MODULE 4 Flashcards
Queensland hotspot for for tree clearing
2/3 the annual rate of deforestation in the Brazillian Amazon.
australia’s ecosystem…
In a poor states and is deteriorating.
____ contributes most to environmental assests
Land
System of Environmental-Economic Accounting framework
an internationally agreed approach for producing comparable statistics on the environment and its relationship to the economy
Value of long-term studies:
- document the changes
- identify the drivers of change
- provide the evidence and knowledge needed to inform better natural resource management
At least ____ Australian ecosystems have been reported to show signs of collapse or near collapse, although none has yet collapsed across the entire distribution
19
Behaviour
part of how organisms respond to the biotic & abiotic environment
Fitness
an individual’s relative contribution to the next generation’s gene pool
does foraging on high quality food provide a fitness advantage?
feeding on high quality food increases reproductive output
Behaviour is ecologically significant because it:
- is a link between individuals & their environment
- affects demographics (population levels outcomes)
- affects interactions among species (community-level outcomes)
Behaviour is evolutionarily significant because it:
- has some genetic basis (think nature vs. nurture)
- affects fitness
- can be selected (benefits > costs)
Behaviour: 3 key aspects
- Obtain food
- Avoid becoming food
- Reproduce
1.Obtain food
- Foraging
- Ambush (camo)
- Active (agile/fast)
Optimal foraging theory
modelled which food items to eat in a non-depleting environment
* predicts foragers should maximise net rate of food (= energy) intake
Marginal value theorem
modelled when to leave a food patch in a depleting environment
* predicts that foragers should leave food patches when capture/harvest rate at patch < average capture/harvest rate
2.Avoid becoming food
- Run away
- Group
- Hide
- Act or be costly
- Feed in safe places/times
Costs to anti-predator strategies
- Feeding near vegetation cover (missed opportunities to forage elsewhere)
- Grouping (competition for food, social aggression)
Behaviour - Reproduce
- Courtship & mating behaviour: non-random
- Parental care
- Increased survival & growth of offspring = fitness
Sexual selection types
- intrasexual selection competition (often ♂-♂) sexual dimorphism (e.g. hefty vs. slight, larger than females)
- intersexual selection mate choice (often by ♀) sexual dimorphism (e.g. flashy vs. plain)
Plant behaviour
- Leaves/stem grow towards light
- Roots grow along chem gradients
- Different time frame/ way of moving
Groups
Multiple organisms of same or different species occupying a common space
* Ephemeral or consistent
* Can be social, indirect, or accidental
Population
A number of organisms of the same species in a defined geographical area
Properties of populations include
- number of individuals or population size
- area they occupy
- age structure
- sex ratio
Importance of population biology
- Understand temporal dynamics
- Spatial distribution
- Natural selection
Rate (r) =
change / unit of time
Variables that drive changes in population size:
- Birth & Death
- Emigration (number leaving population) & Immigration (number entering population)
- Growth (individual)
- Age at maturity
- Sex ratio
Population growth in “closed” systems
No em/immigration
* Nt+1 = Nt + Births - Deaths
Exponential growth
Geometric
* population’s per capita growth remains the same irrespective of pop size; thus populations grow faster as they get bigger
Discrete pop. growth
Saw tooth shape
* reproduction occurs periodically
Continuous pop. growth
Curved line
* reproduction occurs year-round
Logistic curve
- Growth exponential at low numbers
- Growth slows at higher numbers
- Growth stops at carrying capacity (K)
Estimating birth rates
- Histology of reproductive organs
- Capture/counting of fertilised gametes
- Counting of newly born individuals
Estimating death rates (mortality)
- Tagging
- Follow individuals (for sessile organisms)
- Probability based (for more motile organisms)
Population growth in “open” systems
Nt+1 = Nt + Births – Deaths + immigrants - emigrants
Mark-release-recapture (MRR)
no. marked/ pop. size = no. recaptures marked/ no. recaptures total
Metapopulations
- Local populations, but individuals move
- Demographic rates vary spatially
- Large-scale dynamics dependent on local demographics and connectivity
Population viability analysis (PVA) factors
- Population Size/Carrying Capacity (K)
- Fecundity
- Mortality: Adults and juveniles
- Inter-annual variation in parameters
Factors that contribute to extinction
- Genetic stochasticity (small populations)
- Demographic stochasticity (random nature of births and deaths)
- Environmental stochasticity (variability)
- Catastrophes
- Human impacts
what is PVA used for
determine the long-term vulnerability of a species to extinction under a variety of scenarios
Biological species concept:
Groups of actually or potentially interbreeding natural populations, which are reproductively isolated from other such groups
Problems with species concept
- Hybridise
- Asexual?
