5.3 Population TODAY: In your blog: how do living organism affect the abiotic environment during succession? Feedback distributer: Maria L. ANNOUCEMENT: 1. Test – October 11

G2.8 Interactions with organism and the environment Soils become deeper as a result of decay of plants Allows well-draining soil Organic matter (humus) in soil increases as a result of decay of plants Organic matter quickly absorbs and releases water so is a good medium for plant growth Mineral recycling increases bacteria and fungi become more active in soils that have high organic matter Soil erosion reduces plant roots that stabilize the sand Minerals added Alder plants fix atmospheric nitrogen which leads to increase of nitrogen in the soil Organic matter

7 billion people and growing National geographic celebrates 7 billionth person on October 31, 2011 Need 1.5 Earths to support current growing population 19th century: agricultural revolution increase food production, industrial revolution improved method of transporting food 20th century: advance in medicine, sanitation and nutrition http://breathingearth.net/

Logistic growth Q 6, 7, 8 Population growth Add this question at the end: List three abiotic or biotic factors which set limits to population increase

5.3.4 What sets a limit to population increase? density-dependent, biotic factors mortality due to disease mortality due to predation intraspecific competition density-independent, abiotic  factors mortality due to weather mortality due to natural disasters: fire, hurricane, floods, earthquakes

5.3.2 – 5.3.3 Logistic growth curve Exponential growth phase Species doubles per unit time No limiting factors: nutrients, oxygen, space in ample supply Transitional phase Population growth continues but at a slower rate Limiting factors slow growth rate: nutrients, oxygen, space in short supply Plateau phase Population growth slows to zero Limiting factors inhibit population growth: nutrients, oxygen, space in short supply Carrying capacity (K) = maximum number of individuals in a species that can sustainably be supported in an environment

5.3.1 Factors affecting population size Natality: birth rate Immigration: rate at which individuals move into a population Mortality: death rate Emigration: rate at which individuals move out of the population P = (N + I) – (M + E)

Logistic growth curve Exponential growth phase Transitional phase N + I > M + E Transitional phase Plateau phase N + I = M + E

7 billion people and growing National geographic celebrates 7 billionth person on October 31, 2011 Need 1.5 Earths to support current growing population 19th century: agricultural revolution increase food production, industrial revolution improved method of transporting food 20th century: advance in medicine, sanitation and nutrition http://breathingearth.net/