3.5.1.1 - agrosystems - the biotic factors that affect productivity

what are the biotic factors that affect productivity?

- predators
- competitors
- pathogens
- fungi
- weeds
- bacteria

how do pests reduce productivity?

- carry pathogens
- compete for resources
- be predators
- be pathogens
- reduce marketability

what problems do weeds cause?

- compete for nutrients, water and light e.g wild oats

- harvested with the crop which reduces quality

- provide food for pests

- parasitism of crop roots

what problems do insects cause?

- eat the crop

- spoil the appearance of the crop

- act as vectors and spread pathogens e.g aphids carry many pathogenic diseases like potato blight

what problems do fungi cause?

cause the growing plants or harvested crop to rot e.g leaf smut of rice and leaf blight of sugarcane

what problems do bacteria cause?

reduce harvests by causing disease e.g bacterial lead blight of wheat

what problems do molluscs cause?

eat the crop, reduce harvests or spoil appearance e.g many snails or slugs

what problems do nematode worms cause?

- damage roots and reduce water and nutrient uptake

- increase risk of fungi and bacterial disease

- e.g potato cyst and soybean cyst

what problems do vertebrates cause?

eat the growing or harvested crop e.g sparrows

what is an endemic pest?

one that is always present but in small or moderate numbers

what is an epidermic pest?

one that is not usually present but there may be outbreaks where they rapidly become a major problem

what is an indigenous species?

native to the are where they are found

what is an introduced species?

nonnative species that are either intentionally or unintentionally transported to a new habitat