BiologyEcologyEnergy flow

Matter Cycling

Populations

Ecology

Topics

• Ecosystem energy flow

• Cycles in an ecosystem

• Limiting Factors

• Population Growth Graphs

Essential Questions5. Explain the ways in which energy flows through

an ecosystem.

6. What role does the carbon cycle play in photosynthesis and cellular respiration?

7. How are communities influenced? What are the major limiting factors that influence carrying capacity?

8. What do population growth graphs look like? Can you identify them?

Sunlight is the main energy source for life on Earth. Some types of organisms rely on the energy stored in inorganic chemical compounds. Plants use the energy from sunlight to carry out the process of photosynthesis.

Other autotrophs, such as sulfur bacteria, use the energy stored in chemical bonds for chemosynthesis. In both cases, energy-rich carbohydrates are produced.

Energy FlowThe Sun

Autotrophs / Producer – An organism that can capture energy from sunlight or chemicals and use it to produces its own food.

Photosynthesis The process by which producer take carbon dioxide and water and convert it into sugar and oxygen.

(Carbon dioxide + Water Sugar + Oxygen) take place in the chloroplast

Heterotrophs / Consumer – Organisms that rely on other organisms for their energy and food supply

Cellular RespirationThe process that releases energy by breaking down glucose and other food molecules in the presence of oxygen.

(Sugar + Oxygen Carbon Dioxide and Water) takes place in the mitochondria

Energy Flow

Photosynthesis: CO2 + H2O C6H12O6 + O2

CO2 + H2O C6H12O6 + O2 Cellular Respiration

Light

Carbon dioxide water Glucose

sugaroxygen

Photosynthesis

Producer (Autotrophs)

Primary Consumer

(Heterotrophic)

Secondary

Consumer (Heterotrophic)

Tertiary

Consumer (Heterotrophic)

Top level

Consumer (Heterotrophic)

Energy Flow: Food Chains

example

Energy FlowEnergy Flow

Trophic levels are feeding levels for organisms within an ecosystem,

(1) Producers belong to the first trophic level.

(2) Primary consumers belong to the second trophic level.

(3) Secondary consumers belong to the

(4) Third trophic level.Detritivores and decomposers process detritus from all trophic levels.

Energy flow in a food web/chain decreases at each succeeding organism in a chain or web.

The dry weight of all organic matter within the organisms of a food chain/web is called biomass.

Eating at a lower Trophic level

Energy Flow: Ecological Pyramids

Energy flow - Extinction

Ecological pyramids show the decreasing amounts of energy, living tissue, or number of organisms at successive feeding levels. The pyramid is divided into sections that represent each trophic level. The area of each level symbolizes the amount of energy or matter remaining at that level. Because each trophic level harvests only about one tenth of the energy from the level below, it can support only about one tenth the amount of living tissue.

Energy Flow: Ecological Pyramids

Energy Flow: Food Webs

What does the Marsh Hawk feed on?

What would happen if a chemical was introduced that limited the growth of Marsh Grass?

Tropic LevelsEcological efficiency is the term that describes the percentage of usable energy transferred as biomass from one trophic level to another and ranges from 2%-40% with 10% being typical.

The greater number of trophic levels in a food chain, the greater loss of usable energy.

The Flow of Energy And the Cycling of Matter

Cycling of Matter

Biogeochemical Cycles

Keeping up with CarbonThe Flow of Energy And the Cycling of Matter

Carbon Cycle

Nitrogen Cycle

The Study of Population Dynamics

Populations change insizedensity dispersionage structure

Population density —the number of individuals of a population that inhabit a certain unit of land or water area.

Population dispersion —refers to how individuals of a population are spaced within a region.

Age structure of a population is usually described as the pre-reproductive stage, the reproductive stage and the post-reproductive stage.

A population with a large reproductive stage is likely to increase, while a population with a large post-reproductive stage is likely to decrease.

Populations

Ecosystem FactorsEcosystem Factors

Ecosystem characteristics include a range of tolerance to physical and chemical environments by the ecosystem's populations Law of tolerance: The distribution of a species in an ecosystem is determined by the levels of one or more physical or chemical factors being within the range tolerated by that species.

Mini Lab: Range of tolerance

The limiting factor principle states that too much or too little of any abiotic factor can limit or prevent growth of a population, even if all other factors are at or near the optimum range of tolerance.

An abiotic factor such as lack of water or poor soil can be understood here

The Sugar Maple

Ecosystem FactorsEcosystem Factors

limiting FactorsNo population can grow indefinitely due to limited resources such as light, water, and nutrients and also due to competitors and/or predators.

Populations

The biotic potential max (rmax) is the population's capacity for growth. The intrinsic rate of increase (r) is the rate of population growth with unlimited resources.

limiting FactorsNo population can grow indefinitely due to limited resources such as light, water, and nutrients and also due to competitors and/or predators.

Biotic Potential vs. Environmental Resistance

environmental resistance consists of factors that limit population growth.

Limiting Factors Examples:

Extrinsic

Biotic – Density Dependent

Abiotic – Density Independent

IntrinsicSocial HierarchyGender changing

Density-independent population controls affect a population's size regardless of its density. These are abiotic factors in the community.

Density-dependent factors or population controls have a greater affect on the population as its density increases. Infectious disease is an example of density-dependent population control.

Po

pu

lati

on

siz

e (N

)

Time (t)

Carrying capacity (K)

Environmentalresistance

Bioticpotential

Exponentialgrowth

Carrying capacity (K)is determined by biotic potential and environmental resistance.

(K) is is the number of a species individuals that can be sustained indefinitely in a specific space.

As a population reaches itscarrying capacity, itsgrowth rate will decreasebecause resourcesbecome more scarce.

Biotic Potential v. Environmental Resistance (Logistic Population Growth)

Exponential Growth Lessons of Kaibab

The Role of Predation in Controlling Population Size

The Role of Predation in Controlling Population Size

Interactions between predators and their prey change in cycles and appear to be caused by species interactions, but other factors may be involved.

Example: Yellowstone Wolves

Age structureAge structure of a population is usually described as the pre-reproductive stage, the reproductive stage and the post-reproductive stage.A population with a large reproductive stage is likely to increase, while a population with a large post-reproductive stage is likely to decrease.