CHAPTER 5

Biodiversity, Species Interactions, And Population Control

Species Interaction

Species Interact in 5 ways1) Interpecific competition occurs when two

or more species interact to gain access to the same limited resource

Species Interaction Predation occurs when a member of one

species (the predator) feeds directly on all or part of a member of another species (the prey)

Species Interaction Parasitism occurs when one org. (parasite)

feeds on another org. (host) usually by living on or in the host

Species Interaction Mutualism an interaction that benefits both sps

by providing each w/ food, shelter, or some other resource

Species Interaction Commensalism an interaction that benefits

one sp but has little, if any effect on the other

Interspecific competition

Sp compete with one another for certain resources

1) Limited Resource such as food, can result in comp.

2) Each sp plays a role in its ecosystem, called its Ecological Niche

3) If a sp is competing w/ another sp for a part. Resource, then their niches overlap; ↑Overlap = ↑Competition

Interspecific competition

Some Sp evolve ways to share resources1) Resource partitioning occurs when sp

competing for similar scarce resource evolve specialized traits that allow them to use shared resources at diff times, in diff ways, or in diff places

2) An example of resource partitioning is seen when specialized feeding niches of bird sp evolve (pg. 81)

Predation Most consumer species feed on live

organisms of other sp Predator feeds on prey = predator-prey

relationship

A) Predators can capture their prey by:1) Pursuit and ambush

2) Camouflage to hide and ambush

3) Attack with chemical warfare

4) Herbivores can walk, swim or fly up to plants they feed on

5) http://www.youtube.com/watch?v=1rp167WqVo4

Predation

B) Prey have Evolved ways to avoid predatorsAbility to run, swim and fly quickly and a highly

developed sense of sight or smell that alerts them to the presence of predators

CamouflageChemical warfareBad-tasting, bad smelling, toxic, or stinging prey

with warning coloration Engage behavioral strategiesAvoidance adaptationsMimicry

Predation

Avoidance adaptationsEx: protective shells – turtles, thick barkSpines - PorcupinesThorns - Cacti Detaching limbs - lizards

Predation

C) Interactions b/t predator and prey sp can drive each other’s evolution Coevolution occurs when 2 different sp interact over a

long period of time; changes in the gene pool of one sp can lead to changes in the gene pool of the other

Some bats and moths have coevolvedPredators help control prey popPredators easily catch the young, sick, old & week prey

leaving indiv that tend to survive longer leading these indiv. To reproduce

Prey develop mechanisms to avoid capture; predators must overcome those mechanisms in order to survive

Parasitism

Feed off other sp by living on or in them Can live inside or outside; can live in

single or multiple hosts Usually much smaller than its host

(prey) and rarely kills its host Tapeworms and some other parasites

can transfer disease-causing microorganisms to their host

Mutualism

Both sp benefit. When 2 sp behave in ways that benefit

both by providing each with food, shelter, or some other resource.

Birds that ride on backs of large animals, like African buffalo remove pests in a mutualistic relationship

Clown fish & sea anemones

commensalism

One sp benefits and other is not harmed Epiphytes (orchids) are plants that

attach themselves to the trunks or branches of large trees for access to sunlight; use tree as anchor w/o harming it

Growth Limits of Populations Populations can grow, shrink or remain

stablePopulation change = (births + Immigration) –

(deaths + emigration)Population size may vary in cycles based on

births, deaths, immigration, and emigration

Growth Limits of populations Species have different reproductive

patternsHave many, usually small, offspring and give

them little if any parental care or protectionSome have few, usually large, offspring and

give a lot of parental care or protection

No Population can grow indefinitely

Limiting factors such as light, water, space, nutrients, predators, diseases, or competitors keep pop size from uncontrollable expansion

Pop crashes are more likely when the org cannot move easily to other locations

J-curve, S-curveRegardless, limited resources and

competition limit growth

Environmental Resistances Env. Resistance = combo of all factors

that act to limit the growth of pop. Largely determines the carrying capacity

(k) = the max pop. of a given sp that a part. habitat can sustain indefinitely

Growth rate ↓ as pop. Size nears k b/c resources start to swindle

Exponential growth

Starts slowly but then accelerates as the pop ↑ bc the base size of the pop is ↑

Pop has few if any limitations Grows at a fixed rate J-Shaped

Population Crash Not a smooth transition btw exponential and

logistic growth Pop use up their resources & temporarily

overshoot/exceed K Due to reproductive time lag = the period

needed for birth rate to fall & death rate to increase in response to resource overconsumption

Pop suffers unless excess ind. Switch to a new resource or move to an area w/ new resources

K is not fixed and is influenced by: SeasonsWeather/climate/env. conditionsPresence or absence of predatorsScarcity of competitors

Logistic Growth

S-shaped curve Growth rate decreases as pop becomes

larger & faces env. Resistance Over time, pop stabilizes at or near k

Growth limits of Populations Humans are not exempt from nature’s

pop controlsIreland recorded about 1 million human

deaths and 3 million emigrants associated with the 1845 potato crop destruction

During the 14th century, the bubonic plague killed at least 25 million people

Between 1981 and 2007, AIDS killed more than 27 million people and continues to claim another 2 million lives each year

Ecological Succession

The gradual change in sp composition in a given area; Communities and ecosystems change over time

Two types: Primary & Secondary

Primary Succession

involves the gradual establishment of biotic communities in lifeless areas where there is no soil in terrestrial ecosystem or no bottom sediment in an aquatic ecosystem

Usually takes 100s-1000s of yrs bc of need to build up nutrient levels

Secondary Succession

Occurs with a series of communities or ecosystems w/ different sp develop in places containing soil or bottom sediment

Ecosystem has been disturbed, removed or destroyed

Abandoned farmland; burned or cut forests; heavily polluted streams.

Soil is present so new veg can begin to germinate w/in a few wks.

Secondary/Primary succession

Both are impt natural services that increase biodiversity = increased sustainability

Both are types of natural ecological restoration

Ecological Succession

Succession does not follow a predictable path1) The Traditional View holds that succession

proceeds in an orderly sequence along an expected path until a certain stable type of climax community occupies an area

2) The Current View reflects the ongoing struggle by different sp for enough light, water, nutrients, food, and space; state of continual disturbance & change; cant predict course of succession

Limits of Change

1) Inertia (persistence) – the ability of a living system, such as a grassland or forest, to survive moderate disturbances

2) Resilience – the ability of a living system to be restored through secondary succession after a more severe disturbance

Save the Rainforest!!!