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Ecosystem

Ecosystem – is all of the organisms living together in their physical environment with biotic and abiotic factors.
For example – oak forest and coral reefs.

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Everything is connected in an ecosystem

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Components of an Ecosystem

In order to survive, ecosystems need certain basic components, such as

energy,
mineral nutrients,
carbon dioxide,
water,
oxygen, and
living organisms.

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Biotic and Abiotic Factors

An ecosystem is made up of both living and nonliving things.

Biotic Factors - are the living and once living parts of an ecosystem, including all of the plants and animals.

Biotic factors include dead organisms, dead parts of organisms, such as leaves, and the organisms’ waste products.

Abiotic Factors - are the nonliving parts of the ecosystem.

Abiotic factors include air, water, rocks, sand, light, and temperature.

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Organization of an ecosystem

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Organization of an ecosystem: ORGANISM

An organism - is an individual living thing.

For e.g. – You, an ant, a plant and a bacterium in your intestines.

A species - is a group of organisms that can mate to produce fertile offspring.

For e.g. - All humans are members of the species Homo sapiens,

All black widow spiders are members of the species Latrodectus mactans.

Every organism is a member of a species.

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Organization of an ecosystem: POPULATIONS

An organism lives as part of a population.

A population - is all the members of the same species that live in the same place at the same time.

For example, all the field mice in a corn field make up one population of field mice.

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POPULATIONS

An important characteristic of a population is that its members usually breed with one another rather than with members of other populations.

For example - The bison in will usually mate with another member of the same herd.

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Organization of an ecosystem: COMMUNITIES

Every population is part of a community.
A community - is a group of various species that live in the same place and interact with each other.

NOTE: A community is different from an ecosystem. Why?
A community is different from an ecosystem because a community is made up only of biotic components while ecosystems are made up of both biotic and abiotic factors.

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Organization of an ecosystem: COMMUNITIES

All of the living things in an ecosystem belong to one or more communities.

Communities differ in the types and numbers of species they have.

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Organization of an ecosystem: HABITAT

All organisms live in particular places.

A habitat - is the place where an organism lives.

For example - A howler monkey’s habitat is the rain forest and a cactus’s habitat is a desert.

Organisms tend to be very well suited to their natural habitats. Indeed, animals and plants cannot usually survive for long periods of time away from their natural habitats.

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Why is an organism’s habitat important for that organism?

An organism’s habitat is important for that organism because every habitat has specific biotic and abiotic factors that the organisms living there need to survive. If any of these factors change, then the habitat changes.

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Finished!
Review Chapter 4, Section 1.

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Energy Flow in Ecosystems

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Essential Vocabulary

Photosynthesis
Carbohydrates
Producer
Autotrophs
Consumers
Heterotrophs
Decomposers
Herbivores
Carnivores

Omnivores
Cellular Respiration
Food Chain
Food Web
Trophic level

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Sun: Ultimate Source of Energy

Energy from the sun enters an ecosystem through photosynthesis.

Photosynthesis – occurs when a plant uses sunlight to make sugar molecules.

What happens during photosynthesis?
During photosynthesis, plants, algae, and some bacteria capture solar energy. Solar energy drives a series of chemical reactions that require carbon dioxide and water.

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Photosynthesis

The result of photosynthesis is the production of carbohydrates.
Carbohydrate - are energy-rich sugar molecules that organisms use to carry out daily activities.

As organisms consume food and use energy from carbohydrates, the energy travels from one organism to another.

Organisms use this energy to move, grow, and reproduce.

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How do organisms use energy?

Cellular Respiration - is the process of breaking down food to yield energy. This process occurs inside the cells of most organisms.
During cellular respiration, cells absorb oxygen and use it to release energy from food

NOTE - Different from regular respiration!

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Equation for cellular respiration

The chemical equation for cellular respiration is the reverse of the equation for photosynthesis.

Photosynthesis:

During cellular respiration, sugar and oxygen combine to make carbon dioxide, water and, most importantly, energy.

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We use cellular respiration

All living things use cellular respiration to get the energy they need from food molecules.

Even organisms that make their own food through photosynthesis (producers) use cellular respiration to obtain energy from the carbohydrates they produce.

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Transfer of Energy

Energy in an ecosystem flows from producers to consumers.

Producer – is an organism that makes its own food.

Also called ‘autotrophs’ – meaning self-feeders

Consumers - are organisms that get their energy by eating other organisms.

Also called ‘heterotrophs’ – meaning other-feeders

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What eats what?

Herbivores - are consumers that eat only producers.

Example - rabbits, cows, sheep, deer etc.

Carnivores - are consumers that eat only other consumers

Example – lions, hawks, tigers etc.

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What eats what?

Omnivores – are consumers that eat both producers and other consumers.

Example – human, bears, pigs, cockroaches etc.

Decomposers – are consumers that get their food by breaking down dead organisms.

Example - bacteria and fungi.

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What eats what?

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Tracing energy transfer!

Each time one organism eats another organism, a transfer of energy occurs.
We can trace the transfer of energy in an ecosystem by studying food chains, food webs, and trophic levels.

Why should we study paths of energy transfer?
Studying the paths of energy between organisms can also tell us which organisms in an ecosystem depend on other organisms to survive.

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Food chain

A food chain - is a sequence in which energy is transferred from one organism to the next as each organism eats another organism.

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Food Web vs. Food Chain

Energy flow in an ecosystem is more complex than energy flow in a simple food chain.
Ecosystems almost always contain many more species than a single food chain shows.
Most organisms, including humans, eat more than one kind of food.
So a food web includes more organisms and multiple food chains linked together.

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Food Web

A food web - shows many feeding relationships that are possible in an ecosystem

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Trophic Level

A trophic level - is each step through which energy is transferred in a food chain.

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How much energy is transferred between each trophic level?

Each time energy is transferred from one organism to another, some of the energy is lost as heat.

Some of the energy is lost during cellular respiration.

Organisms use much of the remaining energy to carry out the functions of living, such as producing new cells, regulating body temperature, and moving.

About 90 percent of the energy at each trophic level is used in these ways. The remaining 10 percent of the energy is stored in the organism’s molecules. This 10 percent that is stored is all that is available to the next trophic level when one organism consumes another organism.

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Energy Pyramid

One way to show the loss of energy from one trophic level to the next trophic level is to draw an energy pyramid.

Each layer in the energy pyramid represents one trophic level.

Producers form the base of the pyramid, the lowest trophic level, which contains the most energy.

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Energy Pyramid

Herbivores contain less energy and make up the second level.

Carnivores that feed on herbivores form the next level, and carnivores that feed on other carnivores make up the top level.

Organisms in the upper trophic levels store less energy than herbivores and producers.

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Why is an energy pyramid a good way to illustrate trophic levels?

A pyramid is a good way to illustrate trophic levels because the pyramid becomes smaller toward the top, where less energy is available.

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How does energy loss affect an ecosystem?

The organization of an ecosystem is affected by the decreased amount of energy at each trophic level.

First, because so much energy is lost at each level, there are fewer organisms at the higher trophic levels.

Second, the loss of energy from trophic level to trophic level limits the number of trophic levels in an ecosystem. That is, ecosystems rarely have more than four or five trophic levels because the ecosystem does not have enough energy left to support higher levels.

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