Biology Human influences GCSE

Explain acid rain

Fossil fuels containing sulphur impurities are burnt + dissolved in rain

Effects of acid rain on living organisms - direct + indirect

direct - damages cells and tissue in plants (reducing photosynthesis), denatures enzymes, damages lung tissue, skin damage in frogs

indirect - mineral ions dissolve more easily in water, mineral ions e.g. nitrates may be washed away

3 factors that cause eutrophication

Nitrates/ phosphates in fertiliser

Phosphates from washing powder

Sewage

NAPDOD

N - nitrates/phosphates are leeched + washed into waterways

A - algae bloom forms

P - photosynthesis stops as light can’t reach bottom of lake

D - decomposition of plants by bacteria/fungi

O - oxygen used up by aerobically respiring bacteria makes water anoxic

D - death of fish

Advantages + disadvantages of pesticides

e.g DDT

good - increase crop yield, quick, doesn’t disbalance ecosystems

bad - bioaccumulation, short term, can kill wrong insects

Advantages + disadvantages of biological control

e.g ladybugs for aphid

good - don’t need to reapply, no bioaccumulation, does not impact food chains

bad - can become pest themselves if non-native

Define bioaccumulation

Occurs when pesticides given to plants are ingested by animals + so toxins make there way up the foodchains

Explain greenhouse effect

short wave radiation e.g. UV hits earth from sun

Some is absorbed + some is re-emitted as long wave radiation e.g. infrared

Greenhouse gases reflect long wave radiation back to earth which would otherwise escape into atmosphere

Greenhouse gases therefore trap heat in atmosphere + therefore contribute to global warming

Effects of deforestation on soil

Soil erosion is when soil is washed away due to rain when there are less plants to hold onto soil

Leads to leeching + desertification

effects of deforestation balance of co2 / o2

o2 decreases —> less trees = less photosynthesis = less o2 released

co2 increases —> less trees = less photosynthesis = less co2 absorbed

combustion of cut trees = more co2 released

effects of deforestation on evapotranspiration

evapotranspiration is water evaporation from surface of earth + plants. Re-falls as rain

Less plants = less evapotranspiration = drier climates

causes + effects of deforestation

causes - fuel, paper, farming, infrastructure, forest fires, economic opportunities

effects - habitat loss, extinction, more co2, global warming, flooding, more methane released