06 ecol inter
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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
Interactions among organisms
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
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
Many prey items have traits that reduce predation
Mullerian Mimicry: 2 or more distasteful or harmful organisms resemble each other
Many prey items have traits that reduce predation
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
Note: book makes it more complicated by calling it 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 (+,-)
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
Interactions among organisms
4. Commensalism —One organism benefits, while the other is unaffected.
Commensalism is a ( + / 0 ) relationship
Remora and shark
Interactions among organisms
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.