Introduction to Ecology

Ecology is the scientific study of the distribution and abundance of organisms, and their interactions with the environment.

Organismal Ecology Terms Organism: An individual form of life

composed of a single cell or a complex of cells in which organelles or organs work together to carry out the various processes of life.

E.g. Hyena, Grasshopper, Redwood, Mushroom

Biotic: Of, pertaining to, or produced by life or living organisms (of an ecosystem)

E.g. Wolves, Predator-prey, Competition

Abiotic: non-living chemical/physical parts of the environment that affect living organisms and the ecosystem.

E.g. Wind, Sunlight, Weather, Terrain

Ecosystem Defined

The interactions between all living (biotic) and non-living (abiotic) factors in a defined area.

Biotic Factors:FOOD CHAINS & FOOD WEBS Food Web: All feeding connections

between organisms in a biotic community.

Both energy and nutrients flow through a food web, moving through organisms as they are consumed by an organism above them in the food web.

Food Chain: A single path of energy flow (a linear path through a food web)

FOOD WEB

Biotic Factors:TROPHIC LEVELS

Trophic Level: a particular position occupied by a group of organisms in a food chain or food web. Primary Producer

Primary Consumer

Secondary Consumer

Tertiary Consumer

“Apex Consumer”

*Trophic: Relating to feeding or nutrition

Q: Why is it rare to find food chains with more than 4 or 5 “links”?

Biotic Factors:ENERGY PYRAMID

At each trophic level, most of the energy gained by eating is lost through biological processes such as respiration, finding food, or reproduction. Only the energy that is

directly assimilated into an animal's consumable mass will be transferred to the next level when that animal is eaten.

NOTE: Although energy is lost, nutrients are recycled through waste or decomposition.

Trophic Levels: 2 DivisionsAutotrophs v. Heterotrophs Autotrophs: [Auto- = self, -troph = food]

An organism capable of synthesizing its own food from inorganic substances (light or chemical energy).

E.g. Green plants, Algae, certain Bacteria

Heterotrophs: [Hetero- = other, -troph = food] An organism that cannot manufacture its own

food and instead obtains its food and energy by taking in organic substances.

E.g. Fungi, Protozoans, most Bacteria, all Animals

Autotrophs “Producers” because

they produce complex organic compounds (e.g.

sugars, fats, proteins) from simple inorganic matter (minerals, nutrients, etc.)

They do not need a living source of energy:

They do not need a living source of Carbon:

they can “fix” it from atmospheric sources

Photosynthesis: Obtain energy from light (generally sunlight).

Chemosynthesis: Obtain energy from chemical compounds.

Heterotrophs

“Consumers” because they cannot synthesize their own food and must consume other organisms to get organic Carbon.Omnivores: Eat both plants &

meat Carnivores: Eat mostly meat

Herbivores: Eat only plants

Heterotrophs

Detritivores: Typically invertebrates

like earthworms, wood lice, slugs, crabs, etc.

Use enzymes to break down detritus on tissue scale as source of energy, nutrients, and Carbon.

increases surface area for decomposers.

Decomposers: Generally Fungi &

Bacteria

Use enzymes to break down detritus on molecular scale as source of energy, nutrients, and Carbon. Release inorganic ions

(mineralization)

Some consumers are organisms which feed on detritus (biotic waste or dead organic matter)

Two General Types of Food Webs

Grazing Food Web

All ecosystems require a method to recycle material from dead organisms; all grazing food webs have an associated detrital food web.

Photosynthetic organisms at its base, followed by herbivores and various carnivores.

Organisms that feed on decaying organic matter (dead organisms) at base.

Detrital Food Web

Biomass Pyramid 10% Rule: only about 10% of the energy of one

level will be transmitted to the next, higher level.

The 10% passed on is what the organism used for growth.

The other 90% is lost as heat (during respiration, movement, reproduction) or as biotic waste.

Efficient Eating Habits Entire fields of grain are planted and harvested for

the purpose of feeding cattle, and the cattle in turn are raised for the production of meat products.

Is this an “efficient” source of food, why or why not?

Why is it important to develop sustainable farming practices?

The Earth’s population (currently about 8 billion) is estimated to grow by 2 billion people (25%) in the next 30 years. All the while, useable (arable) farmland is decreasing…