Population Dynamics Unit 10- Ecology Natural Dynamics

Measuring Populations Population density = # of individuals of a particular species per unit area Population density = # of individuals of a particular species per unit area

Measuring Populations, cont. Sampling – used to estimate size of population Sampling – used to estimate size of population –Quadrats – count all organisms in a block and use this to estimate population size –Indirect counting – count nests, burrows, etc instead of organisms –Mark recapture – trap animals, mark them, release, recapture and count marked vs. unmarked

Limiting population growth Limiting factor – a condition that can limit population growth Limiting factor – a condition that can limit population growth –Ex: space, food, disease Carrying capacity – the number of organisms in a population that the environment can maintain Carrying capacity – the number of organisms in a population that the environment can maintain –Birth rate and death rate are about equal

Limiting population growth Density-dependent factors – a factor that limits population growth more as the population density increases Density-dependent factors – a factor that limits population growth more as the population density increases –Ex: food, disease that spreads by contact Density-independent factors – a factor that limits population and is unrelated to population density Density-independent factors – a factor that limits population and is unrelated to population density –Ex: extreme weather

Types of population growth Exponential – population multiplies by a constant factor at constant time intervals Exponential – population multiplies by a constant factor at constant time intervals –there are few factors that stop overall growth –Also known as J-curve

Types of population growth S-curve – population begins growing exponentially, but environmental factors begin to limit growth; population stops growing or may begin to decrease S-curve – population begins growing exponentially, but environmental factors begin to limit growth; population stops growing or may begin to decrease

Types of population growth Boom and bust – increase rapidly (boom) and then decrease rapidly (bust) Boom and bust – increase rapidly (boom) and then decrease rapidly (bust)

Population interactions Interspecific competition – two or more species rely on the same limited resource Interspecific competition – two or more species rely on the same limited resource –Competitive exclusion – when one species succeeds over the other due to limited resources –Niche – each organism’s unique living arrangement, such as habitat, food, time when active, etc

Population interactions Predation – an interaction in which one organism eats another Predation – an interaction in which one organism eats another –Predator – doing the eating –Prey – being eaten –Both predator and prey have evolved with adaptations to enhance survival Ex: camouflage, hunting in packs, warning coloration Ex: camouflage, hunting in packs, warning coloration

Prey adaptations

Population interactions Symbiotic relationships – a close relationship between species in which one of the species lives in or on the other Symbiotic relationships – a close relationship between species in which one of the species lives in or on the other –Parasitism – the parasite obtains food at the expense of the other organism (host) –Mutualism – both organisms benefit –Commensalism – one organisms benefits and the other is neither helped nor harmed

Parasitism – blowfly larvae kill purple martin chick

Mutualism – sea anemone protects clownfish from predators; clownfish is territorial and protects anemone from predators and shares food

Commensalism – grey whale carries barnacles; whale not harmed nor helped, barnacles have more access to food

bioaccumulation occurs within an organism, and biomagnification occurs across trophic (food chain) levels.

Disturbances in communities Ecological succession – community change when new species colonize disturbed area –Primary succession – community arises in lifeless area without soil Ex: volcano creating new island Ex: volcano creating new island –Secondary succession – community arises in disturbed area with soil Ex: growth in plowed farm field Ex: growth in plowed farm field

Primary succession – growth on lava rock

Secondary succession after forest fire

Disturbances in communities Pioneer species – predominant species in the early stages of succession; tend to be small, fast-growing, and fast-producing Pioneer species – predominant species in the early stages of succession; tend to be small, fast-growing, and fast-producing Succession proceeds through many stages until it reaches a stable end point called the climax community Succession proceeds through many stages until it reaches a stable end point called the climax community

Pioneer species – can grown on rock and will help form soil