2. Objective
• Yesterday: You needed
to define and give
examples of density
dependent and density
independent limiting
factors
• Today: you need to:
identify, describe, and
give specific examples
of the 3 major
population interactions
– Feeding relationships
– Competition
– Symbiosis
3. What is a Community?
• The interactions between all species living in a
given area
– The boundaries of the area are defined by the
researcher who is studying the community
4. • Trophic structure-the feeding relationships between organisms
– Food chain-the transfer
of energy between
trophic levels
• Decomposers are
a vital part, but aren’t
shown
• Arrows point in
the direction of energy
flow
1. feeding relationships
Primary
producers
Primary
consumers
2o
consumers
3o
consumers
4o
consumers
Autotrophs
Herbivores/omnivores
Carnivores
Carnivores
5. • Food Web- a bunch of interconnected food chains
6. Food chains are limited; there are rarely more than 5-
7 links from the 1o
producer to the top carnivore….
*The 10% rule-
only 10% of organic
matter at each level
is converted into
usable energy that is
passed to the next
level; the other 90%
is used by the
organism or lost as
heat
8. • Intraspecific – same species, often fighting
involved to “win” the resource
– Can be very intense
9. • Interspecific – different species, usually no
fighting, just better at getting it
– Less intense since species have slightly different
niches
10. Competitive Exclusion Principle
• No two species can occupy
exactly the same niche
because competition for
resources would be too
intense
• One species will be better
at getting the resources
• The other species must
leave, adapt, or die
12. Resource Partitioning
• Two species evolve
adaptations that allow
them to use the same
resource in different
ways, at different
times, or in different
places in order to
minimize competition
13. 3. Predation: +/- interaction meaning that one individual
(predator) benefits, and another individual (prey) is
negatively affected
– Evolutionary connection: Predator-prey interactions
may select for unique adaptations
• Cryptic coloration- AKA camouflage
• Aposematic coloration-warning colors
• Batesian mimicry- a harmless animal mimics a harmful or
unpalatable one
• Mullerian mimicy-two or more unpalatable species resemble
each other
15. 2 rules about coloration
• Small + beautiful = poisonous
• Beautiful + easy to catch = deadly
16. Coevolution
• When two species have lived together and
adapted to each other for a long time such that
changes in the gene pool of one species leads to
changes in the gene pool of the other species
17. 4. Herbivory: A +/- interaction; an herbivore eats
a plant or algae
– Evolutionary connection: many plants possess
adaptations that help them avoid herbivory
Strychnos toxifera is a vine that produces strychnine
18. 5. Disease: pathogens (things that
cause disease) are another example
of a +/- relationship
– Differ from parasites in that
they’re usually microscopic
– EX: bacteria, viruses, protists,
fungi, & prions
– Like parasites,they can have a
large, negative effect on
population size
19. 6. Parasitism: a +/- symbiotic relationship between a
parasite & its host
– Many parasites have
complex lifecycles with
multiple hosts
– Parasite
outbreaks
can also greatly
affect host
populations
20. 7.Mutualism: A +/+ symbiotic relationship where both
organisms benefit
The Acacia tree provides nectar
to these ants and the ants provide
protection to the tree
21. 8. Commensalism: A symbiotic +/0 interaction where
one organism benefits and the other is unaffected
– Example: these egrets follow grazing herbivores to eat
the insects that the herbivores kick up as they travel
22. Some species have a disproportionate impact on their community
• These species often affect the biodiversity-variety of
different kinds of organisms-in the community
• Dominant species-Species in a community which are the most
numerous or have the highest biomass
24. • Not always bad - most crops and livestock
are nonnative species
25. • Sometimes - nonnative species takes over
– Often there are no predators for this species,
since it hasn’t evolved alongside them
– This gives the nonnative a competitive
advantage
26. Keystone species
• Have a large effect on the number and type of
other species in the ecosystem
27. Examples:
• Top predators - feed on and help regulate the
size of other populations
• Pollinators - control the size of plant
populations
28. Effects of losing a keystone species
• When a keystone species is lost - it leads to
population crashes and extinctions of other
species
29. Foundation Species
• Aka ecosystem engineers
• Play a major role in creating the
ecosystems in which they live
30. Examples:
• Elephants pull out or break small trees in
the African savannah
• This allows grass to grow and benefits
other grazers and open plains predators
32. What other factors affect the biodiversity of an area?
Two key factors: location & size of the community
– Equatorial-Polar Gradients- The further you move away from the
poles and closer to the equator, the greater the biodiversity of an
area.
