Biodiversity, Species Interactions, And Population Control

Species Interaction  Species Interact in 5 ways 1) 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 resources 1) 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)

Predation B) Prey have Evolved ways to avoid predators Ability to run, swim and fly quickly and a highly developed sense of sight or smell that alerts them to the presence of predators Camouflage Chemical warfare Bad-tasting, bad smelling, toxic, or stinging prey with warning coloration Engage behavioral strategies Avoidance adaptations Mimicry

Predation  Avoidance adaptations Ex: protective shells – turtles, thick bark Spines - Porcupines Thorns - 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 coevolved Predators help control prey pop Predators 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 stable Population 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 patterns Have many, usually small, offspring and give them little if any parental care or protection Some 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-curve Regardless, 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: Seasons Weather/climate/env. conditions Presence or absence of predators Scarcity 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 controls Ireland recorded about 1 million human deaths and 3 million emigrants associated with the 1845 potato crop destruction During the 14 th 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 path 1) 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!!!