what is ecology?
ecology is the study of the interactions that determine the distribution and abundance of organisms.
in defining the place an organism occupies an environment, we need to answer three questions:
- 1.what - the function an organism plays in the habitat in which it occurs e.g. consumer, top predator, producer
- 2. where- where the organism can be found in its habitat, e.g. australian arid desert
- 3. how - how the organism carries out its role in the environment is its niche, which is determined by the limits to the distribution of a species (this is unique to an organism):
- -fundamental niche (the physical limits)
- -realised niche (the biological limits)
explains the geological factors that affect the distribution of habitats where organisms can be found.
are determined by energy and nutrient flow, which are subject to biogeochemical cycles. The role of an organism in its ecosystem will determine the availability of resources, and hence what it does will affect its abundance.
describes the interactions between organisms, and how that affects both their distribution and their abundance, and how they are able to make use of their fundamental niche.
models the dynamics of populations (i.e. changes in their abundance), depending on their life histories and vital rates, and also on their density (i.e. how they make use of available resources).
ecology is crucial in solving problems relating to ....
human diet, conservation, human demographics, climate change and biodiversity
abundance and diversity of organisms depends on available resources:
- -air, co2 and o2
- -energy, e.g. light, temperature
- -nutrients, macronutrients and micronutrients
What are the most limiting factors for terrestrial ecosystems?
- distribution of water:
- -distribution and abundance of organisms depends on the availability of water
what determines the distribution of water on land?
-the movement of air, which is determined by 'simple physics'
- 1. Hot air carries more water than cold air.
- 2. Hot air goes up, cold air goes down. 3. Hopkins’ bioclimatic law: air cools down as it goes higher.180 m higher = 100 km closer to pole4. Coriolis effect: Longitudinal movement on a rotating object results in apparent latitudinal drift.
Consequences of physics
- - It is warmer closer to the equator, because sunshine acts directly rather than obliquely
- - Convection of air is determined by the incidence of sunlight.
- - At the equator and at 60˚latitude ascending air releases water, resulting in and abundance of vegetation.
- - At the poles and at 30˚latitude, descending air sucks water away, resulting in deserts.
- - The direction of winds is determined by the Coriolis force.
- - At the equator land rotates at 40,075km per day (1670 km/h), at the poles it is 0.
- - Winds are easterly in the tropics (trade winds), and westerly in the temperate zone.
- - Rain shadow: Mountains obstructing the prevailing winds force air to move up. Air cools down as it moves up, and loses its water content in the form of precipitation (rain, snow).
- 1.) The surface of the Earth is warmed differently by the Sun as the angle of incoming light is different at the equator than at the poles. The equator is hotter, the poles are colder.
- 2.) Because of the difference in density, hot air at the equator rises, cold air at the poles sinks
- 3.) In theory, the down and updrafts should create a continuous vortex of air: moving towards the equator at the surface, towards the poles at the higher levels of the atmosphere.
- 4.) In practice, our atmosphere can't support the continuous movement of gasses over 10,000km, and the movement of air breaks up into three separate cells.
- 5.) The three cells define the tropical (0-30° latitude, Hadley cell), temperate (30-60° latitude, Ferrel cell) and polar (60-90° latitude, Polar cell) zones.
- 6.) As can be predicted from the direction of air movement in the three vortices, surface winds blow towards the equator in the tropical zone, and towards the pole in the temperate zone.
- 7.) This is where the Coriolis effect will step in. The movement of the earth's surface is faster at the equator (40,075.16 km/day, or 1670km/h, or MACH 1.36) than towards the poles. At the pole the speed is zero.
- 8.) Because air moving towards the equator is moving into a zone moving faster than itself, it will lag behind the land, resulting in an overall east-to-west direction (easterlies). Conversely, air moving towards the poles "overtakes" the land it is moving over, resulting in an overall west-to-east direction (westerlies).
Why is there abundance of vegetation at the equator?
-ascending air is hot air, cooling down, can't hold precipitation anymore, resulting in abundance of vegetation
why are there deserts at the poles?
because descending air sucks water away, resulting in deserts
What determines the direction of winds?
- the coriolis force:
- -at the equator the land rotates 1670 km/h whereas the poles speed is 0km/h
- -winds are easterly in the tropics and westerly in the temperate zone
the rainshadow effect
- Mountains obstructing the prevailing winds force air to move up.
