AnnouncementsSeptember 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.

Evolution does not occur within an individual.

Evolution does not occur within a generation.

Traits must have genetic basis.

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.

What is Evolution?

Proposed by Charles Darwin in his book “On the Origin of Species” published in 1859

Species— Those organisms potentially capable of reproducing naturally among themselves, and producing viable offspring.

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)

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

*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

* More offspring are produced than survive to reproduce

Evolution in action

Pepper Moths in England

two forms: light and dark

Light colored ones could blend in with lichens on trees

Prior to 1845, most moths light colored

Evolution in action

Pepper Moths in England

Light colored moths easy for birds to see on soot-covered tree, dark colored moths harder to see

Increasing pollution led to soot-covered trees without lichens

By 1950, most moths black

Several generations later

Several more generations later

Before 1845 Environment changes, now more black moths and fewer white moths survive to adulthood

1950

Several more generations later

TIME

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

Interactions among organisms

Abiotic – Non-living factorsBiotic – living portion of the environment

What are some biotic factors that contribute to this differential survival and reproduction?

1. Predation

2. Competition

3. Parasitism

4. Commensalism

5. Mutualism

1. Predation (positive for consumer, negative for prey)

One animal consumes another

Interactions among organisms

Types of predators

Active predators: chase & overpower prey

Sit-and-wait predators: motionless until prey close enough to strike

Sit-and-wait predator

Antlion

Cryptic Coloration: blend in with environment

Many prey items have traits that reduce predation

Warning Coloration: conspicuous to convey threat

Many prey items have traits that reduce predation

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

Prey is harmed (-) by being eaten

Predator benefits (+) from food

Predation is a (+ / - ) relationship

Competition: organisms compete for the same limited resource

Ex. light, food, mates, habitat, etc.

2. Competition

Competition is a (- / - ) relationship

Interactions among organisms

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

3. Parasitism

1 organism (parasite) living in or on another organism (host), from which it derives nourishment

Ex. Tapeworm

Interactions among organisms

Parasitism is a (+ / - ) relationship

3. Parasitism (+,-) Ectoparasites—Live on host’s surface

(e.g., Fleas, lice, some molds)

Endoparasites—Live inside host.(e.g., worms, protozoa, bacteria, fungi)

Ex. Heartworm

3. Parasitism (+,-)

Parasitoid

Nest Parasitism

Common Yellow-throat

Adult cowbirds don’t build nests

Cowbird

Malaria carrying mosquito

Vectors: animals that carry parasite from one host to another

Examples: Malaria, Lyme Disease, West Nile Virus, Bubonic Plague

Interactions among organisms

4. Commensalism —One organism benefits, while the other is unaffected.

Commensalism is a ( + / 0 ) relationship

Remora and shark

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

Predation + -

Competition - -

Parasitism + -

Commensalism + Neutral

Mutualism + +

Individual 1 Individual 2

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.