IGCSE BIO 20. human influences on ecosystems

ways to increase food production

agricultural machinery, chemical fertilisers, herbicides and insecticides, selective breeding

monoculture

cultivation of single variety of crop plants in a large area

advantages of monoculture

more yield per unit area, more efficient sowing and harvesting & selling for farmer

disadvantages of monoculture

soil erosion, reduces biodiversity due to usage of insecticides, deforestation, loss of nutrients in soil, loss of habitat, disruption of food chains

features of intensive livestock production

large numbers in small areas, high energy food, regular medications to increase yield, temperature controlled barns to maximize growth rates

advantages of intensive livestock production

efficient production of food, enables cheaper supply of food, more land left for animal habitat

disadvantages of intensive livestock production

suffering of animals, easy spreading of disease, wastes and polluted lands and water, not energy efficient

biodiversity

number of different species that live in an area

reason of habitat destruction

land requirements, extraction of resources, pollution

effect of increased CO2 level in atmosphere

global warming

effect of fewer trees

less transpiration so drier air, less oxygen

sources of CO2

burning of fossil fuels, present in larger amount

sources of methane

from methanogenic bacteria in cows and landfills, stronger effect

process of greenhouse effect

solar radiation hits the earth → earth re-emits radiation with longer wavelength → greenhouses gases absorb those radiation again

effect of climate change

polar ice melting leading to rise in sea levels, extinction of species, changes in rainfall patterns, changes in distribution of species

advantage of increase in concentrations of greenhouse gases

increased rate of photosynthesis, increasing crop production

process of eutrophication

fertilizers leak into river, increasing nitrate ions → growth of producer algae → after death of producers, increase in decomposition → uses up more oxygen by increase in aerobic respiration → reduction in dissolved oxygen in river → death of organisms due to suffocation

prevention of eutrophication

use less and correct amount of fertiliser, use slow-release fertiliser, do not user fertiliser when raining, do not use it near water, only apply when crops are growing

effect of non-biodegradable plastics

visual pollution, loss of biodiversity, release of toxic gases when burnt

sustainable resource

one which is produced as rapidly as it is removed from the environment, so that it does not run out

why should we conserve ecosystems, habitats and species?

to maintain biodiversity, to reduce extinction, to protect vulnerable ecosystems, to maintain ecosystem functions, to prevent natural disasters, to allow eco-tourism, ethical reasons, aesthetic reasons

how to conserve forests

quotas : not cutting down all trees, education about importance of this, replanting, coppicing : cutting down 1m or less

how to conserve fish stocks

creating no catch zones, controlling size and type of nets, restrictions of fishing in certain seasons, restocking by captive breeding, education

how to conserve endangered species

monitoring and protecting species and habitats, education, captive breeding programs, seed banks

techniques to increase number of organisms in endangered species?

artificial insemination, in vitro fertilisation