution changes across an area, e.g. by placing quadrats along a transect
both of these methods give quantitative data (numbers) about the distribution
what is a quadrat?
a square frame enclosing a known area, e.g. 1m^2
what are 2 ways to study the distribution of an organism?
- measuring how common an organism is in two sample areas (e.g. using quadrats) and compare them
- study how the distribution changes across an area, e.g. by placing quadrats along a transect
what type of data do quadrats give about the distribution of organisms?
quantative data (numbers)
what is a quadrat?
a square frame enclosing a known area, e.g. 1 m^2
how would you use quadrats to compare how common an organism is in two sample areas (e.g. shady and sunny spots in a playing field)
- place a 1m^2 quadrat on the ground at a random point within the first sample area. E.g. divide the area into a grid and use a random number generator to pick coordinates
- count all the organisms within the quadrat
- repeat steps 1 and 2 as many times as you can
- work out the mean number of organisms per quadrat within the first sample area
- repeat steps 1 to 4 in the second sample area
- finally compare the two means.
what does “abundance” mean?
the population size of an organism
how can you work out the population size of an organism in one area?
- work out the mean number of organisms per m^2
2. multiply the mean by the total area (in m^2) of the habitat
what can we use transects for?
to help find out how organisms (like plants) are distributed across an area - e.g. if an organism becomes more or less common as you move from a hedge towards the middle of a field
how can we use transects to help find out how organisms (like plants) are distributed across an area?
- mark out a line in the area you want to study using a tape measure
- then collect data along this line
- you can do this by just counting all the organisms you’re interested in that touch the line
- or, you can collect data by using quadrats. These can be placed next to each other along the line or at intervals, e.g. every 2 m
why might you want to work out the percentage cover of an organism in a quadrat?
if it’s difficult to count all the individual organisms in the quadrat (e.g. if they’re grass) it might be easier to work out the percentage cover
what does it mean to calculate the percentage cover?
estimating the percentage area of the quadrat covered by a particular type of organism, e.g. by counting the number of little squares covered by the organisms
how do you work out the percentage cover of an organism?
- count the number of small squares in a quadrat covered by the organism
- make this into a percentage - divide the number of squares covered by the organism by the total number of squares in the quadrat, and then multiply the result by 100
what is a transect?
a line used to help find out how organisms are distributed across an area
how could you estimate the number of organisms in a quadrat, if they are difficult to count?
by working out the percentage cover
what are the 8 stages of the water cycle?
- 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
- some of this water is absorbed by the soil and is taken up by plant roots. This provides plants with fresh water for things like photosynthesis. Some of the water taken up by plants becomes part of the plants’ tissues and is passed along to animals in food chains
- like plants, animals need water for the chemical reactions that happen in their bodies. Animals return water to the soil and atmosphere through excretion (processes that get rid of the waste products of chemical reactions, e.g. sweating, urination and breathing out)
- water that doesn’t get absorbed by the soil will runoff into streams and rivers
- from here, the water then drains back into the sea, before it evaporates all over again
how are elements cycled back to the start of the food chain by decay?
- living things are made of materials they take from the world around them. E.g. plants turn elements like carbon, oxygen, hydrogen and nitrogen from the soil and the air into the complex compounds (carbohydrates, proteins and fats) that make up living organisms. These get passed up the food chain
- these materials are returned to the environment in waste products, or when the organisms die and decay
- materials decay because they’re broken down (digested) by microorganisms. This happens faster in warm, moist, aerobic (oxygen rich) conditions because microorganisms are more active in these conditions
- decay puts the stuff that plants need to grow (e.g. mineral ions) back into the soil
- in a stable community, the materials that are taken out of the soil and used by plants etc. are balanced by those that are put back in. There’s a constant cycle happening
what is the constant cycling of carbon called?
the carbon cycle
what are the 8 stages of the carbon cycle?
- CO2 is removed from the atmosphere by green plants and algae during photosynthesis. 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
- when plants and algae respire, some carbon is returned to the atmosphere as CO2
- when the plants and algae are eaten by animals, some carbon becomes part of the fats and proteins in their bodies. The carbon then moves up the food chain
- when the animals respire, some carbon is returned to the atmosphere as CO2
- when plants, algae and animals die, other animals (called detritus feeders) and microorganisms feed on their remains. When these organisms respire, CO2 is returned to the atmosphere
- animals also produce waste that is broken down by detritus feeders and microorganisms
- the combustion of wood and fossil fuels releases CO2 back into the air
- so the carbon (and energy) is constantly being cycled - from the air, through food chains (via plants, algae and animals, and detritus feeders and microorganisms) and eventually back out into the air again
what happens to the energy that green plants and algae get from photosynthesis?
it is transferred up the food chain
what is biodiversity?
the variety of different species of organisms on Earth, or within an ecosystem
why is high biodiversity important?
it makes sure that ecosystems are stable because different species depend on each other for things like shelter and food. Different species can also help to maintain the right physical environment for each other (e.g. the acidity of the soil). For the human species to survive, it’s important that a good level of biodiversity is maintained
name three human actions that are reducing biodiversity
- deforestation
- global warming
- waste production
why is the global population rising?
mostly because of modern medicine and farming methods, which have reduced the number of people dying from disease and hunger
why are our actions having a far more widespread effect in modern times?
