Chapter 52: An introduction to Ecology and the biosphere Terrestrial & Aquatic Biomes:
Equatorial and and subequatorial regions.
Tropical rain forest:
rain fall is constant, with about 200-400 cm annually.
Tropical dry forest:
precipitation is highly seasonal, about 150-200 cm annually, with a six- to-seven-month dry season.
High-year round, averaging 25-29 C, with little seasonal variation
Tropical rain forest:
Broadleaf evergreen trees, bromeliads, orchids.
Dry rain forest:
Thorny shrubs and succulent plants are common in some common tropical dry forest.
Millions of species
5-30 million still undescribed species of insects, spiders and arthropods
Great diversity: amphibians, birds, reptiles, mammals and arthropods.
Temperature is variable seasonally and daily. Maximum air temperature in hot deserts my exceed 50 C; in cold deserts air temperature may fall below -30 C.
They are located in bands near the 30 north and south latitude or at other latitudes in the interior of continent-the Gobi Desert of north-central Asia.
Precipitation is low and highly variable, generally less than 30 cm per year
low, widely scatter vegetation: cacti, euphorbs( deeply rooted shrubs, and herbs that grow during infrequent periods.
snakes, ants, beetles, migratory and resident birds, and seed-eating rodents.
The Savanna is located in equatorial and subequatorial regions.
Seasonal rainfall averages 30-50 cm per year. The dry season can last up to eight or nine months.
Warm year round, averaging 24-29 C, but with somewhat more seasonal variation than in the tropical forest.
thorny trees with small leaves, plant species are fire-adapted and tolerant of seasonal drought. nonwoody plants called forbs as well.
Large plant -eating mammals: wildebeest, zebras, lions, hyena. Dominant herbivores; insects and termites.
: midlatitude coastal regions on several continents; chaparral in North America, matorral in Spain, and Chile, garigue and maquis in souther France, fynbos in South Africa.
Highly seasonal, with rainy winters and dry summers. Annual precipitation generally falls within the range of 30-50 cm.
Fall, winter, and spring are cool, with average temperatures in the range of 10-12 C. Average summer temperatures can reach 30 C and daytime maximum temperatures can exceed 40 C.
Dominated by shrubs and small trees, along with many kinds of grasses and herbs.
Some shrubs produce seeds that will germinate only after a hot fire.
deer, goats, high diversity of small mammals, amphibians, birds, reptiles, and insects.
Veldts of South Africa, the puszta of hungary, the pampas of Argentina and Uruguay, the steppes of Russia, and the plains and prairies of central North America.
Precipitation in often seasonal, with dry winters and wet summers. Annual precipitation averages between 30 to 100 cm. Periodic drought is common.
Winters are generally cold, with average temperatures below -10 c. Summers with average temperatures often approaching 30 C, are hot.
grasses and forbs
bisons, wild horses, and prairie dogs.
Northern Coniferous Forest:
: Annual precipitation generally ranges from 30 to 70 cm. Droughts are common. Coniferous forest of the U.S Pacific Northwest are temperate rain forest that may receive over 300 cm of annual precipitation.
Extends across northern North America and Eurasia to the edge of the arctic tundra; this is the largest terrestrial biome on earth.
Winters are usually cold; summers may be hot. Some areas of coniferous forest in Siberia typically range in temperature from -50C in winter to over 20 C in summer.
Cone bearing trees; pine and spruce, fir, hemlock
migratoy birds ( temporal); moose brown bears, siberian tigers
Temperate Broadleaf Forest:
Found at midlatitudes in the Northern Hemisphere, wth smaller areas in Chile, South Africa, Australia and New Zealand.
70 to over cm annually. Significant amounts fall during all seasons, including summer rain and in some forest, winter snow.
Winter temperatures average 0 C. Summers with temperatures up to 35 C are hot and humid.
Deciduous trees, which drop their leaves before the winter and when low temperatures would reduce photosynthesis and make water uptake from frozen soil difficult. In Australia evergreen eucalyptus trees dominate these forest.
Mammals hibernate in winter, while many birds species migrate to warmer climates. Other mammals, birds, and insects make use of all the vertical layers of the forest.
covers expansive areas of the Arctic, and 20% of the earth's surface.
High winds and low temperatures produce similar plant communities called alpine tundra; these are located on very high mountaintops at all latitudes including the tropics.
Precipitation average from 20 to 60 cm annually in arctic tundra but may exceed 100 cm in alpine tundra.
: Winters are cold, with averages in some areas below -30 C. Summer temperatures generally average less than 10C.
