Download Ecosystems

SGCEP SCIE 1121
Environmental Science
Spring 2012
Section 20531
Steve Thompson: [email protected]
http://www.bioinfo4u.net/
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Sunday, January 29, 2012
Ecosystems, energy
flows, and biomes
Today’s going to be a bit different.
First I want to fly through a bunch of
definitions, quite quickly; however, you
are responsible for them — they are
important, and will be on the exam.
And then we’ll watch most of a great
documentary from Planet Earth!
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Sunday, January 29, 2012
Ecosystem definitions
• Trophic levels (think feed trough) . . .
• Autotrophs: produce organic material from inorganic
substances through the use of an external energy
source, usually the sun; these are also called producers.
• This includes all green plants, and many single-celled
protists, archaea, and bacteria.
• Primary production: essential production of organic
matter through photosynthesis or chemosynthesis.
• Heterotrophs: must consume organic material to
obtain energy. This includes . . .
• Consumers: eat living prey, either primary consumer
(herbivore), or carnivore or omnivore, and . . .
• Plus . . .
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Sunday, January 29, 2012
The all important decomposers
• Detritus: high potential energy organic wastes,
includes dead organisms and parts of organisms
and feces. Decomposers recycle these nutrients
through the ecosystem.
• Decomposers include —
• Scavengers (e.g. vultures): break down large
pieces of detritus;
• Detritus feeders (e.g. earthworms): eat partly
decomposed matter; and . . .
• Chemical decomposers (fungi, archaea and
bacteria): break down detritus chemically.
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Sunday, January 29, 2012
Decomp’ really matters!
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Sunday, January 29, 2012
These all interconnect in . . .
• Food chains: describe where energy and
nutrients go as they move from one organism
to another.
• Energy moves “up” the food chain.
• Not all energy and nutrients are passed to
other levels. Much is lost at each step.
• Food web: an interconnection of food chains
to form complex webs of feeding
relationships within particular ecosystems.
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Sunday, January 29, 2012
For example,
food webs in
an agricultural
area and the
Arctic ocean.
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Sunday, January 29, 2012
Limits on trophic levels
• Terrestrial ecosystems usually have three or four
trophic levels.
• Marine systems sometimes have five.
• Biomass: the total combined (net dry) weight of
organisms
• Each higher trophic level has about 90% less biomass.
This is because . . .
• There is a huge inefficiency at each trophic level.
• Only a small fraction of energy is passed on when
energy flows from one trophic level to the next.
• Much of the biomass is not consumed by herbivores;
• Some food is used as energy to fuel the hetrotroph’s
cells and tissues, grow, and reproduce; plus . . .
• Some food is not digested and is excreted as waste.
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Sunday, January 29, 2012
From ecosystems to biomes
• Broad ecosystem patterns translate into a predictable
set of organisms that live under particular conditions.
• Biomes: the different climatically and geographically
defined major ecosystem areas of the Earth.
• See http://en.wikipedia.org/wiki/Biome
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Sunday, January 29, 2012
Six major terrestrial biomes
•Desert: regions with less than 10 in’ of rain/yr; some
hot, some cold; thin, poor soils.
•Grassland (prairie) biome: 10 to 60 in’ seasonal rain/yr;
rich deep soils.
•Tropical rain forests: more than 95 in’ rain/yr;
nonseasonal, quite warm and humid; thin, poor soils.
•Temperate deciduous forest: 30–80 in’ rain/yr; distinct
seasons; good soils.
•Coniferous forests: often no free water in winter;
harsh, cold winters with short summers; acidic soils.
•Tundra biome: little free water; bitter cold most of the
year; only small plants that can grow in short summer
above the permafrost.
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Sunday, January 29, 2012
The major terrestrial biomes
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Sunday, January 29, 2012
Aquatic systems
• Aquatic and wetland ecosystems are determined
by depth, salinity, and permanence of water.
• Six major types —
• Freshwater standing in lakes and ponds;
• Freshwater flowing in streams and rivers;
• Freshwater standing or flowing in wetlands,
swamps, and marshes, high productivity;
• Salt and freshwater mixing in estuaries, high
productivity;
• Coastal salt water ocean, high productivity;
• Open salt water ocean, low productivity.
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Sunday, January 29, 2012
Ecosystem disturbance
• Ecological succession: transition from one biotic
community to another (terrestrial or aquatic).
• Pioneer species: colonize a newly opened area first
creating conditions favorable to other species.
• Climax ecosystem: the eventual, relatively stable
assemblage of species after succession in an area.
• Even these communities experience change if new
species are introduced or old ones are removed.
• Primary succession: the process of initial invasion and
progression from one biotic community to another in an
area lacking all plants and soil (e.g., a retreating glacier)
• Secondary succession: an area cleared by some
disturbance (e.g. fire, floods, humans) is reinvaded by
plants and animals from surrounding areas.
• Starts with pre-existing soils and some biota.
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Sunday, January 29, 2012
Fire and succession
• Fire is a major form of disturbance.
• Decades ago, forest managers thought all fire was bad;
• But this accumulated deadwood encourage insects and
disease to attack trees;
• And if a fire did occur, it was way worse because of all
the accumulated tinder.
• Different species have different tolerances to fire:
• Grasses and pines tolerate fire, some even need it to
germinate;
• But, deciduous trees are damaged by fire.
• Fire releases nutrients, and creates meadows
supporting higher biodiversity.
• Fire climax ecosystems: ecosystems that depend on fire
to maintain their existence (e.g., some grasslands and
pine forests)
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Sunday, January 29, 2012
As we’ve seen, there’s all sorts of
ecosystems, all around the world.
But as I’ve complained, this book tries to do
way too much, so . . .
Let’s take the time to watch an episode of
the excellent series, the BBC’s Planet Earth,
on one of the most biodiverse terrestrial
ecosystems of the world, the rainforest!
We’ll discuss aspects of this film in the
lecture next time, when we’ll pick back up
the text with Chapter 6.
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Sunday, January 29, 2012
So here it is . . .
Episode 8, “Jungles,” of the 11 part British
Broadcasting Corporation’s series Planet
Earth, narrated by David Attenborough.
It used to be here:
http://video.google.com/videoplay?
docid=-2934374342545375813# . . .
But copyright infringement most likely took it
down. So I purchased the real thing.
If you’re curious about the series, the
Wikipedia page has a great story on it:
http://en.wikipedia.org/wiki/Planet_Earth_
(TV_series)
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Sunday, January 29, 2012