Term 3 Flashcards
What is a community?
Set of all populations found in a given place
How can interactions between individuals and populations be shown?
Food web
What are the different trophic levels of a food web?
- Producers
- Consumers
What happens at each trophic level?
There is a loss of energy
What does the level of energy mean?
A lot of energy can sustain a lot of trophic levels and therefore a large community
Describe what happens with 2 species in the same realised niche
Can’t maintain the same realised indefinitely one will drive the extinction of the other
- eg weasels
Give an example of how there can be huge differences on a small spatial scale?
MEADOW - differences in soil and sunlight
DESERT - soil moisture varies greatly
How do interactions differ on a temporal scale?
- Day and Night pollinators have different predators
- Species change activites and location seasonally
- Ckastal marine communities follow the rise and fall of the tide
What is primary succession?
how a community forms from nothing to a climax community
what are the stages of primary succession?
- bare rock and pioneer species
- intermediate species
- climax community
what would be found at the bare rock stage of primary succession?
mosses lichens. die and decompose and soil forms. small plants grow eg grasses.
what would be found at the intermediate stage of primary succession?
grasses, shrubs and shade intolerant trees
what would be found at the climax community stage of primary succession?
shade tolerant trees eg oak. Larger animals
what is secondary succession?
life has existed here before but a disturbance has occured
describe secondary succession?
- a fiire
- colonised by r strategy species
- plants then shrubs then trees then climax
what is cyclic succession?
communities can be subject to a continual distubance
- eg world without fire there would be huge areas of climax community in grasslands
what are the natural sources of disturbances?
- abiotic: droughts, floods, hurricanes, fires
- biotic: invasions and extinctions
what are the antropogenic sources of disturbances?
pollution, invasions, exploitation, global warming
what are the two features of community stability
- resistance
2. resilience
what is resistance of a community?
ability to not be disturbed
what is resilience of a community?
how it recovers. elasticity (speed) and amplitude of change
how to measure resistance?
How much does population abundance/community biomass change
How often are invasions are successful
How often do extinction occur
How much does biomass vary
how to measure resilience?
How quickly does population abundance/community biomass return to normal
describe the Exxon Valdez Oil Spill
11 million gallons of crude oil were spilled
Widespread spatially → all the way down the coast
Casualties
Seabirds, sea otters, harbour seals
Clean up costs
3.2 billion dollar
what was the recovery after the oil spill?
Unoiled shore (control)
Oiled then cleaned
Oiled and uncleaned
Rockweed populations returned to normals in 2 years (uncleaned) took 1 year longer than (cleaned)
what was the diversity of sediments 2 years after oil spill?
Uncleaned: reduced abundance but not diversity
Cleaved: reduced diversity and abundance
what are biological invasions?
- Populations entering a novel community
- often natural: process of speciation and extinction
- successful species expand in range
- could have no effect or a profound effect
What are the 4 different consequences of invasions?
- Invader dies out before establishing original community is unaffected
- Invader establishes and augments the community with no effect on the rest of the community
- Invader establishes with one or more extinction ni the resident community
- Invader establishes with one or more extinction in the resident community but eventually the invader dies out
what is ecesis?
the successful establishment of a plant or animal in a new habitat
what is an example of a natural invasion?
Collared dove
Spread from asia minor across Europe to Britain in about 50 years
what is human induced invasions?
Most invasions are currently the result of human activity
Especially as a result of trade and colonisation
Ships provide many opportunities in cargo holds and ballast tanks
what are ballast tanks?
When a ship unloads cargo → to make up for weight it takes up huge volumes of water
Travels back
Expels the water
This water can contain: comb jelly, cholera, zebra mussels → invasive marine species
describe human induced invasions
Leading to a homogenization of the worlds iota
Human-dominated ecosystems are growing, dominated by a few crop species and a handful of ubiquitous commensal species
Greater proportion of land covered with human invasive species
what is a keystone sepcies?
species with a strong interaction with a disproportionate effect on communities
- species whose removal would lead to significant changes in the food web
what are ecosystem engineers?
actively shaping the physical environment, creating habitat that wouldn’t otherwise exist
- eg beavers
what are keystone mutualists?
pollinators of ecologically dominant plants, or nitrogen fixing bacteria supporting legumes and hence a whole plant community and its reliant animals
what is an ecosystem?
community of organisms and physical environemnt
how is energy transferred to producers?
(photosynthetic and chemosynthetic organisms) take up inorganic carbon, nitrogen, phosphorus and other compounds form the environment and convert them into proteins, nucleic acids, lipids and more
how is energy trasnferred to consumers?
Primary producers directly
and/or other consumers
what are decomposers and detritivores?
return nutrients back to the soil
describe a marine ecosystem
photosynthesis by plankton
repsiration
have carbon
how is ecosystem energy not recycled?
- energy must be continually harvested from the environment
- photosynthesis = key producer
- energy stored in organic molecules (bonds)
- lots of energy is lost
what happens to biomass at each trophic level?
- reduces
- a lot of the biomass prodcued at one level isn’t consumed by the next level
- get a pyramid
how much is lost at each trophic level?
only about 10% of energy and biomass is passed on
what controls primary production?
- photosynthesis
- sunlight
- water
- nutrient availability
how does solar availability vary?
- intensity varies due to the curvature of the earth
- seasonality as the earth is on a tilt
how can water availability limit photosynthesis?
- depends on water
- carbon dioxide that can be fixed in a certain time period relies on water
- irrigation
- high water stress where people are living
how does nutrient availability vary?
- plants, algae and photosynthetic bacteria also need nitrogen, phosphorus, sulphur, iron
- abundance of one nutrient cannot make up for the lack of another
what is liebigs law of the minimum?
primary production is limited by the nutrient that is least available relative to its use by primary producers
how does primary productivity vary around the globe?
- little or no water = little or no productivity
- apart from this seems to follow the solar radiation map
- have to factor in altitude