06 ecol inter

AnnouncementsFebruary 9, 2011

Basics of Ecology and Evolution II: Ecological Interactions

Lecture Objectives:

1. Learn basic concepts of Ecology

2. Learn 5 major categories of interactions

3. Be introduced to ways humans alter interactions

Environment can be divided into biotic and abiotic factors

Biotic - Living portions of the environment

Predation, parasitism, competition, etc.

Abiotic - Nonliving factors

Rain, soil type, temperature, etc.

All organism have a range of requirements that determines where they can live

The biotic and abiotic factors of any particular place determine where they do live

Tolerance Limits – refer to minimum and maximum levels beyond which a particular species cannot survive or reproduce.

Niche – Total set of environmental factors that determines a species’ distribution.

Yellow-billed Magpie

Red-cockaded Woodpecker

The House Sparrow was introduced into Brooklyn, New York,

in 1851.

House Sparrow

Native to Europe

Interactions among organisms

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 organism


Types of predators

Active predators: chase & overpower prey

http://www.youtube.com/watch?v=iarsmqA3dck

Antlion

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

Cryptic Coloration: blend in with environment

Many prey items have traits that reduce predation

http://www.youtube.com/watch?v=SCgtYWUybIE

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



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

Note: book makes it more complicated by calling it 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

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)

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

Ex. Heartworm

3. Parasitism (+,-)

Malaria carrying mosquito

Vectors: animals that carry parasite from one host to another

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

Nest Parasitism

Common Yellow-throat

Adult cowbirds don’t build nests

Cowbird


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

Commensalism is a ( + / 0 ) relationship

Remora and shark


5. Mutualism - Both species benefit (+/+).

Acacia and ants

*Tree provides nectar that the ants eat

*Ants defends tree against grazers

Summary of 5 major Interactions

Predation

Competition

Parasitism

Commensalism

Mutualism

Ind. 1 Ind. 2 Explanation Example

Food webs:

All species in a community are interconnected to varying degrees.

An estimate of interactions among species between only 2trophic levels (10,000 plants and 100 herbivores) in Hawaii

Sheppard et al. 2004 Mol. Ecol.

From Cohen et al. 2003 PNAS

Producers convert sunlight to biomass

90% of useful energy lost as heat from one trophic level to the next

Some energy always lost whenever it is converted between forms (2nd law…)

Keystone species: a species that plays anessential role in community stability.

Indicator Species: a species that providesinformation about the quality of an area.(could be rare or a habitat specialist)

Umbrella species: a species that can be usedas a surrogate for the heath/status of theentire community. (tend to need a lot of area)

Do all species matter? Is there redundancy in communities?

Paul Ehrlich made an analogy between species in communities and rivets on the wing of an airplane. Removing a few rivets from an airplane is undoubtedly safe. How many are you willing to remove?

On average, there are only 2 degrees of separation between any two species in a food web.

Percentage of threatened or endangered species in the U.S. imperiled by:

Why are species declining?

Disease - 3%

Overexploitation - 17%

Pollution - 24%

Invasive species - 49%

Habitat degradation and loss - 85%

Dave Wilcove et al. 1998 BioScience

Photo: Darren Irwin

How have people changed these interactions?

1) Introduced species

2) Habitat destruction or alteration

Introduction of novel predators and parasites can devastate natural communities.

3) Hunting / exploitation

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

Practice exam question:

In the trophic pyramid, the relationship between an herbivore (primary consumer) and a producer is best described as which type of ecological interaction?

a) Commensalismb) Mutalismc) Interspecific competitiond) Predator-preye) Host-parasite

By the end of this lecture you should be able to:

1. Define biotic and abiotic environmental factors and explain how each influence a species’ niche.

2. List the 5 main types of species interactions and tell who benefits from each type of interaction (e.g., +/+, +/-, etc.)

3. Recognize examples of the types of species interactions.

4. Understand food webs and degrees of separation within them

5. Explain how humans influence these interactions.

6. List some strategies used by prey species to avoid being eaten.

Technology

06 ecol inter