human population i nteractions in a c ommunity a.r. farmer 13 july 2011
TRANSCRIPT
HUMAN POPULATIONINTERACTIONS IN A
COMMUNITY
A.R. Farmer13 July 2011
Community Ecology
Community Producers, Consumers, Decomposers Predation Competition Intraspecific; Interspecific; Competitive exclusion; Symbioses - 3 typesparasitism mutualism commensalism
IMPORTANT CONCEPTS
CommunityA group of populations occuring in a particular area, e.g. zebras, hyenas, giraffes in the Kruger National Park
Trophic levels:• Produces(mainly plants)
Consumers Primary (herbivores) Secondary (carnivores) Tersiary (Carnivores)• Decomposers(bacteria
and fungi - saprophytes
Feeding levels in a community
Interactions within a Community
The five main types are:
Predation
Competition
Parasitism
Mutualism
Commensalism
PREDATION
In predation, one individual, the predator, captures, kills, and consumes another individual, the prey.
Predators, Prey, and Natural Selection
Natural Selection favors adaptations that improve a predator‘s efficiency at finding, capturing, and consuming prey.
These adaptations include a shark’s jaws, a scorpion’s claws and stinger, and a spider’s web and fangs
Other Predatory Adaptations
Prey Adaptation
Some animals are very fast and can escape capture simply due to their speed
Other prey animals depend on
camouflage, hoping to avoid
detection
Some organisms are poisonous and use bright colors (often yellow and black) to warn other organisms of their toxicity
Mimicry
In mimicry, a harmless species resembles a poisonous or distasteful species.
The harmless species is protected because it is often mistaken for the dangerous look-alike
Examples of mimicry
Prey-predation interaction
A
The cycles of increase and decrease reflects a predator –prey intercation
e.g lions feeding on impalas, lynx feeding on rabbits
Prey population reaches higher density than predator population
Portion A = geometric phase- rapid increas of prey, predator pop too low to hinder increase
More prey means more food for predators and the population increases
More predators = increase in mortality of prey Less prey could cause predators to emigrate /
die , hence prey population can increase again
Graph interpretation
Competition
Competition occurs when organisms in the same community seek the same limiting resource. This resource may be prey, water, light, nutrients, nest sites, etc.
Competition among members of the same species is intraspecific.
Competition among individuals of different species is interspecific.
Intraspecific Competition
Competition between organisms of the
same species
Interspecific Competition
Panthera leo
Crocuta crocuta
Competition between
organisms of the same species
Outcomes of Competition Niches of similar species may overlap. Two
species cannot compete for the same limiting resource for long.
eventually one species outcompetes the other
One species survive, other emigrates OR dies out
Even a minute reproductive advantage leads to the replacement of one species by the other.
This is called the COMPETITIVE EXCLUSION PRINCIPAL.
Evidence for Competitive
Exclusion the Russian ecologist, G.F. Gausse demonstrated that Paramecium aurellia outcompetes and displaces Paramecium caudatum in mixed laboratory cultures, apparently confirming the principle.
Resource Partitioning
When two or more similar species coexist, such as
these varieties of warbler, each species only uses part of the
available resources. This is called resource
partitioning. (species sharing
resources)
Resource partitioning
Resource Partitioning
PARASITISM Parasitism is a species interaction that
resembles predation in that one individual is harmed while the other benefits.
However, in parasitism, the parasite feeds on the host individual.
This does not result in the immediate death of the host. Rather, the parasite may feed on the host for a long time instead of killing it.
Ectoparasites
Ectoparasites are external parasites.
They live on their hosts body, but do not enter it.
Examples include ticks, fleas, lice, lampreys, leeches and mosquitoes
Ectoparasites
Endoparasites
Endoparasites are internal parasites, and live inside the host’s body
Endoparasites include bacteria and other micro-organisms, and many worms
Mutualism Mutualism is a symbiotic relationship in which both
members of the association benefit. Often help organisms obtain food or avoid predation.
Bacteria in human intestinal tact. Need not be equally beneficial to both species.
Cleaning Symbiosis
Cleaning Symbiosis
Pollination
Pollination is the most important of the mutualistic relationships.
The plant provides food for the pollinators, which in turn carries the pollen to another flower
COMMENSALISM
Is a relationship in which one species benefits and the other is not affected
INTERACTION IN A COMMUNITY