 Competition D. Crowley, 2008

Competition  To understand what competition is, and how this may affect the numbers of organisms in a community Monday, July 11, 2016

Ecological Terms - Anagrams  Step – an animal that damages crops, competing with humans for food  Oxnit – a poisonous chemicals  Dwee – a plant growing in the wrong place, competing with a crop  Rfretisile – a chemical added to the soil, providing plants with minerals and salts needed for growth  Porc – a plant grown to be of use by humans  Ciideerbh – a chemical used to kill weeds  Psicieted – a chemical used to kill pests Pest Toxin Weed Fertiliser Crop Herbicide Pesticide

Numbers  What factors will affect the numbers of organisms in a habitat (the place where an organism lives)?  Organisms in a community compete for the resources there – they are in competition with each other  Animals compete for: -  Food  Water  Space

Numbers  Plants compete for: -  Light  Water  Space  Minerals (within the soil)  The number of predators or prey affect the number of organisms  Disease also affects the number of organisms in a habitat

Competition  Organisms compete with each other for available resources in order to survive  Animals and plants that get more of these resources are more successful than animals or plants that get fewer of them  These successful animals and plants are more likely to survive to reproduce, so the size of their population is likely to increase

Pyramids  Look at the following pyramid of number (how many organisms there are) and biomass (how much biological material there is): - Pyramid of biomassPyramid of number Pear tree Aphids Ladybirds Partridge  Draw these out in your book…

Pyramids - Pesticide  What would happen to these if we added some pesticide which killed aphids? Pyramid of biomassPyramid of number Pear tree Aphids Ladybirds Partridge

Pyramids – Pesticide Introduced  If many of the aphids were killed then fewer ladybirds would survive (they have less to eat) which also reduces partridge numbers Pyramid of biomassPyramid of number Pear tree Aphids Ladybirds Partridge

Pyramids - Predator  What would happen to these if we added a natural predator to the partridge, e.g. a hawk? Pyramid of biomassPyramid of number Pear tree Aphids Ladybirds Partridge

Pyramids – Hawk Introduced  The hawk would predate the partridge, allowing the ladybird numbers to increase, which would eventually eat more aphids Pyramid of biomassPyramid of number Pear tree Aphids Ladybirds Partridge  What would happen if all the aphids were eaten?

Cycles  The population of a species is usually limited by the amount of resources available  If the population of the prey increases so will the population of the predators, however as the predator population increases the number of prey will decrease… Time Population Rabbits Foxes More grass = more rabbits More rabbits = more foxes More foxes = less rabbits Eventually less rabbits = less foxes etc… A peak in rabbit numbers is followed by a peak in fox numbers

Biological Control  Pesticides can have unwanted side effects (such as DDT) – instead of chemicals we can use biological control  A natural predator can be introduced which eats the pest, reducing their numbers allowing for increased crop production  However, you need to ensure the predator does not become a pest itself – e.g. does the predator eat useful insects as well as the pest?