Ecology

The study of interactions that take place between organisms and

their environment.

Chapter 2Principles of Ecology

Sections 1 and 2

Organisms and Their Environment

Nutrition and Energy Flow

What is the biosphere?

• Portion of Earth which supports living things.

• Includes both abiotic and biotic factors.

What are abiotic factors?• The nonliving parts of an organism’s environment.

– Air currents, temperature, moisture, light, soil

What are biotic factors?• All living organisms which inhabit an

environment.

Levels of Organization

• Organism

• Population

• Biological Community

• Ecosystem

• Biosphere

Interactions within Populations• Population

– Group of organisms of the same species which interbreed and live in the same area at the same time.

– Some organisms form adaptations to decrease the amount of competition within the population.

Interactions Within Communities

• Biological Community– Made up of interacting populations in a certain

area at a certain time.– A change in one population in a community may

cause changes in the other populations.

Ecosystem

• Made up of interacting populations in a biological community and the community’s abiotic factors.

• Two major types of ecosystems– Terrestrial – located on land– Aquatic – locate in both fresh- and saltwater

What is a habitat?• The place where an

organism lives out its life.• Niche

– the role or position a species has in its environment

– How an organisms meets its needs for food and shelter, how and where it reproduces and survives.

– May change over the life of the organism.

Symbiosis

• A close and permanent association between organisms of different species.

• 3 Types– Mutualism– Commensalism– Parasitism

Mutualism• Both species benefit from the relationship

Commensalism

• One species benefits and the other species is neither harmed nor benefited.

Parasitism

• Harmful to one species yet benefits the other.

How do organisms obtain energy?

• Producers – Autotrophs– Organism that use light

energy or energy stored in chemical compounds to make energy-rich compounds.

– Example: Plants use sunlight to make energy during the process of photosynthesis.

How do organisms obtain energy?

• Consumers – Heterotrophs– Organisms which cannot make

their own food and so have to feed on other organisms.

– Five main types of consumers.

Herbivores

– Heterotrophs that eat only on plants.

Carnivores

– Heterotrophs which eat heterotrophs.

Omnivores

– Heterotrophs that eat both plants and animals.

Scavengers

– Heterotrophs which eat animals which have already died.

Decomposers• Break down the

complex compounds of dead and decaying plants and animals into simpler molecules which can be more easily absorbed.

How Do We Chart the Flow of Matter and Energy in an Ecosystem?

• Food Chain – A model which shows one way in which matter and energy move through an ecosystem.– Arrows indicate the

direction of energy transfer.– Each time energy is

transferred, part of the energy is given off as heat.

• Each organism in a food chain represents a feeding step, or trophic level, in the passage of energy and materials.

• First order heterotroph – Feeds on plants

• Second order heterotroph – feeds on a first order heterotroph

Food Web• Shows all possible feeding relationships at

each trophic level in a community.

Ecological Pyramid• Another way to show the flow of matter and

energy in an ecosystem.

Pyramid of Energy

(Energy decreases at each trophic level in the pyramid through uneaten organisms and heat given off to the environment.)

Pyramid of Numbers

Pyramid of Biomass

(Biomass is the total weight of living matter at each trophic level.)

Matter

• The biosphere contains a fixed amount of water, carbon, nitrogen, oxygen, and other materials required for life.

• These materials are cycled through the biosphere and used by many different organisms.

Water Cycle

• A model that describes how water moves from the surface of the earth to the atmosphere and back to the surface again.

Water Cycle• Components of the water cycle:

– Evaporation• Occurs when liquid water turns into water vapor (gas).

– Transpiration• Occurs when plants release water into the air.

– Respiration• Releases water vapor to the air.

– Animal Wastes• Returns water to the environment.

– Condensation• Occurs when water vapor changes to a liquid.

– Clouds• When water vapor cools, it condenses on tiny particles of matter (like dust) in the air

and forms tiny droplets.

– Precipitation • Eventually the “cloud” droplets become so heavy that they fall to the earth as

precipitation.

Carbon Cycle• During photosynthesis, autotrophs use energy

from the sun to convert carbon dioxide into energy rich carbon molecules.

• The carbon is transferred to heterotrophs through the food chain.

• Carbon is returned to the atmosphere as a waste in the form of carbon dioxide.

• Very slow process.

Nitrogen Cycle• Plants cannot use nitrogen directly from the

air...so, bacteria in the soil convert the nitrogen from the air into compounds that plants can use.

• Animals get the nitrogen they need by eating plants.

• Nitrogen is returned to the environment through animal wastes and dead and decaying organisms.

Phosphorous Cycle• Short-term Cycle:

– Plants obtain phosphorous from the soil.

– Animals get the phosphorous by eating the plants.

– Phosphorous is returned to the soil through decomposing dead organisms.

• Long-term Cycle– Phosphates that are washed into water

become trapped in rocks as insoluble compounds.

– As the rock erodes over millions of years, the phosphorous is released back into the environment.