1. Population Dynamics Unit 10- Ecology Natural Dynamics

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

3. 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

5. 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

7. 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

8. 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

9. 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

10. 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)

11. 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

12. 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

15. Prey adaptations

16. 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

18. Parasitism – blowfly larvae kill purple martin chick

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

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

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

23. 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

25. Primary succession – growth on lava rock

26. Secondary succession after forest fire

27. 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

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