Biodiversity, Species Interactions, and Population

ControlCh. 5

Miller & Spoolman, 16th ed.

Your Goal for this lecture

To be able to explain how interactions between organisms help drive natural selection

Big Idea # 1

Species interactions affect the resource use and sizes of other populations in an area

Species Interactions

There are 3 main types of species interactions:CompetitionPredationSymbiosis

Importance of Species InteractionsThese types of interactions have a significant

impact on each population involvedThese interactions are agents of natural

selection - they influence who survives and is able to reproduce

CompetitionCompetition for

resources2 types:

Interspecific - 2 different species compete for the resource

Intraspecific - members of the same species compete for the resource

Brainstorm

Make a list of resources that species might compete for

Morning Buddies

Intraspecific - often fighting involved to “win” the resourceCan be very intense

Interspecific - usually no fighting, just better at getting it Less intense since species have slightly

different niches

Competitive Exclusion PrincipleNo two species can

occupy exactly the same niche because competition for resources would be too intense

One species will be better at getting the resources

The other species must leave, adapt, or die

Solving the Problem

Resource PartitioningTwo species evolve

adaptations that allow them to use the same resource in different ways, at different times, or in different places in order to minimize competition

How about humans? Are humans subject to the Principle of

Competitive Exclusion? Defend your answer Yes! Our use of resources directly competes with other

organisms, and forces them to leave the area or go extinct in that area (adaptation not possible since we change environment so quickly)

Kicked out of class buddies

Predation All consumers feed on

other organisms Herbivores feed on live

plantsCarnivores feed on

animalsOmnivores feed on both

Predator-Prey RelationshipsChanges in 1 population leads to changes in

other populations

How do changes in population size affect ecosystems?

A change in the size of one population will affect the size of other populations

J-curveExponential Pattern of Growth

Intrinsic Pattern of GrowthS-curve

Intrinsic Pattern of Growth

• The size of the predator population affects the prey population and vice versa

• Who is controlling the rises and falls of these 2 populations? The Hare or the Lynx?

What is an What is an adaptation or adaptation or strategy that would strategy that would be helpful to a be helpful to a predator?predator?

What is an What is an adaptation or adaptation or strategy that would strategy that would be helpful to a prey be helpful to a prey organism?organism?

Song buddies

Structural advantages Natural Weapons - Fangs, claws Flexible bodies Larger Size

Predator Strategies

Predator StrategiesAmbush-

Stalk a victim • VenomGape & Suck (fish)Keen

eyesight

Predator StrategiesSPEED & CUNNING

• More intelligent than prey

• Run faster than prey• Hunt in packs

Predator Strategies

Camouflage Sit in plain site

Predator Strategies

Chemical warfarevenom

Prey Strategies

Defense Techniques

Inflate

Flee

Fight Back

Stab

Poison

Prey StrategiesStructural advantages

Hard Body Coverings Thorns or SpinesBreak away body partsNatural Weapons

Chemical WarfareBlinding inkPoisonOffensive

Smells and Tastes

Prey Strategies

Camouflage Color ChangeCounter-shadingDisruptive PatternsMimicry

Prey Strategies

Mimicry• Mostly a prey technique

Optical and sonic illusions LOOKS like a predator:

• School of fish; false eyes; frilled neck and inflation

Batesian mimicry- a harmless animal mimics a harmful or unpalatable one

Mullerian mimicy-two or more unpalatable species resemble each other

2 rules about coloration

Small + beautiful = poisonousBeautiful + easy to catch = deadly

Food for thought

Think of a local speciesWhat adaptations does it have

to catch prey or avoid being eaten?

food buddies

Predator Prey relationships

Predator benefitsPrey does not…or does it?Predators

strengthen the population in the long term by preying on the weaker individuals

CoevolutionWhen two species have lived together and

adapted to each other for a long time such that changes in the gene pool of one species leads to changes in the gene pool of the other species

Symbiosis

Symbiosis – when different organism live in close, physical contact with one anotherParasitismMutualismCommensalism

Parasitism

A form of symbiosis in which one organism benefits and the other is hurtLeeches, fleas,

ticks, tapeworms, etc

Parasitism

Simple parasites - fleas, ticks, leechesMove from host to hostOr have only one host their

whole life

Complex parasites - plasmodium (malaria), toxoplasmosisMultiple hostsMultiple life stages

Parasitism and Coevolution

Example: malariaParasite infects red blood cellsRBCs are swept into the spleen every few days

and destroyedParasite evolved to latch onto blood vessel with

a sticky proteinBody recognizes protein as foreign and will

attack itParasite evolves to have many different types

of proteins, so body can never catch up

We all get parasites

MutualismA form of

symbiosis in which both organisms benefit

Commensalism

A form of symbiosis in which one organism benefits and the other is not harmed or helped

Example: sharks and remoras

Summarize

Why are population interactions a driving force for natural selection?