Chapter 2: Principles of Ecology

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Energy pyramid • Every time an organism eats, it obtains energy from its food • So energy is transferred from the 1 st trophic level to the 2 nd trophic level to the 3 rd trophic level and so on. • Some of this energy is lost along the way during an organism’s metabolism and as heat • Energy pyramid: picture showing how much energy is transferred to the different trophic levels in a food chain 4 Trophic Level 4 th Tertiary consumers Energy Available 10 kcal/m 2 /year 2 nd Primary consumers 1 st Producers 3 rd Secondary consumers 100 kcal/m 2 /year 1000 kcal/m 2 /year 10,000 kcal/m 2 /year
Food web • A network of connected food chains • More realistic than a food chain because most organisms feed on more than one species for food 5 Limiting Factors There is only a limited amount of resources (water, oxygen, nitrogen, carbon) on the earth Carrying capacity – number of organisms of 1 species that an environment can support Populations increase below the carrying capacity Population decrease above the carrying capacity Limits of the environment Reproductive patterns Example: Mosquitoes reproduce rapidly, and Elephants reproduce very slowly Density Dependent Factors – the more dense, the more it spreads o Disease – spreads in a tighter community o Competition – more people, the more competition o Parasites o Food Density Independent Factors – affect all populations regardless of their density o temperature o storms o floods o drought o habitat disruption o pollution Predation – when predators eat the prey, the prey decreases, but can this decrease the predator population as well? Crowding – when populations become crowded, stress of the animal increases, it can become very aggressive, decrease its parental care, decrease its fertility, and resistance to disease decreases
Page 1 and 2: Chapter 18:Ecology Notes Ecology S
Page 3: Bacteria Food Chains Trophic levels
Page 7 and 8: Nitrogen Cycle 7 1. Nitrogen fixati
Page 9: Oxygen-Carbon Cycle 9 1. Carbon dio

Chapter 2: Principles of Ecology

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