Chapter 47 the biosphere
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Chapter 47 - The Biosphere. What is ecology?. Ecology is the study of the interactions of organisms with one another and with their physical environment. Biosphere - part of the Earth in which life exists. Includes land, air, and water as well as life.

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Chapter 47 - The Biosphere

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Chapter 47 - The Biosphere

What is ecology?

  • Ecology is the study of the interactions of organisms with one another and with their physical environment.

  • Biosphere - part of the Earth in which life exists.

    • Includes land, air, and water as well as life.

    • Living organisms are NOT distributed uniformly throughout the biosphere.

The biosphere is large…

  • …So ecoslgists work with smaller units called ecosystems.

  • Ecosystem - consists of an area’s physical features and living organisms.

    • Abiotic factors - physical features

      • Ex. elevation, humidity, rainfall

    • Biotic factors - living organisms

      • Ex. snails, worms, plants, insects

Members of ecosystems are related

  • Community - all the populations of organisms living in a given area.

  • Ecosystems rarely function independently of one another because they are connected by both living and non living features.

Ecological succession

  • Ecological succession - an existing community of organisms is replaced by a different community over time.

    • Can occur where no living community existed before (like a volcano arising from the sea).

    • Can also occur following a dramatic change (like a forest fire).

  • Succession leads to a collection of organisms called a climax community.

  • Biome - an environment that has a characteristic climax community.

Energy flow through ecosystems

  • Of all the sun’s energy the reaches the Earth’s surface, only about 0.1% is used by living things.

  • Energy cannot be recycled or used again!

    • For this reason, we refer to the movement of energy through an ecosystem as a flow, not a cycle.

Energy flows through ecosystems

  • The sun is the ultimate source of energy for living things.

  • Producers - organisms that make their own food via photosynthesis.

  • Consumers - organisms that get their energy directly or indirectly from producers.

    • Primary consumers - also called herbivores; plant eating animals.

    • Secondary consumers - animals that eat primary consumers.

  • Energy flows through an ecosystem from the sun to producers and then to consumers.

Energy flows through ecosystems

  • Herbivores - organisms that eat plants.

  • Carnivores - organisms that eat animals.

  • Omnivores - organisms that eat plants and animals.

  • Decomposers - organisms that obtain energy from non-living organic matter.

Energy flows through ecosystems

  • Trophic level - each step in a series of organisms eating other organisms.

    • At each higher trophic level, less and less of the energy originally captured by the producers is available.

      • This is because the energy obtained from digested food is used to maintain metabolism.

  • Only about 10% of the energy from one trophic level can be used by the animals at the next trophic level!

Nutrients are recycled through an ecosystem

  • While energy moves in a one-way direction through an ecosystem, nutrients are recycled and used again and again.

  • Biogeochemical cycle - nutrients use these processes to move through the biosphere.

    • Ex. Water, carbon, nitrogen, oxygen cycles

Nutrients are recycled through an ecosystem - Water cycle

  • Water cycle - movement of water between the atmosphere and Earth.

    • Consists of alternating cycles of evaporation and condensation.

    • Evaporation moves water molecules into the air while precipitation returns it to Earth.

    • Some water sinks into the ground (groundwater) while some runs along the surface of the ground until it enters a river or stream.

Nutrients are recycled through an ecosystem - Nitrogen cycle

  • Nitrogen - element required by living organisms to build proteins.

  • Nitrogen cycle - movement of nitrogen through biosphere.

    • Most can’t be used directly by living organisms - it must be converted into more usable forms.

Nutrients are recycled through an ecosystem - Nitrogen cycle

  • Nitrogen fixation - performed by bacteria that live on the roots of some plants - change free nitrogen in the atmosphere into nitrogen compounds (nitrates and nitrites).

  • Denitrification - bacteria in the soil break down nitrogen compounds into free nitrogen that is returned to the atmosphere.

Nutrient limitation

  • The rate at which producers can capture energy is limited by the amount of available nutrients.

  • Limiting factor - the nutrient that is in short supply that limits an organism’s growth.

Ecosystem relationships

  • Food chain - simplest feeding relationship linking animals and plants in the biosphere.

    • Usually contains 3-5 total organisms.

Ecosystem relationships

  • Food web - complex relationship formed by interconnecting and overlapping food chains.

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