agave.html: 52_06CenturyPlant.jpg
Agave, or century plant, an example of big–bang reproduction.
Video:
Bat Pollinating Agave Plant
age_structure.html: 52_25AgeStructPyramids.jpg
Age–structure pyramids for the human population of three countries in 2000.
carrying-capacity.html: 52_11NandRateOfIncrease.jpg
Influence of population size (N) on per capita rate of increase (r).
The logistic
model assumes that the per capita rate of increase decreases as N increases.
If N is greater than K , then the population growth rate is negative, and population size decreases.
An equilibrium is reached at the white line when N = K.
demographic.html: 52_24DemogTransitions.jpg
The demographic transition in Sweden took about 150 years, from 1810 to 1960;
in Mexico, the changes are projected to continue until sometime after 2050, almost the same length of time.
Demographic transition is associated with an increase in the
quality of health care and sanitation as well as improved access to education, especially for women.
dispersion-clumped.html: 52_03Dispersion-clumped.jpg
Clumped.
For many animals, such as these wolves, living in groups increases the effectiveness of hunting, spreads the work
of protecting and caring for young, and helps exclude other individuals from their territory.
This is the most common kind of dispersion
in nature
.
dispersion-random.html: 52_03Dispersion-random.jpg
Random.
Dandelions grow from windblown seeds that land at random
and later germinate.
dispersion-uniform.html: 52_03Dispersion-uniform.jpg
Uniform.
Nesting birds, such as these king penguins on South Georgia Island
in the South Atlantic Ocean, often exhibit uniform spacing
,
maintained by aggressive interactions between neighbors.
ecological_footprint.html: 52_27EcologicalFootprint.jpg
Ecological footprint in relation to available ecological capacity.
Countries indicated by red dots were in an ecological deficit
in 1997 when this study was conducted.
exponential-elephant.html: 52_09ExponGrowthPredict.jpg
Exponential growth in the African elephant population of Kruger National Park, South Africa.
exponential.html: 52_10ExponGrowthElephant.jpg
Exponential growth in the African elephant population of Kruger National Park, South Africa.
After they were protected from hunting, the elephants in Kruger National Park showed
exponential population growth for 60 years.
footprint.html: Ecological_footprint.jpg
Ecological footprint
calculates the aggregate land and water areas
required for consumption and waste disposal.
This includes arable land, pasture, forest, ocean, built–up land, and fossil energy
(land required for vegetation to absorb the CO2 produced by burning fossil fuels.).
fur-seals.html: 52_01FurSeals.jpg
Population of northern fur seals (Callorhinus ursinus) on St. Paul Island, off the coast of Alaska.
These are related to eared sea lions
that can rotate their long hind flippers forward, and do handstands.
growth.html: 52_13PopGrowthCurves.jpg
| How well do these populations fit the logistic growth model? | ||||
|---|---|---|---|---|
| The growth of Paramecium aurelia in small cultures closely approximates logistic growth if the experimenter maintains a constant environment. | The growth of a population of Daphnia in a small laboratory culture overshoots the carrying capacity of its environment and then settles down to an stable population size. | The population of female song sparrows nesting on Mandarte Island, British Columbia is periodically reduced by severe winter weather. | ||
human-growth.html: 52_23HumPopPercentIncreas.jpg
Percent increase in the global human population (data as of 2003).
The dashed portion of the curve indicates projected data.
The sharp dip in the 1960s is due mainly to a famine in China in which about 60 million people died.
human-population.html: 52_22HumanPopGrowth.jpg
Human population growth (data as of 2003).
The global human population has grown almost continuously throughout history,
but it skyrocketed after the Industrial Revolution.
Though it is not apparent at this scale, the rate of population growth has slowed in recent
decades
, mainly as a result of decreased birth rates throughout the world.
kestrel.html: 52_07KestralParentCare.jpg
EXPERIMENT
Researchers transferred European kestrel chicks among nests to produce different brood sizes.
They then measured the percentage of parent birds that survived the following winter.
CONCLUSION
The lower survival rates of kestrels with larger broods
indicate that caring for more offspring negatively affects survival of the parents.
life_expectancy.html: 52_26BabytDeathLifeExpect.jpg
Infant mortality and life expectancy at birth in developed and developing countries).
logistic.html: 52_12LogisticGrowth.jpg
Population growth predicted by the logistic model.The rate of population
growth
slows as population size
(N) approaches the carrying capacity
(K) of the environment.
offspring.html: 52_08SeedCropSize.jpg
population.html: 52_02PopulationDynamics.jpg
Births and immigration add individuals to a population.
Deaths and emigration seeds.html: 52_08SeedCropSize.jpg semelparity.html: 52_06CenturyPlant.jpg
Some animals also spend many years to reach reproductive age, spawn, and die.
survivorship_curve.html: 52_04SquirrelSurviorCurve.jpg survivorship_types.html: 52_05SurvivorshipCurves.jpg
Mammals such as humans that produce few offspring with good parental care exhibit Type I survivorship
with low death rates during early and middle life.
Organisms such as oysters that produce large numbers of offspring with little or no care exhibit Type III survivorship
with high death rates of young.
Type II curves are intermediate, with a constant death rate over the organism?s life span.
territory-cheetah.html: 52_16TerritorialBehavior.jpg territory-gannets.html: 52_17Territories.jpg
Most weedy plants, such as this dandelion, grow quickly and produce a large number of seeds,
ensuring that at least some will grow into plants and eventually produce seeds themselves.
Some plants, such as this coconut palm, produce a moderatelarge number of large seeds.
The large endosperm provides nutrients for the embryo that helps ensure the success of a
relatively large fraction of offspring.
An agave, or century plant, grows slowly for up to 20 years years,
then sends up a large flowering stalk, produces seeds, and dies, exhibiting big-bang reproduction.
Survivorship curves for male and female Belding's ground squirrels.
In these ground squirrels, death rate is relatively constant,
but males have a lower survival rate than females as they get older.
Idealized survivorship curves.
Cheetahs stake out a territory with a chemical marker.
Nesting birds also exhibit territorial behavior.
Gannets nest virtually a peck apart and defend their territories by calling and pecking at one another.