Transcript 06_EcolInter

Announcements
September 6, 2006
Steve “crocodile hunter” Irwin died Monday
morning after being attacked by a stingray while
shooting a TV program off Australia's north coast.
Evolution and Ecological Interactions
Lecture Objectives:
1. Learn basic concepts of Evolution
2. Learn 5 major categories of interactions
3. Understand 2 ways humans alter interactions
Often, there are not enough resources for all
individuals in the population
Many individuals die before reproducing
Some individuals are better at surviving and
reproducing than others
What is Evolution?
The process of change in the traits of populations over time.
Process by which species' characteristics change over generations.
Traits must have genetic basis.
Evolution does not occur within an individual.
Evolution does not occur within a generation.
What is Evolution?
Evolution occurs primarily through natural selection
Natural Selection is the process that determines
which individuals within a species will reproduce
and pass their genes to the next generation.
Proposed by Charles Darwin in
his book “On the Origin of
Species” published in 1859
Genes— Distinct pieces of DNA that determine an
individual’s characteristics.
Population—All organisms of the same kind found
within a specific geographic region. (have the
potential to interact)
Species— Those organisms potentially capable of
reproducing naturally among themselves, and
producing viable offspring.
Natural selection can occur when:
* Individuals within a species show genetically
determined variation in traits
-this variation makes some individuals better at
surviving and reproducing than others
* More offspring are produced than survive to
reproduce
*Offspring with a particular trait survive better
than do those without that trait
*Over several generations, the frequency of that
trait increases in the population
Evolution in action
Pepper Moths in England
two forms: light and dark
Prior to 1845, most
moths light colored
Light colored ones
could blend in with
lichens on trees
Evolution in action
Pepper Moths in England
Increasing pollution led to
soot-covered trees without
lichens
Light colored moths
easy for birds to see
on soot-covered tree,
dark colored moths
harder to see
By 1950, most moths black
Before 1845
Environment changes, now more black
moths and fewer white moths survive to
adulthood
Several
more
generations
later
Several
generations
later
TIME
1950
Several
more
generations
later
Evolution in action
Resistance to herbicides
Evolution in action
Resistance to antibiotics
•Evolution does not just happen on long time scales
•Evolution is important for real-word issues:
agricultural, conservation, health
* Disease dynamics
* Invasive species issues
* Antibiotic and pesticide/herbicide resistance
Coevolution:
When two or more species interact closely they can influence
each other’s evolutionary direction.
In tightly coevolved interactions, evolutionary change in one
species will lead to evolutionary change in other or the second
species may go extinct.
Red Queen Hypothesis
Lewis Carroll's Through the Looking
Glass: “in this place it takes all the
running you can do, to keep in the
same place."
Example: host / parasite coevolution
Abiotic – Non-living factors
Biotic – living portion of the environment
What are some biotic factors that contribute to
this differential survival and reproduction?
Interactions among organisms
1. Predation
2. Competition
3. Parasitism
4. Commensalism
5. Mutualism
Interactions among organisms
1. Predation
One
animal
consumes
another
(positive for consumer, negative for prey)
Types of predators
Active predators: chase & overpower prey
Sit-and-wait predators: motionless until
prey close enough to strike
Sit-and-wait predator
Antlion
Many prey items have traits that reduce predation
Cryptic Coloration: blend in with environment
Many prey items have traits that reduce predation
Warning Coloration: conspicuous to convey threat
Batesian Mimicry: defenseless species (mimic) is
protected from predation by its resemblance to a
species that is dangerous
fly (bee mimic)
bumble bee
Mullerian Mimicry: 2 or more distasteful or
harmful organisms resemble each other
Interactions among organisms
1. Predation
Predator benefits (+) from food
Prey is harmed (-) by being eaten
Predation is a (+ / - ) relationship
Interactions among organisms
2. Competition
Competition:
organisms compete for
the same limited
resource
Ex. light, food, mates,
habitat, etc.
Competition is a (- / - ) relationship
Intraspecific competition — Members of
same species competing for resources
Interspecific
competition:
Members of different
species competing
for resources
May lead to
competitive
exclusion
Photos: Alex Wild
Interactions among organisms
3. Parasitism
1 organism (parasite) living in or on another
organism (host), from which it derives
nourishment
Ex. Tapeworm
Parasitism is a (+ / - )
relationship
3. Parasitism (+,-)
Ectoparasites—Live on host’s surface
(e.g., Fleas, lice, some molds)
3. Parasitism (+,-)
Endoparasites—Live inside host.
(e.g., worms, protozoa, bacteria,
fungi)
Ex. Heartworm
Parasitoid
Nest Parasitism
Adult cowbirds don’t build nests
Cowbird
Common
Yellow-throat
Vectors: animals that
carry parasite from one
host to another
Examples: Malaria, Lyme
Disease, West Nile Virus,
Bubonic Plague
Malaria carrying mosquito
Interactions among organisms
4. Commensalism —One organism benefits, while
the other is unaffected.
Remora
and shark
Commensalism is a ( + / 0 ) relationship
4. Commensalism (+,-)
Interactions among organisms
5. Mutualism - Both species benefit.
Acacia and ants
*Tree provides sugar solution
that the ants eats
*Ants defends tree against
grazers
5. Mutualism (+,+)
Summary of 5 major Interactions
Individual 1
+
Individual 2
-
Competition
-
-
Parasitism
+
-
Commensalism
+
Neutral
Mutualism
+
Predation
+
How have people change
these interactions?
1) Introduced species
2) Habitat destruction
Introduction of novel predators and parasites can
devastate natural communities.
Over 2,000 species of birds have gone
extinct on islands as a result of habitat loss
and the introduction of predators and
parasites.
Hawaii:
Habitat loss,
malaria, rats
and
mongoose
Points to know:
1. Know what evolution is and how is
operates. Understand coevolution.
2. Know the 5 main types of species
interactions.
3. Understand who benefits from each type
of interaction (one or both participants)
4. Understand how humans may influence
these interactions.