- our increasing population puts pressure on the environment, as we take resources we need to survive
- but people around the world are also demanding a higher standard of living (and so demand luxuries to make life more comfortable - cars, computers, etc.). So we use more raw materials (e.g. oil to make plastics), but we also use more energy for the manufacturing processes. This all means we’re taking more and more resources from the environment more and more quickly
- unfortunately, many raw materials are being used up quicker than they’re being replaced. So if we carry on like we are, one day we’re going to run out
- we’re also producing more waste
what effect does our increasing population have on waste production? why is this important?
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
how is water affected by our waste?
sewage and toxic chemicals from industry can pollute lakes, rivers and oceans, affecting the plants and animals that rely on them for survival (including humans). And the chemicals used on land (e.g. fertilisers, pesticides and herbicides) can be washed into water
how does our waste pollute the land?
we use toxic chemicals for farming (e.g. pesticides and herbicides). We also bury nuclear waste underground, and we dump a lot of household waste in landfill sites
how does our waste affect the air?
smoke and acidic gases released into the atmosphere can pollute the air, e.g. sulfur dioxide can cause acid rain
what is the temperature of the Earth a balance between? How is this balance maintained?
- 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.
- if this didn’t happen, then at night there’d be nothing to keep any energy in, and the earth would quickly get too cold.
which two gases are causing the main problems for global warming? Why do we have to worry about these gases in particular?
the main greenhouse gases we have cause for concern over are carbon dioxide (CO2) and methane - because the levels of these two gases are rising sharply
what is global warming?
global warming is a type of climate change in which the Earth is gradually heating up because of the increasing levels of greenhouse gases. Global warming can cause other types of climate change, e.g. changing rainfall patterns
what could be some of the consequences of climate change?
- Higher temperatures cause seawater to expand and ice to melt, causing the sea level to rise. It has risen a small amount over the last 100 years. If it keeps rising it will cause many problems for people and animals living in low-lying places. It will lead to flooding, resulting in the loss of habitats (where organisms live)
- The distribution of many wild animal and plant species may change as temperatures increase and the amount of rainfall changes in different areas. Some species may become more widely distributed, e.g. species that need warmer temperatures may become less widely distributed, e.g. species the need warmer temperatures may spread further as the conditions they thrive in exist over a wider area. Other species may become less widely distributed, e.g. species that need cooler temperatures may have smaller ranges as the conditions they thrive in exist over a smaller area.
- there could be changes in migration patterns, e.g. some birds may migrate further north, as more northern areas are getting warmer
- Biodiversity could be reduced if some species are unable to survive a change in the climate, so become extinct.
why might programmes be set up to protect ecosystems and biodiversity?
it’s important that biodiversity is maintained at a high enough level to make sure that ecosystems are stable - in some areas, programmes have been set up by concerned citizens and scientists to minimise damage by human activites to ecosystems and biodiversity
give some examples of programmes that have been set up to minimise damage by human activities
- Breeding programmes have been set up to help prevent endangered species from becoming extinct. These are where animals are bred in captivity to make sure the species survives if it dies out in the wild. Individuals can sometimes be released into the wild to boost or re-establish a population.
- programmes to protect and regenerate rare habitats like mangroves, heathland and coral reefs have been started. Protecting these habitats helps to protect the species that live there - preserving the ecosystem and biodiversity in the area
- there are programmes to reintroduce hedgerows and field margins around fields on farms where only a single type of crop is grown. Field margins are areas of land around the edges of fields where wild flowers and grasses are left to grow. Hedgerows and field margins provide a habitat for a wider variety of organisms than could survive in a single crop habitat
- some governments have introduced regulations and programmes to reduce the level of deforestation taking place and the amount of carbon dioxide being released into the atmosphere by businesses. This could reduce the increase of global warming
- people are encouraged to recycle to reduce the amount of waste that gets dumped in landfill sites. This could reduce the amount of land taken over for landfill, leaving ecosystems in place/
give some conflicting pressures that have to be taken into account when trying to maintain biodiversity
- protecting biodiversity costs money. For example, governments sometimes pay farmers a subsidy to reintroduce hedgerows and field margins to their land. It can also cost money to keep a watch on whether the programmes and regulations designed to maintain biodiversity are being followed. There can be conflict between protecting biodiversity and saving money - money may be prioritised for other things
- Protecting biodiversity may come at a cost to local people’s livelihood. For example, reducing the amount of deforestation is great for biodiversity, but the people who were previously employed in the tree-felling industry could be left unemployed. This could affect the local economy if people move away with their family to find work
- there can be conflict between protecting biodiversity and protecting our food security. Sometimes certain organisms are seen as pests by farmers (e.g. locusts and foxes) and are killed to protect crops and livestock so that more food can be produced. As a result, however, the food chain and biodiversity can be affected
- Development is important, but it can affect the environment. Many people want to protect biodiversity in the face of development, but sometimes land is in such high demand that previously untouched land with high biodiversity has to be used for development, e.g. for housing developments on the edge of towns, or for new agricultural land in developing countries
what are hormones?
chemical molecules released directly into the blood - they are chemical messengers sent in the blood
where are hormones carried to in the blood, and what do they effect?
they are carried in the blood to other parts of the body, but only affect particular cells in particular organs (called target organs)
