Community Structure and BiodiversityChapter 46, part 1

Bell Ringer, 9/9 Come in and sit down QUIETLY. You can keep

your desks in groups as long as you can do so quietly.

What is one question that you wish had been on the test? Write the question and then answer it.

What are some ways that organisms interact in the environment? (‘I don’t know’ is not an acceptable answer. Brainstorm some ideas!)

Levels of Organization Biosphere: The earth’s surface; where all life

exists Ecosystem: The interactions of all living and non-

living things in an area Community: The interactions of all living things

in an area Population: The members of a species in an area

interacting with one another Organism: One individual living thing

Levels of Organization Organ System: Group of organs that interact with

each other Organ: Group of tissues interacting with one

another Tissue: Group of specialized cells interacting Cell: The basic unit of life

Biosphere

Ecosystem

Community

Population

Organism

Organ System

Tissues

Cell

Biosphere

Ecosystem

Community

Population

Organism

Organ System

You are here

Cell

Tissues

Organ

Factors that Shape Community Structure Habitat: The type of place where a species lives Communities have dynamic structures based on:

Climate and topography Types and amounts of food and other resources Species’ adaptations Species’ interactions Timing and history of disturbances

Bell Ringer, 9/10 Come in and find your seat quietly Get out your notes Answer the following question on your bell ringer:

Pick ONE factor that shapes community structure and explain how it affects the community.

Factors that Shape Community Structure All members of a community have the same

“address” but different “professions” Niche: A species’ ecological role; includes

conditions, resources, and interactions necessary for survival and reproduction Fundamental niche: The niche that an organism can

have Realized niche: The niche that an organism

ACTUALLY has

Factors that Shape Community Structure Example: Barnacles

Factors that Shape Community Structure Ex. Finches

Factors that Shape Community Structure Coevolution: When two species in close

interaction with one another evolve in response to one another Hummingbirds and flowers Garter snake and rough skinned newt

Factors that Shape Community Structure Categories of Species Interactions:

Commensalism: Benefits one species and does not affect the other (bacteria in your gut; barnacles on a whale)

Mutualism: Benefits both species (ants & acacia tree) Interspecific competition: Harmful to both species Predation: Free-living organism kills and eats another

(lion and gazelle) Parasitism: Live in or on host and usually don’t kill it

(fleas, ticks, mistle toe, tape worms)

Exit Slip, 9/9 When will your rewritten notes be checked? Compare and contrast predation and parasitism.

Give an example of each.

Bell Ringer, 9/10 Get your Exit Slips (on 2nd lab table) Get your pink paper (on 2nd lab table) On your bell ringer paper, answer the following

question: Explain the difference between a fundamental niche

and a realized niche. Give an example of each. Pick ONE factor that shapes community structure

and explain how it affects the community.

Bell Ringer, 9/11 Get your FRAYER MODELS from the back and

put them behind your Ch. 47 notes in your binder Answer the following questions on your bell

ringer: A unicorn can survive in warm or cool temperatures.

Their main competition, the magical fairy, thrives in warm temperatures. Based on this information, what is the unicorn’s fundamental niche? Realized niche?

Factors that Shape Community Structure Symbiosis: Species that spend most or all of their

life cycles in close association Symbiont: A symbiotic species Endosymbiont: A species that lives inside its partner Parasitism, mutualism, and commensalism can all be

types of symbiosis http://www.brainpop.com/science/ecologyandbehavi

or/symbiosis/

Commensalism Relationship in which one species benefits and the

other is not affected Cattle egrets and livestock Army ants and birds Stomach bacteria?

Mutualism Interaction in which both species benefit In some mutualisms, neither species can complete

its life cycle without the other Yucca plants and moths

Mutualism Most mutualistic interactions are not life or death

Plants have more than one pollinator Nitrogen-fixing bacteria Lichens

There is often some conflict between partners Lichens: Algae and fungal symbionts

Mutualism Some mutualists defend one another

Clown fish and sea anenomies Ants and the acica tree

Mutualism The Theory of Endosymbiosis

Mitochondria and chloroplasts were once independent bacteria engulfed by a bigger cell

Host relied on ATP produced; symbiont relied on raw materials from the host

Eventually, they became incapable of living independently

Mutualism Evidence for the Theory of Endosymbiosis

Amoeba experiment by Kwang Jeon (1966) Resemblance to bacteria in size and structure Replicates independently of the main cell Internal membranes resemble those of bacteria

See Ch. 20.4 for more information!

