5-2 What Limits the Growth of Populations? Concept 5-2 No population can continue to grow indefinitely because of limitations on resources and because of competition among species for those resources.

Most Populations Live Together in Clumps or Patches (1) Recall that a population is group of ________________ individuals of the same species Population “flock” of snow geese interbreeding

Most Populations Live Together in Clumps or Patches (1) Three general dispersion patterns…. 1.Clumping – most ______________ 2.Uniform dispersion – when resources are ____________ 3.Random dispersion – when resources are ____________ common scarce plentiful

Most Populations Live Together in Clumps or Patches (2) Why clumping? 1.Species tend to cluster where __________________ are available 2.Groups may have a better chance of encountering resources than individuals 3.___________________ from predators 4.Living in packs give some _________________ species a better chance of getting a meal resources Protection predator

Populations Can Grow, Shrink, or Remain Stable (1) Four variables govern population size…. Births Deaths Immigration – moving __________ a population Emigration - ___________ of population Pop. change = (births + immigration) – (deaths + emigration) into Exiting/out

Populations Can Grow, Shrink, or Remain Stable (2) A population’s age structure is its distribution of individuals among various age ____________ Can have a strong effect on how ______________ it increases or decreases Age structure groups Pre-reproductive age – too ______________ to reproduce Reproductive age – capable of reproduction Post-reproductive age – too _______ to reproduce groups rapidly young old

Populations Can Grow, Shrink, or Remain Stable (2) Which age group does the population below have more of… Pre-reproductive? Reproductive? Post-reproductive? How do you think this age group will affect its future growth? It may grow rapidly in the near future

Some Factors Can Limit Population Size Each population in an ecosystem has a range of _________________ to variations in physical and chemical environment Individuals in the population may also have slightly different ranges due to…genetics, health, age, etc. Limiting factor principle Too much or too little of __________ physical or chemical factor can limit or prevent growth of a population, even if all other factors are at or near the optimal range of tolerance tolerance ANY

Trout Tolerance of Temperature Fig. 5-13, p. 113

No Population Can Grow Indefinitely: J-Curves and S-Curves (1) Common limiting factors: Light Water Space Nutrients Exposure to too many competitors, predators or infectious diseases Temperature Salinity (amount of dissolved salt in water) Dissolved oxygen content

No Population Can Grow Indefinitely: J-Curves and S-Curves (2) The combination of all factors that act to limit the growth of a population is called _________________ _________________ Determines an area’s carrying capacity (K)…which is the _________________ population a given habitat can sustain indefinitely environmental resistance maximum

No Population Can Grow Indefinitely: J-Curves and S-Curves (3) Exponential growth ______ Starts slowly, then ___________________ to carrying capacity when meets environmental resistance Logistic growth ________ _____________________ population growth rate as population size reaches carrying capacity J accelerates S Stabilizing

Fig. 5-15, p Population overshoots carrying capacity Carrying capacity 1.5 Population recovers and stabilizes Number of sheep (millions).5 Exponential growth Population runs out of resources and crashes Year

Population Size of Southern Sea Otters Off the Coast of So. California (U.S.) Fig. 5-B, p. 114 Southern sea otters are having trouble experiencing rapid growth

Science Focus: Why Do California’s Sea Otters Face an Uncertain Future? Low biotic potential…._____ pup per year Prey for orcas…increased because their normal prey (sea lions and seals) ________________ Cat parasites and thorny-headed worms from _____________ Toxic algae blooms…triggered by ________________ that wash into coastal waters PCBs and other ___________ accumulate in shellfish Oil spills 1 decreased birds fertilizers toxins

Case Study: Exploding White-Tailed Deer Population in the U.S. Early 1900s: deer habitat destruction and uncontrolled hunting led to low numbers 1920s–1930s: ________ to protect the deer and we starting eliminating their ______________________ Current population ____________________for deer Problem? Deer like to live near the edge of a forest where _________________ areas have expanded Spread Lyme disease Deer-vehicle accidents Eating garden plants and shrubs (all-you-can-eat paradise) Solution: Contraceptives? laws predators explosion suburban

Mature Male White-Tailed Deer Fig. 5-16, p. 115

When a Population Exceeds Its Habitat’s Carrying Capacity, Its Population Can Crash Some species do not make a _______________ transition from J growth to S growth Many temporarily exceeds the area’s carrying capacity due to a reproductive ______________: the time period needed for the birth rate to ________ and the death rate to rise Leads to a dieback or population ________________ Damage may reduce area’s carrying capacity smooth time-lag fall crash

Exponential Growth, Overshoot, and Population Crash of a Reindeer Fig. 5-17, p. 116

Species Have Different Reproductive Patterns (1) R-strategists Produce ____________, usually ____________, offspring Little or no parental care Massive deaths of offspring…but a _________ usually always survive and they can start _________________ growth again Insects, bacteria, algae manytiny few exponential

Species Have Different Reproductive Patterns (2) K-strategists Reproduce _____________ in life Small number of offspring with long _____________ Young offspring grow inside mother (where they are __________) Long time to maturity Protected by parents, and potentially groups Most ______________ mammals…humans, elephants More ___________________ to extinction later life spans safe large vulnerable

Under Some Circumstances Population Density Affects Population Size Population _______________ can also affect population size because some limiting factors have a greater affect on populations as their densities ___________________ __________________________ population controls Predation…large numbers offer protection to individuals, but it’s easy for humans to catch a ______________ of fish Parasites/diseases – spread ____________ in close quarters Competition for resources density increase Density-dependent school faster

Density-Independent Factors….do _______ depend on density Examples: A late spring freeze can kill many individuals in a plant population Natural disasters…hurricanes, floods, fires NOT

Several Different Types of Population Change Occur in Nature Stable – fluctuates only _______________ Irruptive Population _________________, followed by a ____________ R-strategists (insects during the summer months) Regular ___________________ fluctuations Also called _____________________ cycles Top-down population regulation – through ______________ Bottom-up population regulation – controlled through the ___________________ of a resource Irregular…may result from some type of chaos in the system slightly surge crash cyclic boom-and-bust predation scarcity

Fig. 5-18, p Hare Lynx Population size (thousands) Year Predator – prey : cyclic

Humans Are Not Exempt from Nature’s Population Controls Ireland Potato crop destroyed by a fungus in 1845 __________________ people died and _________________ migrated Bubonic plague…disease normally lives in rodents Fourteenth century…spread through crowded, unsanitary European cities and killed __________________ people AIDS - Global epidemic – killed more than _________________ 1 million 3 million 25 million 27 million

Review Question 1 What three types of dispersal patterns are shown? clumpeduniform random

Review Question 2 What is demonstrated by this picture? What is the limiting factor being studied? range of tolerance… for temperature

Review Question 3 Which example is an r-strategist? K strategist? Elephantinsect Which may not experience stabilized S-growth? K-strategist R-strategist insect