The vegetation of the tundra is mostly herbaceous: mosses, grasses, and forbs, dwarf shrubs and trees and linches.
musk oxens, ( migratory caribu and reindeer). Bears, wolves, foxes. Other animals migrate to the tundra for summer nesting.
Understanding Zonation in Aquatic Biomes:
Where there is sufficient light for photosynthesis
lower aphotic zone where little light penetrates.
The photic and aphotic together make up the pelagic zone.
The part of the ocean 2000-6000 m below surface
zone made up of sand, organic and inorganic sediments, and it is occupied by communities of organisms called the
. The major source of food for many benthic species is dead organic matter called
; or food that comes from the surface waters of the photic zone.
Lakes and Physical Characteristics:
Standing bodies of water: ponds that are a few square meters long to lakes covering thousands of kilometers. In lakes light decreases with depth, which creates stratification. Temperate lakes may have a seasonal thermocline year round.
Lakes and Chemical Characteristics:
Salinity, oxygen concentration and nutrient content differ greatly among lakes and can very with season.
are nutrient poor and oxygen rich, and decomposable organic matter in bottom sediment is low.
are nutrient-rich and often depleted of oxygen in the deepest zone in the summer and covered with ice in the winter. In this zone of the the eutrophic lake decomposition is high in deeper layers causing periodic oxygen deprivation.
It is a habitat inundated by water, that supports plants adapted to water-saturated soil. Wetlands are inundated at all times and others flood infrequently.
High organic production by plants and decomposition by microbes and other organisms. Water and soil are periodically low in dissolved oxygen. Wetlands have high capacity to filter dissolved nutrients and chemical pollutants.
Benefits of wetlands:
Wetlands are among the most productive biomes on earth. Water saturated soils favor the growth of plants, such as pond lilies, emergent cattails, sedges, bald cypress, black spruce which have adaptations enabling them to grow in water or soil that is periodically anaerobic owing it to the presence of unarerated water.
Streams and Rivers:
Streams and rivers are characterized by the speed and volume of their flow. Headwaters streams are generally cold, clear, turbulent and numerous. Downstream rivers are warmer and more turbid because of suspended sediment. Streams and rivers are stratified into vertical zones.
Salt and nutrient content of streams and rivers increases from the headwaters to the mouth.. Headwaters are usually rich in oxygen. Downstream water also contains substantial oxygen, except where there has been organic enrichment.
An estuary is a transition area between river and sea. Seawater flows up the estuary channel during a rising tide and flows back down during a rising tide and flows back down during the falling tide. Higher density seawater occupies the bottom of the channel and mixes little with the lower river water at the surface.
Salinity varies spatially within estuaries, from nearly that of fresh water to that of sea water. Salinity also varies with the rise and fall of tides. Nutrients from the river make estuaries, like wetlands, among the most productive biomes.
Physical Characteristics: A
n intertidal zone is periodically submerged and exposed by the tides, twice daily on most marine shores. Changes in physical conditions from the upper to lower intertidal zones limit the distribution of many organisms to particular strata.
Oxygen and nutrient levels are generally high and are renewed with each turn of the tides.
Oceanic pelagic zone:
vast realm of open blue water, that is constantly mixed by wind driven oceanic currents. This photic zone extends to greater depths that in coastal marine waters.
Oxygen levels are generally high. Nutrient concentrations are generally lower than in coastal waters.
Tropical areas of the oceanic pelagic zone have lower nutrient concentrations than temperate oceans.
Turnover between fall and springs renews nutrients in the photic zones of the temperate and high-latitude ocean areas.
Marine Benthic Zone:
The marine benthic zone consist of seafloor below the surface waters of the coastal or zone of the offshore, pelagic zone. Except for shallow, near-coastal areas, the marine benthic zone receives no sunlight. Water temperature declines with depth, while pressure increases. Therefore organisms in the very deep benthic or abyssal, zone are adapted to continuos cold. and very high water pressure.
Except in areas of organic enrichment, oxygen is usually present at sufficient concentrations to support diverse animal life.
Major factors that produce different environment
Global Climate patterns:
Latitudinal Variation in Sunlight intensity
The tropics or regions at south 23.5 latitude and 23.5 s
outh latitude is where sunlight strikes more directly and therefore producing an environment that has more heat and light per unit of surface area.
Global Air circulation and precipitation patterns:
Major precipitation in the tropics
is caused by the high temperatures that evaporate water from the earth's surface and cause warm, wet air masses to rise and flow towards the poles. As the rising air masses cool, they release much of their water content, creating abundant precipitation.
Desert or arid environments
are formed by the 30 north and south latitude where high altitude air masses, which are then dry, descend absorbing moisture from the land, therefore creating arid and dry climate.
At latitudes 60 north and 60 south
, air masses rise and release abundant precipitation, but less than the tropics.