- Air cools down as it moves up, and loses its water content in the form of precipitation (rain, snow).
why is australia green in the east and brown in the west?
because australia is between 0 and 30 so winds are easterly.
aside from the coriolis effect, what also has to be considered when looking at wind direction?
the presence of continents, mountains affect wind direction
wind direction between 0 and 30
easterly (ie east to west)
wind direction between 30 and 60
westerly (ie west to east)
temperate west coasts of australia
- cold water is rushing north
- air moves off the sea on to the land
- far from the equator, water is warmer than land, constant rain supports wet forest
temperate west coasts (further north of 35 degrees)
- gets drier, more scrubland --> less tall forests
- air moves from east to west, bringing dry air from central australia
- air moves off sea on to land
temperate east coasts of australia
- rainfall caused by easterly winds coming in and rainshadow effect
- result in lush eastern side of australia
Temperature depends on how close you are to water because
- water moderates temperature fluctuations
- closer to water --> temperature fluctuations will be much less
- i.e. wet air loses heat more slowly than dry air does
- a biome at the extreme limits of plant growth
- arctic or alpine tundra
- subsoil is permanently frozen
swampy coniferous forests of high northern latitudes
found in tropical regions around the equator, high rainfall, abundance of organisms
- high rainfall in some seasons, low rainfall and fire in some seasons
- support highest diversity of wildlife
- found between tundra and rainforests
- the conversion of energy into chemical energy stored in organic compounds in living organisms
- ie primary producers are the organisms that convert non living energy into living energy
examples of sources of energy that can power life
- photon energy -- ie sunlight
photosynthesis reaction/respiration reaction
- photosynthesis: water + carbon dioxide +light --> glucose + oxygen
- respiration: glucose + oxygen --> water + ATP + carbon dioxide
the availability of biochemical energy (ATP) depends on...
- air (co2 and o2)
limitations of aquatic environment?
- air (co2 and o2)
why is it a problem getting sunlight air and nutrients in one place in the ocean?
- light is found at the surface of the ocean, nutrients found at the bottom of the ocean.
- swamps have so much net primary production because the distance between all the resources is smaller. ie nutrients close to sunlight.
the different feeding relationships in an ecosystem which determine the route of energy flow and the pattern of chemical cycling.
energy is ___ between trophic levels.
- -as waste
- -life maintaining processes
primary consumers are
the animals eg deer
predator of the primary consumer
how much of the avaialable energy the organism is able to utilise and incorporate in to its own self/ body mass
energy can go three ways
- waste: unassimilated energy
- growth: energy assimilated as biomass
- respiration: energy used to maintain life
respiration levels highest in
- homeotherms (ie organisms that maintain a constant body temperature)
- and e.g. hummingbirds
how do ecosystems work that have a high primary consumer biomass compared to that of primary producers?
these types of ecosystems can exist if primary production has a high rate of replenishment.
_________ is the ultimate limitation to ecosystems at a large scale
e.g. lichen is the primary source of reindeer's energy. it sits on permafrost and so accumulates all the nutrients in them physically (can't go further down). this gets grazed off by the reindeer (further level of accumulation). eskimos eat the reindeer, another level of magnification. strontium 90 isotope from nuclear explosions built up in lichen first, then in the bodies of the reindeer and then in the bodies of the eskimos.
the abundance of species
the number of species is limited by the number of available...
The full range of environmental conditions and resources an organism can possibly occupy and use, especially when limiting factors are absent in its habitat.
The part of fundamental niche that an organism occupies as a result of limiting factors present in its habitat.
sanderling was good at shallow water hunting for food with small beak but other shallow water birds have more specialised beaks for special niches, making use of special/different resources.
so one big niche to start out with that could fill it quite happily and maintain its population, the only way other organisms could compete was by becoming specialised at 4 different niches. (EXAMPLE OF COMPETITIVE EXCLUSION)
- avocet - upward curve of beak, can pick up things that stick their head out of the mud
- curlew - also in competition with sanderling, perpendicular beak, can get worms that live underneath the surface
- spoonbilled-sandpiper - catch swimming crustaceans
- wrybill- beak always curves to the right, stick beak under pebbles, get snails
- specialists are ecologically more efficient than generalists. (sanderling example with 4 other birds)
- specialists will be spaced evenly along the axes of resource use
- evolutionary time is required for specialisation
coping with disturbance
- disturbance limits the availability of resources
- therefore generalists are more ecologically efficient than specialists
coping with no disturbance, maximal disturbance and intermediate disturbance
- no disturbance:high biomass, low diversity, so the coral ends up specialising and competing and one wins
- maximal disturbance: all dead
- intermediate: the biodiversity increases, species compete with each other but not long enough for one to win because they dont have the evolutionary time.
the intermediate disturbance hypothesis states that
- diversity will be the highest when interference prevents competition but is of low enough intensity to allow many species to prosper
- disturbance may be due to the environment eg cyclone or other organisms, e.g. predation - starfish eating mussels keeps mussel population under control, prevents them dominating the coastline.
- menhaden fish (primary consumer) in chesapeake bay aquatic system
- used to filter 10 liters of seawater per minute, filtering all the algae
- company fished them all out of the bay
- now algae with high growth rate kills everything out in the bay
- disproportionate effect on its environment relative to its biomass
- can be primary producers as well (species of banksia in western australia that flowers when no other species flowers, thanks to this species, pollinating birds can stay alive during these months. pollinating birds stay alive and keep sexual reproduction amongst plants happening)
equilibrium theory of biogeography
species diveristy on islands will represent a dynamic balance between the probability of successful colonisation by new immigrant species and extinction of existing resident species
- single large or several small?
- one big island with high biodiversity
- several small less biodiversity
- islands together better than clump far away
- immigration ease
- 4 small subdivision islands worse than one island
- smaller only better in the case of fire