- Fossil taxa
Do species really matter?
- Labelling
- History
- Conservation
Species richness
= number of species in a sample (S)
* vary with sample size
Species diversity
No. of species and no. of individuals in each species
Alpha (or α) diversity
No. of species within a particular areas or habitats
* Local
Beta (β) diversity
The difference in species between areas or habitats
* Comparing
Gamma (or γ) diversity
No. of species from all areas or habitats combined
* Regional
How many species are there: world?
1.5 – 1.82 million
* More that aren’t named/discovered
* Est. ~2.238 billion
* Bacteria
Autotrophs
Producers
* Synthesis organic from inorganic (CO2 etc.)
Heterotrophs
Consumers, degraders, decomposers
* Depend on autotrophs
* Animals
Food chains are usually…
Short
* Energy hypothesis
* Dynamic stability hypothesis
Energy hypothesis
There is energy loss between trophic levels
* high productivity ecosystems have longer chains
Dynamic stability hypothesis
Longer food chains less stable because fluctuations at low trophic levels magnify at high levels
* Predictable (stable) environments should have longer chains
Competition
(-/-)
Predation
(+/-)
Parasitism
(+/-)
Herbivory
(+/-)
Mutualisms
(+/+)
Commensalism
(+/0)
Amensalism
(0/-)
Obligate mutualism
Symbiosis: partners can only survive together
* Lichens: fungus and algae
Facultative mutualism
Partners gain benefit from associating, but can survive on their own
* Caterpillar protected by ants and ants feed of sugary secretions
Communities
Two or (usually) more species that occur together in space and time
* Interact with each other as an ecological unit
Assemblages
A group of taxonomically related species living in the same place
Succession
When an ecosystem develops through distinct stages from an empty or highly disturbed condition
Primary succession
Bare area without soil
e.g. sand-dune, bare rock, mining site
Secondary succession
In a habitat modified by other species
e.g. forest gaps, abandoned agricultural fields
Facilitation
Early arriving species make environment more favourable for later species
* Fixing nitrogen, retain water in soil etc.
Tolerance
neither negative nor positive interactions between early and late species
Inhibition
early species inhibit later species
____ is a driver of species richness and community composition
Disturbance
Intermediate Disturbance Hypothesis
Patchy mosaic of disturbance creates highest diversity
Resilience
how long before a community returns to an “equilibrium” after disturbance?
Ecosystems
The community of living organisms considered in conjunction with the abiotic components of their environment, interacting as a system
The water cycle
Processes of convection, precipitation, transpiration and respiration move water around the cycle
Nitrogen cycle
Plants cannot absorb atmospheric N
Absorbed as ammonium/nitrate after fixation of nitrogen by symbiotic bacteria/soil
N becomes limiting if microbial activity is inhibited
The carbon cycle
Most carbon is locked up in earth’s rocks as carbonate (fossil fuels)
Most active pool is CO2, 0.04 per cent of the atmosphere ++
CO2 is used in photosynthesis, released during respiration
Large amounts CO2 dissolved in ocean
Sea otters
Eat sea urchins which feast on kelp
* Kelp forest = C storage
* W/o otters, poor storage of C
Phosphorus cycle
Local
* Taken up by plants as phosphate from sparingly soluble soil storage pool
Australian enviro conditions
2/3 desert
Soils low in N & P
Variable rainfall
* Pulse & reserve
Silent Spring - Rachel Carson (1962)
Warned of synthetic chemicals accumulating in mammals and birds
* Raptors
* Bioaccumulation
* Pesticides
Bioaccumulation
Occurs when an organism absorbs a toxic substance at a rate greater than that at which the substance is lost
* Occurs in body tissues
* Higher predators at the top of food chains/webs
Toxins introduced in 40s-50s
Herbicides, pesticides, PCBs, heavy metals.
Inuit & PCB
PCB found in breast milk of mothers
* contaminated fish
* eat the tissue
* chem transported long distances
Fractionation
Chemicals evaporate from soils and carried by winds.
