Ecology Chapter Notes

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• Our book lists 5 levels

-> organism->population->community->ecosystem->biosphere

• What about -> cell-> organ-> system are they levels of biological organization?

• and.... What is living!!!

These are all living factors, levels of Biological Organization.... but cells are made of molecules, molecules are made of atoms.

Does that make molecules and atoms living since they make up living organisms??? Thus -> atoms -> molecules?


Some Biotic Factors to consider when studying Environment


Population Density

Population density is the biological measurement most used by conservationists vs population size.

Population density = Population of an organism / Area population lives in. In Km2

indicates areas of high growth or potential stress on ecosystems

What are the 3 countries with the greatest overall Population?


What are the 3 countries with the greatest Population Density?


Population Density Problem (Solve in your NOTES!)

1. Calculate the Population Density for these 3 countries and rank each from highest population density to lowest. Use a calculator

Area (km2)












South Korea




 Show World Population video


Biotic potential: The maximum reproductive capacity of a population under optimum environmental conditions is the biotic potential.

Often restricted by conditions that inhibit the increase in number of the population. (Food availability, disease, lack of mates)

Generally only reached when environmental conditions are very favorable.

A species reaching its biotic potential would exhibit exponential population growth (many offspring are produced per mother

Biotic Potential is a basic characteristic of a species.


Carrying Capacity

In ecological terms, carrying capacity of an ecosystem is:

The size of the population that can be supported indefinitely with the available resources and services of that ecosystem.

Living within the limits of an ecosystem depends on three factors

1. the amount of resources available in the ecosystem,

2. the size of the population, and

3. the amount of resources each individual is consuming.

(ex: food, habitat, water etc)

In the natural world, when a population's density is less than the carrying capacity of the ecosystem that population can increase…

As animal population density increases beyond the carrying capicity, birth rates often decrease and death rates typically increase.

o resources decline and become Limiting Factors


Limiting Factors (restricting factors)

•things that limit individuals in a specific population

can be abiotic (lack of water - heat etc)

or biotic ( predators, disease, competition for food sheep and cows)


Interrelationships between species

Symbiosis ( the study of the relationship between two or more species) three types


1. Mutualism a relationship where both (all) species benefit

ex lichen - algae and fungi Algae get a place to live give Fungi food in form of sugar.


2. Commensalism - benefits one species, not the other species

ex: orchids on tree orchid gets place to live, tree gets nothing, but doesn't lose anything either.


3. Parasitism - one species harms the other ex tapeworm harms human, mistletoe, trichina


 deer population over time in bothell wa


What is the Deer's habitat?


What is the Deer's niche?


Habitat - creature's home... where a creature lives in the environment

ex: wetland creature, arctic tundra plant, swamp plant etc.

Niche - what a creature does to make a living in the environment...

ex: what it eats is what it does to "Make a living".

Another way of looking at it is a niche is how an organism gets energy to survive, ie herbivore get energy from plants to survive.



Abiotic Factors - non living factors in the environment -

• It's not as simple as the book says - they list four major (water, soil, light, temp)

• In reality, there are other abiotic factors - energy, air, fire, spacing, essential elements, etc




Discuss cycles = Diagrams that follow specific nutrients through the environment

ex. Water cycle, Nitrogen cycles, Carbon cycle, Rock cycle.....


  Nutrient Cycles: Cycle vital elements and minerals that organisms need to live through the environment. Some examples of nutrients are:

Water: (Water Cycle) Required for all living things

Carbon: (Carbon Cycle) Required for all living organisms.

Oxygen: Photosynthesis (Oxygen Cycle) CO2 + H2O + Sun => Sugar + Oxygen

Nitrogen: (Nitrogen Cycle) both plants and animals need Nitrogen to build new nitrogenous bases which are the foundation of DNA.

Rock cycle - Forms basis of soil. Contains vital trace minerals (Micronutrients)

- Ex: plants need Magnesium to make chlorophyll so they can photosynthesize.

Others are Sulfer, Phosphorous, Selinium, Iron, Potassium, etc



Following Matter and Energy through the Environment

Matter Basics:

1. Matter can neither be created nor destroyed... it just changes form!


Go over the Food Chain / Web Exercise - with yarn




Energy Flow, and Energy Pyramids

Energy Basics:

1. Energy can't be created nor destroyed either.... it just changes form!

2. Energy flows into, through and out of the environment.

3. Most organisms only about 10% energy efficient in transferring energy into their bodies.

4. Energy comes from the sun, earth, and the actual bonds that hold matter together

Food provides Energy for organisms

- Food is digested and energy is released to the organism.



Ecologists can track the energy flows through living things in a food chain.

Each level of energy consumption is called a Trophic Level.

Each Trophic level has a name.


 Trophic Levels

Primary Producer: takes matter from soil and energy from sun and uses each to grow. (plants/chemosynthetic bacteria)

1st level Consumer: Herbivore (cows, goats etc) get matter and energy from plants

2nd level Consumer: Omnivore (ex Bears) gets matter and energy from eating plants and animals

3rd level Consumer: Carnivore (ex Cougar, Bobcat) gets matter and energy from eating animals

Top Consumer: Top of the Energy Pyramid/Food Chain

Decomposer/Recyclers (ex Bacteria, fungi) get energy from eating once living creatures





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