Earth's tilted axis of rotation and its annual passage around the sun causes strong seasonal cycles in middle and high latitudes.
Equator faces sun directly, and neither pole tilts toward sun, therefore all regions on Earth experience 12 hours of daylight and 12 hours of darkness.
During this time of the year the northern hemisphere is tilted towards the sun, therefore, creating the longest day and shortest night at this region; On the other side the southern hemisphere is is tilted away from the sun and has the shortest day and longest night.
September equinox: Equator faces sun directly, neither pole tilts towards sun; all regions of Earth experience 12 hours of daylight and 12 hours of darkness.
Northern hemisphere tilts way from the sun and has shortest days and longest night; Southern hemisphere tilts toward sun and has longest day and shortest night.
Bodies of Water
Ocean current influence climate along the coast of continents by heating or cooling overlaying air masses that pass across the land.
Ex. Mediterranean Climate
Rain Shadow effect:
Cool air flows inland from the water moderating temperatures near the shore
Air that encounters mountains flows upward, cools at higher altitudes and releases water as precipitation.
Less moisture is left in the air reaching the leeward side of the mountains, which therefore has little precipitation; therefore creating a desert on the back of mountain.
Understanding terrestrial biomes:
: having green leaves throughout the entire year, the leaves of the past season not being shed until after the new foliage has been completely formed
is something that sheds after a period of time, such as a tree or a shrub that sheds its leaves annually
a layer of water in an ocean or certain lakes, where the temperature gradient is greater than that of the warmer layer above and the colder layer below
Chapter 53: Population Ecology
What is a population?
A population is a group of individuals of a single species living in the same general area.
In terms of populations what does
The density of a population is the number of individuals per unit are or volume.
Example: The number of oak trees per square kilometer...
What are some factors that affect or cause changes in population density?
Which include all types of reproduction
The influx of new individuals from other areas.
movement of individuals out a population and into other locations
What does dispersion in term of population mean?
It is a pattern of spacing individuals within the boundaries of the population.
What are some patters on dispersion?
In this pattern individuals are aggregated in groups. ( form groups for survival)
Ex. Plants and fungi are clumped together where soil conditions favor germination and growth
Ex. effective predation or defense: a groups of wolves will more likely subdue a moose than a single wolf.
Evenly spaced, pattern of dispersion my result from direct interactions between individuals in the population.
Ex. Some plants secrete chemicals that inhibit the germination and growth of nearby individuals that inhibit the germination and growth of nearby individuals that could compete for resources.
Random Dispersion: ( unpredictable spacing)
The position of each individual is independent of other individuals: There is an absence of strong attractions or repulsions among individuals.
Ex. Plants established by windblown seeds such as dandelions.
Helpful chapter vocabulary:
The study of the vital statistics of populations and how they change over time.
Per capita birth rate:
it is the number of offspring produce per unit time by an average member of the population.
Per-capita death rate:
allows to calculate the expected number of death per unit time in a population of any size.
per-capita rate of increase: This per capita is represente by r; r is= to the difference between the per capita birth rate and per capita death rate.
The value of r i
ndicates weather a given population is growing ( r>0 or declining r<0
Zero population growth
occurs when the per capita birth and death rates are equal ( r=0)
symbolized by K, it is the maximum population size than an environment can sustain
Semelparity: one single reproduction before it dies.
iteroparity: repeated reproduction
Survivorship curves and their meaning
Type 1 curve is flat at the start reflecting low death rates during early and middle life, and then drops sharply as death rates increase among older age-groups.
Ex. Humans represent this kind of survivorship curve
Type II curves are intermediates, with constant death rate over the organism's life span.
Ex. Rodents such as squirrels represent this kind of survivorship curve
This curve drops sharply from the start, reflecting high rates for the young, but flattens out as death rates decline for those few individuals that survive the early period of die -off.
Ex. This curve is associated with organisms that produce very large numbers of offspring but provide very little or no care, such as long-lived plants, many fishes, and marine vertebrates.
Models of population growth:
Exponential population growth:
This model reflects an increase in population under unlimited conditions and where resources remain abundant; exponential population growth then occurs when r is greater than zero and is constant at each instant in time. This means that the per- capita rate of increase may assume the maximum rate for the species.
This model created a J- Shaped curve of exponential growth. The curve is characteristic of some populations that are introduced into a new environment or species that have been reduce drastically by a catastrophic event.
EX: exponential growth of elephants when protected from hunting.
Population grows more slowly as it nears its carrying capacity; per capita rate of increase approaches zero as as the population size nears the carrying capacity.
The logistic model of population growth produces a sigmoid shape indicating that the rate of population growth decreases as population size approaches the carrying capacity of the environment.