Parasitism Parasites spend all or part of their life living in or

on other organisms Steal nutrients from the host Have big impacts on host populations: Disease,

weaken host so it is vulnerable to predation or unattractive to potential mates, cause sterility, shift sex ratios of host species, and many more!

Parasitism Parasites usually don’t kill the host right away

Ideally, a host will live long enough to give the parasite time to reproduce

The longer the host survives, the more offspring are produced

Host usually only dies from the parasite (not secondary effects) when: It is overwhelmed with parasites or A parasite invades a novel host with no defenses against

it

Parasitism Parasites often lead to secondary effects on the

host Gradual drain of nutrients leads to the inability to

fight off secondary infections

Parasitism

Roundworms MistletoeOphiocordyceps unilateralis

Flea

Lymphatic Filariasis Tapeworm

Bell Ringer, 9/12 What evidence have scientists found for the

Theory of Endosymbiosis? Why is it beneficial to parasites to keep the host

alive as long as possible? Why do some scientists believe that

commensalism does not really exist in nature?

Fish Dating Service

Videos http://www.youtube.com/watch?v=zTGcS7vJqbs Mutualism

http://www.youtube.com/watch?v=Xm2qdxVVRm4 Ants:

http://www.youtube.com/watch?v=UozWJTuhbMQ http://www.youtube.com/watch?v=R3Mt2E1M6dU

Parasites: http://www.youtube.com/watch?v=i80DvTmLPeE http://www.youtube.com/watch?v=uvdiYg6ZN-U http://www.youtube.com/watch?v=xDMzubAvzgg

Bell Ringer, 9/13 Put your homework in the tray On your bell ringer…

Choose a parasite that you learned about yesterday and explain its interaction with its host.

List the levels of organization.

Virtual Lab http://www.biologycorner.com/worksheets/virtual_

lab_population.html#.UjJ2odJQEud

Bell Ringer, 9/14 In Friday’s virtual lab, what happened when the

two paramecium were grown together? Why?

Competitive Interactions Competition among members of the same species

is very intense; leads to evolution by natural selection Natural selection: Process of evolution in which

individuals of a population vary in the details of a heritable trait and reproduce with varying amounts of success

Evolution: Change in a line of descent

Competitive Interactions Interspecific competition is not usually as intense

Interference competition: One species actively prevents another from accessing from a resource

Exploitative competition: Species don’t interact directly; they reduce the amounts of resources available for the other by using it

Competitive Interactions

Competitive Interactions Any two species differ in their resource

requirements Competition is the most fierce when the supply of

a shared resource is the main limiting factor for both

Competitive Interactions G. Gause (1930) conducted an experiment

involving two species of ciliated protists Both compete for the same prey (bacteria) Separately, their growth curves are almost the same When grown together, one grew slightly faster and

outpaced the other, driving it to extinction

Competitive Interactions

Time (Days)

4 8 12 16 20 24 4 8 12 16 20 24

Time (Days)

P. caudatumP. aurelia

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Time (Days)

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4 8 12 16 20 24

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P. caudatum and P. aurelia

Competitive Interactions This experiment is the basis of the competitive

exclusion principal Whenever two species require the same limited

resource to survive or reproduce, the better competitor will drive the less competitive to extinction in that habitat

Competitors can only coexist if their resource needs are not exactly the same Example: Gause’s second protist experiment

Think About It… Can you think of any examples of times this has

occurred in nature? If yes, describe the situation. If no, make up a hypothetical situation and explain

it.

