Ecology Ecology is the study of interactions between organisms and their environment.

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1 Ecology

2 Ecology Ecology is the study of interactions between organisms and their environment. Population ecology Community ecology Ecosystem ecology

3 Ecology vs. Environmentalism Ecology - the study of interactions between organisms and their environment Population Ecology relationship between members of a species Community Ecology the study of groups of populations Ecosystem Ecology the study of the structure and function of physical, chemical and biological components of the environment Environmentalism - the practical application by humans of this understanding. Not all environmentalists are ecologists.

4 General Model of Nutrient Cycling

5 Nitrogen Cycle Nitrogen is 78% of the atmosphere, in gaseous form N 2. It has to be transformed into a usable form for all organisms to use. Nitrogen fixing bacteria make NH 3 from N 2 and may produce organic compounds with nitrogen, or excrete it. Other bacteria make nitrite and nitrate (NO3) from NH 4 Denitrifying bacteria convert nitrate to N 2 for release back into the atmosphere.

6 Nitrogen cont Nitrogen is also a component of fertilizers. High ammonia or nitrates in a stream or pond means there is probably some nutrient source flowing into it, such as animal waste or fertilizer. Plants and animals need it to make proteins and enzymes.

7 Nitrogen Cycle

8 Phosphorous The major source of phosphorous in the ecosystem is the weathering of rocks. Organisms use phosphorous for phospholipids in cell membranes, nucleic acids, and ATP and in mineral form for bones. Plants pick up dissolved phosphorous from soil and use it in cells and as energy.

9 Phosphorous cont Decomposers return phosphate to the soil by decomposition of detritus. People put lots of phosphate in the soil when they apply fertilizers. If it is applied too heavily or at the wrong time, much of it runs off into the streams and causes algal blooms.

10 Phosphorus Cycle

11 Dissolved Oxygen Dissolved oxygen levels are an important indicator of the health of ponds or streams. Low dissolved oxygen usually is from low flow and/or high bacterial communities. An areator was installed in the our fish tank to increase dissolved oxygen levels and to keep the fish tank from going anaerobic. WHY?

12 Typical levels Phosphorous levels: <0.1ppm, usually ppm Silica 0-75 ppm Ammonia and nitrate <10 ug/l = normal Nitrates <0.1 to 6 mg/l (produced by ammonia breakdown) Hardness (sum of calcium and magnesium) ranges from mg/l. Dissolved oxygen 8-9 mg/l = saturation

13 Exponential and Logistic Growth Curves

14 Human population growth

15 Carrying Capacity K K is the maximum population that a specific environment can support. Factors affecting carrying capacity include: Nutrient availability Energy Water Nesting sites if animals Sunlight for plants Predators space

16 Exponential Growth dn/dt = rn dn/dt is pop. growth rate Looking at population size during exponential growth we use N t = N o e rt So if we have 10 duckweeds growing for 4 days and r (rate of growth) is 0.2 then: N 4 = 10 x e (0.2x4) = 10 X 2.22 or 22.2 duckweeds after 4 days

17 To determine the intrinsic rate of growth: r = ln(n t /N o ) t In the last example r = ln(22.2/10) 4 r = or 0.2

18 Logistic Growth dn/dt = r max N (K-N) K Where dn is change in population t is time and dt is change in time dn/dt is the population growth rate K is carrying capacity K-N is # of extra individuals an environment can sustain (effect of crowding or environmental resistance) r max is exponential rate of increase (K-N)/K is part of K available for population growth

19 Logistic Growth cont. If N is small (K-N)/K is close to 1 and population growth is rapid If N is large, (K-N)/K population growth is slow If N = 5 and K = 50 and r =1 we have 1x50x(50-5)/50 =4.5 =dn/dt If N = 45, 1x50x(50-45)/50 = 0.5 = dn/dt

20 Limitations to growth Resource availability Sunlight Space Nutrients Pollinators Proper environment for growth

21 Competition Competition between species may be for Space Sunlight Nutrients

22 Lemna minor - Duckweed

23 Lemna minor A very good food source for waterfowl and fish. Used in wastewater treatment because of their ability to absorb excess nutrients such as phosphorus and NH 4. Also reduces BOD.

24 Salvinia

25 Salvinia An aquatic fern that is a pest species Reproduces only by vegetative reproduction. Forms thick mats that damage to irrigation equipment, fencing, and boat engines. Thick mats can trap and drown children and livestock and can cause stagnation of water.