Topic 9 Flashcards
Ecological network:
Description of interactions that occur among species in a community.
General relationship
Trophic networks
E.g. food webs
• Description of feeding relationships among species in a community
Can be biased b/c it’s so complex to figure out
—> which species are included
—> greater focus on some sps groups (e.g. vertebrates) compared with other sps groups (e.g invertebrates)
—> results in missing data
—> Focus more on larger organisms
- difficult to create (data hard to collect)
- many diagrams in class are simplified—> real networks are complex
- stomach contents can sometimes be used to figure food webs out
TROPHIC LEVEL
position in food web; determined by # energy transfers from primary producers to that level
• Primary producers - 1st trophic level
• Herbivores (primary consumers) - 2nd trophic level
• Carnivores (secondary consumers) - 3rd trophic level
• Carnivores that feed on carnivores (tertiary consumers) - 4th level
Do this b/c almost all energy comes from sun and can learn how an ecosystem is structured
Trophic Dynamics
trophic levels & energy content in each are limited by inefficient transfer of energy up the food chain & NPP
10% rule Trophic Pyramids
- to know how much energy transferring through system
E movement through ecosystem affects how an ecosystem can be structured
—> only 10% get passed from 1 tropic level to the next
—> so ecosystems typically only have 4-5 tropic levels
Lower levels in a good web tend to be more abundant
—> E transfer is so inefficient between tropic levels that ecosystems cannot support large #’s of 2ndary or tertiary consumers
Nutrients vs. Energy Cycling
• Energy: 1-way trip through ecosystems
• Nutrients: used over & over
— elements required for development, maintenance, and reproduction
— can strain the ecosystem, limiting productivity
Ex: carbon cycle, nitrogen (important for plant growth)
— cycles can millions of years
Global P Cycle
Is an example of a cycle that involves deposits in rock
—> nutrient cycling between different compounds (ex: atmosphere, ocean, sediment) can occur over a long period of time
Human Induced Changes to P Cycle
(Significantly alterations)
• Increased additions – e.g., (fertilizer)
• P causes euthrophication
Blue-green algea is toxic to humans and animals, can be fatal
Examples
— Human movement of P from terrestrial to freshwater ecosystem.
— Atmospheric deposition of P onto land
— P moving from land to atmosphere
— Movement of P between oceanic atmosphere and atmosphere over land
— Atmospheric deposition into oceans
— Phosphorus can move from oceans to atmospheric pool.
— The largest pool of P is in marine sediments
— The amount of P dissolved in the oceans is about 1,000 times the amount in organisms.
— Uplift of marine sedimentary rocks can return phosphorus to terrestrial ecosystems
— Cycling of P between organisms and soil
Landscape
Mosaic of linked communities & ecosystems; patchwork of ecosystems
At landscape scale, communities & ecosystems linked via exchanges of materials (nutrients), energy & organisms
Global Biodiversity
— Can see a change in this.
— used to understand how organisms are doing
Landscape Ecology: Habitat Fragmentation
When habitat is broken up into smaller pieces (smaller fragments(
—> linear features (roads, cut lines for oil and gas operations)
—> pieces of habitat removed or altered (forestry cutting down chunks of forest)
Consequences of Habitat Fragmentation
— animals and other organisms can not move freely across the landscape
—> prevent them from accessing food, mates, or other resources (Ex: big horn sheep)
Climate Change
Some solar radiation is reflected by earth and the atmosphere
—> some radiation is absorbed by earth’s surface and warms it
—> some of the infrared radiation passes through the atmosphere.
Some is absorbed by greenhouse gases and re-emitted in all directions by the atmosphere.
The effect of this is to warm earths surface and the lower atmosphere.
—> infrared radiation is emitted by earth’s surface
Natural process but added green house gasses —> increases process
Enhanced green house effect —> human activity
More E is reflected back on earth, this is what causes increase in temp
Impacts:
Change in global average temperature (increasing)
— causes changes in precipitation and wind + weather patterns
Change in sea ice (melting)
— less ice, less reflection of radiation
Change in CO2 levels (increasing)
Change in sea level (increasing)
Consequences of Climate Change
Polar bears
Northern sps
Adaptations
—> less activity during summer (unlike other North American bears)
—> depend on sea ice b/c hunt seal
- climate change
—> reduce amount if sea ice, reducing amount of time that they can hunt - see changes in Trophic network in future due to climate change
Ex; sea ice habitat which will impact all sps at all trophic levels
Invasive Species
Sps introduced outside their native habitat that compete with native sps
Native species —> where they evolved/lived before humans moved them around
Ex: European starling
— in natural habitat pops are in decline (UK)
— introduced to North America
— doing well but they outcompete native bird sps —> especially nest habitat
Consequences of Invasive Species
Gila woodpecker is being outcompeted by starling
The sps that starling are outcompeting are typically sps at risk of becoming extinct
Zebra mussels are invasive sps that grow rapidly that cover surfaces in lakes, they outcompete native sps causing ecological harm. They also cover human infrastructure and this cause economic harm
Overexploitation
When a natural resource is removed at such a high rate that the ecosystem cannot recover
Consequences of Overexploitation
—> sps decline
Ex: Atlantic cod
—> fished almost to the point of extinction causing its pop to crash and the east cost cod fishery to collapse
Ex: passenger pigeon
—> went extinct in 1914 due (in part) to overhunting
— commercial hunting (hunt to sell) had little regulations at the time
— believed would never go extinct b/c their pops were so numerous, would darken the sky and sound like a thunderstorm when flying by
Consequences of Climate Change
Nitrogen cycle
Nutrient cycle (nitrogen)
Will see changes to nutrient cycling due to climate change
Ex: increasing in some nutrients due to human activities, these changes will impact ecosystems b/c it’ll change nutrient availability
Successfully Conserving Biodiversity
NOAA
Working to improve fishing —> we’re making improvements on short time frames
—> fewer fish pops are being over fished(over exploited) and more fish pops are recovering from over fishing
Successfully Conserving Biodiversity
California condor
Almost went extinct
—> few remaining individuals were brought into captivity
—> able to increase the pop through captive breeding
—> this sps plays an important role in nutrient cycling — we are successfully bringing it back from the brink of extinction
Went from a couple dozen to 400 in the wild