Ex. small animal populations growth by laboratories; such as beetles and crustaceans fit the S- curve; populations experience exponential growth, but limited resources bring then close tot carrying capacity and depending on other factors such as predation or scarce resources the population experience an increase in population size and as consequence a decrease population due to limited food.
Factors that affect population growth
Density independent: Birth or death rate that does not change with population density
Examples of density-independent limiting factors include:
• unusual weather
• natural disasters
• seasonal cycles
• certain human activities—such as damming rivers and clear-cutting forests
Density dependent: death rate that increases with population density or birth rate falls with rising density.
( As population density increases, many density-dependent mechanisms slow or stop population growth by decreasing birth rate or increasing death rates.
Predation cause density-dependent mortality if a predator captures more food as the population density increases. This also means that the when the prey population increases, predators will feed on that type of species.
Diseases are more spread when density of population in high. Therefore the rate of transmission is dependent on population density
Competition for resources:
Increased population density intensifies competition for resources, this causes a reduction on reproductive rate.
Some species compete for space. In this form population growth is limited.
Ex. The presence or surplus or nonbreeding, individuals is a good indication that territoriality is restricting population growth.
intrinsic physiological factors can regulate population size.
Ex. Reproductive rates of white footed mice is a field enclosure drop even when resources are abundant.
population density will decrease depending on toxic tolerance levels.
yeast population is dependent on the presence of alcohol.
Human population Growth history
1650: 500 inhabited our earth
The following two centuries the population double to 1 billion
1930: The population double to two billion
1975: The population had more than 4 billion
The population currently has more than 7 billion
The human population currently increases by 78 million each year, and 2000000 people per day; it is predicted that by 2050 the population of the earth will be 8.1-10.6 billion
Infant Mortality and Life Expectancy
Infant mortality is the number of infant death per 1000 live births
life expectancy at birth: The predicted average length of life at birth.
What does the ecological footprint concept tells us?
The ecological footprint concept summarizes the aggregate land, water area required by each person city or nation to produce all the resources it consumes and to absorb all the waste it generates.
The ecological footprint is estimated through the addition of all ecological resources and divided them by the population.
The calculation will yield that 2 hectares or 2.47 acres are needed per person.
Regional pattern of population change
In stable regional population, birthrate equals death rate. Zero population growth= High birth rate-High death rate or Zero population growth= Low birth rate-Low death rate
demographic transition: The movement from high birth rate and death rates towards low birth and death rates, which tends to accompany industrialization and improved conditions is called the demographic transition.
How does birth rates affect the growth of world's population?
Delayed population helps to decrease population growth rates and to move a society towards zero population growth under conditions of low birth rates and low death rates.
What does age structure diagrams predict?
Age structure diagrams predict a population's growth trend and projects social conditions of a community.
: Ethology is the branch of biology that focuses on animal behavior.
Innate behavior is instinct behavior; a behavior that organism have from the time the are born.
Example: Baby sucking finger right after birth
Ex. Snake spitting smelling substances an acting dangerous as a mechanism of defense right after hatching from their eggs.
Fixed Action Pattern:
Instinct behavior that has developed, and that is shown unconsciously.
Ex. Ducks unconsciously repeated behavior; behaving the same way with pool balls than with their eggs.
Ex. Adults, unconsciously gesture responses; such as responding with the same gestures with witch they were called. The "eyebrow flash."
a form of learning in which a very young animal fixes its attention on the first object with which it has visual, auditory, or tactile experience and thereafter follows that object.
Ex: Baby animals following their mothers and copying their behavior to
A behavior that is activated through a stimulus:
Ex. Dogs salivating every time they hear a bell.
Ex. Bears attracted to a place when there bird feeders in area; bears will stop coming to the area when bird feeders are remove from the area.
Trial & Error:
It is way that organism use to learn new behaviors:
Ex;Crows learning to place quarters in vending machine in order to obtain food
Ex; Skinner box; mice learning to use a lever to obtain food.
Habituate to stimulus after many repetitions; getting used to think in a similar way until behavior is ignored.
Ex. Prairie dog's behavior habituates, or gets to humans when they are hurt by them or other animals.
Ex. Sea anemone: Get's used to the taste of plastic, decreasing its response overtime
Looking and observing and learning that way.
Ex. Octopus learn behavior through observation when they are observe one another.
Ex.Monkeys looking at each other.
It is a behavior that is directed to problem solving
Ex: Given different things or objects and figuring out how to put them together. The candle example.
Ex. Placing a banana in the ceiling of a room and placing different box sizes ...eventually the monkey will figure out what to do with the boxes and used them to reach the banana.