Protective colouration and sucession Flashcards
Aposematic colours
Warning colours to show that they are poisonous
Mimicry
Bastian = palatble (not harmful) insects resemble brightly coloured distasteful species
Mullerian = unrelated distasteful species resemble one another
Predator-prey co-evolution
predators evolve to overcome prey’s anti-predator defense mechanisms
Co-evolution
Parallel developement of adaptions in a population or species that are so constantly interacting with each other that start to exert selective pressure on each other.
Interspecific competition forms
Interference - Individuals of one species harm another species directly. Animals fight for resources . Plants release toxins that prevent other plants growing close.
Exploitative - 2 or more populations exploit the same limited resource. Presence of 1 species reduces the resource availability for others.
Gause experiement
Studies competition among 3 species of Paramecium grown in culture tubes feeding on the same bacteria.
2 experiments = growing alone and growing together. Constant carrying capacity. Same bacteria. Removed waste materials. Monitored population growth over time.
Conclusions:
Competitive exclusion principle - populations of 2 or more species that rely on the same limiting resource and exploit them in the same way cannot exist indefinitely.
One species in more successful and will harvest resources more efficiently and produce more offspring.
Ecological niches
No 2 species can have the same niche.
How it utilizes resources of its environment.
Space, Food consumption, temperature range, Moisture requirements.
What is a habitat?
The place where an organism lives. Same habitat but different niches.
Fundamental niche
The environemntal conditions and the resources that a population can tolerate and use = total abiotic niche available
Realised niche
The environmental conditions and resources that a population truly uses = used by organisms after competition have been taken into account.
Smaller than the fundamental niche.
Some resources are utilised by other species
Interactions and ecological niches
Experiments by Joseph Connel
Studies rocky shores and interspecific competition in barnacles.
How interspecies interaction affects the niche.
Resource partitioning
Simpatric species divide resources to prevent direct competition.
Utilise different resources for the different species.
They are uniquely adapted for a specific resource
Focus on one specific adaption to avoid competition.
What is character displacement?
Reducing interspecific competition
Allopatric - same but different geographic area
Sympatric - Different but in the same geographic area
3 types of symbiosis?
Commensalism - one species benefits other is unaffected.
Mutaluism - both species benefit
Parasitism - One benefits the other is harmed.
What is commensalism?
One species have positive gai whilst the other is unaffected.
Highly co-evolved mutualism
What is mutal cooperation?
Both species gain something. both make inputs
Ants an acacia
What is parasitsm?
Exremely small predators
Prey loses something and they gain something.
Ecto-parasites:
External
Have elaborate sensory and behavioural mechanisms.
Endo-parasites:
Internal
complete lifecycle inside hosts
Parasitoids = insects that lay eggs inside larvae, young consume the tissues as they grow.
What is a keystone species?
Changes the entire community composition.
Beavers, figs and rhinos
Conserving keystone species = conserves other species.
Trophic structure
Primary producers
Primary consumers
secondary consumers
tertiary consumers
quatenary consumers.
Food chain
What eats what?
One organism eats another
Links organisms from food to the consumers.
Factors that influence biodiversity
Disturbance
Evolutionary age
Climate - type of environment
Immigration rate - the area is conducive for immigrating or extinction
Are extinction effects - How easily does an are expend extinction
Ecological succession
Communities change over time = succession
response to disturbance
alter habitats and resources in ways that favor other species
Primary succession
devastated lifeless basin with no previous communiy or after a volcanic eruption.
Secondary succession
After fire in fynbos
Existing communities are disturbed,
Climax vs. Pioneer
Pioneer - was the first and can be dispersed quite far.
Climax - end of succession has a long lifecycle and limited offspring. It occurs once the ecosystem has been established.
What are the 3 different models of succession?
Tolerance
Facilitation
Inhibition
Tolerance
succession proceeds because competitively superior species replace competitively inferior ones
early-stage species neither facilitate nor inhibit the growth of later-stage species
more species arrive at a site and resources become limiting, competition eliminates species that cannot harvest scarce resources successfully
Facilitation
that species modify the local environment in ways that make it less suitable for themselves but more suitable for colonization by species typical of the next successional stage
changes in species composition are both orderly and predictable because the presence of each stage facilitates the success of the next
Inhibition
that new species are prevented from occupying a community by whatever species are already present
Succession is neither orderly nor predictable because each stage is dominated by whichever species happen to colonize the site first
Processes of Succession
results from a combination of facilitation, inhibition, and tolerance
with interspecific differences in dispersal, growth, and maturation rates
Disturbance and density-independent factors also play important roles, in some cases speeding successional change
In other cases, disturbance inhibits successional change, establishing a disturbance climax (disclimax) community
Effect of disturbance on communities
intermediate disturbance hypothesis, species richness is greatest in communities that experience fairly frequent disturbances of moderate intensity
Moderate disturbances allow K-selected species to survive while creating openings for r-selected species to arrive
Where disturbances are severe and frequent, communities include only r-selected species with fast life cycles
Where disturbances are mild and rare, communities are dominated by long-lived K-selected species
Why is species richness is the highest in the tropics and decrease as you move towards the poles?
High temperatures allows for high metabolic activity in animals and areas of plentiful food sources.
Evolutionary age and latitude diversity gradient
The poles experienced ice ages.
Nearly all the species in the poles died during the ice age and thus these regions may still be busy recovering.
Latitude and Climate gradients
the primary reason for latitudinal species richness.
The two major climatic factors: sun light and water availability
Variations in Species Richness
Difference in species richness based on latitude and climate
Species richness on islands depends on?
- Size of island
- Distance from mainland
- Immigration and emigration
- Extinction
equilibrium theory of island biogeography
Robert MacArthur & Edward O Wilson
addresses variations in species richness on islands of different size and different levels of isolation from other landmasses
An equilibrium between immigration and extinction ultimately determines the number of species that occupy an island
The mainland forms a species pool from which species immigrate to offshore islands as new colonizers
As the number of species on an island increases, the extinction rate rises –influenced by competition and predator-prey interactions
MacArthur en Wilson
Island species richness depends on the balance between colonisation and extinction.
The mainland holds a species pool that act as source of immigration.
Balance between immigration and extinction
Islands further away from the mainland is harder for colonisers to find
Larger islands can maintain larger populations as they have a lower chance of extinction
Effect of Island Size
At equilibrium, large islands have more species than small islands
Large islands have higher immigration rates than small islands do because they present a larger target
Large islands have lower extinction rates because they can support larger populations and provide a greater range of habitats and resources
Effect of Distance from Mainland
At equilibrium, islands that lie closer to a mainland source have more species than more distant islands
Islands near the mainland have higher immigration rates than distant islands because dispersing organisms are more likely to locate them
Distance does not affect extinction rates
why is island biogeography so important?
Species overall area started to reduce
More compititons
More chance of extinction
One species will always start to out-compete the others
Species start to diversify and speciate.
Immigration of Arthropods to Mangrove Islands
The island nearest to the mainland had more species than the most distant island
