The Biosphere

Chapter 3

What is Ecology?

scientific study of interactions among organisms and between organisms and their environment

Biosphere

Combined portions of the planet in which all of life exists, including land, water and air or atmosphereExtends from 8 kilometers above Earth’s

surface to 11 kilometers below the surface of the ocean

Interactions and Interdependence

Interactions within the biosphere produce a web of interdependence between organisms and the environment in which they live

Levels of OrganizationIndividual: interactions between an organism and

its surroundings cottontail rabbit

Population: groups of individuals that belong to the same species and live in the same areagroup of cottontail rabbits

Levels of OrganizationCommunities: different populations that live

together in a defined area rabbits, coyotes, ravens, lizard

Ecosystem: collection of all the organisms that live in a particular place, together with their nonliving, or physical, environment rabbits, coyotes, ravens, lizard, rocks, dirt,

climate, water

Levels of OrganizationBiome: group of ecosystems that have the same

climate and dominant communities desert, tundra, tropical rain forest

Biosphere: planet Earth

Ecological MethodsThree approaches to ecological research:

Observing: Use of 5 senses to ask ecological questions

Experimenting: Used to test hypotheses artificial environment in a lab within natural ecosystems

Ecological Methods

Modeling: Used to gain insight into complex phenomena such as the effects of global warming

may include mathematical formulas based on data collected through observation and experimentation

predictions tested by further observations and experiments

Energy Flow

Energy flows from the sun or inorganic compounds to producers.

Consumers eat producers to get energy. The primary source of energy on Earth is the sun!!

Producers

Autotrophs – “self feed” Use sunlight to create carbohydrates via

photosynthesis Ex – Plants, algae and some bacteria Some bacteria create organic compounds from

inorganic chemicals – ChemosynthesisLive in remote places.

Producers

Consumers

Heterotroph – “Different food”Must eat to obtain energy.Ex – animals, fungi, some protists

Types of Heterotrophs Herbivore – eats plants Carnivore – eats animals Omnivore – eats plants and animals Detritivore – eats detritus (plant and animal

remains)Ex- snails, crabs, earthworms

Decomposer – breaks down organic matterEx – bacteria and fungi

Feeding Relationships

Energy flows through an ecosystem in one direction, from the sun or inorganic compounds

autotrophs (producers) various heterotrophs (consumers).

Food Chain

A series of steps in which organisms transfer energy by eating and being eaten.i.e. Wheat mouse snake hawk

Food Chain Example

Food Web

Network of complex interactions formed by the feeding relationship among the various organisms in an ecosystem.

Trophic Levels

Each step in a food chain or food web1st level = producers2nd, 3rd, or higher levels = consumers

Usually no more than 5 levels because 90% of energy is lost at each level.

Ecological Pyramid

A diagram that shows the relative amounts of energy or matter contained within each trophic level in a food chain or food web.

Energy, biomass, and population numbers can all be represented by a pyramid.

Ecological Pyramid

Cycles of Matter

Recycling in the BiosphereMatter is recycled within and between

ecosystems.Matter moves through an ecosystem in

biogeochemical cycles.

Water Cycle

Carbon Cycle

Nitrogen Cycle

N2 in Atmosphere

NH3

NO3-

and NO2-

Nitrogen Cycle

78% of Earth’s atmosphere is Nitrogen gas = N2

Nitrogen containing products:Ammonia (NH3)

Nitrate ions (NO3-)

Nitrite ions (NO2-)

Nitrogen is needed for protein and nucleic acid synthesis

Nitrogen CycleConverting nitrogen gas into ammonia is called

nitrogen fixation.Only certain types of bacteria can do this.Plants use the converted products (NH3, NO3- ,&

NO2-) to make plant proteins.

Some bacteria convert nitrates into nitrogen gas (denitrification).

Phosphorus Cycle

Phosphorus Cycle

Phosphorus is important for the formation of DNA and RNA molecules.

Phosphorus is not very common and does not enter the atmosphere, instead it is found mostly on land in rock and soil.

Primary Productivity

The rate at which producers create organic matter. Determines the size of the community. Limited by availability of nutrients.

Land – phosphorus (P), nitrogen (N), potassium (K)Marine – nitrogenFresh water - phosphorus

Algal Bloom