• Why?? 1. Many polar and temperate regions have “started
over” due to glacier movement
2. Climate-the tropics receive more direct sunlight for longer
periods
» The differences in sun
exposure can be measured
by measuring evaporation
from soil & plants=
evapotranspiration
33. What other factors affect the biodiversity of an area?
• Two key factors: location & size of the community
– All other factors being equal, the larger the geographic area of a
community, the greater the number of species
• Why?? This is because the greater the area, the greater the
variety of available habitats
34. A special case: Islands
• In ecology, an island can be in the ocean, or any community that’s
otherwise isolated
• Island biodiversity is affected by the rate of species immigration vs.
extinction
– These two processes are affected by island size and distance
from the mainland
• If the colonization of an island is a chance event (for example
the probability that a seed will land on an island), then small
islands are less likely to be inhabited in this way.
• The closer an island is to the mainland, the more likely it is
that migration will occur between the mainland and the
island
35. When immigration is high, then extinction is low
since organisms are populating the island at a
higher rate
36. What is an ecological disturbance?
• Disturbance-storm, fire, drought/flood, overgrazing, or any
human activity which can remove organisms or resources from
a community
– A disturbance isn’t necessarily a negative event…some
communities rely on disturbances for the natural
progression of their “life cycle”
• Ex-Lodgepole pine trees require periodic fires in order to
release their seeds
Closed cone
Open cone after fire
37. What happens to a community after an
ecological disturbance?
• Ecological succession-the order in which an area is
recolonized after a major disturbance has stripped
away the existing vegetation
38. Two main types of succession:
• Primary succession- think of this as a blank canvas…
– The first organisms to colonize the area are autotrophic
prokaryotes, followed by lichens & mosses. Soil gradually
develop, more plants grow, and animals move in
• Community maturation could take 100s or 1000s of years
– When might primary succession occur?
When a new volcanic
island forms or in an area
where a glacier has
receded
39. Two main types of succession:
• Secondary succession- Occurs after a
disturbance, for example a fire, has wiped out a
community, but has left the existing soil intact
– Often, herbaceous plants colonize the area first,
followed by insects, larger animals, and trees
Hinweis der Redaktion
The Blue-Ringed Octopus is very small, only the size of a golf ball, but its venom is so powerful that can kill a human. Actually it carries enough poison to kill 26 adult humans within minutes, and there is no antidote. They are currently recognized as one of the world痴 most venomous animals.Its painless bite may seem harmless, but the deadly neurotoxins begin working immediately resulting in muscular weakness, numbness, followed by a cessation and breathing and ultimately death.They can be found in tide pools in the Pacific Ocean, from Japan to Australia.
The puffer fish produce rapid and violent death..Puffer poisoning causes deadening of the tongue and lips, dizziness, vomiting, rapid heart rate, difficulty breathing, and muscle paralysis. Victims die from suffocation as diaphragm muscles are paralyzed. Most of the victims die after four to 24 hours. No known antidote
Box Jellyfish. It has caused at least 5,567 recorded deaths since 1954. Their venom is among the most deadly in the world. Its toxins attack the heart, nervous system, and skin cells. And the worst part of it is that jelly box venom is so overpoweringly painful, that human victims go in shock, drown or die of heart failure before even reaching shore. Survivors experience pain weeks after the contact with box jellies.You have virtually no chance to survive the venomous sting, unless treated immediately. After a sting, vinegar should be applied for a minimum of 30 seconds. Vinegar has acetic acid, which disables the box jelly痴 nematocysts that have not yet discharged into the bloodstream (though it will not alleviate the pain). Wearing panty hose while swimming is also a good prevention measure since it can prevent jellies from being able to harm your legs.Jelly box can be found in the waters around Asia and Australia.