Ecosystems

Realm of

Ecology

Organisms

Populations

Communities

Ecosystem

Biosphere

Realm of Ecology

• Species– All organisms of the same kind that are

genetically similar enough to breed in nature and produce live, fertile offspring

• Population– All the members of a species living in an area at

the same time

Realm of Ecology, cont.

• Community– All of the populations of organisms living and

interacting in a particular area

• Ecosystem– Composed of a biological community and its

physical environment

Ecosystems

• Ecosystem– A community of different species interacting

with one another and with their nonliving environment

• Can be small or large, e.g. a stream or Great Plains• Can be natural or artificial, e.g. cropfields

• All of the Earth’s ecosystems together make up the biosphere

Biodiversity

• The forms of life that can best survive the variety of conditions currently found on earth

• Types of Biodiversity– Genetic Diversity– Species Diversity– Ecological Diversity

Components of Ecosystems

• Biotic (living components)– Producers = make their own food from compounds

obtained from their environment• Photosynthesis = capturing sunlight to make sugars

• 6CO2 + 6H2O + sun C6H12O6 + 6O2

– Consumers = get their energy and nutrients by feeding on other organisms

• Aerobic respiration = uses oxygen to convert organic nutrients into carbon dioxide and water

• C6H12O6 + 6O2 6CO2 + 6H20 + energy

Types of Consumers

• Herbivores– Plant eaters– Primary consumers– Feed directly on producers

• Carnivores– Meat eaters– Feed on other consumers– Secondary and tertiary consumers

Types of Consumers, cont.

• Omnivores– Eat both plants and animals

• Scavenger– Feed on dead organisms

• Decomposers– Bacteria and fungi– Complete the final breakdown and recycling of

organic materials

Components of Ecosystem

• Biotic (living components)

• Abiotic (nonliving components)– Sunlight– Temperature– Precipitation– wind

Major components of an ecosystem in a field

Major components of a freshwater pond ecosystem

How does energy flow through ecosystems?

• Food chain– The sequence of organisms, each of which is a source

of food for the next

– Energy enters most ecosystems as high quality sunlight, which is converted to nutrients by producers. The energy is then passes on to consumers.

– As each organism uses the high-quality energy in its food to move, this energy is converted into low-quality heat (2nd law of thermodynamics)

Model of a Food Chain

Food Chain

• Trophic Level– All organisms that are the same number of

energy transfers away from the original source of energy that enters an ecosystem

• Producers = 1st trophic level• Primary consumers = 2nd trophic level• Secondary consumers = 3rd trophic level

• But real ecosystems are more complex than this …

Food Web

• Most consumers feed on more than one type of organism

• Food web = complex network of many interconnected food chains

Food Web

Energy Transfer in a Food Web

• In a food chain or web, energy is transferred from one trophic level to another, with some usable energy degraded and lost to the environment as heat.

• At each successive trophic level, some of the available biomass isn’t digested and expelled as waste

• Only a small portion of what is eaten is converted into an organism’s biomass, and the amount of usable energy available to each successive trophic level declines (80-90% is lost)

Biomass Transfer

Pyramid of Energy Flow

• A diagram representing the flow of energy through each trophic level in a food chain or web

• With each energy transfer, only a small part (typically 10%) of the usable energy entering one trophic level is transferred to the organisms at the next trophic level

Generalized pyramid of energy flow

Energy Pyramid

Energy Pyramid for Grassland