Ecology: The Study

of Ecosystems

Organization of Life

AKA

Biological Organization

Ecosystem

• The interaction between organisms and their environment

• The interaction of abiotic and biotic factors

• Can be small (pond, rotting log, local forest, our school) or large (Biomes like tundra, desert, savannah, etc. are super large ecosystems).

Biotic vs. Abiotic Factors

Biotic factors: factors that are or came from a living thing.

Examples: plants, bacteria, fungi, animals, fish, birds, insects, leaves, skin, animal wasteAbiotic factors: factors created by non-living things.

Examples: sunlight, temperature, weather factors, elevation, air, chemicals, minerals, rocks, roads

1

2

Trophic Levels (Feeding Levels)

• Producers– Also known as Autotrophs– Make their own food, mostly by photosynthesis. – Most autotrophs are green plants, but some are

microorganisms like bacteria. – They convert the suns energy into chemical

energy. – They are the First Trophic Level.

Trophic Levels

• Consumers– Also called Heterotrophs– Cannot make their own food– Must consume another living thing to get energy– Can be animals, fungi or bacteria – Even a few plants are considered

consumers….the venus fly trap plant “eats” insects

Types of Consumers

• Herbivore – animal that eats plants (ex. deer)• Carnivore – animal that eats animals (ex. lion)• Omnivore – animal that eats both plants and animals• Detritivore – animal that eats dead organisms or their wastes

(detritis). They are also called scavengers (ex. vulture) • Decomposer/Saprotroph – break down dead

organisms/animal wastes and return/recycle nutrients to the ecosystem

• Ex. Fungi, Bacteria, or Detritivores• A type of consumer

Some other terms to know

• Nutrients: Substances that are required by an organism for its normal functioning, growth and repair. Nutrients include fats, carbohydrates, proteins, vitamins, minerals and water as well as the elements that they are composed of.

• Organic: matter that contains the element carbon. All living things contain this element and therefore living things are organic matter.

• Inorganic: matter that does not contain the element carbon. For example, water does not contain carbon atoms and is therefore an inorganic substance. (H20)

Food Chains

A linear sequence of who eats who in an ecosystem

1st

2nd

3rd

4thTop Carnivore

Predator

Prey

The tip of the arrow points towards the thing doing the eating

Food Webs

Interconnected food chains showing who eats who

Video• Watch Bill Nye’s “Food Webs” and answer the

questions on the worksheet (just first 13 min)

http://www.youtube.com/watch?v=sVB82laAJl0&safe=active

Energy in Ecosystems

• Ultimately, the source of all energy in ecosystems is the sun

• Producers convert the sun’s energy to food energy

• Consumers eat plants or they eat animals that ate plants

Energy Flow in Ecosystems

• Energy flow is one way – from the sun to plants to animals

• The energy used by living organisms is either used up for their life activities or it is lost along the way as heat

• Energy does not cycle (lost energy or heat from ecosystems does not return to the sun)

The Cow eats grass. Some of the energy from grass goes into making new cow tissue, but lots of the energy (90%) is lost as heat, during respiration or as urine and feces

Grass

Thermodynamics

Definition – the study of how energy is transferred

1st Law – energy is conserved; it is not created or destroyed

2nd Law – every time there is an energy transfer, some energy is lost along the way

Ecological Pyramids

• Used to show the energy available at each trophic level

• There are 3 types:

– Pyramid of Energy– Pyramid of Biomass– Pyramid of Numbers

Ecological Pyramids

Energy PyramidsEnergy in Joules or Kilocalories shown at each level

Pyramid of Energy

Only 10% of the energy from a trophic level is available to the next trophic level – called the 10% rule

Pyramid of BiomassShows the dry weight of organisms at each level

Pyramid of Numbers

Shows actual counts of numbers of organisms

A Pyramid of Numbers may not give a great picture of what is going on….

Why Food Chains aren’t longer

The 90% loss of energy at each trophic level explains why there can’t be more than 5 trophic levels. By the time quaternary consumers get to eat, there just isn’t much energy left.

Eat Low on the Food Chain

Find out! EqualsBONUS Marks

Ecological Pyramids Worksheet

• Complete the worksheet for homework• Due next class

Worksheet Answers

1) Decreases2) 10%3) Heat, Respiration, Wastes4) 2nd 5) Energy emitted from the sun never returns

back to the sun6) Dry weight/mass of living things7) Biomass = dry mass; Numbers = actual counts

8) Because there is a 90% loss of energy/biomass at each step, so by the time tertiary or quaternary consumers get to eat, there isnt much food left

9) There has to be more herbivores than carnivores because there has to be more energy at the trophic level that is being fed on than in the one doing the eating because of how much energy is lost between levels.

10) The trophic level above always has less energy compared to the one below it.

11)

ProducerGrass

Primary ConsumerGrasshopper

Secondary ConsumerChicken

Tertiary Consumer

Hawk

BONUS QUESTION• Ecologically friendly - More food to feed more

people (10 x more). Human population is increasing so need enough food for all. Less land is needed to raising plants compared to raising animals.

• Healthier – less toxins(less biomagnification) and less bad fats from meat.

1 Human

10 Chickens

100 Corn

10 Humans

100 Corn