Distillation
Chemicals from fractionation condense in the cold
* Toxic snow and rain
Bioaccumulation: effects on growth and development
- Long-term tissue effects
- Lethal in many species
- Effects on developmental problems
Oil impacts on coastal communities
Clean-up can be as damaging as the oil itself
* Strong pervasive biological interactions in rocky intertidal and kelp forest communities contribute to cascades of delayed, indirect impacts and expand damages, delay recoveries
Biomass collapse
Fragmented landscape
* Land clearing
* Burning
* Decline in above-ground biomass after
Ecological meltdown
Mostly large animals and predators lost
* Hyperabundancy of small animals
* Plants cannot keep up with demands.
Climate change impact on plants and animals
- Range shifts (latitudinal/altitudinal)
- Abundance changes
- Change in growing season length
- Earlier flowering, emergence of insects, migration and egg-laying in birds
- Morphology shifts
Climate change impact on hydrology and glaciers
- Shrinkage
- Permafrost thawing
- Later freeze & earlier break up of river/lake ice
Effects of loss of ice
Species favouring ice-dominated systems with shallow benthic communities will diminish and be replaced by systems dominated by pelagic fish
Pollutants…
- Lead to fitness declines in species (accumulation)
- Are mobile, can’t be easily managed at the local level
Australia’s recent mammal extinctions
- Lost ~34 species in 200 yrs
- Critical weight range = 5.5-35kg
Aims of Conservation Biology
- To describe problems and understand processes
- To predict impacts of threats
- To develop solutions: undo the ‘human footprint’
- Ultimately: stop more species/communities/ecological processes going extinct
Jared Diamond’s “Evil Quartet” of extinction forces
- Alien species
- Over-hunting
- Habitat loss
- Co-extinction
Edward O. Wilson’s “HIPPO” of extinction forces
- Habitat destruction
- Invasive species
- Pollution
- Human over-population
- Over-harvesting
Key diff. between Evil Quartet and HIPPO
HIPPO included human over-population, underpins everything else.
Alien species NZ & AUS
- NZ more alien than native
- Aus 56 introduced species of vertebrates
Our new Megafauna
New invaders brought new megafauna
* 200-100 years ago with Europeans
* Cattle, sheep, goats, pigs, buffalo, donkeys, deer, horses, and camels are now all feral
* Many are major pests
Our new “Microfauna”
- Cats, rats, mice arrive with early explorers
- Rabbits, hare, foxes, cane toads and others released
- bees, wasps, new plants (e.g., blackberry, lantana, gorse, buffel), ants and much, much more
Invasion
1.Deliberate introductions
2.Human traffic
3.Native invaders
4.Success rates for invaders
“Tens rule”
- 1 in 10 of the plant and animal species brought into a region will escape to appear in the wild
- 1 in 10 of those escaped species will become naturalised
- 1 in 10 of these will become invasive
Invasive species tend to have characteristics that :
- maximize or enable high reproduction
- enable great ecological dispersal
- enable species to be greatly ecologically flexible
- cf. traits of pioneer species in succession
Overhunting
- Bounties
- Fisheries
- Bushmeat
- Over exploitation risks higher in data-deficient systems
Habitat loss and the extinction debt
Habitat destruction major cause of species extinction
* Extinction debt reflects the future ecological cost of current habitat destruction
Co-extinction
Critical ecosystem functions lost when species are lost
* Cascade
Solutions to extinction: Experiments
Key to identifying processes driving extinction and allowing management and future predictions.
* Predation experiments (removal/supplementation)
* Meta-analyses – towards a general pattern across experiments and studies
Operation Western Shield
- 1080 poison used
- Brush-tailed bettongs removed from endangered list, numbats, rock-wallabies, possums, bandicoots and chuditch also more common
- Successful mammal conservation program
Modelling
Useful to predict impacts and to identify management options (PVA)
* Comparing management options
* Minimum viable population (MVP) size
* Data hungry process, but very helpful and effective
Legislations
- Federal listing
- Provides recovery plans
- Identify critical habitats
- List threatening processes
Ecological restoration
Process of repairing damage caused by humans to the diversity and dynamics of indigenous ecosystems
* Restoring ecosystems to some pre-impact or reference state
* Enhancing habitat quality
* Restoring ecosystem functions via reintroductions
Succession of plant species
Follows a pattern of pioneer species occupying an area which was disturbed
* Consist of annual plants and these are replaced by perennial plants and grasses, shrubs and then trees as the community moves toward being comprised of climax species.