Competitive Interactions When two competitor species coexist they

suppress each other’s population growth Concept shown in experiment by Nelson Hairston Hairston studied two species of salamanders In two plots, he removed one of each type of

salamander. In the control plot he left the populations the same

In plots with one salamander, populations soared On control plot, populations stayed in check

Competitive Interactions When two species in an ecosystem are similar,

they must find a way to coexist or one will be driven to extinction

They do this in two main ways: Resource partitioning Character displacement

Competitive Interactions Resource partitioning

Subdividing an essential resource Reduces the competitions among species that require

it Ex. Plant roots

Competitive Interactions Character displacement

Over generations a trait of one species diverges to lower the competition with other species

Natural selection favors individuals that differ most from the other species These are the individuals that get to survive and

reproduce (the goal of nature) These are the traits that are passed on to future

generations

Predator-Prey Interactions Predators: Consumers that get energy and nutrients

from prey Prey: Living organisms that predators capture,

kill, and eat

Predator-Prey Interactions The quantity and type of prey species available

affects predator types and vice versa The extent of this affect depends on how the

predator responds to changes in prey density Prey density: The population of prey in an area

Predator-Prey Interactions There are three main predator responses to prey

density: Type I: Depends solely on prey density Type II: Depends on the predator’s ability to capture,

eat, and digests prey Type III: Depends on both prey density and the ability

of the predator to capture the prey Knowing the type of predator response helps

ecologists predict long-term effects of predation on a prey population

Predatory-Prey Interactions Type I Response

The proportion of prey killed is a constant so the number killed depends solely on density

Passive and filter-feeding predators Ex. Spiders, whales, flamingos

Predator-Prey Interactions Type II Response

The number of prey killed depends on the predator’s ability to capture, eat, and digest it

When prey density increases, kills rise sharply at first (more prey available)

Eventually kill rate slows (more prey than predator can handle)

Ex. Wolf and caribou

Predator-Prey Interactions Type III Response

Number of kills increases until prey density exceeds a certain level, then rises rapidly, then levels off

Common in three situations: Predator switches among prey, concentrating on the

most abundant prey (“prey switching”) Predators need to learn how to effectively catch the

prey Number of hiding places for the prey is limited

Predator-Prey Interactions Sometimes a predator’s lag in response to changes

in prey density leads to a cyclic change in the abundance of predators and prey When prey density is low, predators decline Prey is safer and density increases Predators increase Predation leads to a decrease in prey The cycle repeats

Predator-Prey Interactions Charles Kreb tracked population densities of the

Canadian lynx and snowshoe hare in Alaska for 10 years Set up 1 sq. km plots Used fences to keep predators out of some plots Put extra food and fertilizers on some plots

Predator-Prey Interactions Results

Predator-free plots: Hare density doubled Plots with extra food: Hare populations doubled Found that all these precautions delayed the cycle

but did not stop it Other predators flew over the fences Some hares starved to death These models are WAY more complicated than high

school biology gives them credit for!

Predator-Prey Interactions If a genetic trait helps a species escape predation,

that trait will increase in frequency If a genetic trait helps a predator overcome its

prey, that trait will increase in frequency Each development requires a counterdevelopment This creates a “never ending arms race” for

evolutionary developments (coevolution)

Prey Defense There are a myriad of prey defenses:

Spikes and hard outer parts Camouflage Warning coloration Mimicry Toxins Last minute survival tactics

Prey Defense Spikes and hard outer parts

Make the prey much more difficult to eat Predators abandon prey in pursuit of an easier catch

Prey Defense Camouflage

Body shape, color pattern, behavior, or a combination thereof that makes an individual blend in with its surroundings

Predators can’t eat prey that they can’t find

Prey Defense Warning coloration

Flashy patterns and colors that predators learn to recognize as bad tasting or toxic

Predators learn to avoid organisms with that coloration

Prey Defense Mimicry

Evolutionary convergence in body form (species come to resemble each other)

Batesian mimicry: When one mimic doesn’t have any undesirable characteristics, but looks like an organism that does

Prey Defense Mimicry

Muellerian: When two species with similar appearance both have unpalatable characteristics

Prey Defense Toxins

Some organisms produce chemicals that make them unpalatable or toxic if eaten Plants

Some organisms use toxins they get from their prey Sea slugs

Prey Defense Last minute survival tactics

When an animal is cornered, there are many “last minute” defense tactics

Playing dead “Puffing up” Spitting venom or unpleasant odors

Adaptive Predator Response Predators must adapt to prey defenses

Stealth Camouflage Avoiding repellents Speed

Adaptive Predator Response Stealth

Predator is able to sneak up on prey

Adaptive Predator Response Camouflage

Predators blend in with the surroundings and can’t be seen by prey

Adaptive Predator Response Avoiding repellants

Ability to “dodge” toxins released by prey Speed