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 Interactionshave a significant impact on each population

involvedare 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

WhiteboardsFor the species pictured, list some

resources they might compete for and identify if it is inter or intraspecific competition

Intraspecific - fighting often 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

The less competitive species must leave, adapt, or die

Examine the three graphs and determine what species is the better competitor and what evidence you have for that answer

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)

Predation

All consumers feed on other organisms

Herbivores feed on live plants

Carnivores feed on animals

Omnivores 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

Carrying capacity - the maximum population size of a species that the environment can sustain indefinitely, given the food, habitat, water, and other necessities available in the environment.

Could the carrying capacity of an ecosystem change? If yes,

how?

• 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?

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 StrategiesCamouflage

Sit in plain site

Predator Strategies

Chemical warfarevenom

Prey StrategiesDefense Techniques

InflateFleeFight BackStabPoison

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

Whiteboard

Think of a local speciesWhat adaptations does it have

to catch prey or avoid being eaten?

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

ParasitismSimple parasites - fleas,

ticks, leechesMove from host to hostOr have only one host their

whole lifeComplex parasites -

plasmodium (malaria), toxoplasmosisMultiple hostsMultiple life stages

Parasitism and CoevolutionExample: 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

Exit TicketSummarize

How do population interactions act as a driving force for natural selection?