Your questions…your review

Your questions…your review

The Nitrogen Cycle 78% of the troposphere is composed of

nitrogen gas. Nitrogen is an important element for the

making of proteins, nucleic acids, and vitamins.

Processes convert nitrogen gas into compounds that can be used in the food webs:

Atmospheric electrical discharge makes nitrogen and oxygen gases react to form nitrogen oxide.

Specialized bacteria fix nitrogen gas into ammonia to be used by plants (nitrogen fixation).

Ammonia not used by plants may go through nitrification to form nitrite ions (toxic to plants) and nitrate ions (easily taken up by plants).

After nitrogen fixation and nitrification… Plant roots absorb these dissolved substances

called assimilation and use them to form DNA and proteins. Animals consume nitrogen through plants or plant-eating animals.

In ammonification, decomposer bacteria convert waste into simpler nitrogen-containing compounds such as ammonia and water-soluble salts containing ammonium ions.

Nitrogen returns to the atmosphere through denitrification by converting ammonia and ammonium ions into nitrite and nitrate ions and then into nitrogen gas and nitrous oxide gas.

This begins the cycle again.

Layers of the Atmosphere Composed of

different layers with different temperatures, pressures, and compositions.

Fig. 17-2 p. 419

Soil Particle

Size

Soil Difference between porosity and permeability

Soil Soil horizons: series of layers with distinctive

textures and compositions

Matter and Energy Law of Conservation of Matter: we cannot

create or destroy atoms only rearrange them into different spatial patterns (physical changes) or different combinations (chemical changes). Matter is essential a closed system on Earth

We will eventually run out of matter. There is “no away” We have to deal with

pollutants(degradable, biodegradable, slowly degradable, and nondegradable).

Matter can be recycled.

Matter and Energy First Law of Thermodynamics/Conservation

of Energy: in all physical and chemical changes, energy is neither created nor destroyed, but it may be converted from one form to another. Energy input = energy output. We can’t get something for nothing in terms of

energy quantity. Energy can be converted into different forms

Matter and Energy Second Law of Thermodynamics: when energy is

changed from one form to another, some of the useful energy is always degraded to lower quality, more dispersed, less useful energy. Energy conversions result in lower quality energy that

flows into the environment. Energy cannot be recycled – there is a one-way flow of

it.

Matter and Energy: How does this apply to living systems?

There is a one-way flow of high quality energy through materials and living things which is dispersed eventually as low-quality energy (heat).

Since matter is a closed system, it must be recycled (think chemical cycles).

Food chains indicate how energy flows through a sequence of organisms while a food web demonstrates the complex network of connecting food chains.

Pyramid of energy flow shows that there is a decrease in the amount of energy available for each trophic level. Assumes 10% of energy is available to next trophic level. Limits number of trophic levels. Makes top carnivores the most vulnerable.

Matter and Energy: How does this apply to living systems?

Productivity Gross primary productivity (GPP) is the rate at

which producers convert solar energy into chemical energy as biomass.

Net primary productivity (NPP) is the amount of energy stored in organic molecules after respiration loss is factored. NPP = GPP – RL (respiration loss)

The planet’s NPP ultimately limits the number of consumers (including humans) that survive on Earth.

Productivity

Freshwater Lakes

Oligotrophic Lakes

Fig. 7-21 p. 158

Eutrophic Lakes

Fig. 7-21 p. 158

Speciation Speciation: when two

species arise from one where they can no longer breed and have fertile offspring. Allopatric Speciation occurs

through geographic isolation or reproductive isolation.

Sympatric Speciation occurs through a mutation or behavior difference.

Population Density

J-Curves and S-Curves Exponential growth: occurs when resources

are not limiting and a population can grow near intrinsic rate of increase or biotic potential.

Logistic growth: rapid exponential growth followed by a steady decrease in growth with time until population size stabilizes at carrying capacity (K).

Also see Figure 9-4 on page 166

J-Curves and S-Curves

Natural Population Curves

r-Selected vs. K-Selected Species

Fig. 9-10p. 196

Survivorship Curves

Fig. 9-11 p. 198

Age Structure Diagrams

Demographic Transitions