ecology

describe the stages of the carbon cycle

carbon from atmosphere into living things (eg plants take in carbon dioxide for photosynthesis, co2 dissolved in seawater)

carbon transferred between living things (eg plants eaten by animals)

carbon returned to atmosphere by living things (decomposition and respiration)

carbon returned to atmosphere by other means (eg burning of fossil fuels, forest fires)

what is decomposition?

respiration by microbes

how do plants use water?

transport dissolved substances in the phloem

needed for photosynthesis

keep cells turgid

how do animals use water?

transport dissolved substances

makes up cytoplasm (where chemical reactions take place)

how does deforestation affect the carbon cycle?

plants take in water from the soil via their roots

they then release water vapour into the atmosphere through transpiration (loss of water vapour from stomata)

if plants are removed, less water vapour is returned to the atmosphere. This means less precipitation (rainfall)

can increase surface run off → flooding

food chain

flow diagram showing feeding relationships in an ecosystem

producer

organism that makes its own food, eg green plants

primary consumer

organism that feeds on producers

herbivore

animals that feed on plants

carnivore

animal that feeds on other animals

trophic levels

different feeding levels in a food chain

tertiary consumer

organism that feeds on secondary consumers

quaternary consumer

organism that feeds on tertiary consumers

food web

diagram showing the way in which food chains are linked together in an ecosystem

pyramid of numbers

diagram in which blocks making up a pyramid represent the total numbers of organisms at each trophic level

pyramid of biomass

diagram in which blocks making up a pyramid represent the total mass of organisms at each trophic level

what is nitrogen used for?

make amino acids

amino acids used to make protein

protein needed for growth and repair of tissues

make DNA

where does nitrogen come from?

the air, however we can’t take it in directly, we get it from eating and digesting plants. Plants get it from taking it in from soil through root hair cells by active transport

describe the nitrogen cycle

Nitrogen gas in atmosphere → nitrogen-fixing bacteria convert it into nitrogen compounds in soil → plants absorb nitrogen compounds and make proteins → animals obtain nitrogen by feeding → dead organisms and waste are broken down by decomposers → nitrogen compounds returned to soil → nitrifying bacteria convert them to nitrates → plants absorb nitrates → denitrifying bacteria convert nitrates back to atmospheric nitrogen.

why do we lose energy at each part of the food chain?

some is used in respiration (energy to move)

not all of the producer (plant) can be digested

the primary consumer’s body isn’t all broken down

some used in homeostasis

some excreted

how can farmers reduce energy loss in their animals?

keeping them in smaller areas (reduce movement)

feeding them high protein food

keeping them indoors

habitat

a part of an ecosystem where a specific organism lives

population

all of the organisms of one species living in the same habitat

community

all of the different organisms/species that live in the same place at the same time

ecosystem

a system of organisms interacting with each other and their physical environment

biodiversity

the range/variety of organisms living in a habitat

niche

the role that each organism plays in the ecosystem

biomass

the mass of living material in the organism (bones. tissues, cells etc) excluding water

how do you calculate biomass?

find out the average dry mass of one individual multiplied by the number of individuals living in a given area

describe the process of eutrophication

increased fertiliser use in soil

high rainfall washes fertiliser into waterways

increased nitrates in water stimulates plant growth

increased plant death means more decomposers/microorganisms

decreased oxygen concentration as oxygen is used by microbes (increased BOD)

increased death of aquatic organisms

describe the method for random sampling

use a random number generator to generate coordinates and place a 1m2 quadrat on the ground in the first sample area

count all of the organisms we’re interested in

repeat multiple times (minimum 10, ideally much more)

work out mean number of organisms per quadrat within the first sample area

repeat process with second sample area

compare the two means

how do you use belt transects to study distribution across a habitat?

mark out a line in the area you want to study (eg from a hedge to middle of field)

collect data along the line using quadrats placed next to each other. If the transect is quite long, you could place the quadrats at regular intervals (eg every 2 metres) instead.

count the organisms of species you’re interested in (or estimate percentage cover)

you could also record other data, such as mean height of plants or the abiotic factors in each quadrat (eg using a light meter to measure light intensity)

repeat several times, then find mean number of organisms 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

explain how deforestation affects leaching

trees take up nutrients from the soil before they can be washed away (leached) by the rain, but return them to the soil when leaves die

when trees are removed, nutrients get leached away, but don’t get replaced, leaving infertile soil